The results of the experimental analysis carried out on sandwich structures with rigid PUF core and different skin materials have been reported. The flammability tests have been carried out on core as well as the skin materials. From 3-point bending test FBS, CSS have been evaluated for the sandwich structures. These tests have been conducted on 4 different compositions of the core materials and 6 varieties of hybridized skin materials. Comparisons of results have been between the hybridized and non-hybridized sandwich structures. A macroscopic and microscopic analysis of the fractured surfaces have been made to identify the nature of failure under bending loads. It has been demonstrated that the debond strength of the core–face and core plays an important role in enhancing the flexural property and controlling of the failure mechanisms. It has been observed that with increasing the debonding strength of the core–face interface, the failure mode changes from debonding of the core–face interface to the failure of the face.

This study reports the result of an investigation into the effects of chiral vector of carbon nanotubes (CNTs) and modulus of matrix on the interfacial stresses of CNT-reinforced composites. Based on the molecular structural mechanics approach, the assumption that CNTs and matrix are perfectly bonded to each other, and the equation of multi-node constraints, the molecular structural mechanics model of single/multi-walled CNT-reinforced composites is established. Results show that the use of Armchair CNTs may be more beneficial than the use of Zigzag CNTs in CNT-reinforced composites when the radius of Armchair CNT is equal to that of the Zigzag CNT, and the matrix with higher elastic modulus may be more beneficial in CNT-reinforced composite structures. Besides, it is found that the load transfer efficiency from van der Waals force is only about 30%, so that the use of single-walled CNTs may be more beneficial than the use of multi-walled structures in CNT-reinforced composite structures.

Processing and properties of composite-to-composite bonding using Scotch-Weld^TM AF-555M structural adhesive were investigated. Bonding surfaces of T800H/3900-2 composite were prepared by co-curing the dry and wet peel-plies. Surface topologies of the peel-plies and the co-cured composite surfaces were examined by microscopy, contour mapping using a coordinate measuring machine equipped with a ruby sphere probe, and contact angle goniometry. Curing of the adhesive was conducted in an autoclave or vacuum press at 177°C (350°F) for 2 h under 310 KPa (45 psi). Common bagging practices for composite fabrication in an autoclave were followed. It was found that a prolonged vacuum application (i.e., overnight) prior to the application of temperature and pressure was a critical element to produce porosity-free, high-quality bonds with this adhesive system. Following this procedure, a strong bond line was consistently produced, which routinely provided a single-lap shear strength more than 10% higher than the nominal value of the adhesive (i.e., 35.9 MPa or 5200 psi) when tested at room temperature. An adhesive failure mode at the interface was noted on the fractured surfaces of specimens with strong bonds whereas a premature cohesive failure mode was more evident for the specimens with weaker bonds, probably due to porosities in the bond lines. Photomicrographs showed that the weak single-lap shear strengths occurred on specimens with significant porosity in the bond line, apparently caused by entrapped air from insufficient vacuum application prior to curing. The results of this study are discussed herein.

In this article, a methodology is presented for detecting biodegradation and debonding damage in composite-wrapped wood structures using a coplanar capacitance sensor. The presence of damage in the composite/wood interface alters the dielectric characteristics, causing a variation in the measured capacitance by the sensor. The theoretical background employed in developing the proposed capacitance technique is highlighted. A glass fiber reinforced polymers (GFRP)-wrapped wood column, containing pre-induced defects to simulate biodegradation damage and debonding of the GFRP at the composite/wood interface, was constructed and inspected in a laboratory setting. A coplanar capacitance sensor was designed and used for the inspection of simulated defects of different severity. The capacitance signals were measured and the sensor sensitivity was evaluated for each defect type. The proposed technique can be used for rapid damage screening, scheduled or random inspection, or as permanent sensor network within the composite/wood system as a structural health monitoring technique.

In this investigation the complex copper core spun yarn (Cotton Sheath and Polyester Sheath) of 179, 118, 98, and 84 tex count of copper core yarns were produced by Dref friction spinning machines and the count of 74 and 59 tex of copper core yarns (cotton sheath and polyester sheath) were produced by ring spinning machines with core attachments device for electromagnetic shielding yarn production purpose. The article reports the effects of the process variables on tensile properties of the copper core yarn as well as individual core and sheath components. Various parameters such as Spinning drum speed, the sliver material, core materials, and count of the yarn were changed to investigate how various parameters affects the tenacity of the complex copper core spun yarn.

Different contents of Kevlar pulps were employed as reinforcement for polyimide (PI) composite. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of Kevlar pulps content on tribological properties of the PI composites were investigated. The worn surface morphologies of neat PI and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. Results show that all the filled polyimides have superior tribological characteristics compared to the unfilled ones. The optimum wear reduction was obtained when the content of Kevlar pulps is 15 vol%.

This article deals with the evaluation of material wear of injection molds made of aluminium alloy Alumec 89 and copper alloy Moldmax HH in friction couples with polymer materials with various filler contents. The friction relations in injection molding were simulated in an adhesion dry wear test using an Amsler machine, with an area contact of the friction couple materials. The wear intensity was evaluated by determination of friction coefficient and relative wearing by the mass loss. Surface morphology changes of evaluated alloys after wear and the thermal conditions in particular friction couples were analyzed simultaneously.

This article presents analytical and computational models for reinforced concrete beams strengthened in flexure using an emerging composite material, steel-reinforced polymer (SRP). The SRP composite consists of unidirectional high-carbon steel fabric embedded in a polymeric resin, providing high strength and stiffness at a reasonable cost. The models developed and examined include finite element analysis, strain compatibility analysis, and closed-form equations reported in the literature and design codes. The study focuses on the load–deflection and load–strain responses, strain variation along the SRP sheets, shear stress distributions and concentrations near the cut-off points of SRP sheets, and cracking behavior. In general, the study shows that flexural strength and deflection at service loads can be well predicted using the models. The shear stress concentration near the cut-off points of SRP sheets may be approximated to 10% of the resin tensile strength just prior to SRP delamination. Confining effects by the adequate end-anchorage effectively redistribute the applied stress in the strengthened beam.

The objective of this research effort was to gain a better understanding of in-plane tensile and compressive properties of epoxy resin composites reinforced with glass and satin fabric. The effect of fiber content and orientation on the in-plane properties of these laminates has been investigated and the experimentation was performed to determinate property data for material specifications, quality assurance, and structural analysis. The laminates were obtained by hand lay-up process following an appropriate curing cycle and then the laminates were cut to attain the ASTM standards. Specimen configuration varies with variation in percentage of fiber content and orientation, the test ready specimens were subjected to tensile/compressive loads on universal testing machine with a constant cross head velocity. The analysis of the tensile strengths of the laminates was derived as a function of the fiber orientation, while compressive strength is mainly dependent on the percentage of glass content. ANOVA technique was also used to identify the parameter contribution and to generate regression model, the model adequacy is done against the experimental results and found that the results of the regression model are accurate with reasonable degree of approximation.

In this article, the mechanical, morphological, and dynamic-mechanical properties of the blends of PLA and kenaf bast short fiber were investigated. The composites, with different fiber loading and triacetin content, were prepared by melt blending techniques using a Brabender internal mixer at 60 rpm and 170°C for 10 min and their properties were examined. Pure PLA was used as a reference for the biocomposite samples. Triacetin was used as a plasticizer for PLA and PLA/kenaf composites in order to study the improvement in tensile properties. The tensile strength and stiffness of unplasticized biocomposite materials decreased with the addition of kenaf bast fibers but improved with the addition of triacetin. The optimum fiber loading was 30 wt% kenaf fibers in the PLA matrix with the addition of 5% triacetin. The dynamic mechanical analyses showed that triacetin improved the thermal stability of the biocomposites. The triacetin increased the storage modulus and gave a lower softening temperature for plasticized biocomposites. The micrographs of the tensile specimens and their fractured surfaces, which were examined by scanning electron microscopy, demonstrated that better adhesion between the fibers and the matrix was achieved with the addition of the plasticizer.

Coir and abaca fiber-reinforced polypropylene composites were manufactured using a single extruder and an injection molding machine. Raw coir and abaca were chemically treated with benzene diazonium salt. Both raw and treated coir and abaca fibers at level of fiber loading (10, 15, 20, 25, and 30 wt%) were utilized during composite manufacturing. Mechanical tests of the resultant composites and PP were conducted. A comparison has been made between the mechanical properties of the coir and abaca fiber-reinforced composites. Chemically treated fiber-reinforced specimens yielded better mechanical properties compared to the raw composites, while coir fiber composites had better mechanical properties than abaca fiber reinforced ones. Based on fiber loading, 30% fiber-reinforced composites had the optimum set of mechanical properties.

The mechanical and water absorption behavior of the bamboo–glass mat (strand and woven) reinforced epoxy and polyester laminate composites are studied. The hybridization with glass mat increases the mechanical and water resistant properties of the hybrid composites. The increase in properties is higher in the woven glass mat reinforced hybrid composites compared to the strand mat. For both the epoxy and polyester matrix composites, when two layers of strand glass mat were used the mechanical properties increase, but with three layers it shows a decrease in value. Whereas, with woven glass mat reinforcement the mechanical properties increase as the number of glass mat layer is increased. Addition of glass fiber results in reduction of water absorption by the epoxy and polyester bamboo composites. Water absorption is reduced with increase in the glass fibers in the composite.

Jute fabric-reinforced urethane acrylate-based composites were prepared using urethane acrylate oligomer (M-1200) in methanol solvent along with photoinitiator (Darocur-1173) followed by ultraviolet (UV) radiation. Different formulations were prepared by varying oligomer in the solvent by 50–90% (by weight). Jute fabrics treated with 70% oligomer, 28% methanol, and 2% photoinitiator followed by UV radiation showed the best mechanical properties of the resulting composites. For further improvement of the mechanical properties of the composites, jute fabrics were first treated with different percentages of methylmethacrylate (MMA) in methanol with photoinitiator and cured under UV radiation and then again the composites were fabricated by the oligomer. Urea was incorporated into the MMA formulation and was found to have the potential to improve the mechanical properties of the composites.

High-strength carbon fibers were oxidized by exposure to nitric acid and single-fiber wettability predictions were compared to the actual wettability of multiple fibers in resin. Single-fiber wettability was predicted through contact-angle measurements and surface-energy calculations. Multiple-fiber wettability in resin was evaluated by immersing treated fiber bundles in catalyzed vinyl ester resin, followed by cross-sectional viewing after curing. Fiber cohesion, macro-composite void content, and transverse tensile strength were also examined as a function of fiber treatment time. Fiber surface energy increased with treatment time, suggesting improved wettability. However, fiber cohesion also increased and composite wetting was found to suffer. Increasing fiber treatment times resulted in larger unwetted areas, higher void content, and declining transverse tensile strength.

Perforated plates and shells with variously shaped cutout are often used in engineering structures. Despite the importance of the effects of cutout on the load-bearing capacity and stress concentration of such plates little research has focused on stress analysis of plates with special shaped cutout. This study investigates problems associated with the maximum stresses in perforated composite plates with quasi-square shaped cutouts. Analytical solution based on Lekhnitskii’s theory of anisotropic plate is utilized for stress analysis of composite plates with central square shaped cutout. The solution is capable of considering large variety of cutout shapes and loading conditions analytically. Parametric studies were conducted to investigate the effects of variation in cutout bluntness and orientation, material properties, and loading direction on the location and the value of the maximum stress in a flat composite plate subjected uni-axial tension load. Based on results presented herein, the maximum normalized stress of perforated composite plates can be significantly changed by using proper combination of material properties, fiber orientation, loading angle, cutout bluntness, and orientation.

This study utilized a 3D crimped hollow fiber web and high tenacity nylon-6 fiber web blended with low-melt polyester staple fibers to form a compound nonwoven fabric with a sandwich structure processed by needle punching and thermal pressing. The compound nonwoven fabric was layered with Kevlar fabric to form bullet-resistant complex fabrics. Impact properties and buffer effect were analyzed via the drop weight impact test and the bullet-shooting test. The compound nonwoven fabrics made of high-tenacity nylon-6 fiber and 3D crimped hollow fiber increased the buffer effect of ballistic resistance and decreased non-penetration damage and the layer of Kevlar fabrics. This study was expected to increase the safety of the ballistic resistant cloth and decrease its cost.

This article presents the development and the characterization of composite material (laminate) containing natural jute fiber reinforcement. Thermal characterization of jute fiber reinforcement shows the influence of the temperature on the mechanical behavior of fiber. At 180°C the jute fabric loses 50% of its mechanical characteristics. The laminate obtained by a process known as infusion is polymerized at a temperature lower than that which affects the mechanical properties of dry fabric. The digital image correlation carried out on laminated jute/epoxy (warp and weft direction) under tensile test shows the presence of a considerable gradient of deformation. This gradient is explained by the variability related to the local voluminal change of jute fibers of one place to the other and the nature of the weaving of the jute fiber. The three-point bending tests show a significant dispersion of rupture stress. The thermomechanical tests carried out on samples in the two principal directions, show that the thermal coefficient of expansion in warp direction is 48% larger compared to the weft direction. The thermogravimetric test shows that this laminate absorbs up to 4% water mass after 8 h in a climatic chamber with 70% moisture content.

Palm fiber reinforced polypropylene (PP) composites were manufactured using a single extruder and an injection molding machine. Raw palm fiber was chemically treated with benzene diazonium salt to increase its compatibility with the polymer matrix. Both raw and treated palm was utilized and six levels of filler loading (10, 15, 20, 25, 30, and 35 wt%) were used during composite manufacturing. Microstructural analysis (scanning electron microscopy and Fourier transform infrared spectroscopy) and mechanical testing (tensile, flexural, impact, hardness) were conducted. Treated palm fiber reinforced composites showed better mechanical properties compared to the raw ones. Among all composites, 30% fiber-reinforced ones had the optimum set of mechanical properties.

The friction and wear properties of pure poly-tetra-fluoro-ethylene (PTFE), 35% carbon filled poly-tetra-fluoro-ethylene (PTFE+35%C), and 17% glass fiber-reinforced poly-tetra-fluoro-ethylene (PTFE+17%GFR) sliding against stainless steel under dry sliding conditions were studied by using a pin-on-disc tribometer. The effect of applied pressure and sliding speed on tribological properties of the polymer-stainless steel combination under dry sliding conditions was investigated. Tests were carried out at sliding speeds of 0.32, 0.64, 0.96, 1.0, 1.5, and 2.0 m/s and under applied pressures of 0.17, 0.34, 0.68, 1.02, 1.76, 3.53, 5.30, and 7.07 MPa. Optical microscopy was utilized to examine the worn surfaces of pure PTFE and it’s composite. The results indicated that, for pure PTFE, carbon-filled PTFE and glass fiber-reinforced PTFE composites are used in this investigation; the friction coefficient decreases with the increase in applied load values. The maximum reduction in wear rate was obtained by glass fiber-reinforced PTFE composite. The specific wear rate for pure PTFE, carbon filled PTFE composite, and glass fiber-reinforced PTFE composite were in the order of 10^-13, 10^-14, and 10^-15 m²/N, respectively. The wear mechanism include adhesive and abrasive processes.

To study the behavior of composite materials to erosive wear, we have carried out bench tests simulating the erosive wear according to ASTM D 673 standard. The principle consists in impacting composite specimens by an abrasive water jet containing sand particles, taking into account several parameters affecting the erosive wear. The first material consisting of thermoplastic matrix reinforced with E-glass fiber and the second with 8H Satin carbon fiber where as the thermoset matrix material was reinforced with 2/2 Twill glass fiber. Influential parameters such as composite hardness, abrasive particle size, speed, and impact angle were taken into account. During the experimental study, only the most influential parameters have been taken into account such as: hardness of the composite materials, abrasive size, abrasive particle speed, and angle of impact. Applying Design of experiment (DOE) strategy with experimental planning, a mathematical model was obtained describing the wear of these materials as a function of the most influential parameters led to the following results: Wear is maximum when the angle of incidence of the jet is normal to the specimen surfaces; wear is minimum when the angle of incidence of the jet is ( = 30°); mass loss is proportional to abrasive particle size and speed and inversely proportional to composite hardness.

This article deals with the AC electrical characterization of epoxy reinforced with neat silicon carbide (SiC) whiskers and SiC whiskers coated with titanium nitride. The AC electrical characterization was studied as a function of frequency in the range from 100 kHz to 1.2 MHz, temperature in the range from 20°C to 110°C. It was found that AC electrical conductivity increases with reinforcements, temperature, and frequency. Some AC electrical characterization of SiC whiskers composites as dielectric constants, activation energy, and relaxation time were determined. The observed enhancement in AC conductivity is attributed to increase in the number of conduction paths created by the whiskers contacts in the epoxy matrix gives higher electrical conductivity. It was found that the coated whiskers enhanced AC conductivity better than the uncoated. The universal power-law model of AC conductivity is observed for composites. The calculated Power exponent (about unity) is physically acceptable within this applied model.

To evaluate the effect of fungal decay on the physico-mechanical properties of natural composites, a commercial extruded bagasse/polypropylene composite from a manufacturer was sampled. Weight loss, long-term water absorption, flexural modulus, flexural strength, and unnotched impact strength were determined after incubation with white and brown rot fungi for 14 weeks. Results indicated higher water absorption for all incubated samples. However, the water absorption capacity of brown-rotted samples was significantly higher than that of white rotted ones. The brown rot fungus caused more weight loss than the white rot fungus. Modulus of rupture and modulus of elasticity declined after incubation with fungi. The brown rot fungus generally caused a greater reduction in flexural strength than did the white rot fungus. Fungal decay had no significant influence on unnotched impact strength.

The aim of this study was to explore post-buckling strength potential of two different stiffener types and evaluate structural efficiencies of those by making a comparison. This has been done by first determining the buckling and post-buckling behavior of J- and hat-stiffened composite panels under compression loading. By making a structural efficiency definition, the experimental results of J- and hat-stiffened panels for initial buckling and post-buckled responses of the panels were compared with predicted and analytical results.

The present study focuses on short flax fiber, as well as long flax fiber-reinforced polypropylene (flax/PP) composites, manufactured by the injection molding method. Compounding of flax with two different grades of PP (with and without maleic anhydride (MA-PP) grafting) is carried out by four methods: kneading process, Henschel kinetic mixer, extrusion compounding, and production of long fiber thermoplastic (LFT) granules through pultrusion. The effect of the compounding method and injection molding on the fiber length and mechanical properties of the composites is being investigated. Furthermore, the effect of fiber–matrix adhesion on the mechanical response is being discussed. It can be concluded that the reduction in fiber length, associated with injection molding, did not affect the tensile properties significantly for the studied systems due to improvements in fiber orientation along the polymer flow direction and increased fiber efficiency through dimensional changes due to fiber opening. The addition of MA-PP led to improvements in the tensile strength of injection-molded composites. Kneader compounded composites showed maximum tensile strength as well as stiffness when compared with other compounding methods.

The hybrid composites of coir/silk unsaturated polyester-based hybrid composites with different fiber lengths were prepared. Coir–silk fibers are taken in the ratio of 1 : 1, and these fibers are incorporated with unsaturated polyester resin with different fiber lengths like 1, 2, and 3 cm. The variation of mechanical properties such as tensile strength, flexural strength, and compressive strength of these composites with different fiber lengths has been studied. In the present work hand lay-up method was used for making the composites. Coir fibers are treated with NaOH and the effect of alkali treatment on the tensile, flexural, and compressive properties of the coir/silk hybrid composites has also been studied. Significant improvement in tensile, flexural, and compressive strengths of the coir/silk hybrid composites has been observed by these treatments.

Poly(methyl methacrylate) (PMMA)/hydroxyapatite (HA) composites have potential applications in bone cement, prosthesis, and dental implant. In this study, PMMA containing 5 wt% of HA is prepared using polymerization followed by compression molding. PMMA and HA powder are ground using planetary ball milling. The grinding time takes from 30 to 120 min. The effects of the grinding time and particle size of the PMMA/HA powder on the flexural properties and morphology of the composites are investigated. The structure patterns of PMMA/5HA are characterized using X-Ray diffraction (XRD). No new phase is observed in the XRD pattern with the different sizes of PMMA/HA powder. This indicates that planetary milling solely reduces the size of PMMA/HA powder. However, it does not modify the structure of PMMA and HA. A reduction of 40% in the particle diameter is observed in both PMMA and PMMA/5HA powder after subjected to planetary milling for 60 min. For the planetary ball mill-ground PMMA/HA powder, the flexural modulus of the respective PMMA composites is slightly increased. Planetary milling can increase the volume of fine particles in the composites specimens, which results in a more homogeneous distribution of HA and a reduction of void contents in PMMA matrix. The reduction in void content is observed on the fractured surface of PMMA composites through field emission scanning electron microscopy.

A thermosetting epoxy polymer was modified by incorporating 9 wt% of a CTBN rubber microparticles. The stress-controlled CA tensile fatigue behavior at stress ratio, R = 0.1 for both the neat and the modified epoxy was investigated. The addition of rubber particles increased the epoxy fatigue life by a factor of about three to four times. The rubber particle cavitation and plastic deformation of the surrounding material was observed to contribute to the enhanced fatigue life of the epoxy polymer. Then, the neat and the rubber-modified epoxy resins were infused into a quasi-isotropic, lay-up E-glass fiber, non-crimp fabric in a RIFT set -up to fabricate GFRP composite panels. Further, the stress-controlled CA tensile fatigue tests at stress ratio, R = 0.1 were performed on both of these GFRP composites. Matrix cracking and stiffness degradation was continuously monitored during the fatigue tests. Similar to bulk epoxy fatigue behavior, the fatigue life of GFRP composites increased by a factor of about three times due to the presence of rubber particles in the epoxy matrix. The suppressed matrix cracking and the reduced crack propagation rates in the rubber-modified matrix contribute towards the enhanced fatigue life of GFRP composites employing a rubber-modified epoxy matrix.

This study investigates the ballistic response of laminated composite plates using numerical simulations. Numerical simulations were carried out to determine the ballistic response of thick Kevlar/epoxy composite plates, commonly used in body armor. These plates were impacted at velocities between 100 and 1000 m/s. The numerical parametric study of ballistic impact caused by cylindrical projectile is undertaken to obtain an estimate for the ballistic limit velocity, energy absorbed by the plate, and the contact duration. The effect of mass and diameter of the projectile on ballistic limit velocity was also studied. The results obtained hereby are in good agreement with the experimental data presented by other researchers.

Jute fabrics (hessian cloth) reinforced polypropylene (PP) matrix composites were fabricated by compression molding. Jute fabrics and matrices were irradiated with gamma and UV radiation at different doses. Mechanical properties of irradiated jute fabrics and matrices based composites were found to increase significantly. Optimized jute fabrics were treated with starch solution of different concentrations for different soaking time and composite made of 0.5% (for UV) and 0.3% (for gamma) starch treated jute fabrics (5 min soaking time) showed the best mechanical properties. Scanning electron microscopic analysis of untreated and treated composites was also performed.

Polypropylene (PP) filled with diatomite particles was manufactured using a twin-screw extruder. Melt volume flow rate (MVR) is an important parameter for characterization of flow properties of polymer. The MVR of the PP/diatomite composites was measured by means of a melt flow rate instrument to investigate the effects of die diameter and extrusion conditions (temperature 210–230°C, load 5.0–12.5 kg) on the melt flow properties of the composite systems. The results showed that the MVR of the composites increased as a quadratic function with the increase of the die diameter, while it decreased with increase of particle size; the MVR was a linear function of temperature when the die diameter and load was constant; and the MVR was also a quadratic function of the die diameter when load and temperature were fixed. In addition, the effects of load, temperature, and particle size on the MVR was enhanced with an increase in the die diameter.

An experimental investigation was carried out to correlate the impact response of nanocomposites with the dynamic, inherent damping, and glass transition properties of Derakane 411-350 vinyl ester thermoset reinforced with 1.25 and 2.5 wt% Cloisite 30B nanoclay and exfoliated graphite nanoplatelets (xGnP).

Dynamic mechanical analysis was performed to obtain the visco-elastic properties such as storage modulus (E'), loss modulus (E''), glass transition temperature (T_g) and loss factor (Tan ). Low velocity impact tests were performed at an approximate strain rate of 15 s^-1 on notched and un-notched Charpy samples using a drop-tower impact test system. Storage modulus was observed to increase with increasing nano reinforcements (max 40% for graphite platelet/vinyl ester nanocomposite). Loss factor also showed a significant increase of 80% with the addition of nanoclay, and 125% with graphite platelet. Glass transition temperature and loss modulus of nanoclay and graphite platelet reinforced nanocomposites also showed significant improvements over the pristine polymer. Low-velocity impact tests showed an increase of almost 100% energy absorption for un-notched samples with increasing nano reinforcement. However, a 70–90% reduction was observed in the case of notched samples. A direct correlation between impact response and dynamic mechanical properties for these vinyl ester nanocomposites was observed.

Two kinds of wood particles with different sizes and properties were compounded with polypropylene (PP) in highly concentrated levels (by 50% and 60% weight concentration). Their flow abilities were estimated by viscosity–shear rheological test and spiral flow mold respectively; the results show that higher concentrations result in poor flow ability. However, to estimate the relation between particle size and flow ability, spiral flow-mold testing results are not consistent with those of the rheological test. The thermal melting, crystallization, and stability of the highly filled wood/PP composites were measured by differential scanning calorimetry (DSC). The results clearly showed that the melting temperature, thermal stability, and crystalline degree of composites decrease when filler contents and size increase. The mechanical properties of these materials were assessed by tensile test machine and testing results also show that the filler concentration and size dramatically affect the mechanical properties, such as E module, tensile strength, and breaking strength of wood-particle-filled PP composites. The weld-line strength of all wood composites with the contents was also tested in the same way. By testing, one found that the usual defect of weld line in injection-molding process had a very significant negative impact on the mechanical properties of wood composites and the relation of wood-particle-filling fraction and size to weld-line strength was also analyzed and clarified.

This article depicts the processing and mechanical characterization of a new class of multi-phase composites consisting of epoxy resin reinforced with jute fiber and filled with silicon carbide (SiC) particulates. The SiC used as filler material in this work was prepared from rice husk through plasma-processing technique. The effect of filler in modifying the physical and mechanical properties of jute–epoxy composites has been studied. It is found that the incorporation of rice husk derived SiC modifies the tensile, flexural, and inter-laminar shear strengths of the jute–epoxy composites. The micro-hardness and density of the composites are also greatly influenced by the content of these fillers.

An irradiation grafting method was applied for the surface modification of titanium dioxide nanoparticles so that the latter can be added to polymeric materials for improving their mechanical performance. The modification of filler has been developed by coating this with an acrylate monomer, trimethylol propane triacrylate (TMPTA), followed by electron beam irradiation. Nanocomposites of polypropylene with different loading of unmodified and modified nano-fillers were prepared. The mechanical properties including modulus and tensile strength of the resultant nanocomposites are discussed as a function of filler loading. The composites with treated filler showed enhanced mechanical properties. It was found that the reinforcing effects of the treated nanoparticles on the polymer matrix could be fully brought into play at a rather low filler loading in comparison to conventional particulate-filled composites. Unlike the approaches for manufacturing of the other types of nanocomposites, including intercalation polymerization, the current technique is characterized by many advantages, such as simple, low cost, easy to control, and having broader applicability. Finally, experimental results were compared with theoretical predictions.

The underlying mechanisms of manufacturing distortion in composite components have been suggested to be anisotropy, material property gradients, and part-tool interactions. These mechanisms have been sub-divided into those that result in shape change with changing temperature (thermoelastic) and those that are one-time-only effects (non-thermoelastic), generally related to isothermal cure shrinkage. The responses related to anisotropy and material property gradient mechanisms are predicted to include both thermoelastic and non-thermoelastic contributions; however, stresses imposed on the laminate and the resulting distortion due to part–tool interaction is merely non-thermoelastic in nature. Previous research has suggested that this non-thermoelastic component is critical to generating a composite angle bracket on net-shape tooling that is simultaneously distortion-free and shape-stable with temperature.

The current research investigates the degree of tailorability available in both the part–tool interaction and in the thermoelastic response to local corner asymmetry. Autoclave-cured angle brackets were produced with variations in the local stacking sequence in the corner to balance the thermoelastic contributions and with different mold releases to affect the stress transferred from the tool to the part. Two asymmetric stacking sequences are compared to the baseline symmetric laminate. The fraction of the corner radius that is made up of these regions of asymmetry is also adjusted to vary the thermoelastic effect. Mold release variations are investigated to evaluate the effect of changing levels of non-thermoelastic distortion. To measure the response, the curvatures of flat composite laminates are measured using an LVDT-based panel measurement technique, which enables measurement of changing curvature with temperature. The included angle of various composite angle bracket specimens is also measured as a function of temperature, using a laser reflection technique.

The results of this testing indicate that tailoring of both non-thermoelastic and thermoelastic components of process-induced distortion can be accomplished. The balancing of the compensation of these effects is shown to result in an angle bracket specimen, which has very little distortion and is much more stable with temperature than the baseline laminate. Further, it is found that the variation in laminate stiffness with changing local laminate stacking sequence plays an important role in the tailoring of the distortion of this geometry. Overall, the results of the research point very clearly to a methodology for the composites engineer to tailor the laminate, and the process, to generate a distortion-free/shape stable angle bracket molded on net-shape tooling.

Glass fiber (GF)-reinforced biodegradable poly(propylene carbonate) (PPC) composites were prepared by melt blending. The effects of reinforcement on the mechanical, thermal, and morphological properties of the PPC/GF composites were investigated. The mechanical properties of the composites were found to be improved obviously by the incorporation of GF. Experimental results of the thermal properties indicated that the GF addition led to the improvement on the thermal stability of the composites, and that the Vicat softening temperature (VST) of the composites was much higher than that of pure PPC resin. Scanning electron microscopic examination revealed a uniform dispersion of GF within PPC matrix at low GF loading level. It was observed that the GF appeared to be oriented within the PPC matrix to some extent, and there was good interfacial adhesion between GF and PPC matrix.

Single-fiber fragmentation tests and degradation tests of carbon/poly(-caprolactone) composites were used to investigate the effect of two fabrication methods: in situ polymerization and film stacking. The resulting specimens were tested in the as-molded state and after time periods of up to 2 months in an aqueous environment. The results demonstrate considerably significant improvements in the flexural properties for samples from the in situ process compared with film stacking. This is attributed to superior wetting of the reinforcement. Single-fiber fragmentation tests confirm the superior interfacial shear strength from the in situ polymerized specimens.

An experimental study was conducted to investigate the effectiveness of strengthening the intersection of flanged concrete block shear walls using surface-bonded composite laminates. A total of 15 specially designed flange-web intersecting wall specimens were tested using four different retrofit schemes. Tests included wall intersections reinforced with unidirectional laminate with the fibers oriented perpendicular to loading direction (90°), and bi-directional laminate with orientations of (90°/0°), (90°/0°)², and (45°/135°) to the applied load direction. The behavior of each specimen type is discussed with respect to its failure mode, strength, and deformation characteristics. Results showed that the composite laminates significantly increased the shear strength of concrete block shear wall intersections. In addition, the fiber orientation influenced the failure mode and controlled the development of the post-peak deformation capacity of the flange-web intersection. The improved post-peak behavior demonstrated the benefits of retrofitting concrete block wall intersections for strength enhancement. The retrofit scheme resulted in 100%–400% increase in strength compared to non-retrofitted specimens constructed with traditional steel joint reinforcement.

This article presents results from an experimental study, investigating the effects of core thickness on the mechanical properties of composite sandwich structures with polypropylene(PP)-based honeycomb core and glass fiber-reinforced polymer (GFRP) face-sheets fabricated by hand lay-up technique. Epoxy matrix and non-crimp glass fibers were used for the production of GFRP laminates. Flatwise compression (FC), edgewise compression (EC), three-point bending (3PB) and double cantilever beam (DCB) tests were performed to evaluate the mechanical behavior of the composite sandwich structures (CSSs). Based on the FC tests, an increase in the compressive modulus and strength was observed with an increase in the core thickness. For EC tests, peak loads up to crush of the sandwich panel is discussed using core thickness. According to the 3PB tests, a decrease in core shear stress and facesheet bending stress was observed as the core thickness increases.

In this study, five series of wood–polyvinyl chloride composite samples were prepared by granules production followed by extrusion process for insulation of cuprous wires. The effects of wood flour content and its size on thermal stability, physical, mechanical, and electrical properties of these composites were investigated. The obtained results show that the density as well as the mechanical properties decreases, as the wood flour content increases. Also, wood flour composites with smaller particles have better mechanical properties and lower density. Thermal decomposition of these composites was investigated by thermogravimetric analysis (TGA). In general, thermal decomposition of polyvinyl chloride is inhibited by the addition of wood flour to the polyvinyl chloride compound. Moreover, electrical tests showed high amounts of wood flour can't be used when high volume resistivity is necessary.

Jute fiber reinforced polypropylene composites were manufactured using a single extruder and an injection molding machine. Raw jute fiber was oxidized and manufactured composites were post-treated with urea to increase the compatibility of the jute fiber with the polypropylene matrix. Both raw and oxidized jute fiber was utilized and four levels of fiber loading (20, 25, 30, and 35) was used during composite manufacturing. Microstructural analysis (scanning electron microscopy) and mechanical tests (tensile, flexural, impact, hardness, and water absorption) were conducted. Post-treated jute fiber reinforced specimens yielded better mechanical properties compared to the oxidized and raw ones. Based on fiber loading, fiber reinforced composites had the optimum set of mechanical properties. Authors propose that the bonding between the polypropylene matrix and urea treated jute fiber must be increased in order to have improved mechanical properties at higher fiber content.

In this study, the fatigue and fracture behavior of woven steel/reinforced high-density polyethylene thermoplastic composite, having a middle tension specimen with inclined through-thickness cracks, under fatigue loading were examined. The composite material was manufactured from bidirectional woven Cr–Ni steel fibers and high-density polyethylene with a fiber volume fraction (V_f) of 0.04. The separate cracks on the sample are oriented at different angles such as 15°, 30°, 45°, 60°, and 75°. According to each crack geometry, fatigue crack growth was investigated. During the fatigue test, crack initiation, fatigue life, fatigue crack growth rate (da/dN), and stress intensity factor ranges (K_I, K_II, K_Ieq, K_IIeq, and K_eq) were examined. In addition, strain energy release rate (G) was checked out, since it was also an effective parameter in crack propagation. Crack growth rate was used as a damage parameter related to the crack geometry. In the results, crack growth rate was controlled through stress intensity factor ranges (K ) and strain energy release rates (G). Graphs of a/N, da/dN - K and da/dN - G such as material properties under consideration were plotted on log scale. Material constants were determined using Paris–Erdogan equation. Also, G values were determined using linear elastic fracture method and compliance method, and the results were compared.

The performance of damaged metallic plates reinforced with fiber-reinforced polymer composite materials (composite patches) are presented in this study. A square aluminum plate with a central circular cutout is considered as a damaged structural element. Numerical studies using commercial finite element code were conducted to investigate the effects of variation in patch geometries and lamination parameters on buckling responses of repaired plates. The varying laminate parameters, such as fiber angles and stacking sequences, are considered in this study. A quantitative measure for the effectiveness of the composite patches is taken to be the relative change in buckling loads of the reinforced plates compared to that of the unreinforced one. The results presented herein indicated that, for buckling response of a repaired metallic plate with central cutout, a set of laminated composite patches with different number of plies and stacking sequences can be found which improve the load-carrying capacity of damaged plates.

The natural fabric from the tree of Grewia tilifolia was coated with polycarbonate. The tensile properties of both the uncoated and polycarbonate coated fabrics were studied. The tensile parameters such as maximum stress, Young's modulus and percentage elongation at break were determined using a Universal Testing Machine. The effect of alkali treatment and the polycarbonate coating on tensile properties was studied. The improvement in the tensile properties on polycarbonate coating was attributed to the filling up of the void regions of the uniaxial fabrics with polycarbonate facilitating continuity.

In this study, the effect of oligomeric siloxane on the mechanical properties of jute fabric-reinforced low-density polyethylene (LDPE) composites is examined. After alkali treatment of jute fabric, oligomeric siloxane treatment is conducted to promote adhesion between jute fiber and polyethylene matrix. Mechanical properties of fabricated composites such as tensile strength, flexural strength, and interlaminar shear strength (ILSS) were evaluated. The tensile strength is observed to increase from 17.5 MPa for untreated jute fabric/LDPE composite to 27.7 MPa for oligomeric siloxane-treated alkalized jute fabric/LDPE composite. Provided that jute fabric is treated with alkali and oligomeric siloxane, a 39% increase is observed in the flexural strength. It is interesting to note that the effect of siloxane treatment after alkalization procedure of jute fabric on ILSS of jute/LDPE composite is due to the fact that 98% improvement is obtained. It can be observed that the adhesion between jute fiber and LDPE also improves to a great extent through both alkali and oligomeric siloxane treatment, respectively. These results are also confirmed by the SEM observations of fracture surfaces of jute/LDPE composites.

Hybrid composites of polypropylene (PP) reinforced with short sisal and glass fibers were prepared using twin-screw extruder, followed by injection molding in the presence and absence of maleic anhydride grafted PP (MAPP) as a coupling agent. The mechanical properties such as tensile strength, flexural strength, and impact strength increased by an optimum value at 15% sisal and 15% glass fiber loading in the presence of 2% MAPP. The rate of water absorption in the composites decreased due to the presence of glass fiber and coupling agent. The storage modulus of sisal/glass reinforced PP hybrid composites (SGRP) showed maximum improvement after treatment with MAPP. The fiber matrix morphology of the interface region in the composites was examined using scanning electron microscopy. The differential scanning calorimetry thermogram confirms higher thermal stability in the case of hybrid composites.

The purpose of this study was to develop a new kind of high strength, low thermal expansion material employing microfibrillated cellulose obtained from bamboo fibers. A possible application for such material is, for example, as a viable alternative to ceramics for probe cards industrially employed in wafer chip testing. High strength, low coefficient of thermal expansion, and low moisture absorption are among the different requirements for this application. The effect of processing conditions over mechanical properties of the obtained biocomposite was investigated; different levels of fiber homogenization were analyzed and morphology changes were monitored by optical and scanning electron microscopy examinations. Different technologies and treatments were employed to get adequate characteristics. In order to control thermal expansion or mechanical properties, nanoparticles of amorphous silica or bacterial cellulose were added to the material. The remarkable water absorption of cellulosic fibers can have undesirable effects on the mechanical properties and the dimensional stability of the material. The effect of acetylation treatment to reduce water uptake was thus investigated.

This article presents results of an experimental study conducted to investigate the influence of fiber volume fraction, fiber type, and presence of fly ash on mechanical properties of fiber-reinforced, lightweight aggregate, cellular concrete (FRLACC). Steel fibers are added at V_f of 0.5, 1.0, and 1.5%, and 25% of cement weight is replaced with fly ash in the control and FRLACC specimens that had shown the highest compressive strength in our preceding work. With the addition of 0.5% V_f of fibers, the increase in compressive strength of the polypropylene FRLACC specimens is slightly higher than that of the steel FRLACC specimens, whereas decreases in their peak load and modulus of rupture over those of control specimens are observed. The findings of the experimental study also show that the utilization of 25% fly ash is more efficient in improving the mechanical properties of the steel FRLACC specimens than those of the polypropylene FRLACC specimens.

The analysis of the large deformation of a non-linear cantilever functionally graded material (FGM) beam is made. When subjected to an end moment, explicit expressions for deflection and rotation are derived for a functionally graded beam with work hardening of power law. The effects of the gradient distribution of Young's modulus and the material non-linearity parameter on the deflections of the FGM beam are analyzed. Our results show that depth-dependent Young's modulus and material non-linearity have a significant influence on the deflections of the beam, and a FGM beam can bear larger applied load than a homogeneous beam. Moreover, to determine an optimal gradient distribution, an optimum design of a beam of a lighter weight and larger stiffness is given. The influence of the geometric non-linearity of the beam is also studied. Large and small deformation theories predict nearly the same deflections with 5% error when rotation is less than 45°, and the predictions based on the small deformation theory are overestimated to exceed 10% when rotation is greater than 60°.

In this study, the various epoxy/graphite particulate composites were prepared with different particulate fractions and were characterized for their mechanical, electrical, and morphological properties. The epoxy resin (araldite (GY-257)) and hardener (HY-951) was used to prepare composite sheets by compression molding techniques. The graphite filler content was varied from 5 to 25 wt% of the total matrix. These composites were then characterized for electrical properties and mechanical properties, i.e., tensile and flexural. There was a good adhesion between the filler and the matrix. The epoxy/graphite composite showed improved tensile modulus and Young's modulus in bending properties with increasing filler content. The electrical conductivity at different frequencies increased with increase in the filler content.

Treated mica, micro-particles, were used as model fillers to study the effect of filler loading on physicomechanical properties of polymer composites. The mica particles were surface treated by silane coupling agents. The effect of gamma rays, in air up to 50 kGy, on the physicomechanical properties of such composites was also investigated. The modulus and tensile strength of filled composites increased while the strain at break decreased with increasing filler–matrix interactions. Physical crosslinking due to a network of filler particles with polymer layer supplemented radiation crosslinking of the polymer matrix. As a result, the overall crosslink density was effectively enhanced. The strength of the networks, and hence the stiffness of the composites, increased with increasing particle–matrix interactions. However, strong matrix–filler interaction caused a loss of polymer flexibility at the particle–matrix interface, resulting in a gradual decreased elongation at break of the particle-filled composites. The thermogravimetric analysis of the composites showed that the presence of treated mica in the composites reduced the rate of decomposition. The activation energy of decomposition of the composites increased with increasing filler loading. The activation energy of decomposition was also affected by the irradiation dose.

For particulate composites undergoing linear heat flow, a general expression for the relative curvature in the inclusions, relative to the radius of curvature in the matrix alone in the absence of inclusions, has been developed in terms of the ratios between the values of thermal and elastic constants of the matrix and the dispersed phase material (i.e., inclusion). Cases where the property ratios may have some specific values or extreme values, giving some particular results, have been identified and discussed. Results presented with the help of plots covering a wide range of ratios of the constituents’ properties are expected to be helpful in assessing the behavior of particulate composites under steady-state heat flow condition.

This article presents the results of experimental studies on concrete cylinders confined with CFRP composites. Thirty small-scale specimens (150 x 300 mm²) were subjected to uniaxial compression up to failure and their stress–strain behaviors were studied. Various parameters such as wrap thickness and fiber orientation were considered. Different wrap thicknesses (1, 2, 3, and 4 layers), fiber orientation of 0°, 90°, ±45°, and their combinations were investigated. The results demonstrated significant enhancement in the compressive strength, stiffness, and ductility of the CFRP-confined concrete cylinders as compared to plain cases. An analytical model for ultimate stress and strain of confined concrete has been proposed.

Modified nanosilica was filled into stereolithography (SL) resin by means of mechanical and ultrasonic dispersion. While the concentration of SiO₂ was below 3 wt%, viscosity measurement showed that the nanoparticles were well dispersed in the resin. Then these modified photosensitive resins were applied to SL prototyping. The results of experiments indicated that, compared with the unmodified resin, the critical exposure of the modified resins increased and their penetration depth decreased. In addition, the mechanical properties of cured specimens increased, and glass transition temperature and the thermal stability of cured specimens were also improved.

The objective of this work is to investigate the effect of using different types of nanoclay fillers on the cell morphology and mechanical properties of rigid PVC foam. Four different types of commercially available nanoclays were used: natural calcium montmorillonite (unmodified), sodium montmorillonite modified with a quaternary ammonium salt, aluminum magnesium silicate clay, and magnesium lithium silicate clay. The individual and combined effect of nanoclay concentration and blowing agent content on the foam density and mechanical behavior are reported. Optical Microscopy, SEM, XRD, and TEM imaging were used in the analysis of foam cell morphology and the dispersion and exfoliation of nanoclays in the polymer matrix. Specific compression strength, specific flexural modulus, and density were found to improve by introducing nanoclay in the polymer matrix whereas tensile strength and modulus of elasticity showed some deterioration with the presence of nanoclay. Meanwhile, impact strength and specific flexural strength did not show any significant changes

The solid particle erosion behavior of polymer composites has been reviewed. Attention is paid to the effects of testing variables (e.g., erodent type, impact angle, impact velocity) on the erosion wear rate. The occurring failure mechanisms are discussed. Various predictions and models proposed by different investigators to describe the erosion rate (ER) are listed. Implementation of design of experiments (DOE) and statistical techniques in analyzing the erosion behavior of composites is reviewed. Recent findings on erosion response of multi-component hybrid composites are also presented. Recommendations are given to solve some open questions related to hybrid polymer composites.

Natural fibers can be used as reinforcements in thermoplastic non-structural applications. Commingling them with matrix fibers lowers the melt flow distance of molten matrix during the processing. In this study, polypropylene (PP) and textile cotton fibers were commingled and fabricated to composite laminates. Process variables like temperature, pressure, and holding time affect the mechanical properties like impact strength and tear resistance. Fiber content and winding pattern or fiber orientation were also important for the optimization of the mechanical properties. The modification of the interface by chemical treatments of the matrix or reinforcement with reagents like potassium permanganate, benzoyl peroxide, and maleic anhydride modified PP enhances some mechanical properties like tear strength of cotton fiber-reinforced PP commingled composite systems. Fiber content, treatments, and moisture also varies dielectric constant and volume resistivity.

Erosion behavior of polyetherketone (PEK) reinforced by short glass fibers with varying fiber content (0–30 wt%) has been studied. Steady-state erosion rates have been evaluated at different impact angles (15°–90°) and impact velocities (25–66 m/s) using silica sand particles as an erodent. PEK and its composites exhibited maximum erosion rate at 30° impact angle indicating ductile erosion behavior. The erosion rates of PEK composites increased with increase in amount of glass fiber. Also, artificial neural networks technique has been used to predict the erosion rate based on the experimentally measured database of PEK composites. The effect of various learning algorithms on the training performance of the neural networks was investigated. The results show that the predicted erosion rates agreed well when compared with the experimentally measured values. It shows that a well-trained neural network will help to analyze the dependency of erosive wear on material composition and testing conditions making use of relatively small experimental databases.

Modifications were made in the well-known inherent flaw model as well as in the stress fracture models namely, point stress criterion and average stress criterion for accurate prediction of notched tensile and compressive strength of composite laminates containing holes. The adequacy of these modified fracture models were examined by considering the fracture data of center-hole specimens made of carbon/epoxy composites, weft-knitted glass fiber composites, and pultruded composites. Any one of these three fracture models can be utilized to predict the notched strength.

Phosphate glass fibers (20Na₂O–24CaO–16MgO–40P₂O₅) were prepared with varying pulling speeds from 50 to 2000 m/min. Fiber diameters ranging from 48 ± 6 µm to 12 ± 4 µm were obtained at pulling speeds of 50 and 2000 m/min respectively. Degradation tests of the fibers (up to 7 days) were carried out in aqueous medium at 37°C and indicated that phosphate glass fibers experience a higher mass loss initially before reaching a plateau. Before composite fabrication, fibers were treated using 3-aminopropyltriethoxysilane. Phosphate glass fiber reinforced poly(-caprolactone) matrix unidirectional composites were prepared by using both in-situ polymerization and compression molding techniques. For in-situ polymerized composites (25% fiber by volume), flexural strength (FS), flexural modulus (FM), tensile strength (TS), tensile modulus (TM), and impact strength (IS) were found to be 105 MPa, 5.9 GPa, 88 MPa, 6.8 GPa, and 27 kJ/m², respectively. For compression molded composites (10% fiber by volume), FS, FM, TS, TM, and IS were found to be 55 MPa, 2.1 GPa, 46 MPa, 1.6 GPa, and 14 kJ/m² respectively. After 6 weeks of immersion in aqueous media (37°C), the fibers inside the composite had degraded as determined by scanning electron microscope.

In this study acrylonitrile-butadiene-styrene (ABS) terpolymer was reinforced with HNO₃-treated short carbon fibers (HCFs). The effects of HCF concentration on the tensile properties of the composites were examined. Increasing the HCF concentration in the ABS matrix from 10 to 30 wt% resulted in improved tensile strength and tensile modulus. To obtain a strong interaction at the interface, polyamide-6 (PA6) at varying concentrations was introduced into the ABS/10 wt% SCF composite. The incorporation and increasing amount of PA6 in the composites increased tensile properties of the ABS/PA6/HCF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/HCF composites, which exhibited an improved adhesion between the SCFs and the ABS/PA6 matrix.

The main objective of this article is to develop high wear resistance carbon fiber reinforced polyether ether ketone (PEEK) composite, with addition of multiwall carbon nanotube (MWCNT). These compounds were well mixed in a Haake batch mixer and compounded polymers were fabricated into sheets of known thickness by compression molding. Samples were tested for wear resistance with respect to different concentration of fillers. The wear resistance properties of these samples depend on filler aspect ratio. Wear resistance of composite with 20 wt% carbon fabric increased when MWCNT was introduced. The worn surface features have been examined using scanning electron microscope. Photomicrographs of the worn surfaces revealed higher wear resistance with the addition of carbon nanotube. In addition, better interfacial adhesion was observed between carbon and vinyl ester in carbon-reinforced vinyl ester composite.

A parametric experimental study has been conducted to investigate the effect of polypropylene fiber on the shrinkage of cement-stabilized macadam. Four different fiber volume fractions were used: 0.04, 0.06, 0.08, and 0.1%. Tests without mixing fibers were also carried out. Using the micrometer gauge method and the strain gauge method, the dry shrinkage coefficient and thermal shrinkage coefficient of cement-stabilized macadam were measured, respectively. The results indicate that polypropylene fiber can effectively decrease the average dry shrinkage coefficient and average thermal shrinkage coefficient of cement-stabilized macadam. The average dry shrinkage coefficient of long curing period is smaller than that of short curing period, while the average thermal shrinkage coefficient of long curing period is much larger than that of shot curing period. When the fiber volume fraction is not beyond 0.1%, the average dry shrinkage coefficient and average thermal shrinkage coefficient are gradually decreasing with the increase in fiber volume fraction. Furthermore, polypropylene fiber appears to be highly effective in controlling dry and thermal shrinkage cracking of cement-stabilized macadam.

This research reports the formulation and characterization of polymer/date pits composites. Polymers used in this study were high-density polyethylene (HDPE) and polystyrene (PS), while date pits used were locally called khlaas (K) and sekari (S), wastes of two types of date palm fruit grown in Saudi Arabia. Tensile strength (TS) and Izod impact strength (IIS) tests were conducted to assess the mechanical properties of the prepared composites. Thermal properties of the composites were measured and discussed in view of glass transition and melting temperatures, T_g and T_m, respectively, as well as the heat of fusion, which reflects the degree of crystallinity of the polymer/date pits composites. Generally, mechanical properties, i.e., TS and IIS, were reduced upon date pits incorporation in the composites. Results showed that IIS of HDPE/date pits composites drastically suffered from the addition of as low as 5 wt% of date pits. Addition of date pits regardless of the type, either S or K, tended to reduce T_g of the PS100/date pits composites and the heat of fusion of the HDPE/date pits composites at relatively higher date pits content, >10 wt%. The reduction in both degree of crystallinty represented by heat of fusion of the HDPE and mechanical properties of all composite systems used in this study at the high loading presence of date pits may be related to the anticipated coarse morphology of the composites evolved during the mixing of polymers, with date pits in the absence of an appropriate coupling agent system.

During compression molding of sheet molding compounds air bubbles are formed that can deteriorate several properties of the final composite. The story of such bubbles is directly set by the local pressure distribution during pressing. A number of experiments have therefore been performed in order to derive the relation between the pressure and dissolution rate of some gases into relevant resins. The experimental results follow Henry’s law up to a pressure of 0.7 MPa and the rate of dissolution is highest for CO₂ in pure polyester. When applying the results to the process in focus it is found that even large bubbles can be dissolved into the liquid resin during manufacturing. Hence, there is a potential to produce parts with very low void content.

Seawater aging response was investigated in marine-grade glass/epoxy, glass/vinyl ester, carbon/epoxy and carbon/vinyl ester composites with respect to water uptake, interlaminar shear strength, flexural strength, tensile strength, and tensile fracture surface observations. The reduction of mechanical properties was found to be higher in the initial stages which showed saturation in the longer durations of seawater immersion. The flexural strength and ultimate tensile strength (UTS) dropped by about 35% and 27% for glass/epoxy, 22% and 15% for glass/vinyl ester, 48% and 34% for carbon/epoxy 28%, and 21% carbon/vinyl ester composites respectively. The water uptake behavior of epoxy-based composites was inferior to that of the vinyl system.

Flax/polypropylene (PP) weft-knitted environmentally friendly technical composites were developed. The relationship between the tensile properties of some composites and volume fractions as well as knitting structures was investigated. Analysis revealed that the full-gage rib was superior to the 1 x 1 rib as far as the tensile strength of the laminates was concerned. The research concluded that 50 : 50 volume fraction of flax/PP was considered to be optimum when the tensile strength was the major concern. The laying direction of the fabric in the laminates played an important role for the composite strength.

Jute fiber (hessian cloth)-reinforced polypropylene matrix composites (50 wt% fiber) were fabricated by compression molding. Tensile strength, tensile modulus, bending strength, bending modulus, and impact strength of the composites were found to be 48 MPa, 2.5 GPa, 56 MPa, 4.5 GPa, and 18 kJ/m², respectively. Then E-glass fiber (woven)-reinforced polypropylene-based composites (50 wt% fiber) were fabricated and the mechanical properties were compared with those of the jute-based composites. It was revealed that E-glass fiber-based composites had almost double the mechanical properties as compared to jute composites. The interfacial shear strength of the jute and E-glass fiber-based systems was investigated and found to be 2.13 and 4.66 MPa, respectively, measured using the single-fiber fragmentation test. Fracture sides after flexural testing of both types of the composites were studied by scanning electron microscope and the results revealed poor fiber matrix adhesion for jute-based composites when compared to that of the E-glass fiber composites.

Hybrid composites of glass and banana fiber (obtained from the pseudo stem of Musa sapientum) in polyester matrix, are subjected to dynamic mechanical analysis over a range of temperature and three different frequencies. The effect of temperature on the storage modulus (E'), loss modulus (E''), and loss factor or damping efficiency (tan ) is determined. All the properties are compared with those of the neat polyester samples and the un-hybridized composites. The effects of the layering pattern of the two fibers on the ultimate viscoelastic behavior of the composites are also investigated. Composites are prepared with banana as the surface layer and glass as the surface layer and also as an intimate mixture of glass and banana. At temperatures above T_g,, the storage modulus values are found to decrease even with the addition of glass fiber for the geometry where glass is the core material. The value of the storage modulus of the composites with the above mentioned geometry is found to be different, above and below T_g, the value above T_g being lower than that below T_g unlike in unhybridized composite. The loss modulus curves and the damping peaks are found to be flattened by the addition of glass. Layering pattern or the geometry of the composites is found to have a profound effect on the dynamic properties of the composite. An intimately mixed composite is found to have the highest storage modulus values in all compositions. The values are consistent with the results of tensile strength. The tan curve is found to be affected by the layering pattern followed and gives insight into the interaction in the material. The dielectric behavior of the composites are also found to be dependent on the glass fiber volume fraction as well as the layering pattern employed.

In this study, 25-year-old oil palm biomass (OPB) fiber–polypropylene (PP) composites are prepared by five different fiber loadings (10, 20, 30, 40, and 50%). The types of OPB used are oil palm empty fruit bunches, oil palm frond, and oil palm trunk. Transmission electron microscopy has confirmed that the cell wall structures of the various oil palm fibers have different cell wall thicknesses and exhibit the same ultrastructure as that of wood. The fibers consist of middle lamella, primary, and thick secondary walls with different thicknesses for different types of fibers. The secondary wall is differentiated into a S₁ layer, a unique multi-lamellae S₂ layer, and a ₃ layer. OPB fibers are compounded with PP using a Brabender DSK 42/7 twin screw extruder. The mechanical features such as tensile, flexural and impact properties of the OPB–PP composite are studied. The melt flow index (MFI) of the composite materials is also studied. Generally, the results show that lower fiber loading (10%) exhibits the highest tensile strength and MFI properties as compared to higher fiber loading (50%). Evidence of a fiber–matrix interphase is analyzed using scanning electron microscopy.

Soil burial tests were carried out to evaluate the effect of biodegradation on the mechanical properties (tensile, flexural, and impact) and the mass loss of OPT fiber-filled RPP composites, as compared to control samples (virgin PP and RPP without filler). The composite samples were prepared using 30% w/w of OPT filler with a size of 100 µm. Compounding was carried out using a Haake Rheodrive 500 twin-screw compounder operating at 190°C and 8 MPa for 30 min. The effect of biodegradation was performed in a perspex plastic apparatus for 12 months. Assessments of the mechanical properties and the percentage of mass loss were carried out at 3, 6, and 12 months of exposure in soil. The mechanical properties (tensile, flexural, and impact) of materials deteriorate with an increase in exposure time. The effects of biodegradation increase with burial period, i.e., from 0 to 12 months. The tensile properties, flexural properties, and impact strength of the composites decrease by about 38–47%, 37–50%, and 47%, respectively, as compared to the value before the biological test. In contrast, the mass of the composite samples increased by 12.7%, whereas for PP and RPP, it increased by around 10.7 and 9.2%, respectively. SEM analysis was conducted to analyze the deterioration and the poor fiber–matrix bonding of composites.

In this study, the finite element is used to analyze and compare the performances of the double- and single-sided composite repair in aircraft structures in mode I and mixed mode. The stress intensity factors in modes I and II at the crack tip are computed to perform the objective of the study. The effects of the different parameters of repair such as adhesive and patch properties on the SIF variation were highlighted. The obtained results show that the adhesive properties must be optimized in order to increase the advantage of the double patch and to avoid adhesive failure. The patch properties have a significant effect on the beneficial effects of the double symmetric patch.

Low-viscosity novel bismaleimide was mixed with surface-modified Si₃N₄ nanoparticles to form nanocomposites using high shear and ultrasonic process. Impact strength, flexural strength, and storage modulus of the nanocomposites with various contents of Si₃N₄ nanoparticles were investigated. The mechanical properties were optimal with 3.0% mass fraction of surface-modified Si₃N₄ nanoparticles. In comparison to the neat bismaleimide resin the impact and flexural strengths of the nanocomposites increased by 52.3% and 20.9%, respectively, and the storage modulus showed a 54% increase at room temperature while the glass-transition temperature of nanocomposites was slightly decreased with the addition of Si₃N₄ nanoparticles. Surface-modified Si₃N₄ nanoparticles as fillers reinforced the toughness of the bismaleimide resin, which was confirmed by scanning electronic microscope.

The tensile and thermal properties of chemimechanical pulp/high-density polyethylene composites made using virgin high-density polyethylene as the matrix polymer, chemimechanical pulp as reinforcing fiber, and maleic anhydride grafted polyethylene as compatibilizing agent were examined by assessing the tensile properties and thermogravimetric analysis. The results indicated that 2% compatibilized composites and uncompatibilized composites exhibited the highest and the lowest tensile strength values, respectively, while the tensile modulus is partially independent of compatibilizing agent. Using maleic anhydride grafted polyethylene increases composites' failure strain and tensile energy absorption as well. Based on the TGA analysis during the manufacturing of the composites, blending and injection temperatures should be less than 230°C to prevent the chemimechanical pulp from decomposition.

Explicit expressions are developed for the buckling analyses of rectangular (long) plates: for ‘linearly varying axial load’ the known results for hinged supports are corrected and new results are presented for built-in and constrained edges; for ‘shear load’ new results are presented for constrained edges; for ‘uniform compression’ new results are presented when the longitudinal edges are rotationally constrained by stiffeners. The results are based on the Rayleigh–Ritz method.

The flexural, compressive properties of bamboo/glass fiber-reinforced epoxy hybrid composites were studied. The effect of alkali treatment of the bamboo fibers on these properties was also studied. It was observed that both flexural and compressive properties of the hybrid composite increase with glass fiber content. These properties were found to be higher when alkali-treated bamboo fibers were used in the hybrid composites. The elimination of amorphous hemi-cellulose with alkali treatment leading to higher crystallinity of the bamboo fibers with alkali treatment may be responsible for these observations.

Local buckling analysis of thin-walled open or closed section fiber-reinforced plastic beams is presented. In the analysis, the web is modeled as a long orthotropic plate with rotationally restrained edges. Explicit expressions were developed for the buckling analyses of rectangular (long) plates in a companion paper. These results are applied to develop explicit expressions for the calculation of the web buckling of beams with thin-walled cross sections. At last, the applicability of the method is demonstrated by numerical examples and the results are verified by finite element calculations.

The mechanical properties of single glass-fiber/epoxy composites were found to be affected by either the loading rate or the type of the fiber embedded, which was contrary to the traditional assumption. Stress–strain measurements, optical microscopy, and electron microscopy observations (in situ and ex situ) revealed that the sample embedded with a thick fiber (42 µm) underwent a brittle fracture while the sample embedded with a thin fiber (26 µm) exhibited a ductile fracture at the same loading rate of 2 x 10^-5 s^-1. But both the fiber composites underwent a ductile fracture at the loading rate of 4 x 10^-6 s^-1 and a brittle fracture at 2 x 10^-2 s^-1. The origin of this phenomenon is attributed to the fracture initialized by the fiber breakpoint inside the matrix and the external tensile loading rate.

Polymer composites have been widely used in industrial applications because of their high-specific strength and modulus. During their maintenance and service life small scratches can be formed on the surface of the composite material. These small scratches can result in crack initiation causing material failure and also some esthetic defects. When we consider that polymer composites may have various fiber orientations, it is possible to develop a remarkable increase in their scratch resistance. For this reason it is necessary to investigate the effect of fiber orientation on scratch resistance for polymer composites. In this study, scratch resistance of continuous carbon-fiber-reinforced polyetherimide composites were investigated as a function of fiber orientations by means of CSM microscratch tester machine. During the experiments the relation between the scratch resistance and operational parameters are determined as a function of scratch hardness, penetration depth, and coefficient of friction.

Polymer composites have been widely used in industrial applications because of their high-specific strength and modulus. During their maintenance and service life small scratches can be formed on the surface of the composite material. These small scratches can result in crack initiation causing material failure and also some esthetic defects. When we consider that polymer composites may have various fiber orientations, it is possible to develop a remarkable increase in their scratch resistance. For this reason it is necessary to investigate the effect of fiber orientation on scratch resistance for polymer composites. In this study, scratch resistance of continuous carbon-fiber-reinforced polyetherimide composites were investigated as a function of fiber orientations by means of CSM microscratch tester machine. During the experiments the relation between the scratch resistance and operational parameters are determined as a function of scratch hardness, penetration depth, and coefficient of friction.

In micromechanical modeling of composites, it is well known that the Voigt formula or the rule-of-mixture method gives the most general upper bound estimate of the effective Young's modulus. In this article it is shown that the effective longitudinal Young's modulus of a continuous unidirectional fiber composite significantly exceeds the rule-of-mixture when both constituents possess equal or almost equal Young's moduli and opposing Poisson's ratio signs.

The performance of damaged metallic plates reinforced with fiber-reinforced polymer composite materials (composite patches) is presented in this study. A square aluminum plate with a central cutout is considered as a damaged structural element. Numerical studies using commercial finite element code were conducted to investigate the effects of variation in patch lamination parameters on flutter velocity of the repaired plates. The various laminate parameters such as fiber angles and stacking sequences are considered in this study. The results presented herein indicate that, for flutter pressure of a repaired metallic plate with central cutout, a set of laminated composite patches with different number of plies and stacking sequences can be found, which improve flutter pressure of damaged plates.

In this study, tribological behaviors of polymer-based particle-reinforced PTFE bearings have been investigated and evaluated. Tribological properties of these particle-reinforced PTFE composite bearings have improved two- or three-fold.

This work reports hygroscopic, thermal, and mechanical properties of biomass composites comprising sisal fiber reinforcing castor oil PU resin. The effects of reinforcement geometry and alkaline treatment of fibers were evaluated. In general, alkaline treatment improved quasi-static tensile properties of composites with short randomly oriented and long aligned sisal fibers, respectively. On the other hand, an adverse effect of alkaline treatment was observed in the mechanical behavior of the composite with bidirectional fabric architecture. The outstanding influence of moisture on thermo-mechanical properties of biomass composites was confirmed through thermogravimetric and differential scanning calorimetry techniques. Dynamical-mechanical thermal analysis showed increased storage modulus (i.e., stiffness) and decreased damping properties of biomass composites as compared to neat PU matrix. Dynamical-mechanical testing also detected unexpected decrease on glass transition temperature of composites in regard to the neat polymer resin; resin plasticization due to moisturized fibers and/or alkaline treatment residues was identified as probably the culprit.

To evaluate the natural durability of a composite obtained from bagasse fibers and polypropylene against rainbow fungus (Coriolus versicolor), materials containing 75% bagasse fibers, 23% polypropylene, and 2% compatibilizer were sampled. After specimen and culture medium preparation the specimens were exposed to the purified fungus at 25°C and 75% relative humidity for 1, 2, 3, and 4 months. Identical specimens of the same composite, without being exposed to the fungus, were provided as the control specimens. After the mentioned periods, mass loss, bending strength, elastic modulus, hardness, water absorption, and equilibrium moisture content of specimens were measured. The obtained results indicated that mass, bending strength, elastic modulus, hardness, and equilibrium moisture content of composites decreased, whereas water absorption amount of specimens increased. The calculation of correlation coefficients between the rates of mass loss and bending strength, elastic modulus and hardness decreases, as well as equilibrium moisture percentage in composite specimens revealed that a significant correlation existed between the values. Comparing mechanical properties after exposure to fungus, it is observed that elastic modulus was affected by the fungus exposure to a greater extent, whereas hardness decrease was less than the other properties.

A thermal expansion process was applied to prepare stitched sandwich structures using the pressure generated by the foam core inside a closed mold. In this way, buckling of stitches was avoided. The mechanical properties of the specimens prepared by thermal expansion process were significantly improved when compared to that of specimens prepared using the hot press. In order to increase the thermal expansion pressure, the foam cores were pre-compressed, and then stitched with the face sheets. The pre-compressed foam cores underwent thermal expansion easily and their thermal expansion pressure increased with increase in pre-compressive ratio.

Bisphthalamic acids were prepared by reaction of phthalic anhydride and aromatic diamines. Novel poly(ester-amide)s were prepared by the reaction of epoxy resin with bisphthalamic acids. Acrylation of PEAs was carried out using acryloyl chloride and the products derived are acrylated poly(ester-amide)s. PEAs and APEAs were characterized by elemental analysis and by average molecular weight. IR spectra were also recorded for both PEAs and APEAs. Blending of APEAs was carried out with methyl methacrylate monomer. Curing of APEA–MMA blends was monitored on the differential scanning calorimeter. Composites of APEA–MMA blends were laminated and characterized. Unreinforced cured samples of the APEA–MMA blends were analyzed thermogravimetrically.

The present study investigates the effect of acrylonitrile treatment of bamboo mats on bamboo-reinforced epoxy and polyester resin composites. Acrylonitrile treatment has been done for 1 and 5 h. The tensile strength and modulus of the composites have been improved with both the resins after acrylonitrile treatment (cyanoethylation) of fibers. Moisture regain decreases significantly on cyanoethylation. Acrylonitrile-pretreated bamboo-reinforced polyester composite decreases the water uptake drastically from 75 to 14%.

Shellac, a forest product, was reacted with various proportions of maleic anhydride. The resultant maleated shellac (MS) samples were characterized by acid value. The MS samples were then reacted with commercial epoxy resin i.e., DGEBA (diglycidyl ether of bisphenol-A) according to the acid value of MS samples. The resultant MS–DGEBA systems were monitored on differential scanning calorimetry (DSC). Based on DSC data, the glass fiber-reinforced composites of MS were prepared and the resultant products were characterized by physical and mechanical properties.

Short carbon fiber (C_f) reinforced nano-hydroxyapatite (HA)/poly(methyl methacrylate) (PMMA) matrix bio-composites were prepared by an in situ processing and solution co-mixing process. The influence of carbon fiber content, initiator dosage, and nano-HA mass fraction on the flexural properties of the composites were particularly investigated. The flexural strength and modulus were tested by universal testing machine. The flexural fracture surface morphologies were characterized using scanning electron microscope. Results reveal that the as-prepared C_f/HA-PMMA composites have excellent flexural properties. With the increase of carbon fiber content, benzoyl peroxide (BPO) dosage, HA mass fraction and reaction temperature, the flexural strength, and modulus of C_f-HA/PMMA composites first increase to a maximum and then decrease. The flexural strength and flexural modulus will reach the maximum value of 129.56 MPa and 4.47 GPa when carbon fiber mass content, BPO dosage, and HA mass content arrive at 4, 1.6, and 8 wt%, respectively and reaction temperature is 80°C.

This study presents punching shear behavior of two-way slabs strengthened with prestressed or non-prestressed carbon fiber reinforced polymer (CFRP) sheets. Four two-way slabs (2360 x 2360 x 150 mm³) with a steel reinforcement ratio of 1.44% are tested under concentric load. All slabs exhibit a punching shear failure mode. The strengthened slabs show an increase of up to approximately 20% in load-carrying capacity and an increase of up to 25% in cracking load with respect to the unstrengthened control slab. A detailed stress analysis in reinforcement is conducted along the loading span of the slabs, including the critical shear perimeter surrounding the column stub. The effective strain zone near the slab–column connection, where a sudden increase of strains in the reinforcement is observed, is also studied. The development of shear stresses in the vicinity of the slab–column connection is examined. A non-linear 3D finite element analysis is conducted and analytical predictive models for the punching shear failure are evaluated as well.

In this study, multiaxis 3D woven preform was developed with five yarn sets: + bias, -bias, warp, filling, and z-yarns. The orientation of the yarns on the five axis have improved the mechanical properties of the preform. The yarns of the preforms, which were made of polyacrylonitrile (PAN)-based carbon fibers, were consolidated with an epoxy resin. These preforms were tested and compared with the 3D orthogonal woven carbon composites. It was found that in-plane shear strength and modulus of multiaxis 3D woven composite were higher than that of the 3D orthogonal woven composite. However the bending strength, bending modulus, and the interlaminar shear strength of the multiaxis 3D woven composite were slightly lower than that of the 3D orthogonal woven composite because of the orientations of +/-bias yarns on both surfaces of the multiaxis 3D woven structure. The failures of both woven samples were also analyzed for the assessment of their mechanical behaviors. The unit cell of the multiaxis 3D woven preform was described. Depending on the unit cell geometry, some relationships were developed to predict the volume fraction of each yarn set in the preform and these predicted results were also compared with the measured values.

Jute fabrics reinforced polypropylene (PP) composites (40% fiber by weight) are prepared using compression molding. Different formulations using oligomer urethane diacrylate (M-1100), monomers 2-ethyl hexyl acrylate (EHA), 1-vinyl 2-pyrrolidone (NVP), and photo-initiator (Irgacure-369) in methanol were prepared in order to modify the surface of jute fabrics. Jute fabrics are soaked in the prepared formulations and then cured by UV radiation source of varying intensities. The formulation containing 5% NVP, 5% EHA, 2.5% oligomer, and 2% photo-initiator and cured at 15 UV passes perform the highest mechanical properties. Tensile strength (TS), bending strength (BS), tensile modulus (TM), and bending modulus (BM) of the composites are found to be 54, 62, 915, and 2030 MPa, respectively. To investigate the effect of thermal initiator, benzyl peroxide is used in the optimized formulation instead of the Irgacure-369 photo-initiator. The TS, BS, TM, and BM of the composites are found to be 54, 63, 998, and 2150 MPa, respectively by treating jute with 2% benzoyl peroxide as the thermal initiator.

As the major component of WPCs, wood flour species plays an important role on the properties of the resulting composites. The effect of wood species as filler and reinforcement and MAPE as compatibilizer on mechanical properties of wood flour/high-density polyethylene composite was investigated. The wood species used in this study were loblolly pine and hybrid Euro-American poplar. The mechanical properties such as tensile properties and notched impact toughness were tested. Poplar flour provides an improvement in tensile strength, tensile modulus, tensile energy absorption, and failure strain over pine. Tensile strength of both the composites was much higher for compatibilized composites as compared with uncompatibilized ones. For the pine composites, tensile modulus improvements were attained even with 1% compatibilizer. There was little difference in the properties obtained between the 1% and 2% compatibilizer. For the poplar composites, adding 1% compatibilizer did not have significant effect on tensile modulus and there was a significant drop in tensile modulus with further 2% increase in the compatibilizer. Wood species and compatibilizer percent did not have significant effect on the notched Izod toughness.

Physical and mechanical properties of a new composite of 70% (by weight) old corrugated container recycled fibers, 27% high-density polyethylene, and 3% compatibilizer (maleic anhydride polyethylene) were evaluated with a focus on dimensional stability. Maximum water absorption, thickness swelling, width swelling, and length swelling were 25, 14, 5, and 1.5%, repectively. Relationships between water absorption and dimensional swelling were established using nonlinear curve fitting and statistically significant relationships were obtained. Swelling rate constants were determined for the 3D swelling behavior of the composite material using a previously published model which showed decrease in swelling rate in width and length directions. In all directions, the swelling model satisfactorily predicted the swelling behavior. Mechanical properties of the composite material were evaluated prior to and after exposure to simulated freeze–thaw cycling and it was concluded that the cycling was ineffective on mechanical performance.

A numerical process model was created to simulate unsteady flow through non-homogeneous unidirectional fibrous media. Permeabilities calculated at the fiber level were applied over small spatial and temporal regions to improve accuracy of macroscopic analysis. Consideration was given to non-ideal aspects of the fiber bed, especially fiber array randomness and fiber bed compressibility. Experimental results indicated that permeant driven fiber compaction had a major influence on flow front advancement. Overall, the process model developed in this work showed marked improvement in predicting flow front locations over a standard bulk property model.

Strain distribution in adhesive joints with untapered and normal-tapered laminates has been investigated using an experimental method. An optic measurement system, ARAMIS, was used to monitor the strain field in the adhesive layer. The results indicated that normal tapering of the laminate did not affect the shear and principal strain components, but it increased the maximum peeling strain in the joint for the tapering length examined in this study. The strength and failure mode of joints were also studied. It was found that normal tapering of the laminate did not improve the strength of the joint in comparison to joints with untapered laminates. Failure took place at the steel–adhesive interface in both configurations.

This paper describes a series of tests to failure of concrete filled (composite) tubular beams subjected to cyclic loading. The beams made from steel grade of Yst310 at 345 MPa nominal yield stress, square hollow sections (SHS), depth-to-thickness ratios in the range of 20.5 were tested. The effects of these loading protocols on the elastic hysteretic behavior of the SHS beams were examined. The SHS beams exhibited stable hysteretic behavior up to local buckling, and then showed considerable degradation in strength and ductility depending on d/t ratios. First-cycle yield load moments predicted in tested composite beam specimens were compared with standard CIDECT moments. The effect of strength, ductility, and energy absorption capacity of the beams were examined.

Interfacial interactions and interphases play a key role in all fiber reinforced composites. However, a clear distinction must be made between interface and interphase. Interphase becomes interface if its thickness decreases to zero. In most of the available micromechanical models the interface is considered perfect (no interphase). However, such a condition is hardly fulfilled in real composites. It is possible to find the volume of interphase by using DSC or identification of interphase region using SEM or some other sophisticated instrument techniques as it is a region created between the two main phase of a composite. All these techniques require special technical skill. In the present study attempt is made to identify the existence of the interphase region in fiber matrix composites using SEM. It was also decided to develop an equation for volume fraction and thickness of interphase by considering the composite as three-phase RVE. Developed equations of interphase volume fraction was used by considering the soft and stiff interphase parameters. Comparisons were made to study elastic behavior of fiber reinforced composites in longitudinal and transverse directions with available experimental data and published model in the literature and they are in good agreement.

Introduction of reinforcing fillers in RPP matrix help to enhance the properties of the matrix. In this study, waste jute fibers called jute caddies have been used as the filler material to RPP and their properties have been studied. The composites have been prepared by solution impregnation method. A silane coupling agent has been used in two weights (2 and 6 wt%) to enhance the interaction between the non-polar PP and the polar jute fiber wastes. Treatment with 6% VTMO enhanced the mechanical properties significantly. Thermal stability was also enhanced after treatment with coupling agent. SEM investigations revealed the fiber/matrix bond at the interface.

The interactions between basalt chosen as a reinforcement material and low-density polyethylene (LDPE) chosen as a matrix material in polymer matrix composite (PMC) were investigated in this study. A variety of mechanical tests were performed on the resultant composites, which had appropriate compositions. Tensile, flexural, density, and hardness tests have been carried out, and the relationship between the basalt content and properties were examined. Energy Dispersive Spectrometer (EDS) and Scanning Electron Microscopy (SEM) facilities were applied on surfaces of composites. The addition of basalt increases the flexural strength, elastic modulus, density, and hardness while decreasing the tensile strain to fracture, toughness, and fracture energy.

In this article an effort has been made to derive the transfer function of an ionic polymer metal composite (IPMC) actuator. The transfer function obtained is based on the experimental deflection data and following the pseudo-rigid modeling technique. Initially an experiment is conducted with an IPMC actuator to measure its bending characteristics with input voltages. Subsequently expression for bending moment with radius of curvature is established. IPMC has been modeled then following the pseudo-rigid body modeling technique as fix-pin support type of cantilever mode with end-moment loading and its derivation is explained in detail. Based on the experimentally obtained bending moment, IPMC has been modeled to obtain the distributed force, spring constants, characteristic radius factor, and pseudo-rigid body angles. Energy based dynamic model of the IPMC actuator has been formulated following the Lagrangian principle based on the tip position in 2D. Transfer function is then obtained with respect to pseudo-rigid body angle and input voltage. Simulations have been performed to demonstrate the system response.

In this article, an original survey on the stresses between the structure and the fibers composite (FRP) was finalized, taking into account, the mechanical and thermal load and the effects of the FRP plate fibers orientation. This originality, puts in evidence a new approach theory and the physical and geometric parameters coupled with the thermal model, which is one aspect that has not be taken into account by previous studies.

Foam core sandwich composites in conjunction with various facings composed of glass, stitching glass, carbon, carbon/Kevlar hybrid, and Kevlar fabric were fabricated by using RTM process; and low-velocity impact performance was studied at three energy levels. This article proposes that the damage extent of foam core sandwich construction may be characterized by the average damage angle, penetration depth, and maximal cracking width. The results show that the foam core samples with Kevlar facing are optimal for the peak load at load versus time plot, the shortest history course and the lowest impact damage extent at 25 J; the range of average damage angle of Kevlar facing samples is biggest at 90–67°, and the range of maximal cracking width and penetration depth of Kevlar facing samples are smallest: one is at 4.5–15.5 mm, the other is at 16.8–18.0 mm at 25, 45, and 70 J.

This article presents modeling of bond performance and short-term prestress losses of prestressed carbon fiber-reinforced polymer (CFRP) composite sheets for strengthening prestressed concrete beams, using an integrated anchor system that consists of steel plates bonded with CFRP sheets. A simple fracture mechanics model, validated with the experiment, is developed to examine the bond performance of the CFRP sheets for the plate-type anchor system. To predict the short-term prestress losses of the prestressed CFRP sheets used in the integrated anchor system, a closed-form solution is developed. Seven prestressed concrete beams strengthened with prestressed CFRP sheets are used to validate the proposed model. Fracture energy and tensile modulus of the CFRP sheets are the most critical factors affecting debonding failure of the plate-type anchor system. For design purposes, it is recommended that the short-term prestress loss be 10% of the applied prestress using the proposed anchor system.

In this study, the flexural fatigue behavior of wood flour/high-density polyethylene composites is characterized. A non-dimensional analysis is adopted to establish a prediction equation for the fatigue life of the composites, and S–N curves and survivability diagrams are then constructed to show the fatigue life prediction of the wood/plastic composites (WPCs). Small coupon samples of the composites are tested in flexural fatigue. The predicted results in the non-dimensional (non-linear) fatigue model are better related to the testing data than the classical S–N curve (linear experimental data) fitting, and they could be used as the predicting model for fatigue life analysis of the WPCs. The best-fit S–N curve and its corresponding bounds based on 95% confidence are provided for the composites, and the fatigue data are well distributed within 95% confidence range. Fatigue life distribution diagrams are produced for the WPCs using a two-parameter Weibull cumulative density function based on the probability of survival concept, and this concept is then used to predict the fatigue life of the composites under an applied load. From these diagrams, the fatigue life can be easily determined at any given reliability index. The S–N plots under different reliability index present considerable value to the designer if the structure contains a critical component where any failure is catastrophic. The proposed experimental fatigue study and related analyses verify the applicability of non-dimensional fatigue model and theory of two-parameter Weibull distribution to fatigue life prediction and reliability analysis of WPCs, and they can be used to predict fatigue behavior of similar materials.

The purpose of this study is to develop analytical equations using micromechanical methods that can effectively and accurately estimate the mechanical properties of polymer composite materials containing clay nanoparticle fillers. Various modeling techniques using the micromechanical approach are researched, including conventional micromechanical models. An analytical model was developed with consideration of the effects of imperfect bonding between the nanoparticle fillers and the matrix in the composite materials. The mechanical properties of the considered nanocomposites were estimated, and the estimated values were validated using the experimentally determined mechanical properties. For the experimental program, clay/epoxy nanocomposite specimen were fabricated and tested. The developed model was also compared to the conventional and previously developed micromechanical models.

This article proposes a new concept of residual strength master curves for damaged carbon fiber-reinforced plastic (CFRP) after various spectral creep and fatigue loadings by using master curves for pristine CFRP, based on an accelerated testing methodology (ATM) and a statistical linear cumulative damage (SLCD) rule. Three-point bending fatigue tests for plain-woven CFRP composites were carried out under various cyclic loadings with both constant and variable amplitudes and frequencies. It was shown from the viewpoint of statistics that the SLCD rule can be applicable to the prediction of the flexural fatigue life of these CFRP composites under variable amplitudes and frequencies of cyclic loading. A method to construct the master curve of residual strengths for damaged CFRP from the master curves of creep and fatigue strengths for pristine materials was introduced.

The structure of T-stiffened skins molded integrally by co-curing or co-bonding is widely used in aircraft industry nowadays. Ongoing research focuses on the study of the compaction of simple structure composite components and the analysis of mechanical properties of T-stiffened skins. In this article, using carbon fiber/bismaleimide prepregs, T-stiffened skins were integrally fabricated by different tool assembly schemes in autoclave. The influence of tool assembly schemes and integral molding technologies on the compaction of T-stiffened skins was discussed in detail. A method of self-designing solid pressure testing was introduced to measure the pressure distribution upon T-stiffeners during cure process. The compaction of T-stiffeners was studied quantitatively by thickness distribution and analyzed qualitatively by pressure transferring. The experimental results showed that the pressure distribution in T-stiffeners was significantly influenced by tool assembly schemes and tool radii, which directly affected the compaction of T-stiffeners. The optimum assembly of rigid tool and triangle flexible tool with appropriate stiffness was adopted. In comparisons of co-curing and co-bonding, little difference of compaction in web and flange of T-stiffeners were found except higher thickness in corner section for co-curing.

The present experimental work is aimed at studying the performance of recycled newspaper and recycled newspaper/glass fiber hybrid polypropylene composites. The effects of glass fiber loading and maleic anhydride (MA) as a coupling agent on the tensile behavior and impact strength of composites containing 30 wt% fiber were examined. The results suggest that the tensile strengths of the recycled newspaper/PP composites increase with increasing glass fiber content. A value of 55 MPa for tensile strength and 4.1 GPa for the tensile modulus is achieved from a hybrid composite containing 10 wt% of newspaper and 20 wt% of glass fiber. The impact strength of the newspaper/PP composites progressively decreased with increasing glass fiber content. Adding (MA) by 2 wt% in the composite formulation significantly improved both the dimensional stability and mechanical properties. Microstructure analysis of the fractured surfaces of modified composites confirmed improved interfacial bonding. Dimensional stability and strength properties of the composites can be improved by increasing the glass fiber content and or by addition of coupling agent. This project has shown that the composites treated with glass fiber and coupling agents will be desirable as building materials due to their improved stability and strength properties.

In this study, the performance of boric acid (H₃BO₃)-filled polyamide composites were studied and evaluated at dry-sliding friction conditions. Wear tests were carried out using configuration of composite pin on a rotating AISI D2 steel disc. Test conditions were atmospheric conditions, 10, 30, 50 N applied load values, and 0.4, 0.80, 1.20 m/s sliding speeds. The results show a large drop in the coefficient of friction of PA6 with the addition of H₃BO₃ filler and a significant change in specific wear rate. Furthermore, the coefficient of friction decreases while the specific wear increases with the increase in sliding speed and applied load values, respectively. Moreover, for the range of load and sliding speed values in this study, the coefficient of friction also registered lower values with the increase in H₃BO₃ content percentage. The influence of boric acid on the coefficient of friction and wear is more pronounced at severe working conditions. Finally, the coefficient of friction of H₃BO₃-filled composite is a round 0.1 value and its specific wear rate is in the order of 10^-4 m³/N m.

Polypropylene/wood flour composites with different nanoclay and maleic anhydride grafted polypropylene (PP-g-MA) contents were fabricated by melt compounding and then by injection molding. The mechanical properties, such as flexural modulus, tensile modulus, elongation at break, and impact strength, were evaluated. Results indicated that the flexural modulus, tensile modulus, and elongation at break increases with increase of nanoclay up to 3 phc at the same concentration of PP-g-MA, and then decreases. However, the impact strength of the composites decreases with increased nanoclay loading. Also, the effect of compatibilzer was positive in terms of enhancing the mechanical properties of the composites. The morphology of the nanocomposites has been examined by using X-ray diffraction and transmission electron microscopy. Morphological findings revealed that intercalation form, the sample with 3 phc concentration of clay, which implies the formation of the intercalation morphology and better dispersion than 6 phc, and the d-spacing of clay layers in the composite were improved in the presence of compatibilizer.

Zirconium diboride (ZrB₂) is difficult to prepare as high-density ceramics, which limits its application. To obtain high-density ZrB₂ ceramics for improving its high-temperature properties, ZrB₂ particles were coated with Al₂O₃–Y₂O₃ particles to prepare 20%YAG–ZrB₂ ceramics with SPS. The optimum sintering condition is a temperature of 1700°C, a pressure of 20 MPa, and a holding time of 4 min. The relative density of prepared 20%YAG–ZrB₂ multi-phase ceramics is 97.2% under optimization sintering technology, which indicate that high density YAG–ZrB₂ multi-phase ceramics are successfully prepared.

Hydrophilic character of jute fibers was reduced by acrylation of alkali treated fibers. Jute (treated and untreated) composites of mixed matrix material (25 wt% epoxy resin of bisphenol-C (EBC) and 25 wt% bisphenol-C-formaldehyde (BCF) of jute fibers) were prepared by hand lay-up technique at 150°C under 7.6 MPa pressure for 2 h. Tensile strength was found to increase from 44.3 to 63 MPa (42.2 %) and flexural strength was found to increase from 56.2 to 64 MPa (13.9 %) on alkali treatment and acrylation. Similarly electric strength was found to increase from 0.18 to 0.72 kV / mm (400 %) and volume resistivity was found to increase from 4.13 x 10¹⁶ to 5.1 x 10¹⁶ -cm (123.5 %). Water absorption of the composites was carried out at room temperature in distilled water and 10 % each of aq. HCl and aq. NaCl solutions, and also in boiling water. The equilibrium water uptake is reduced drastically from 17.3–12.3 % to 8.8–4.9 % on acrylation. Similarly diffusivity was also found to reduce from 5.7–3.9 x 10^-12 m² s^-1 to 4.8–2.2 x 10^-12 m² s^-1. Drastic reduction in water uptake and diffusivity are due to replacement of hydrophilic hydroxyl groups to hydrophobic vinyl ester groups. No effect of boiling water was observed on the stability of the composites. Saturation time in boiling water was reduced to about 34 and 30 times without any damage to the JEBCF-50 and TJEBCF-50 composites, respectively.

The aim of the present research article was to study the perspectives of using natural fibers in polymer composites. Keeping in view the enormous advantages of natural fibers, in the present communication a study on the synthesis of pine needles reinforced polymer composites using phenol-formaldehyde (PF) as a novel polymer matrix through compression molding technique has been reported. Effect of fiber loading on mechanical properties such as tensile strength, compressive strength, flexural strength, and wear resistances has also been determined. Reinforcing of the PF resin with pine needles was done in particle form (200 µm). The present study reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength, and wear resistance of the PF resin increases up to 30% fiber loading and then decreases for higher fiber loading when fibers are incorporated into the polymer matrix.

Predictive method of overall thermomechanical properties of symmetric composite laminates with matrix cracks in multiple plies is presented. A general 2n-ply symmetric cracked laminate is divided into n - 1 cracked sublaminates. Each sublaminate containing obliquely-crossed matrix cracks is analyzed using a two-dimensional shear-lag model and its effective in-plane properties are calculated. Application of lamination theory to the n - 1 sublaminates with effective properties results in estimation of overall properties of the cracked laminate. Effectiveness of this simplified method is verified by comparing with available FE results. Finally, this article shows the applicability of this predictive method to energy release rate analysis associated with matrix cracking.

Using composite cylinders assembly (CCA) model, a generalized algorithm has been developed to evaluate the micro stresses developed in the constituent phases of multiply (N-phases) coated hollow/solid fiber reinforced polymer matrix composites (PMCs) under different hygrothermal loading conditions. In the formulation all the N-phases are considered to be transversely isotropic. Results have been presented for S-glass/epoxy and AS-graphite/epoxy composites treating them as a five-phase (fiber, coating, matrix, and the composite) composite, void being the fifth phase along the centre line of the fiber. Results reveal the differences in the nature and the magnitude of stresses developed when solid fibers are replaced by the hollow ones. The algorithm can be utilized for evaluating the stresses in the constituent phases of multiply coated fiber reinforced metal matrix composites also where more than one coating layer and reaction zones, each with different constituent properties, are to be considered and the composite has to be treated as multiphase composite.

Ethylene-vinyl acetate copolymer, EVA (containing 28% vinyl acetate (VA)) and organoclay, tallow benzyl dimethyl ammonium ion with montmorillonite (ranging from 1 to 8 wt%) were melt processed in order to determine the relationship between the polarity of the polymer matrix and the organoclay structure on the properties of the resulting nanocomposites. The effect of clay loading on the rheological and mechanical properties of the nanocomposites is systematically investigated. The intercalated nanocomposites showed a dependence of the properties on the amount of clay loading. Increasing the amount of clay resulted in an improvement in tensile strength and elongation at break. In addition the EVA/clay nanocomposites displayed an enhancement of both storage modulus, E', and loss modulus, E'', at low frequencies. Addition of clay decreased the flow activation energy, thereby enhancing the polymer melt flow. Thus clay acted as a lubricant for the EVA polymer.

Composite samples of YBa₂Cu₃O_7-x (Y-123) and linear low density polyethylene (LLDPE) are prepared using Y-123 as filler. The electrical and magnetic properties and microstructure of these composites are presented. Although these composites do not show zero resistivity, the intrinsic diamagnetic properties of the superconducting materials are preserved in the composites and there is no change in the transition temperature of the superconductor. Scanning electron microscopy (SEM) studies indicated a systematic variation in the microstructure in terms of the pores present and the extent of the intergrain contacts of the Y-123 filler.

Short randomly oriented banana and sisal hybrid fiber reinforced polyester composites, banana/polyester composites and sisal/polyester composites were fabricated at different fiber loading say, 0.20 to 0.50 V_f. Composites were prepared by varying the relative volume fraction of the two fibers at each fiber loading. When the fiber loading was increased; tensile, flexural, and impact properties increased. Better performance was shown by composites having volume fraction, 0.40 V_f. Tensile strength, tensile modulus, flexural strength, and flexural modulus showed a positive hybrid effect when the volume ratio of the fiber was varied in the hybrid composites at each fiber loading. Maximum tensile strength was observed in composites having volume ratio of banana and sisal 3 : 1. When the volume ratio of sisal was increased, the impact strength of the composite increased. Different layering patterns were tried at 0.40 V_f, keeping the volume ratio of fibers 1 : 1. Tensile properties were slightly greater in the trilayer composite with banana as the skin material. Bilayer composites showed higher flexural and impact property. SEM studies were carried out to evaluate fiber/matrix interactions. Experimental results were compared with theoretical predictions.

This article deals with the effect of nano silica on the cure, mechanical, solvent transport, dielectric, and thermal behavior of poly(ethylene-co-vinyl acetate) (EVA). X-ray diffraction is used to analyze the composite morphology. The cure time and scorch time of the composite was found to be decreasing with filler content. The mechanical properties of the composites such as tensile strength, hardness, and abrasion resistance increased with filler incorporation. The mechanical properties of the composites have been compared with some of the other EVA composites. The solvent resistance of the composite has also been tremendously improved with filler loading. The overall thermal stability of the composite has been found to be improved with filler loading.

This paper aims to investigate the mechanical behavior of columns with partial deteriorated strength and to evaluate the availability of the partial confinement. Five steel reinforced concrete columns have been tested. Different layers of CFRP sheets have been wrapped on the deteriorated strength part. Columns are subjected to axial compression until failure. Axial load, and axial and transverse strains are measured to investigate confinement levels supplied by CFRP sheets. Experimental results indicate that both the load capacity and the ductility of the deteriorated strength part could be significantly increased, subsequently; the load capacity of the entire column can be enhanced higher than those of the original columns. An existing analytical model on FRP reinforcement is used to predict the ultimate load and to evaluate the improvement effectiveness of partial confinement. The prediction provided by theoretical model shows good agreement with the experimental results. Findings of this paper show that partial confinement on deteriorated parts of concrete columns would be developed as an alternative to diminish cost and time consumption in practice.

Studies on some properties such as mechanical, degradation temperatures, and features of the ligno-cellulose fabrics were carried out in both untreated and alkali-treated form. The alkali-treated fabrics are found to have higher initial and final degradation temperatures and tensile modulii. The removal of the amorphous hemi-cellulose on alkali treatment may be the reason for the improved properties. The fabric of Hildegardia was coated with polystyrene and its effect on tensile properties was also studied. The tensile properties were found to improve on alkali treatment, polymer coating and the coupling agent.

The three-component resin system consisting of 4,4'-bismaleimidodiphenylmethane (BMI), O,O'-diallylbisphenol A(BA) and organic rectorite (OREC) was prepared to develop a novel fiber reinforced BMI/BA/OREC composite. The effects of the content of OREC on the mechanical properties, the hot-wet resistance, the hot air aging property, and the thermal mechanical property of fiber reinforced BMI/BA/OREC composites were discussed. The morphologies of composites were characterized using a scanning electron microscope (SEM). The results indicate that the appropriate content of OREC can significantly improve the mechanical properties such as the flexural strength, the interlaminar shear strength and the modulus of flexural elasticity of fiber reinforced BMI/BA composite. The addition of OREC may enhance the hot-wet resistance and has no negative influence on the hot-air aging property of fiber reinforced BMI/BA composite. OREC may reduce the storage modulus and the glass transition temperature (T _g ) of fiber reinforced BMI/BA composite.

This article presents results of an experimental investigation conducted to determine the mix proportion and to characterize the corresponding engineering characteristics of a fiber-reinforced lightweight aggregate, cellular concrete (FRLACC) that was produced without autoclaves. A special foam agent was used to produce air bubbles in the cement matrix. A preliminary compression test was conducted to determine the mix proportion for FRLACC. A series of characterization tests on FRLACC specimens were then carried out to investigate engineering characteristics of FRLACC. The strength aspects of FRLACC were further evaluated by comparing the performance of FRLACC with that of other types of lightweight cellular concrete. It is shown that polypropylene fibers remarkably increase the compressive and splitting tensile strengths of lightweight cellular concrete, whereas the flexural strength of the lightweight cellular concrete is slightly decreased by adding the fibers. It is also shown that FRLACC has superior engineering characteristics in comparison with other types of lightweight cellular concrete.

Fly ash based geopolymer composite cubes were cast using class F fly ash, ground granulated blast furnace slag (GGBFS) as binders. The fluid-to-binder ratio was varied keeping all other parameters constant. The geopolymer composites were cured in different conditions. The composites were tested for compression at different ages. It is interesting to note that the variation of the strength with various fluid-to-binder ratios is unique irrespective of combination of materials, curing conditions, fluid content, and molarity of the fluid. The strength data generated was generalized to arrive at a phenomenological model. The model represents an unique pattern of strength development for the series of composite materials. The validity of the model was examined with an independent set of experimental data generated by the authors and Rangan. It was found that the predicted strengths were in line with the experimental strengths having a percentage error less than 6.0. The model is effective in re-proportioning of geopolymer composites in the field.

The main objective of this study was to study the effects of length, alignment and diameter distribution of the carbon nanotubes (CNTs) on the percolation threshold of nanocomposites using computational simulations. Furthermore, the effects of the aforementioned parameters on the efficiency of the produced networks are investigated. The best distribution for optimum connectivity and the lowest CNTs concentration for the onset of percolation is determined via analyzing the geometrical characteristics of carbon nanotubes. The critical volume fraction of CNTs for percolation was found to be 0.1% while the mean number of bonds per object was 1.3 at the best distribution condition. The results from this study are compared to available experimental data and good agreement was found.

Using three orthotropic elastic finite element models with elastic and elastic–plastic PEEK resin-rich layers included, three-dimensional elastic–plastic analyses of interlaminar stresses in AS4/PEEK thermoplastic composites under tensile loading for [0/90]_s, [0/±45/90]_2s, and [±25]_s4 laminates are presented, in order to ascertain the influence of matrix plasticity upon the free-edge effect in AS4/PEEK laminate. The nonlinear tension behaviors of the whole laminate are predicted by means of the above numerical models and compared with experimental results in detail. The applicability of these FE models with elastic–plastic resin layers models is discussed.

Clay/epoxy nanocomposites were fabricated using shear mixing to determine the increase in mechanical properties over those of pure epoxy. The effectiveness of the fabrication process was improved and explained in detail to provide composites researchers with the ability to fabricate thermosetting nanocomposites efficiently. The effects of process variables on the resulting nanocomposite materials were determined through repeated fabrication and testing. The effects of void removal and shear mixing variables were determined through alteration of the fabrication process. When the effects of the process variables had been determined, a fabrication procedure based on the results was used to fabricate nanocomposites containing 2, 4, and 6% nanoparticles by weight. Tensile tests were performed to determine the extensional moduli and tensile strengths of nanocomposite samples. Experimental values were compared to the developed mathematical models as well as to the values of the neat resin.

Poly(vinyl alcohol) (PVA) has a wide application in industry and the biomedicine area, but its poor water resistance and insufficient mechanical strength have severely limited its application. To overcome these limitations, in this study, inorganic silica sol was used to modify organic PVA. The tensile results show that the tensile strength and Young's modulus of these hybrid films were greatly improved compared to the neat PVA film. For the sample containing 20 wt% silica, compared to PVA matrix, considerable increases in tensile strength and Young's modulus by factors of 1.9 and 3.2, respectively, were achieved. The solubility measurements showed that the hybrid has an enhanced water resistance, in other words, the solubility and degree of swelling decreased with the addition of silica. FTIR, DSC, XRD, and ESEM were used to investigate the chemical and crystal structure of the hybrids, morphology, and composition of the particles in the matrix, respectively. Strong interfacial bonding between the silica and the PVA matrix and homogenous distribution of the silica particles in PVA are supportive of markedly improved mechanical strength. These modified properties of PVA with the addition of silica broaden the applications of PVA, especially giving insight in to the applications of PVA in medical materials.

In this study, the potential of recycled polyethylene terepthalate (rPET) as a well-defined reinforcing material for the in situ microfibrillar reinforced composite was investigated in comparison with that of liquid crystalline polymer (LCP). Each dispersed phase (LCP or rPET) was melt blended with polypropylene (PP) by using an extrusion process. The rheological behavior, morphology, and thermal stability of LCP/PP and rPET/PP blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of LCP or rPET into PP significantly improved the processability. Especially for the blends with 20 and 30 wt% rPET, the potential of rPET as a processing lubricant by bringing down the melt viscosity of the blend system was as good as LCP. The elongated LCP domains were clearly observed in as-extruded strand. Although the viscosity ratio of the rPET/PP system was lower than that of the LCP/PP system, most rPET domains appeared as small droplets. An addition of LCP and rPET into PP matrix improved the thermal resistance significantly in air but not in nitrogen. The obtained results suggested the high potential of rPET as a processing aid and thermally stable reinforcing material similar to LCP.

The bistable behaviors of deployable composite shell structures are experimentally studied. First, carbon/epoxy and glass/epoxy thin-walled composite shell structures are fabricated using resin transfer mould technology, respectively. Second, deployable behaviors of the thin-walled composite shell structure are investigated including deployable process, bending moment, and flexural radius. Finally, the bistable critical conditions of the thin-walled composite shell structure are discussed. The results show that the bistable behaviors of composite structure are directly related with material type, material properties and lay-ups.

In this paper, the alkali treated keratin present in natural fibers like chicken feathers are used as reinforcing phase in epoxy matrix to form composites. Mechanical properties of these composites such as tensile strength, flexural strength, etc. are evaluated and possible chemical reactions taking place during composite making are identified. The present communication also throws light on the structural features engraved on alkali treated keratin and the functional groups involved in the composition of the resulting composite material by Fourier transform infrared (FTIR) spectroscopic analysis.

The purpose of the current research was to investigate water/moisture absorption and associated thickness swelling and their rates in hybrid wood flour/E-glass fiber/propylene composite immersed in water, exposed to steam, and the influence of application of the glass fiber as well as maleic-anhydride-polypropylene (MAPP 2%) as coupling agent on those properties.

The sample strips with 10 mm thickness and 70 mm width were made by using a laboratory twin-screw extruder. The specimens were immersed in water and exposed to steam for 4320 min to determine the water/moisture absorption and the thickness swelling as well as their rates in the composites.

Results revealed that application of the glass fibers increased in the water/moisture absorption significantly in the hybrid composites due to formed micro-gaps in interfaces between wood flour and the glass fibers. However, application of the coupling agent (MAPP 2%) significantly reduced the micro-gaps and diminished the water/moisture absorption as well as the related thickness swelling in the hybrid composites.

The tribological performance of PA6 and carbon fiber-reinforced polyamide 6 (CF/PA6) under dry sliding condition was examined. Different contents of carbon fibers were employed as reinforcement. All filled and unfilled polyamide 6 composites were tested against CGr15 ball and representative testing was performed. The effects of carbon fiber content on tribological properties of the composites were investigated. All filled polyamide 6 has superior tribological characteristics to unfilled polyamide 6. The optimum wear reduction is obtained when the content of carbon fiber is 20 vol%.

In this study, the effects of material optimization and compounding processes on the properties of natural fiber composites were studied. The thermal stabilities of sisal fiber and jute fiber were compared by thermogravimetric analysis. The influences of fiber content, coupling agent, fiber geometry, and fiber distribution on the properties were also researched. It was observed that sisal fiber had more thermal stability than jute fiber. Addition of coupling agent, long fiber length, and uniform fiber distribution led to higher performance composites. For the sisal fiber-reinforced polypropylene composites, the critical fiber length was 2.27 mm and the interfacial shear strength was 22.03 MPa with MAPP. The tensile strength of composites was also theoretically predicted based on Kelly–Tyson model.

Studies were carried out on RT-cured glass/epoxy composite specimens, subjected to different post-cure schedules (50, 60, 70, and 85°C and durations) and immersed until saturation in distilled water at 50°C. The effects of different post-cure schedules, on the moisture diffusion characteristics of the composite were studied. Results showed that the saturation moisture levels decreased with increased post curing, a trend attributed to increased matrix cross-linking, as evidenced by the increase in T_g (glass transition temperature) values with extent of post cure. The diffusion parameter-like composite diffusion coefficient (D_c) and time of saturation (t_m) showed either insignificant or marginal changes, within the range of post-cure schedule considered in these studies.

Epoxy composites loaded with different concentrations (5–50 wt%) of high abrasion furnace carbon black (HAF) with and without the addition of 10 wt% Mg(OH)₂ were prepared and subjected to electrical, mechanical, flammability, and thermal measurements. It was found that the permittivity ' and dielectric loss '' increased by increasing HAF content. This increase is slightly lowered by the addition of Mg(OH)₂. The electrical conductivity of HAF-epoxy composites increased from the pure polymer towards that of pure carbon. A low frequency region with relaxation time ₁ in the range 3.5–4.5 x 10^-4 s is found to be unaffected by either filler content or the presence of Mg(OH)₂. The higher frequency range with relaxation time ₂ is nearly the same for lower concentrations of HAF up to 10 wt% (percolation threshold concentration). Above this concentration a dramatic increase was noticed.

Incorporation of 10 wt% of HAF led to an increase in the compressive strength value. Further increase in HAF content resulted in a decrease in compressive strength values. The tensile strength values of the composite samples before and after the addition of 10 wt% Mg(OH)₂ are higher than that of the unloaded one.

The addition of 10 wt% Mg(OH)₂ improved both the thermal stability and the fire retardant efficiency of HAF–epoxy composites.

In this study, jute fabrics/modified epoxy composites were fabricated by means of hand lay-up process. In order to enhance adhesion between the alkalized jute fabric and epoxy, modification processes was carried out by applying an oligomeric siloxane at different concentrations into epoxy matrix. The influence of resin modification processes on mechanical properties was examined. Tensile and flexural properties and interlaminar shear strength (ILSS) of the composites were measured. It was shown that the ILSS values are increased from 14.18 MPa for alkalized jute fabric/epoxy composite to 22.82 MPa for alkalized jute fabric/3% (w/w) oligomeric siloxane modified epoxy composite. The improved adhesion between the fiber and the matrix may be a result of modification of epoxy matrix with an oligomeric siloxane. This conclusion was confirmed by the morphology observations investigated by scanning electron microscopy. Besides, the modification of epoxy with 3% (w/w) oligomeric siloxane resulted in 30.4% increase in the tensile strength of alkalized jute fabric/epoxy composite. From results of the flexural modulus, application of oligomeric siloxane into epoxy matrix leads to much stiffer jute fiber–epoxy composite.

The effect of notch orientation, service temperature, post-heat treatment, and the sea water immersion on the impact durability of glass/textile fabric hybrid composites have been experimentally investigated. The results of the experimental analysis carried out on the impact toughness of these laminates have been reported. Impact tests were conducted on the specimens with two notch configurations. Results have shown that the notch along the laminate is highly prone to the catastrophic failure and the notch across the laminates will sustain the impact loads to a considerable extent. The results have reveled that there is a particular level of service temperature within which these composites will yield maximum strength. The post-heat treatment and the sea water immersion have also shown maximum influence on the impact strength of these laminates. The durability of laminates with 45% of glass and 15% of textile fabric was found to be very high.

Polypropylene (PP) matrix synthetic phosphate based degradable fiber reinforced unidirectional composites (10% fiber by weight) were fabricated by compression molding. Tensile strength (TS), tensile modulus (TM), elongation at break (%), bending strength (BS), bending modulus (BM), and impact strength (IS) were found to be 38 MPa, 1.5 GPa, 12%, 44 MPa, 4.9 GPa, and 7.58 kJ/m² respectively. Degradation tests of the fibers and composites were performed for six months in aqueous medium at room temperature (25°C). After six months, the mechanical properties of the composites retained almost 80% of their original properties. The interfacial shear strength (IFSS) of the composites were also measured by single fiber fragmentation test (SFFT). The IFSS of the composite system was found 5.9 MPa that indicated good fiber matrix adhesion.

This article presents an analytical study performed on concrete girders reinforced with FRP bars with the goal of evaluating current design guidelines for FRP rebar development lengths. The analytical model is based on finite element formulation of embedded bar problems with inelastic constitutive laws for the constituent materials. The bond stress–slip behavior between FRP bars and concrete was calibrated from experimental data obtained from a large database set of 48 test specimens, most of which were collected from the open literature. The collected data was modified to emulate a specific bar size and embedment length for various scenarios. A large number of analytical simulations were conducted in order to investigate the effect of different parameters on the development length. These parameters include: bar type (GFRP, CFRP), bar strength, bar modulus of elasticity, bar diameter, bar surface coatings, concrete strength, and confinement. For each specimen, the analytical model was conducted for a set condition until an embedment length which satisfied a predetermined criterion was found. The analytical study resulted in the proposal of a refined design equation for development length of FRP bars for consideration by current building and bridge design codes.

The current work develops an analytical model which can consider the crack initiation process of double cantilever beam (DCB) specimens. The current model is based on the first-order shear deformation beam theory, and thus includes the effect of shear deformation in the beams on the crack initiation process. The relationship between the remote peel load P and loadline deflection u is explicitly established based on a parametric equation of crack tip separation  for the crack initiation process. The nonlinear response in the ascending branch of the loading process is captured by the present analytical model. With properly defined cohesive laws (such as exponential type), it might not be necessary to define a clear final separation _f for the crack propagation. The comprehensive comparisons with test and numerical results validate the accuracy of the present model for predicting the crack initiation and propagation of DCB specimens. This model can be used for predicting the debonding process of adhesively bonded composite joints.

3-D spacer fabric is a new sandwich structure textile developed by integrally woven technique. Mono-spacer fabric composite made by 3-D spacer fabric has super-high specific strength and specific stiffness. However, its mechanical properties cannot meet the demand of structural applications. In this article, facesheet-reinforced 3-D spacer fabric composites were investigated by laminating additional glass weave at the skin sheets. Mechanical behavior of this facesheet-reinforced 3-D spacer fabric composite was studied experimentally. Effects of various factors on the mechanical properties were also discussed, such as the additional layer number, the type of glass weave, and the lay-up type. Furthermore, an innovative integral multi-facesheet structure composite was developed by directly weaving three uniformly spaced facesheets in one construction. The mechanical performance was compared with bonded multi-facesheet spacer fabric composite and mono-spacer fabric composite under the same conditions. The results indicated that additional weaves could strengthen the composite facesheets greatly, and the multi-facesheet structure could improve the properties correlated with the piles effectively.

This article evaluates the use of bagasse flour – a waste generated by sugarcane refinery–as a filler in the PVC matrix. The aim of the study is to develop a value-added product from the sugar mills. For this purpose, bagasse powder was obtained after grinding the dried waste from sugar mills having particle sizes of 100–150 µm and <50 µm. In order to evaluate the effect of filler content and alkali treatment of bagasse, several PVC formulations were obtained by dry-mixing PVC compound with filler of varying particle size. The compounds were obtained by blending on a hot roll mill followed by compression molding. The test specimens were punched out from the sheets and the effect of filler content, particle size, and alkali treatment of bagasse powder on the properties of PVC were evaluated. Tensile strength, percent elongation at break, and impact strength of composites decreased whereas stiffness, modulus, and hardness of the composites increased with increasing amount of filler. The particle size had a large effect on the properties of composites, and the filler having particle size <50 µm gave better properties as compared to filler with particle size of 100–150 µm. Some improvement in properties was observed when treated bagasse powder was used as filler. An increase of ~48% in tensile modulus, ~10% in thermal stability, and 14% in impact strength was observed as compared to neat PVC at a filler loading of 30 phr. Morphological characterization was done using a scanning electron microscopy. A uniform dispersion of filler was observed.

Bamboo matting-reinforced epoxy composites were fabricated. Untreated and alkali-treated bamboo matting were treated with different silanes. The mechanical properties (tensile strength, elastic modulus, flexural strength and flexural modulus) were determined. It was found that tensile strength of composite reinforced with only silane-treated fibers is comparable to that of composite with untreated fiber. The elastic modulus of composite with untreated fiber is better than the silane-treated composites. In the case of mercerized fiber treated with silanes, there is reduction in the tensile strength compared with only alkali-treated bamboo-reinforced composite.

In this study the effects of the dispersion of carboxylated single-walled carbon nanotubes (SWCNT-c) in epoxy matrices using two different routes were investigated. In the first route, SWCNT-c were dispersed in the resin using solvent and tip sonication. In the second route, SWCNT-c were dispersed in the hardener in two different ways: with and without solvent, but both with tip sonication. For comparison purposes, neat epoxy was also prepared using the same curing conditions. The samples were characterized via mechanical and dilatometric testing, raman and FTIR analyses, SEM images, and dilatometric tests. An increase of 88% was found for Young’s modulus in the route with dispersion in the resin aided by solvent. Dispersing the SWCNT-c into the hardener showed a significant increase in some mechanical properties, indicating that this is a possible route for preparing nanocomposites. In addition it was observed that all nanocomposites presented smaller volumetric expansion than neat epoxy.

The limit state of serviceability of deflection and cracking is verified for recron3s fiber-reinforced ferrocement hollow slabs with mesh and skeletal reinforcements. About nine slabs are considered for the investigation. The slabs were subjected to one-way cyclic loading by applying two line loads at one-third span. A theoretical model is developed for the deflection of recron3s fiber-reinforced ferrocement hollow slabs and it is validated by the experimental data. The experimental results are very close to the analytical values, especially at the service load, and it is established that such slabs satisfy the serviceability requirements of deflection and crack width as specified by the Ferrocement Model Code.

This article focuses on the experimental investigation carried out on controllability of structural performance of RC panels modified with optimal fiber hybridization system (hybrid combination of steel and polypropylene fibers) up to a volume fraction of 1.0%. Strength effectiveness of the mechanical properties, namely, compressive and splitting tensile strength as well as the structural performance of RC panels modified with optimal fiber hybridization system were studied. The results clarify that the optimal fiber hybridization system is seen to enhance the strength effectiveness of mechanical properties, the controllability-efficient of structural performance of RC panels as cracking behavior, and load–deflection curves, causing an increase in flexural ductility, toughness, and load-carrying capacity. Consequently, the hybrid combination of steel and polypropylene fibers can be used instead of individual fibers, in which innovation and responsible application of concrete construction technology results in better efficiency of the composite.

In this study, the effect of the number of applied anchorages, arrangement, and types of anchorage on stress distribution between the CFRP strip and the concrete surface were studied. Two different anchoraging arrangements with two types of anchorage and three different numbers of anchorages are tested on 12 test specimens by keeping the concrete compressive strength and the CFRP strip bond length constant. In addition, two test specimens without any anchorages, totalling 14 specimens, were tested. It is observed that the anchorages had an impact on the stress distribution of the CFRP strips and increased the strength and the stiffness of the specimens. The specimens did not fail by peeling of the CFRP strips, instead they were ruptured at the point where the anchorages were situated.

In order to quantify the effect of temperature on the mechanical properties of hemp fiber polypropylene composites, formulations containing 25% and 40% (by weight) hemp fiber were produced and tested at three representative temperatures of 256, 296, and 336 K. Flexural, tensile, and impact tests, as well as dynamic mechanical analysis, were performed and the reduction in mechanical properties were evaluated. Impact resistance was independent of temperature, whereas flexural and tensile properties were strongly affected. The highest reductions were observed in stiffness (modulus) values and flexural properties were reduced to a higher degree. The reductions in mechanical properties were well explained by a simple quadratic curve-fitting procedure applied to experimental data. Dynamic mechanical analysis revealed no change in glass transition temperature when the fiber content was increased but the composite material had better temperature resistance at higher fiber content. The results of the present study will be helpful in determining the end-use application of these composite materials.

Utilization of recycled polypropylene obtained from post-consumer products and fly ash particles, obtained as a by-product from thermal power plants, has environmental as well as economical benefits for society. A valuable addition can be made to these waste materials by converting them into composite materials. In this study, an attempt has been made to develop a composite material from RPP and fly ash in 1 : 1 weight ratio, using two types of coupling agents. A silane coupling agent (VTMO) and a maleated polypropylene (Epolene G 3003) were used as the coupling agents. The composites were characterized for their flexural properties, water absorption behavior, and thermal degradation behavior. There was a significant improvement in properties when VTMO was used as the coupling agent compared to Epolene.

This article deals with the residual stresses in stainless steel fiber-reinforced aluminum composite plates under in-plane loading that have a central filleted hole. In many cases, the residual stresses in the plates increase ability to carry a larger load. The dimensions of the central hole vary from square to circle by increasing fillet radii at the corners. In the study, the effects of the hole dimension, the fillet radius, and the orientation angles on the residual stresses are investigated using the finite element method (FEM) software ANSYS. Results are presented in tabular and graphical forms.

Through-the-thickness stitching is a method that increases the translaminar strength??and apparent fracture toughness of laminated composites. A novel test fixture was developed to measure mixed mode fracture toughness under combined Mode I and Mode II loadings. This fixture allowed the ratio between Mode I and Mode II to be varied in order to perform tests under a wide range of mixed mode conditions. Through testing it has been shown that stitching increases Mode I fracture toughness 20???50 times while playing a less significant role in increasing Mode II fracture toughness.

An attempt has been made to study the effect of steel fibers on the compressive and flexural behavior of conventional concrete. Thirty cubes and 10 flexure beams were cast, out of which three cubes and a flexure beam belonged to the control mix. The variables in the study were aspect ratio (15, 25, and 35) and vol% fraction of fibers (0.25, 0.50, and 0.75). A marginal improvement in the ultimate strength was observed due to the addition of fibers. The optimum volume fraction of fibers for better performance in terms of strength and ductility was found to be 0.5%. Accelerated curing was adopted for all the specimens. Indian standards give only the correlation of 28-day characteristics compressive strength from the accelerated compressive strength. There is no relationship between the 28-day flexural strength and accelerated flexural strength. Hence an analytical model representing the relationship between 28-day flexural strength and accelerated flexural strength was suggested. Also models for compressive strength and flexural strength for varying aspect ratio and percentage of volume fraction were given.

This article is concerned with a study on the energy absorption behavior of polyurethane (PU) foams such as flexible high resilience (HR), flexible viscoelastic (VE) and semi-rigid (SR) foams as a function of the overall foam density. Foam samples were prepared in the form of cubes by mixing appropriate polyol and isocyanate compounds produced by Huntsman International India Pvt. Ltd. in varying proportions leading to a range of densities for each type of foam. The cubical samples were tested under compressive load in a standard UTM. Based on the measured load–displacement behaviors, variations of peak load and energy-absorption attributes with respect to density are plotted for each type of foam and the possible existence of an optimum foam density is shown.

In the present investigation plasma spray intermetallic coating of nickel–aluminide was deposited on mild steel substrates. The response of plasma sprayed nickel–aluminide coatings to the impingement of solid particles has been presented in this study. Nickel pre-mixed with alumina powder is deposited on mild steel substances by atmospheric plasma spraying at various operating power level. The coatings are subjected to erosion wear test. Dry silica sand of average particle size 400 µm is used as the erodent. The erosion rate is calculated on the basis of coating mass loss. The erosion studies are made at different velocities and impingement angles. It is observed that, the erosion wear is strongly influenced by the angle of impact. The test is conducted at room temperature, i.e., at 27°C and 60% RH. Coatings deposited at different power levels are found to exhibit different wear rates under similar test conditions. Microstructure of the coating is analyzed with SEM.

In this study, wood treated at different temperatures (175, 190, and 205°C) was used to ease the thermal instability caused by the introduction of wood to the composites. Composites consisting of different amounts of wood and coupling agent and HDPE were produced by the injection molding method. The mass loss measured by thermogravimetric analysis (TGA) was used as a tool to evaluate thermal stability of the materials. The results of this study show that heat treatment of wood increased DTG_max degradation temperatures and ash contents of wood especially when treatments took place at 190 and 205°C. An increase in wood content from 25 to 50% made the composites more sensitive to high temperatures. In comparison with untreated wood/HDPE composites, adding heat treated wood to the composites increased the thermal stability and ash contents of the composites. Coupling agent enhanced thermal stability of the composites when untreated wood was used as filler. The role of coupling agent on thermal stability was imperceptible when heat treated wood was used as filler.

Torsional buckling of multi-walled carbon nanotube embedded in an elastic matrix subjected to thermal fields is studied using a continuum-based multilayered shell model. The model takes into account the multilayer van der Waals (vdW) interaction between any two layers of the MWCNT as radius dependent function. The elastic matrix surrounding the outermost tube is modeled as Pasternak foundation to account for not only the normal stresses, but also the shear stress between the outermost tube and the surrounding medium. The effect of inner tube radius, number of tubes, stiffness of surrounding elastic medium and temperature change on the critical torsional load is examined. Numerical results show that the vdW interaction will lead to a higher critical torsional load and at room or lower temperature the critical torsional load for infinitesimal buckling of a multi-walled carbon nanotube increases as the value of temperature change increases, while at a temperature higher than room temperature the critical torsional load for infinitesimal buckling of a multi-walled carbon nanotube decreases as the value of temperature change increases.

The present article summarizes an experimental study on two-body abrasive wear behavior of nano-clay filled LDPE/EVA composites with and without compatibilizer. Poly (ethylene-co-glycidyl methacrylate) was used as the compatibilizer. Nano-clay filled LDPE/EVA composites with and without compatibilizer were melt-mixed using Brabender Co-Twin extruder followed by compression molding. Two-body abrasive wear studies were carried out using a Pin-on-Disc machine under multi-pass condition against the waterproof silicon carbide (SiC) abrasive papers in dry conditions. The effect of grit size, load and different abrading distance on the abrasive wear behavior was reported. The results indicate that the nano-clay filled LDPE/EVA with compatibilizer composite exhibits superior abrasion resistance. In addition, the worn surfaces of the samples were examined by scanning electron microscopy and the morphology was also discussed.

Interface geometry before joining has been an important factor for the welding quality of hot plate welding. In the present study, weld interfaces of six different geometries were studied, namely flat, triangular (30°, 45°, and 60°), rectangular, and semi-circular interfaces. Three materials were used in the study: virgin polypropylene, and 20 and 30% glass fiber-reinforced polypropylene composites. All specimens used in the experiments were molded using a pin injection gate on a reciprocating injection molding machine. After welding, the joint strength of the composites was determined by a tensile tester. Welded 20% glass fiber-reinforced polymers were found to exhibit the highest joint strengths. For the parameters selected in the experiments, hot plate temperature, heating time, and geometry of weld interface were found to be the principal factors affecting the joint property of hot plate welded composites. In addition, the triangular and rectangular weld interfaces were found to weld parts of the highest strengths for virgin polypropylene and 20% glass fiber-reinforced polypropylene composites, respectively, while the joint strengths of 30% fiber-reinforced composites were improved by adopting non-flat weld interface geometries.

Blending polytetrafluorothylene (PTFE) with PA6 in different compositions was carried out in a co-rotating twin-screw extruder where PTFE acts as the polymer matrix and PA6 as the dispersed phase. The effects of PA6 content on the tribological properties of the composites were investigated. The worn surface morphologies of neat PTFE and its composites were examined with scanning electron microscopy (SEM) and the wear mechanisms were discussed. The presence of PA6 particles dispersed in the PTFE continuous phase exhibited superior tribological characteristics to unfilled PTFE. The optimum wear reduction is obtained when the content of PA6 is 30 vol%.

In this article, injection processing of wood flour/PP composite and the effects of processing parameters on its mechanical properties are investigated. Injection pressure and pressure holding time were systematically chosen as the critical processing parameters. The results of this research work indicate that increasing injection pressure and holding time has considerable effect on final modulus of elasticity, noticeable decreasing effect on elongation, and insignificant effect on tensile strength.

The natural fiber environmental friendly composites of untreated and alkali treated silk-sisal unsaturated polyester-based hybrid composites were prepared by using hand lay-up technique. The fiber length was taken as 2 cm and the sisal fibers were treated with 2% NaOH. The chemical resistance of the treated and untreated silk/sisal hybrid composites to various acids, alkalis, and solvents was studied. The chemical resistance tests of these hybrid composites were performed in order to find out whether these composites can be used for manufacturing products that are resistant to chemicals.

The effects of weight fraction and length of short bamboo and glass fibers on flexural strength and inter-laminar shear strength (ILSS) of vinyl ester resin and unsaturated polyester (USP) resins were investigated. The bamboo fibers were isolated from the bamboo plant by treating them with dilute solution of sodium hydroxide (0.1 and 1 N NaOH) for 72 h and then boiling them in a pressure cooker for 30 min. The fibers were separated, dried, and cut into 5 or 10 mm lengths. Composites were fabricated using vinyl ester resin or USP resin as binders. The flexural properties of glass/bamboo fiber reinforced vinyl ester resins were higher than those based on USP resins. This may be due to better wetting of the fibers by VE resins due to their low viscosity and possibility of hydrogen bond formation with hydroxyl group on bamboo fibers. Hybrid composites were fabricated using 50 wt% of fibers. The wt% of bamboo fibers in these hybrid composites was varied as 25, 50, and 75 wt% of chopped glass fibers (5 mm). Replacement of 25 wt% of glass fibers did not affect the flexural modulus and a marginal increase in ILSS was observed. However, replacement of 75% glass fibers by bamboo fibers resulted in a significant decrease in flexural strength, modulus and ILSS.

Surface grafting of polyethylene (PE) fiber with methyl methacrylate (MMA) and acrylic acid (AAc) were prepared with two-stage method. Functionalization was first carried out in aqueous solution of potassium peroxydisulfate at 80°C. The fiber was then surface grafted with MMA and AAc. Single fiber composite of grafted fibers/Orthocryl® acrylic resin were prepared and adhesion evaluated with pull-out test. Acrylic matrix was prepared in two methods. In the first method, acrylic powder was bonded together with acetone. In the second, the powder was mixed with liquid monomer to form self-cure material. It was found that in the former case, in which only interdiffusion of polymer chains can occur, MMA-modified polyethylene fiber had slightly higher pull-out strength than AAc-modified fiber. In the latter case, in which chemical reaction occurred, AAc-modified fiber provided much higher pull-out strength than MMA-modified fiber. The difference in adhesion level is discussed.

The aim of this study is to determine the failure behavior of laminated glass–epoxy composite plate which is subjected to a traction force by four pins. The failure load and failure mode of composite plates which have the stacking sequence of [0/90/±45]_S has been observed experimentally. The ratio of edge distance from the hole center to pin diameter (E/D), the ratio of longitudinal holes distance to pin diameter (F/D) and the ratio of transverse holes distance to pin diameter (G/D) were selected as parameters. The results showed that the specimens except for E/D = 2 have similar behavior in terms of failure loads and failure modes.

The mechanism of translaminar failure in hybrid polymer matrix composites is a typical combination of tensile and bending loads. Experimentations have been carried out on pin loaded single edge notched tensile specimen. The results of the experimental analysis carried out on the influence of failure zone and environmental conditions on the stress intensity factor in glass/textile fabric (GF/TF) polymer hybrid composites have been reported. The results have shown that the failure zone varies with the fabric volume, the initial crack size and the environment. The results have shown that the acidic environment has maximum influence on the failure pattern and the critical stress intensity factors.

The friction and dry slide wear behavior of short glass fiber (SGF) reinforced thermoplastic polyurethane (TPU) composites was studied in this article. The SGFs were mixed by 20, 30, and 40 wt% in TPU matrix. Composites were processed by the injection molding technique. The un-lubricated pin–on-disk wear tests were conducted by varying the load and sliding velocity. The results reveal that the slide wear loss increases with increasing load/sliding velocity. The coefficient of friction increases with increase in sliding velocity. The coefficient of friction and wear rate of the composites decreased with increase in SGF content. Further, 40% SGF reinforced TPU composite exhibited lower friction coefficient and wear rate than 20 and 30% SGF reinforced TPU composites. The worn surface features have been explained using scanning electron microscopy.

An elaborate review of the literature of composite shells reveals that vibration characteristics of delaminated shell roofs have received very limited attention. Hence in this article dynamic behavior of delaminated composite shallow cylindrical shells with corner-point supported, simply supported and clamped boundary conditions is analyzed by finite element method using eight-noded isoparametric shell element. To ensure compatibility of deformation and equilibrium of forces and moments at the delamination crack front, a multipoint constraint algorithm is incorporated, which leads to unsymmetrical stiffness matrix. Stacking sequence, position and extent of delamination area are varied to compare the performances of delaminated cylindrical shells against those with no damage. The results are carefully observed and a set of conclusions is presented at the end of the article.

In this study, palm oil-based polyurethane (PU)/montmorillonite (MMT) nanocomposite foams were produced via an in situ polymerization method. The palm oil-based polyol synthesized by transesterification reaction of palm oil and pentaerythritol was reacted with commercial polymeric diphenylmethane diisocyanate in the presence of water (blowing agent), N,N-dimethylcyclohexylamine (catalyst), polydimethylsiloxane (surfactant) and MMT to produce rigid PU nanocomposite foams. The obtained foams containing different MMT contents (1, 3, and 5 wt%) were characterized for their structure, morphology, density, hardness, compressive strength and thermal stability. X-ray diffraction patterns revealed that the nanocomposites formed were exfoliated. Scanning electron micrographs showed that the cells of the obtained PU foams were closed cells. The nanocomposite foams showed a higher number of cells with a smaller cell size as the amount of MMT increased. The density and the compressive strength of the foams increased with the increasing amount of MMT and were in the range of 38.5–46.6 kg/m³ and 116.7–171.6 kPa, respectively. Moreover, addition of MMT also improved the thermal stability of the foams.

Comparison was made between properties of recycled newspaper (RNP)/carbon black (CB) and recycled newspaper (RNP)/silica hybrid filled polypropylene (PP)/natural rubber (NR) composites. The properties of composites consisting of processing characteristics, mechanical properties, thermal analysis via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), scanning electron microscopy (SEM) morphology and water absorption were studied. The results revealed that the incorporation of CB and silica in the weight ratio of RNP/CB and RNP/silica hybrid has increased stabilization torque of the composites. Certain mechanical properties of the composites such as tensile strength and elongation at break (E_B) were found increased, while Young's modulus decreased with increasing CB and silica content. The incorporation of CB in the weight ratio of RNP/CB hybrid shows higher stabilization torque, tensile strength, elongation at break (E_B) compared with RNP/silica hybrid of the PP/NR composites. However, RNP/silica hybrid exhibited higher Young's modulus than RNP/CB hybrid of the PP/NR composites. TGA and DSC results indicate that primary and secondary peak of DTG curve, initial degradation temperature (T₀), degradation temperature (T_deg), melting temperature (T_m), heat of fusion of composites (H_f(com)), crystallinity of composites (X_com) and PP (X_PP) increased, while total weight loss and thermal degradation rate decreased for both hybrid composites. The RNP/silica hybrid is likely to be more thermal resistance and more crystalline than RNP/CB hybrid of the composites. A correlation between the increment of tensile strength and morphology of the composites was also studied. Results show that the presence of CB and silica has increased interfacial interaction between polymer and filler of the composites.

A flow-induced crystallization kinetics model for semi-crystalline polymer polyethylene terephthalate (PET) was proposed based on the hypothesis that the energy of dissipation speeds up crystallization. By assuming that the effect of flow on crystallization only influenced the crystallization rate constant, the basic quiescent-state crystallization equation could be directly applied to the model flow-induced crystallization kinetics. The model predicts most of the features of flow-induced crystallization and can be easily used, especially when the real manufacturing process is considered because unknown parameters can be kept to a minimum. As an illustrative example, the injection molding of a PET part was simulated, during which the development of crystallization was controlled through the temperature of the mold resulting in a feasible method, through which transparent PET products were produced.

Glass–sisal (treated and untreated) composites of mixed matrix material (25 wt% epoxy resin of bisphenol-C (EBC) and 25 wt% bisphenol-C-formaldehyde (BCF) of glass–sisal fibers) were prepared by hand lay-up technique at 150°C under 7.6 MPa pressure for 2 h. Hydrophilic character of the sisal fibers was reduced by acrylation of alkali-treated fibers with acrylic acid. Tensile strength, flexural strength, electric strength, and volume resistivity were increased from 26.4 to 35.3 MPa (33.7%), 46.7–64.1 MPa (37.3%), 1.41–1.93 kV/mm (36.9%), and 1.27 x 10¹²–1.81 x 10¹² -cm (42.5%), respectively, on alkali treatment and acrylation. The edges of 5 x 5 cm² specimens were sealed with matrix material and subjected to distilled water and 10% each of aq. HCl and aq. NaCl solutions at room temperature for water uptake study. The equilibrium water uptake is reduced from 10.07–8.47% in water, 7.91–6.4% in 10% aq. NaCl and 12.13–11.00% in 10% aq. HCl on acrylation. Diffusivity was found to increase from 0.71–0.82 x 10^-11 in water, 1.02–1.73 x 10^-11 in 10% aq. NaCl and 0.4–0.59 x 10^-11 m²/s in 10% aq. HCl. Drastic reduction in water uptake is due to replacement of hydrophobic vinyl ester groups. No effect of boiling water is observed on stability of composites. Saturation time in boiling water reduced 24 times without any damage to the untreated and treated sisal–glass fiber composites, respectively. Composites may be useful for low load bearing applications and also in harsh acidic and saline environments.

Bagasse fiber is a residue of the sugar cane milling process. In this research bagasse fiber has been used as a reinforcing component in epoxy resin to open up further possibilities in waste management. The chemical treatment acetylation was carried out to modify the fiber properties. The effect of fiber treatment on the mechanical properties such as flexural strength has been studied. It has been shown that treated fiber composites shows improved strength. SEM investigation also indicates that the surface modifications improve the fiber–matrix interaction.

Composites of high-density polyethylene (HDPE) and alkali-extracted steam-exploded Acacia mangium fiber (AEF) were prepared using 2-roll mill and compression molding. AEF was acetylated (AAEF) to three different wt% gains (WPG) and maleic anhydride grafted polyethylene (MAPE) was used as compatibilizer. Acetylation of AEF (AAEF) did not improve the tensile properties, particularly tensile strength of the composites. Addition of maleic anhydride-grafted polyethylene (MAPE) to either HDPE–AEF or HDPE–AAEF composites improved the composite strength. The effectiveness of MAPE, however, was limited by the weight percent gain (WPG) of AAEF resulting in a decrease in composite strength and stiffness. Sorption kinetics and characteristics of water absorption of the composites immersed in distilled water at room temperature for 30 days were determined and compared. All composites were found to exhibit Fickian diffusion process. Results showed that acetylation and MAPE reduced equilibrium water uptake as well as rate of water absorption (diffusion coefficient) of the composites. A synergistic effect, however, was only observed for the equilibrium water uptake when both were considered in a composite formulation.

In this article the results of experimental works pertaining to the crash behavior and crashworthiness characteristics of a novel multi-cell cost-effective crashworthy composite sandwich structure are presented. All the samples are based on the concept of the ‘triple-layered’ foam-filled block, i.e., three polyurethane foam core sheets, which are wrapped by reinforcement fiberglass woven fabric, that acts as the reinforcement face and meanwhile ties the foam layers and faces together, thus preventing catastrophic failure. The design, manufacturing, and crush testing of rectangular blocks are described. Experimental results indicate an efficient progressive collapse mechanism with high values of crushing force efficiency and specific energy absorption.

The prediction of the fracture strength of carbon/epoxy laminates containing sharp notches through the damage model depends on the un-notched strength and the critical length of the damage zone ahead of the notch. In general, the critical length of the damage zone depends on the material, specimen, and size of the sharp notch. Modifications are made in one of the stress fracture criteria known as the average stress criterion for accurate prediction of notched tensile strength of composite laminates containing sharp notches. To examine the adequacy of these modifications, fracture data of center-cracked carbon/epoxy composite laminates with various lay-ups are considered. The notched strength estimates are found to be close to the test results. The modified average stress criterion is very simple to predict the notched tensile strength.

Properties of composites based on short regenerated cellulose lyocell fibers as a reinforcement and high-density polyethylene (HDPE) matrix were analyzed in this study. The effect of the fiber content and chemical pre-treatments (silane coupling agent, grafting of polymethyl metacrylate, PMMA) on composite mechanical and physical properties were investigated by mechanical tensile testing, water absorption test and fracture surface microstructure analysis. Mechanical tensile test indicated that fiber-reinforced composites show higher modulus than pure HDPE. In addition, silane and grafting (with PMMA) treatments of lyocell fibers resulted in a significant increase of the Young's modulus. Also, the effect of silane pre-treatment on fiber–matrix adhesion resulted in better mechanical properties when treatment was performed on lyocell fibers compared with flax fibers (used as reference fibers). Moreover, it was observed that the tensile strength of composites with a fiber content higher than 13.8% lay below the tensile strength of HDPE due to an inadequate stress transfer between fiber and matrix which was confirmed by scanning electron microscopy (SEM) analysis. Water absorption test indicated that moisture absorption decreased for chemically treated lyocell, improving the dimensional stability of the composites.

The effect of MAPE as compatibilizer on mechanical and morphological properties of a wheat straw/high density polyethylene composite was investigated. Tensile strength, tensile modulus, tensile energy absorption, failure strain, and notched Izod toughness were much higher for composites with compatibilizer as compared with the composites with no compatibilizer. The use of 2% compatibilizer improved the tensile strength as high as 43%, tensile modulus to 116% and impact strength (notched) by 12%. Remarkably improvements were attained even with 1% compatibilizer. There was little difference in the properties obtained between the 1% and 2% compatibilizer. SEM micrographs of tensile fracture surfaces with 2% compatibilizer indicated a continuous failure and the particles are not released from the matrix which is the case in samples without compatibilizer.

Short-term flexural creep and stress relaxation tests were conducted on a wood plastic composite containing 30% high density polyethylene (HDPE), 67% fir wood flour, 2% compatibilizer (MAPE), and 1% lubricant. In creep tests, applied stress levels ranged from 30 to 60% of measured flexural strength. The principle of time–stress superposition was applied to form a master curve extending for a maximum of 4 years. The horizontal shift factors conformed to an Arrhenius type equation. Stress relaxation tests were also carried out at strain levels ranging from 30 to 60% of the ultimate strain. The principle of time–strain superposition was applied to form a stress relaxation master curve that extended for 67 days. The horizontal shift factors also conformed to an Arrhenius type equation. The resulting master curves were compared with extrapolated creep and stress relaxation models. To determine whether time–stress superposition is valid for the studied composite material, creep shift factors were applied to stress relaxation data and vice versa. In both creep and stress relaxation tests, it was found that the application of superposition was verified. The results indicated that the studied composite material was rheologically simple, and a single horizontal shifting on time axis was adequate to predict the long term performance of the material.

The present investigation is focused on the utilization of abundantly available industrial waste, i.e., fly-ash in a useful manner by dispersing it into aluminum/aluminum–magnesium matrix to produce composites by a liquid metallurgy route. Composites are produced with different percentage of reinforcing phase. Further, these composites are characterized using XRD, wet chemical analysis, and image analysis. Mechanical and wear properties of the composites are evaluated.

The effect of silane coupling agent, 3-(aminopropyl) triethoxy silane (3-APE) on mechanical properties of feldspar filled polypropylene (PP) composites was investigated. Silane treated feldspar filled polypropylene composites were prepared using a Polydrive Thermo Haake internal melt mixer. The tensile strength, elongation at break, Young's modulus, and impact strength were found to be increased in silane treated composites. The improvement in tensile strength and elongation at break was due to enhancement of the interfacial adhesion between feldspar and PP matrix. FTIR spectra analyses were performed on the untreated feldspar/PP composites and the silane treated feldspar filled PP composites to study the interaction between the polypropylene –(C–H₂), feldspar (–OH) group and the amino functional group of silane.

In the present work, core shear modulus and flexural rigidity of sandwich panels with three different densities ranging from 100 to 300 kg/m³ and with two different thicknesses (8 and 6 mm) of polyurethane foams separated by glass fiber bi-woven impregnated with epoxy resin as facings have been experimentally determined as per ASTM C 393 and analyzed in the light of data obtained by other researchers. The influence of different volume fractions (0.1 and 0.2) of rigid inserts made of polyurethane foam of 900 kg/m³ density between facing and core at beam center on core shear modulus have been examined. The results have also been analyzed with core shear modulus obtained from direct shear test. Also, the failure modes of the sandwich panels and the corresponding strengths of the sandwich panels tested have been analyzed in detail. The influence of rigid inserts on the failure mode and strength of the sandwich panel has also been investigated.

In this investigation, coatings of fly ash (an industrial waste) mixed with illmenite (a low grade ore mineral) have been deposited on mild steel and copper substrates using conventional atmospheric plasma spray technique. Micro-hardness measurement, phase composition analysis, coating porosity measurement, and surface and interface morphology are studied to characterize the coatings.

Studies were carried out on RT cure epoxy (LY556+HY951) composite system comprising of metallic and non-metallic fillers. The results of the studies carried out on the composites containing three distinctly different particulate fillers, representing metallic (Cu and Al), ceramic (SiC) and solid lubricant Gr materials showed that the viscosities of the composite formulations (slips) increased with increased filler loading for a given composite. The composite formulations containing Gr and SiC exhibited respectively the highest and lowest increments in their viscosities. Further, the densities of these composites increased with increased filler content, in the order of respective densities of the fillers used. Also, the hardness of the composites increased with the increased filler content, except for the Gr filled composites, which showed an opposite trend.

This article deals with the alternating current electrical properties of epoxy/silicon carbide whiskers composites coated with titanium dioxide and poly(divinylbenzene). The alternating current conductivity and dielectric properties was studied as a function of frequency in the range from 100 kHz to 2 MHz, and temperature in the range from 30 to 120°C. It was found that alternating current conductivity increases with increasing temperature and frequency. Some alternating current conductivity and dielectric properties of epoxy/SiC whiskers composites coated with titanium dioxide and poly(divinylbenzene) as dielectric constants, activation energy, and relaxation time were determined. The observed enhancement in alternating current conductivity is attributed to increase in the number of conduction paths created by the whiskers contacts in the composite to give higher electrical conductivity. The universal power-law of alternating current conductivity is observed in silicon carbide whiskers composites. The calculated power exponent (less unity) is physically acceptable within this applied model.

Particleboards were produced from three-year-old poplar clones (e.g., Populus euramericana.costanzo, Populus euramericana. 561.41, Populus euramericana triplo, Populus euramericana vernirubensis, Populus euramericana marilandica, Populus euramericana. I-214, Populus deltoides 77.51, Populus trichocarpa, Populus nigra. betulifolia). One-layer laboratory particleboards were made with the above materials, with, board density of 0.7 gr/cm³, the resin type of (UF), a hardener content of (1%), a hardener type of (NH₄Cl), a press pressure of 30 kg/cm², and a press temperature of 160°C. Modulus of elasticity (MOE) and modulus of rupture (MOR), internal bond strength (IB). Thickness swelling of the specimens were tested according to EN Standard. Overall results showed that most panels made from above materials exceeded the EN Standards for IB, MOE, and MOR. However, thickness swelling (TS) values were higher (poor) than requirements. The highest MOR, MOE, IB were reached with P.e. costanzo, P.e. 561.41, P.e. vernirubensis and P. trichocarpa poplar clones. The lowest TS 2 h and TS 24 h were reached with P.e. 561.41 and I-214 of the three-year-old poplar clones. Most types of panels made in this study covered the MOE, MOR, and IB strength requirements for interior fitments stated in the EN Standards. Nevertheless, the TS of the panels were very poor. Poplar clone panels are suitable for interior decoration (furniture, wall, and ceiling paneling).

A prediction method for the fatigue life of polymer composites under arbitrary frequency, load ratio and temperature was extended to that of polymer composite structures. The three-point bending tests for honeycomb cored sandwich (SW) panels with GFRP skin plates and Nomex honeycomb core under constant strain rates (CSR) and fatigue loading at various strain rates and temperatures were conducted. The maximum bending moments for CSR and fatigue loadings strongly depend on time and temperature, and the time–temperature superposition principle for the storage modulus of matrix resin holds for the maximum bending moments for fatigue loading as well as CSR loading. The long term fatigue strength at any time, temperature and number of cycles to failure can be predicted using the master curves of the bending moment by fatigue loading based on the accelerated testing methodology.

Wood fiber-reinforced recycled plastic composites (WRPCs) manufactured from sawdust and post-consumer high density polyethylene (HDPE) were studied in this article. The thermal, flexural properties and impact strength of the manufactured WRPCs were determined according to the relevant standard specifications. Effects of mix ratio, wood fiber length, type, and content of coupling agent on the mechanical properties of WRPCs were investigated. The fracture surfaces of WRPCs after impact test were examined and the fracture mechanism of WRPCs due to impact was also analyzed in this article. The results indicated that incorporation of wood fibers resulted in higher melting and slower crystallization rate of WRPCs. A linear relationship between cooling rate and crystallization rate was observed. With the increasing of the wood fiber weight fraction, the flexural strength of WRPCs increases. The longer the wood fiber length, the less the flexural strength of WRPCs under the conditions of this study. The Charpy impact strength decreases with the increasing of wood fibers content in WRPCs. It appears that the optimum compatibilizer content for wood and recycled HDPE mixing is 5% in weight fraction.

A majority of the existing research studies focus on the effects of individual environmental conditions, such as freeze–thaw cycles and wet–dry cycles, while investigations on the combined effects of various environmental conditions are very rare. Therefore, the objective of this study was to evaluate the effects of various environmental conditions on reinforced concrete (RC) columns wrapped with FRP sheets with focus on the combined effects. Two different scales of RC columns wrapped with carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) sheets were conditioned under various environmental conditions. Then, uni-axial compression tests were conducted in order to evaluate their strength, stiffness, and ductility. The environmental conditions considered in this study included freeze–thaw cycles, high-temperature cycles, high-humidity cycles, ultraviolet (UV) radiation, and saline solution. Based on the test results, design guidelines were suggested, which included equations to determine axial capacity of RC columns wrapped with FRP sheets, and strength reduction factors to account for the effects of environmental conditions considered in this study.

This article deals with short spruce fiber-reinforced recycled polypropylene materials. Polypropylene has been subjected to n extrusion and crushing cycles, in order to simulate the recycling process. Recycling consequences have been studied on five times and 10 times-recycled PP. Then, short spruce fibers have been added in the 10 times-recycled PP, with different fiber weight fractions: 10, 30, and 40%. For microstructural aspects, results obtained by DSC and WAXS show that added fibers lead to an increase of the polymer degree of crystallinity, and to the development of a new crystalline phase with the β form. Tensile tests have shown that fiber presence obtains high rigidity values, but embrittles materials. Fracture tests coupled with digital image correlation technique have also been performed. Results show the better accommodation of overstrains at the crack tip in the composite material. Thus, this new type of composite, made of recycled polymers and natural fibers, seems to be full of promise.

We investigate the fabrication of continuous carbon fiber/poly(-caprolactone)composites for biomedical applications. Two fabrication methods: in-situ polymerization and filmstacking are compared at two different thicknesses. Analysis of void content produced via the two fabrication methods showed that the in-situ polymerization specimens had considerably lower void content than the film stacked samples. Significantly higher mechanical properties were obtained forthe in-situ polymerized samples, and an almost three-fold increase in properties was seen as compared to the film stacked samples. Scanning electron microscopy images of surfaces supported the findings above. Dynamic mechanical analysis revealed higher dynamic modulus for the in-situ polymerized samples which was consistent with the above results.

In the present study, the effect of fiber orientation and stress level on the strength of stressed beams retrofitted with GFRP jackets is studied. The beams were initially stressed up to 60, 75, and 90% of their safe load and then retrofitted with GFRP jackets with fibers in different orientations. The results show that the beams retrofitted using GFRP jackets with fibers at 45° to the longitudinal axis yield a higher increase in the maximum load carrying capacity, i.e., approximately 30–35% in case of under-reinforced sections and 13–17% in case of balanced sections as compared to beams retrofitted using fibers at 0° to the longitudinal axis. A considerable increase in the ductility ratio is also observed for both the fiber orientations.

This study focused on the mechanical properties of pure sisal, pure glass, and hybrid sisal/glass compression-molded composites, in which various stacking sequences of fiber mat layers were used. It is shown that hybridization originated a material with general intermediate properties between pure glass and pure sisal. However, the importance of controlling the stacking sequence to enhance properties was evident. For instance, to optimize flexural behavior, there must be glass fibers mainly on the top and bottom surfaces. Furthermore, depending on the type of loading and stacking sequence, some hybrid composites may show properties very close to those of pure glass.

The hybrid shear lag (HSL) model for hybrid fiber reinforced plastic composite I-section beam under bending loads was put forward by the principal of minimum potential energy method considering the shear deformation effect. The correctness of the HSL model was proved with finite element analysis (ANSYS). Furthermore, based on the HSL model, three conclusions were reached: first, the HSL model must consider the shear deformation effect; second, anisotropy is the main reason why the shear deformation will influence the shear lag of the composite beams; finally, four influential factors are the primary factors that affect the shear lag coefficients.

A geometrical correction to previous models for the elastic modulus of particulate composites is proposed in this article in a closed-form analytical expression. By comparing the geometrically corrected models (which adopt spherical particulates) to previous models (which employ cubic particulates) a set of correction factors and functions are extracted. The correction factors modify the influence of filler volume fraction while the correction functions describe the effect of filler–matrix boundary shape to the overall composite modulus. With the aid of geometrical correction, the validity, or otherwise, of earlier models are discussed with reference to previous experimental data and are elucidated through their representative volume element's assumed boundary conditions. These correction parameters allow the practitioner to easily incorporate geometrical correction to previously known models.

Hybrid palm ash/silica/natural rubber composites were prepared using a laboratory sized two roll mill. The effects of partial replacement of palm ash by silica on curing characteristics, mechanical properties, and morphology of hybrid palm ash/silica/natural rubber composites were investigated. Compared to the control composite (30 phr of palm ash), increasing the silica in the weight ratio of silica/palm ash increases the scorch time and cure time, the maximum and minimum torques, and enhances the rubber-filler interaction, tensile strength, tensile modulus, and fatigue life. However the incorporation of palm ash also exhibits the beneficial effects by shorter curing time of hybrid palm ash/silica/natural rubber composites.

Studies were carried out on RT cure epoxy (LY556 + HY951) composite system comprised of metallic and non-metallic fillers. The results of the studies carried out on composites with three distinctly different particulate fillers, representing ductile (Cu and Al), brittle (SiC), and soft (Gr) type of materials regarding the mechanical properties, showed that the tensile and flexural strength of the particulate composites degraded with filler loading, whereas the modulus (both tensile and flexural) of the composites increased with the filler loading for the range of filler contents considered (10–40 wt%). The compression strength of all the composites increased to a maximum up to a filler loading of 30% and then decreased beyond this value, with the SiC-Ep composites exhibiting the highest improvement in the compression strength.

In the presented article, an experimental study has been carried out to investigate the effect of tightness level on mechanical properties of weft-knit 1 x 1 rib glass fiber reinforced epoxy composites. Three different glass fiber reinforced epoxy composites with different tightness level were produced. Mechanical properties of the composites have been determined. The results show that tensile strength, compression strength, and shear strength of the composites increase with increasing of tightness level.

With an aim to enhance low temperature impact strength, blends of PP-cp (Impact Grade PP) and metallocene-catalyzed plastomer (EXACT® ethylene--octene copolymer) were prepared using a co-rotating, intermeshing twin-screw extruder in 90 : 10, 80 : 20, 70 : 30, and 60 : 40 weight ratio. Rheological properties studied by Haake' single-screw extruder with torque rheometer attachment and capillary die showed pseudoplastic melt behavior at 220°C in the shear rate range of 400–4000 s^-1. Density and MFI determinations showed minimal change. Morphology studied by low voltage scanning electron microscope (LVSEM) of blend samples showed distinct biphasic blend morphology wherein PP-cp as continuous phase and plastomer as spherical domains (0.5–2 µm size) with stabilized distribution and dispersion. Izod impact strength of the blends at varied temperatures (23, 0, -10, -20, -30, and -40°C) showed substantial enhancement in low temperature impact strength compared to the base polymer (from 44 J/m in case of pure PP-cp to 539 J/m in case of 40% plastomer blend at -40°C).

The aim of this study was to carry out RTM experiments to determine in-plane permeability of glass mats, non-woven polypropylene flow media (PP) and hybrids (glass + PP), with different stacking sequences, and to compare these with various sisal mats and hybrids (glass + sisal). RTM composites were also molded. Permeability decreased for higher fiber content and, for the same fiber volume content, the permeability of the sisal mats was much higher than that of glass mats and also higher than that of the PP non-woven core, often used as an infiltration medium. Besides, a tendency of increasing permeability with sisal fiber length (up to 30 mm) was noticed. The use of the sisal mat as a flow medium increased the permeability of the hybrid reinforcement and slightly improved the mechanical properties of the composite. Hence, the sisal mat may be indicated in engineering applications as a substitute for commercial flow media, widely used in the process called RTM light.

An experimental study has been carried out to investigate the mechanical properties of glass-fiber reinforced epoxy composite filled with different proportions of Al₂O₃ particles. As a comparison, the mechanical properties of unfilled glass-fiber reinforced epoxy composite were also evaluated under identical test conditions. The results showed that while ultimate tensile strength and shear strength of the composites decreased with increasing Al₂O₃ particles content, flexural strength increased with the Al₂O₃ particles content of up to 10% beyond which it decreased. Compared with the flexural properties of the unfilled glass-fiber reinforced epoxy composite, with the addition of 10 wt% of Al₂O₃ particle in the matrix, flexural strength, and flexural modulus were increased by 33 and 78%, respectively.

The main objective of the article is to provide a deeper understanding of the wear and wear transition of Al-6061/alumina particulate composite. Detailed experiments were performed under unlubricated conditions within a load range of 10–150 N and a sliding speed range of 1.25–10 m/s. A mild wear region and a severe wear region have been observed during the experiment. At mild wear, mechanical mixture layer (MML) are formed on the worn surface mainly in composites, which plays a vital role in reducing the wear rate and delaying the transition to severe wear. It is observed that the transition to severe wear occurs when severe plastic deformation induces the wear. The scanning electron microscope (SEM) is used to identify and classify the wear regions in wear mechanism.

In the present study epoxy and polyester resins have been reinforced with physically modified (alkali treated) bamboos strip matting to develop bamboo fiber-reinforced plastic (BFRP) composites. Bamboo mats were treated with 1, 2, 5, 10, 15, 20, and 25% concentration of NaOH in distilled water for 30 min at 20°C (room temperature). The mechanical properties of the alkali treated bamboo composites (tensile strength, elastic modulus, flexural strength, flexural modulus, toughness, and impact strength) were determined. Optimum results have been obtained by bamboos treated with 5% NaOH solutions. Higher percentages of NaOH concentration result in poor mechanical properties of composites. The morphology analysis reveals that the bamboo treated with 5% NaOH exhibited better compatibility with the epoxy and polyester resins than the untreated bamboo. The improvements in tensile strength and flexural strength were higher by 55.15 and 43.92%, respectively, for composites with epoxy matrix. In the case of alkali-treated composites with polyester matrix, the tensile strength and flexural strength were higher by 69 and 59%, respectively.

Bamboo fiber (BF) filled polypropylene (PP) composites were manufactured by melt compounding and injection molding. The incorporation of BF to neat PP increased the decomposition temperatures of the composites compared to neat PP. The loading of BF to PP decreased the melting temperature, melting enthalpy, crystallization enthalpy, crystallization temperature, and crystallinity. Tensile modulus, impact resistance, and creep improved as BF loading increased. However, tensile strength and water desorption were decreased by the increase of BF loading. The addition of maleated polypropylene (MAPP) as a coupling agent increased the tensile strength and modulus. The melting enthalpy and crystallization enthalpy were decreased by the addition of MAPP. The loading of MAPP also improved the water desorption, impact resistance, and bamboo fiber dispersion into neat PP matrix, while lowering creep. There was no significant effect of MAPP on the thermal deformation and melting temperature of the composites. The melting enthalpy, crystallization temperature, crystallization enthalpy, and crystallinity were decreased by the addition of MAPP.

Red mud is an industrial waste generated during the production of alumina by Bayer's process. Using this red mud as the filler, particulate reinforced polyester composites have been prepared and their dry sliding wear behavior has been studied experimentally. For this a standard pin-on-disc test set-up and Taguchi's orthogonal arrays were used. Taguchi's experimental design method eliminates the need for repeated experiments and thus saves time, materials, and cost. It identifies the significant control factors and their interactions predominantly influencing the wear rate. From the experimental findings, an optimal combination of control factors was obtained on the basis of which a predictive model was proposed. This model was validated by performing a confirmation experiment with an arbitrarily chosen set of factor combinations. Finally, the optimal factor settings for minimum wear rate under specified experimental conditions have been determined using a genetic algorithm.

Nanosilica was used to reinforce the selective laser sintering (SLS) parts of nylon-12. A dissolution–precipitation process was successfully developed to prepare a nanosilica/nylon-12 composite powder (containing 3 wt% nanosilica) for SLS process. The dispersion of nanosilica in the SLS specimens of the composite powder was examined by scanning electron microscope (SEM), and the effects of nanosilica on the thermal and mechanical properties of the SLS parts were investigated. The results show that: nanosilica disperses uniformly on a nano-scale level in the SLS parts of the composite powder; nanosilica has a heterogeneous nucleation effect on nylon-12; the composite powder has much higher thermal stability than neat nylon-12; the tensile strength, tensile modulus, and impact strength of the SLS specimens made from the composite powder are 20.9, 39.4, and 9.54% higher than those of neat nylon-12 SLS specimens, respectively, and the elongation at break decreases by about 3.65%.

The goal of this study was to investigate the use of old newsprint (ONP) fiber as raw material for laboratory made medium density fiberboard (MDF). Effect of ONP fiber mixed with virgin aspen (Populus deltoides) fiber and the press time (3, 4, and 5 min) on the properties of MDF panels were determined. Panels were produced using aspen fibers in surface layer and combination of aspen fibers and ONP fibers in core layer. Physical (thickness swelling) and mechanical properties of the panels were determined according to the procedure of EN standards. This study showed reduction in bending strength and internal bond strength of the panels as ONP fiber was loaded from 35 to 70% in core layer. Thickness swelling of MDF panels was drastically increased with addition of ONP fiber to the panels' furnishes. Based on the findings of this study, it appears that ONP can be considered as a potentially suitable raw material for manufacturing MDF products without having any significant adverse influence on the panel properties.

In this research wood-plastic composite (WPC) panels were produced from high density polyethylene, MDF, and particle-board waste at 60, 70, and 80 wt% fiber loadings using the dry blend/hot press method. Physical and mechanical properties of the panels were studied and compared with conventional MDF and particle-board panels.

The results indicated that the studied properties of the composites were strongly affected by the kind and proportion of the wood fiber and polymer. Maximum values of the flexural modulus of the WPC panels were reached at 70% fiber content. The flexural strength and impact strength of the WPC panels declined when fiber content increased from 60 to 80%. The flexural modulus of the WPC panels was lower than that of the virgin MDF panels but the flexural modulus of the composites with 70% fibers was close to that of particle-board panels. Flexural strength of MDF panels was noticeably higher than those of wood-plastic composites whereas the flexural modulus of particle-board panels was comparable to that of the wood-plastic composites at 80% fiber content.

Furthermore, water uptake of wood-plastic samples increased with the increase in fiber content; however, it was relatively low compared with virgin MDF and particle-board panels.

The stress corrosion crack growth behavior of ±45°, ±55°, and ±75° filament wound composite pipes with surface crack subjected to 0.6 M HCl acid under alternating internal pressure was investigated. E-glass/epoxy pipes consist of six layers with stacking sequences of (+45/-45)₃, (+55/-55)₃, and (+75/-75)₃. Dilute (0.6M) HCl acid was applied to the surface crack region by a corrosion cell mounted on the outer surface of the pipe. The specimens were tested at room temperature and exposed to open-ended fatigue tests in which the pipes can deform freely in the axial direction. The tests were performed in accordance with the ASTM D-2992 standard. The surface notches with different a/t and a/c forms were cut on the outer surface of the pipe parallel to the pipe axis. The internal pressure was generated by conventional hydraulic oil for fatigue loading. The low cycle tests were applied with 0.42 Hz frequency and R = 0.05 stress ratio. After the corrosion fatigue test, the fracture surfaces were examined and observed damage mechanisms discussed.

A new approach based on plate laminate theory (PLT) is developed to calculate the mechanical properties of woven and braided composites. It supposes that, for each woven or braided composite oriented at ±, there is an equivalent ± angle-ply laminate made out of two unidirectional plies. An inverse algorithm based on PLT was developed to calculate, from the known mechanical characteristics of a composite reinforced by engineering fabrics, the properties of the mechanically equivalent angle-plies. The virtual angle-ply and cross-ply laminates obtained by inverse calculation include the effects of undulation and strand shear. The difference in properties between experience and theory is clear, especially for Poisson's ratio. Comparisons performed between numerical predictions and experimental tests have shown a good correlation.

In this article, potential use of ductile adhesives in structural applications is taken into consideration and their possible advantages over traditional structural adhesives are discussed. For this purpose, the performance of a very ductile adhesive with high strain to failure was investigated in the single lap joint (SLJ) configuration in tensile loading, and the joint was modeled using the finite element method (FEM) to analyze its non-linear solutions. In analyzing the joint, consideration is given to the stress distributions in the adhesive layer and the load to failure was predicted. The predicted values were well in agreement with the previous experimental results, and the stress distributions of the ductile adhesive differed in many respects from traditional structural adhesives. In order to see the differences, a structural modern epoxy has also been analyzed.

Plasma spray technology is being widely used for the development of protective coatings to prevent degradation of critical components working under severe conditions. Plasma sprayed alumina–titania have many industrial applications. These coatings provide a dense and hard surface which is resistant to abrasion, corrosion, cavitation, oxidation, and erosion. Plasma sprayed alumina–titania coatings are regularly used for wear resistance, electrical insulation, thermal barrier applications, etc. Alumina pre-mixed with titania powder is deposited on mild steel substances by atmospheric plasma spraying. Microstructure of the coating is analyzed by SEM. Adhesion strength of alumina–titania coatings are measured. The response of plasma sprayed alumina–titania coatings to the impingement of solid particles has been presented in this study. The erosion rate is calculated on the basis of ‘coating mass loss’. It is observed that the erosion wear rate varies with erodent dose, angle of attack, the velocity of erodent, standoff distance, and size of the erodent. Cumulative coating mass loss varies with time of erosion.

The variability of tensile mechanical properties of a polymer matrix composite material with woven fabric reinforcement is studied using both experimental work and numerical simulations. Four E-glass/vinyl ester composite plates were fabricated using the vacuum-assisted resin transfer molding (VARTM) by a US Navy contractor. The materials and process selected are representative of Marine grade composites typically used by the US Navy. Standard and modified D3039 tensile coupons were obtained from the plates and the laboratory results were compared with those of a 3D probabilistic finite element analysis (FEA). In the probabilistic FEA model, elastic properties, strength parameters, and geometric properties of the woven fabric E-glass/vinyl ester coupons were considered as random fields, and generated using Monte Carlo simulations. The study evaluates the effects of spatial correlation, finite element size, probability distribution functions (PDF) types, and failure criteria on statistical strength properties of the [(0_w/90_f)/(0_f/90_w)]_2s tension coupons. Comparisons of experimental and probabilistic FEA results provide useful information on how to assign mean, COV, and PDF of material properties to individual finite elements within a mesh. The results are relevant in developing design properties for these composites.

The increasing preoccupation with the environment and use of natural products has strongly contributed in the use of material derived from biomass, and in particular vegetal fibers. Within this context curaua fiber, originating from the Brazilian Amazon, has become prominent for its mechanical performance in relation to other vegetal fibers. This work is part of a wide research about the development of hybrid composites with curaua fibers. Its main objective is to present a brief description and characterization of the curaua fiber, still little known in the scientific community, compared to other vegetal fibers traditionally employed in polymeric composites. The characterization consists of tensile test, morphological analysis, and thermogravimetric analysis.