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. 2020 Nov 18;12(11):2733.
doi: 10.3390/polym12112733.

Tensile and Flexural Properties of Silica Nanoparticles Modified Unidirectional Kenaf and Hybrid Glass/Kenaf Epoxy Composites

Napisah Sapiai  1 , Aidah Jumahat  1   2 , Mohammad Jawaid  3 , Mohamad Midani  4 , Anish Khan  5
Affiliations

Tensile and Flexural Properties of Silica Nanoparticles Modified Unidirectional Kenaf and Hybrid Glass/Kenaf Epoxy Composites

Napisah Sapiai et al. Polymers (Basel). .

Abstract

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.

Keywords: flexural properties; glass fiber; kenaf fiber; nanosilica; polymer composites; tensile properties.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Kenaf fiber in yarn form, viewed under scanning electron microscopy (SEM) at magnification of 50×. (b) Glass fiber woven roving (CRW200).
Figure 2
Figure 2
Nanosilica-modified epoxy, viewed under transmission electron microscopy (TEM) at magnifications of 20,500× for (a) 5 wt %, (b) 13 wt % and (c) 25 wt %.
Figure 3
Figure 3
The example of a unidirectional kenaf fiber reinforced polymer (KFRP) composite sample after the curing process.
Figure 4
Figure 4
(a) Tensile properties of nanosilica-modified KFRP composites (5 wt % nanosilica in UD kenaf fiber reinforced polymer composites (5NS-KFRP), 13 wt % nanosilica in UD kenaf fiber reinforced polymer composites (13NS-KFRP) and 25 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer (25NS-KFRP)) compared with KFRP. (b) Example of fractured samples after tensile test.
Figure 5
Figure 5
Morphological structures of the fractured surfaces of (a) KFRP, (b) 5NS-KFRP, (c) 13NS-KFRP and (d) 25NS-KFRP after they were subjected to the tensile test.
Figure 6
Figure 6
(a) Tensile properties of nanosilica-modified 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)) compared with GKFRP. (b) Example of fractured GKFRP samples after tensile test.
Figure 7
Figure 7
(a) Flexural properties of nanosilica-modified KFRP (5NS-KFRP, 13NS-KFRP and 25NS-KFRP) compared with KFRP. (b) Example of fractured KFRP samples after flexural test.
Figure 8
Figure 8
(a) Flexural properties of nanosilica-modified GKFRP (5NS-GKFRP, 13NS-GKFRP and 25NS-GKFRP) compared with GKFRP. (b) Example of fractured GKFRP samples after flexural test.
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