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The effect of nanosilica on compressive properties of an Epikote 828 epoxy at room temperature was studied. A 40 wt% nanosilica/epoxy masterbatch (nanopox F400) was used to prepare a series of epoxy based nanocomposites with 5-25 wt% nanosilica content. Static uniaxial compression tests were conducted on cubic and cylindrical specimens to study the compressive stress-strain response, failure mechanisms and damage characteristics of the pure and nanomodified epoxy. It was found that the compressive stiffness and strength were improved with increasing nanosilica content without significant reduction in failure strain.The presence of nanosilica improved ductility and promoted higher plastic hardening behaviour after yielding in comparison with the unmodified resin system. This result suggested that nanoparticles introduced additional mechanisms of energy absorption to enhance the compressive properties without reducing the deformation to failure.

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This paper investigates the influence of silica nanoparticles on the mechanical properties of a unidirectional (UD) kenaf fiber reinforced polymer (KFRP) and hybrid woven glass/UD kenaf fiber reinforced polymer (GKFRP) composites. In this study, three different nanosilica loadings, i.e., 5, 13 and 25 wt %, and untreated kenaf fiber yarns were used. The untreated long kenaf fiber yarn was wound onto metal frames to produce UD kenaf dry mat layers. The silane-surface-treated nanosilica was initially dispersed into epoxy resin using a high-vacuum mechanical stirrer before being incorporated into the UD untreated kenaf and hybrid woven glass/UD kenaf fiber layers. Eight different composite systems were made, namely KFRP, 5 wt % nanosilica in UD kenaf fiber reinforced polymer composites (5NS-KFRP), 13% nanosilica in UD kenaf fiber reinforced polymer composites (13NS-KFRP), 25 wt % nanosilica in UD kenaf fiber reinforced polymer composites (25NS-KFRP), GKFRP, 5 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (5NS-GKFRP), 13 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (13NS-GKFRP) and 25 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (25NS-GKFRP). All composite systems were tested in tension and bending in accordance with ASTM standards D3039 and D7264, respectively. Based on the results, it was found that the incorporation of homogeneously dispersed nanosilica significantly improved the tensile and flexural properties of KFRP and hybrid GKFRP composites even at the highest loading of 25 wt % nanosilica. Based on the scanning electron microscopy (SEM) examination of the fractured surfaces, it is suggested that the silane-treated nanosilica exhibits good interactions with epoxy and the kenaf and glass fibers. Therefore, the presence of nanosilica in an epoxy polymer contributes to a stiffer matrix that, effectively, enhances the capability of transferring a load to the fibers. Thus, this supports greater loads and improves the mechanical properties of the kenaf and hybrid composites.

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The usage of nanofillers reinforcement in polymer matrix has been recently explored for natural fibres composites to improve mechanical properties of polymers. In this study, 0.5 wt% , 0.75 wt% and 1.0 wt% of Carbon nanotubes (CNTs) were added into epoxy resin. The CNTs-modified epoxy resins were then used to produce kenaf/glass hybrid composites. The laminates were prepared using dry filament winding machine and hand lay up method. All samples were tested according to the ASTM Standards, i.e. D790 and D3039  for flexural properties and tensile properties, respectively. Experimental results obtained showed that the flexural strength decreases with increasing CNTs content, while the flexural modulus increases with increasing CNTs content. The tensile strength was found to decrease with the addition of 0.5 and 0.75 wt% CNTs but increase with the addition of 1.0 wt% CNTs. Hybridization with glass also showed an improvement in flexural and tensile properties of kenaf composite.