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.

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.

Nowadays, continuous natural fibre reinforced polymer nanocomposites have attracted substantial attention among researchers due to various benefits possesses by the natural fibres. Kenaf fibre has become one of the high potential candidates to replace synthetic fibres in polymer composite. Kenaf fibre exhibits good strength and modulus properties, low density, non-abrasive during processing and biodegradable. This study is aimed to evaluate the effect of nanosilica on longitudinal and transverse tensile properties of unidirectional (UD) kenaf composite. The UD kenaf composite samples were prepared based on three different nanosilica content; i.e. 5, 13 and 25 wt.%. The samples were prepared using filament winding and vacuum bagging techniques. The 0o and 90o tensile tests were conducted in accordance to ASTM standard D3039 in order to obtain longitudinal and transverse tensile properties of unmodified and nanosilica-modified kenaf composites. The fracture surfaces of the specimens were observed using scanning electron microscope in order to identify fracture mechanisms involved during tension. The results showed that the addition of nanosilica reduced longitudinal tensile Young’s modulus, strength and failure strain of the kenaf composite. SEM micrographs revealed incomplete resin wetting and  fibre pull-out mechanism at high nanosilica content that contributed to premature failure of the kenaf composites.  However, it was found that the addition of nanosilica improved transverse tensile properties of kenaf composites since these properties were mostly governed by the properties of the matrix. A stiffer matrix improved the transverse tensile modulus and strength of kenaf composites.

A homogeneous dispersion of nanofillers in epoxy polymer still remains as one of the biggest challenges in advanced nanocomposites research. In this paper, the effects of nanoclay content (1wt%, 3wt%, 5wt%) and nanosilica content (5wt%, 13wt%, 25wt%) on tensile and compressive properties of epoxy polymer were studied. The nanoclay and nanosilica were dispersed in epoxy using the three-roll milling and mechanical stirrer machine, respectively.  The compressive and tensile properties were evaluated using Instron universal tester machine according to BS standards. The Transmission Electron Microscopy (TEM) was used to evaluate the degree of dispersion of nanofillers in epoxy. The results showed that the intercalated structure of clay/epoxy nanocomposites gave detrimental effect on the tensile and compressive strength of the polymer. Whereas, the results of nanosilica/epoxy nanocomposite system showed that a well-dispersed nanosilica contributes to the improvement of tensile and compressive strength and Young’s modulus of the polymer.

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