Mechanical properties of laminated bamboo strips from Gigantochloa Scortechinii/polyester composites

In this study, the mechanical properties of culm fiber composites with various thicknesses from the inner through the outer layer of bamboo strips were investigated. This study utilized a specific type of bamboo species named Gigantochloa Scortechinii (Buluh Semantan), which was collected from the Bukit Larang village in Melaka, Malaysia. In these experiments, unsaturated polyester (UP) and bamboo fiber (BF) strips were prepared through the hand lay-up technique using 3 mm thick aluminum mould. The composite bamboo strips were prepared in 1.5–2.5 mm thicknesses. The weight of the inner, middle and outer bamboo parts varied from a minimum of 0.742 g to a maximum of 2.600 g. The specimens were then characterized using several techniques including tensile, flexural, hardness, and impact tests. The results indicated that the properties of the middle part of the bamboo strips improve as the bamboo strip thickness increases due to the incorporation of unsaturated polyesters. However, the hardness properties increase for the outer layer of the laminate. These findings suggest that bamboo strips, based on unsaturated polyesters, yield excellent mechanical properties and are a viable alternative to composite-based reinforcing fibers.     

Study on the interface modification of bagasse fibre and the mechanical properties of its composite with PVC

The surface treatments of bagasse fibre (BF) with benzoic acid as a surface/interface modifier and the mechanical properties of BF-polyvinyl chloride (PVC) composite were studied. A typical process for the preparation of the composite was as follows: A mixture of PVC, BF, benzoic acid, and other processing additives were dry-blended in a two-roll mill followed by compression molding. The experimental results indicated that the ratio of PVC/BF, the content of benzoic acid, and processing temperature had a significant effect on the mechanical properties of the composite, which was examined by the orthogonal optimal method. The interface modifier improved significantly on the tensile strength and little on the impact strength of the composite, for example, the tensile strength changed between 42 and 52 MPa comparing to the tensile strength of untreated BF/PVC composite (38 MPa), and the impact strength changed between 8.3 and 9.2 kJ/m² comparing to the impact strength of untreated BF/PVC composite (7.5 kJ/m²) when the content of benzoic acid changed between 3 and 10%.     

Thermomechanical properties of bio-based composites made from a lactic acid thermoset resin and flax and flax/basalt fibre reinforcements

Low viscosity thermoset bio-based resin was synthesised from lactic acid, allyl alcohol and pentaerythritol. The resin was impregnated into cellulosic fibre reinforcement from flax and basalt and then compression moulded at elevated temperature to produce thermoset composites. The mechanical properties of composites were characterised by flexural, tensile and Charpy impact testing whereas the thermal properties were analysed by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The results showed a decrease in mechanical properties with increase in fibre load after 40 wt.% for the neat flax composite due to insufficient fibre wetting and an increase in mechanical properties with increase fibre load up to 60 wt.% for the flax/basalt composite. The results of the ageing test showed that the mechanical properties of the composites deteriorate with ageing; however, the flax/basalt composite had better mechanical properties after ageing than the flax composite before ageing.     

The effect of thermal cycles on the mechanical properties of fiber–metal laminates

The effect of thermal-shock cycles on the mechanical properties of fiber–metal laminates (FMLs) has been evaluated. FML plates were composed by two AA2024 Al sheets (1.6 mm thick) and one composite ply formed by two layers of unidirectional glass fiber epoxy prepreg and two layers of epoxy adhesive tape of glass fiber reinforced epoxy adhesive. The set was manufactured by hand layup and typical vacuum bag technique. The curing cycle was in autoclave at 125 ± 5 °C for 90 min and an autoclave pressure of 400 kPa. FML coupons taken from the manufactured plate were submitted to temperature variations between −50 and +80 °C, with a fast transition between these temperatures. Tensile and interlaminar shear strength were evaluated on samples after 1000 and 2000 cycles, and compared to nonexposed samples. 2000 Cycles corresponds to typical C Check interval for commercial aircraft maintenance programs. It was observed that the thermal-shock cycles did not result in significant microstructural changes on the FML, particularly on the composite ply. Similarly, no appreciable effect on the mechanical properties of FML was observed by the thermal-shock cycles.     

Experimental study on the mechanical properties and microstructure of chopped basalt fibre reinforced concrete

With high ductility and sufficient durability, fibre reinforced concrete (FRC) is widely used. In this study, the effects of the volume fraction and length of basalt fibre (BF) on the mechanical properties of FRC were analyzed. Coupling with the scanning electron microscope (SEM) and mercury intrusion porosimeter (MIP), the microstructure of BF concrete was studied also. The results show that adding BF significantly improves the tensile strength, flexural strength and toughness index, whereas the compressive strength shows no obvious increase. Furthermore, the length of BF presents an influence on the mechanical properties. Compared with the plain concrete, the compressive, splitting tensile and flexural strength of concrete reinforced with 12 mm BF increase by −0.18–4.68%, 14.08–24.34% and 6.30–9.58% respectively. As the BF length increasing to 22 mm, corresponding strengths increase by 0.55–5.72%, 14.96–25.51% and 7.35–10.37%, separately. A good bond between the BF and the matrix interface is observed in the early age. However, this bond shows degradation to a certain extent at 28 days. Moreover, the MIP results indicate that the concrete containing BF presents higher porosity.     

Effects of thermal treatment on the mechanical properties of poly(p-phenylene benzobisoxazole) fiber reinforced phenolic resin composite materials

Thermal degradation behaviors of the poly(p-phenylene benzobisoxazole) (PBO) fiber and phenolic resin matrix were investigated. The unidirectional PBO fiber reinforced phenolic resin composite material laminates were fabricated and exposed in a muffle furnace of 300 °C, 550 °C, 700 °C, and 800 °C for 5 min, respectively, to study the effects of thermal treatment on mechanical properties of the composites. After undergone thermal treatments at 300 °C, 550 °C and 700 °C for 5 min, the flexural strength was reduced by 17%, 37% and 80%, respectively, the flexural modulus was decreased by 5%, 14% and 48%, respectively, and the interlaminar shear strength (ILSS) was lowered by 12%, 48% and 80%, respectively. Thermal treatment at 300 °C, the phenolic resin began to pyrolyze and shrink resulted in the irreversible damage of the composites. After 550 °C thermal treatment, the phenolic resin pyrolyzed mostly but the PBO fiber had no obvious pyrolyze, the interface had sever broken. After 700 °C thermal treatment, the phenolic resin formed amorphous carbonaceous and PBO fiber pyrolyzed mostly so the mechanical properties dropped dramatically. At being heated at 800 °C for 5 min, the fiber was nearly totally pyrolyzed and and kept fibrous carbonaceous although the specimen became too brittle to stand any load thereon.     

Synergy of fiber length and content on free vibration and damping behavior of natural fiber reinforced polyester composite beams

This work addresses the results of experimental investigation carried out on free vibration characteristics of short sisal fiber (SFPC) and short banana fiber (BFPC) polyester composites. Influence of fiber length and weight percentage on mechanical properties and free vibration characteristics are analyzed. Composite beam specimen is fabricated with random fiber orientations at17 MPa compression using compression molding machine. Natural frequencies and associated modal damping values of the composite laminates were obtained by carrying out the experimental modal analysis. It is found that an increase in fiber content increases the mechanical and damping properties. For SFPC, 3 mm fiber length and 50 wt% fiber content yielded better properties, whereas for BFPC, 4 mm fiber length and 50 wt% fiber content was the best combination. Scanning electron microscopy was performed to study the interfacial mechanism.     

Study on the mechanical properties,environmental effect,degradation characteristics and ionizing radiation effect on silk reinforced polypropylene/natural rubber composites

Natural silk fiber (20%) reinforced polypropylene (PP) composites were prepared by compression molding. Tensile strength, tensile modulus, bending strength, bending modulus, impact strength and hardness of the prepared composite were found 54.7 MPa, 1826.2 MPa, 58.3 MPa, 3750.7 MPa, 17.6 kJ/m² and 95 shore A, respectively. To improve the biodegradable character of the composite, natural rubber (NR) was blended (10%, 25%, 50% by weight) with PP. It was found that the mechanical properties of the composite decrease with increasing NR in PP (except IS which increased rather decreasing). Environmental effect on the composite and degradation in various media were investigated in this study. Gamma radiation was used to increase the mechanical properties of the prepared composites. Increase in TS and BS were maximum at 250 krad dose for silk fiber/PP, silk fiber/PP:NR (90:10), silk fiber/PP:NR (75:25) and silk fiber/PP:NR (50:50) composites.     

Mechanical,thermal expansion,and flammability properties of co-extruded wood polymer composites with basalt fiber reinforced shells

Basalt fiber (BF) filled high density polyethylene (HDPE) and co-extruded wood plastic composites (WPCs) with BF/HDPE composite shell were successfully prepared and their mechanical, morphological and thermal properties characterized. The BFs had an average diameter of 7 μm with an organic surfactant surface coating, which was thermally decomposed at about 210 °C. Incorporating BFs into HDPE matrix substantially enhanced flexural, tensile and dynamic modulus without causing a noticeable decrease in the tensile and impact strength of the composites. Micromechanical modeling of tensile properties for the BF/HDPE composites showed a good fit of the selected models to the experimental data. Compared to neat HDPE, BF/HDPE composites had reduced linear coefficient of thermal expansion (LCTE) values. The use of the pure HDPE and BF/HDPE layers over a WPC core greatly improved impact strength of core–shell structured composites. However, the relatively less-stiff HDPE shell with large LCTE values decreased the overall composite modulus and thermal stability. Both flexural and thermal expansion properties were enhanced with BF reinforced HDPE shells, leading to well-balanced properties of core–shell structured material. Cone calorimetry analysis indicated that flammability performance of core–shell structured composites was improved as the BF content increased in the shell layer.     

Effect of basalt fiber hybridization on the impact behavior under low impact velocity of glass/basalt woven fabric/epoxy resin composites

The low velocity impact behavior of E-glass/basalt reinforced hybrid laminates, manufactured by resin transfer moulding technique, was investigated. Specimens prepared with different stacking sequences were tested at three different impact energies, namely 5 J, 12.5 J and 25 J. Residual post-impact mechanical properties of the different configurations were characterized by quasi static four point bending tests. Post-impact flexural tests have been also monitored using acoustic emission in order to get further information on failure mechanisms. Results showed that basalt and hybrid laminates with an intercalated configuration exhibited higher impact energy absorption capacity than glass laminates, and enhanced damage tolerance capability. Conversely, the most favorable flexural behavior was shown by laminates with symmetrical sandwich-like configuration (E-glass fiber fabrics as core and basalt fiber fabrics as skins).     

Effect of fiber loading on mechanical and morphological properties of cocoa pod husk fibers reinforced thermoplastic polyurethane composites

In this study, cocoa (Theobroma cacao) pod husk (CPH) fiber reinforced thermoplastic polyurethane (TPU) was prepared by melt compounding method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber loading: 20%, 30% and 40% (by weight), with the optimum processing parameters: 190 °C, 11 min, and 40 rpm for temperature, time and speed, respectively. Five samples were cut from the composite sheet. Mean value was taken for each composite according to ASTM standards. Effect of fiber loading on mechanical (i.e. tensile, flexural properties and impact strength) and morphological properties was studied. TPU/CPH composites showed increase in tensile strength and modulus with increase in fiber loading, while tensile strain was decreasing with increase in fiber loading. The composite also showed increase in flexural strength and modulus with increase in fiber content. Impact strength was deteriorated with increase in fiber loading. Morphology observations using Scanning Electron Microscope (SEM) showed fiber/matrix good adhesion.     

Ablation,mechanical and thermal conductivity properties of vapor grown carbon fiber/phenolic matrix composites

The ablation, mechanical and thermal properties of vapor grown carbon fiber (VGCF) (Pyrograf III™ Applied Sciences, Inc.)/phenolic resin (SC-1008, Borden Chemical, Inc.) composites were evaluated to determine the potential of using this material in solid rocket motor nozzles. Composite specimens with varying VGCF loadings (30–50% wt.) including one sample with ex-rayon carbon fiber plies were prepared and exposed to a plasma torch for 20 s with a heat flux of 16.5 MW/m² at approximately 1650°C. Low erosion rates and little char formation were observed, confirming that these materials were promising for rocket motor nozzle materials. When fiber loadings increased, mechanical properties and ablative properties improved. The VGCF composites had low thermal conductivities (approximately 0.56 W/m-K) indicating they were good insulating materials. If a 65% fiber loading in VGCF composite could be achieved, then ablative properties are projected to be comparable to or better than the composite material currently used on the Space Shuttle Reusable Solid Rocket Motor (RSRM).     

Experimental investigation of high-strain rate properties of 3-D braided composite material in cryogenic field

This paper reports the high-strain rate properties of 3-D braided basalt/epoxy composite materials at 26 °C, −50 °C, −100 °C and −140 °C with strain-rate range from 1300 s⁻¹ to 2100 s⁻¹ by experimental study. A simple and effective cryogenic device was applied to the SHPB system to create the low-temperature field of the samples. It was found that the compression modulus, peak stress, failure strain and specific energy absorption of the 3-D braided basalt/epoxy composite materials had different sensitivity to temperatures and strain rates. In the out-of-plane impact, there were two failure modes, namely, compression-failure mode and shear-failure mode. Fracture of fiber tows was irregular with abundant pull-out of fiber and much finely-divided fragmentation of resin among fibers at room temperature. In cryogenic field, the fracture of fiber tows was neat and tidy with few pull-out of fiber and few finely-divided fragmentation of resin. However, in the in-plane impact, there was only compression failure mode. And there was no fracture of fiber tows and no big difference among samples tested under different gas pressures. Because of the function of squeezing and buckling, split-off separation of the composite could be blocked by the tangled fiber tows. As a whole, the reinforcement could still keep its structural integrity.     

Effects of electron beam irradiation on mechanical properties and nanostructural–morphology of montmorillonite added polyvinyl alcohol composite

This paper is aiming to analyze the effects of electron beam irradiation on the mechanical properties and structural–morphology of nano-sized montmorillonite (MMT) added polyvinyl alcohol (PVOH) composite. MMT particles were added to the PVOH matrix at various loading level that ranges from 0.5 to 4.5 phr MMT and electron beam irradiated with dosages ranging from 6 to 36 kGy. The results showed that tensile strength of MMT added PVOH composites at 1.5 and 2.5 phr MMT were observed marginally higher compare to neat PVOH when irradiation dosages increased to 26 kGy. However, when the concentration of MMT exceeded 2.5 phr, the application of irradiation seems to cause adverse effect to the PVOH–MMT composite. Besides, according to the X-ray diffraction analysis, the application of low irradiation dosage (⩽16 kGy) has significantly enhanced the intercalation effect of MMT particles at high loading (4.5 phr) in PVOH matrix. This also found to be consistent with the scanning electron microscopy observation where the dispersion of MMT particles in PVOH matrix was noted to be more homogeneous than non-irradiated samples. Further increment in irradiation dosage up to 36 kGy has significantly reduced the crystallinity which indicates the higher radiation energy could rupture the crystallite structures in PVOH matrix.     

Assessment of three oxide/oxide ceramic matrix composites: Mechanical performance and effects of heat treatments

Mechanical performance of three oxide/oxide ceramic matrix composites (CMCs) based on Nextel 610 fibers and SiOC, alumina, and mullite/SiOC matrices respectively, is evaluated herein. Tensile strength and stiffness of all materials decreased at 1000 °C and 1200 °C, probably because of degradation of fiber properties beyond 1000 °C. Microstructural changes in the composites during exposure at 1000 °C and 1200 °C for 50 h reduce their flexural strength, fracture toughness and work of fracture. A literature review regarding mechanical properties of several oxide/oxide CMCs revealed lower influence of fiber properties on composite strength compared with elastic modulus. The tested composites exhibit comparable stiffness and strength but higher fracture toughness compared with average values determined from a literature review. Considering CMCs with different compositions, we observed an interesting linear trend between strength and fracture toughness. The validity of the linear relationship between fracture strength and flexural toughness for CMCs is discussed.     

Effects of extrusion temperature on the rheological,dynamic mechanical and tensile properties of kenaf fiber/HDPE composites

The effects of extrusion processing temperature on the rheological, dynamic mechanical analysis and tensile properties of kenaf fiber/high-density polyethylene (HDPE) composites were investigated for low and high processing temperatures. The rheological data showed that the complex viscosity, storage and loss modulus were higher with high processing temperature. Complex viscosities of pure HDPE and 3.4 wt% composite with zero shear viscosity of ⩽2340 Pa s were shown to exhibit Newtonian behavior while composites of 8.5 and 17.5 wt% with zero shear viscosity ⩾30,970 Pa s displayed non-Newtonian behavior. The Han plots revealed the sensitivity of rheological properties with changes in processing temperature. An increase in storage and loss modulus and a decrease in mechanical loss factor were observed for 17.5 wt% composites at high processing temperature and not observed at low processing temperature. Processing at high temperature was found to improve the tensile modulus of composites but displayed diminished properties when processed at low processing temperature especially at high fiber content. At both low and high processing temperatures, the tensile strength and strain of the composite decreased with increased content of the fiber.     

Mechanical and thermal properties of natural fibers reinforced polymer composites: Doum/low density polyethylene

Polymer composite materials with vegetable fibers were an attractive field for many industries and researchers, however, these materials required the issues of compatibility between the fibers and the polymeric matrix. This work evaluates the thermal and mechanical properties of Doum-fibers reinforcing a low density polyethylene (LDPE) composite to follow the effect of adding fibers into polymer matrix. Doum-fibers were Alkali treated to clean the fiber surface and improve the polymer/fibers adhesion. The Doum-fibers were compounded in LDPE matrix at various contents and extruded as continuous strands. An enhance on mechanical properties of composites was found, a gain of 145% compared to neat polymer at 30 wt.% fiber loading in Young’s modulus, a gain of 135% in flexural modulus at 20 wt.% fiber loading and a gain of 97% in torsional modulus at 0.1 Hz. Thermal properties were evaluated and the results show a slight decrease with increase of added Doum.     

Dramatic mechanical and thermal increments of thermoplastic composites by multi-scale synergetic reinforcement: Carbon fiber and graphene nanoplatelet

We report an easy and efficient approach to the development of advanced thermoplastic composites based on multi-scale carbon fiber (CF) and graphene nanoplatelet (GN) reinforcement. Poly (arylene ether nitrile) (PEN)/CF/GN composites, prepared by the twin-screw extrusion, exhibited excellent mechanical properties. For example, the flexural modulus of PEN/CF/GN composites was 18.6 GPa, which is 1.7, 4.5 and 6.4 times larger than those of PEN/CF composites, PEN/GN composites and PEN host, respectively. Based on the SEM image observation, such mechanical enhancements can be attributed to the synergetic effect of micro-scale CF and nano-scale GN in the PEN matrix (decreased matrix-rich and free-volume regions and enhanced interfacial interactions). For 5 wt.% GN-filled PEN/CF/GN composites, the T_d30% of PEN/CF/GN composites was 145 °C and 62.8 °C compared with those of PEN host and PEN/CF composites, respectively. This study has demonstrated that multi-scale CF and GN have an obvious synergetic reinforcing effect on the mechanical properties and thermal stabilities of thermoplastic composites, which provides an easy and effective way to design and improve the properties of composite materials.     

One-step mechanical processing to prepare LSM/ScSZ composite particles for SOFC cathode

Novel one-step mechanical processing was proposed to prepare LSM/ScSZ composite particles from the starting raw powders of LSM (strontium doped lanthanum manganite) and ScSZ (scandium stabilized zirconia) fine powder. In this paper, the properties of composite particles made by this method and the properties of the resultant cells were evaluated. As a result, LSM/ScSZ composite particles were obtained by only 10 min mechanical processing using three kinds of raw powder materials of LSM and ScSZ fine particles without extra heat. The maximum power density of the cell made by the composite particles at 800 °C reached 320 mW/cm². It was higher than that made by commercially available LSM nanosized powder. Besides, the polarization resistance of the cathode made by the composite particles at 800 °C was 0.5 Ω cm² which was lower than that made by using commercially available LSM powder. It suggests that the proposed method is very promising for producing high quality composite particles used for SOFC cathodes by more simple and energy-saving way.     

Effects of SiC interphase by chemical vapor deposition on the properties of C/ZrC composite prepared via precursor infiltration and pyrolysis route

Silicon carbide (SiC) interphase was introduced by chemical vapor deposition (CVD) process to prevent carbon fiber degradation and improve fiber–matrix interface bonding of C/ZrC composite prepared via precursor infiltration and pyrolysis (PIP) process. Moderate thickness of SiC interphase in fiber bundles could increase the density of the composite, but when the thickness of SiC interphase was over 0.5 μm, more close pores formed and the density of the composite decreased. The SiC interphase could protect carbon fiber effectively from carbo-thermal reduction, but could not enhance the mechanical properties of C/ZrC composite. The flexural strength and fracture toughness of C/ZrC composites with 0.05 μm thickness SiC layer were 252 MPa and 13.6 MPa m^1/2, and for those with 0.5 μm thickness SiC layer 240 MPa and 12.8 MPa m^1/2, both close to the value of the composite without SiC interphase (254 MPa and 14.5 MPa m^1/2), while those with 0.7 μm thickness SiC layer were only 191 MPa and 10.8 MPa m^1/2, respectively. Moderate content of SiC interphase could improve the ablation property of C/ZrC composites; however excessive content of SiC interphase would decrease the ablation property.