High volume-fraction silk fabric reinforcements can improve the key mechanical properties of epoxy resin composites

Abstract

Silk fabric reinforced epoxy composites (SFRPs) were prepared by simple hot-press and vacuum treatment, to achieve a maximum reinforcement fraction of 70 vol.%-silk. Mechanical behaviour, specifically tensile, flexural, interlaminar shear, impact, dynamic and thermal properties of the SFRPs, were investigated. It was shown that reinforcement by silk fabric can greatly enhance the mechanical performance of SFRPs. In particular, the tensile modulus and breaking energy of 70 vol.%-silk SFRP were 145% and 467% higher than the pristine epoxy resin. Moreover, the flexural modulus, ultimate strength and breaking energy were also markedly increased for SFRPs. The flexural strength increased linearly with increasing silk volume fraction from 30 to 60 vol.% but diminished slightly at 70 vol.%. Additionally, interlaminar shear results showed that the silk and the matrix epoxy resin had better adhesion properties than plain woven flax fibre. Of most significance is that the impact strength reached a maximum of ~71 kJ/m 2 for the 60 vol.%-silk SFRP, which demonstrates the potential of silk reinforcements in impact-resistant composites for applications such as wind turbine blades. Our study may shed light on improving the strength and toughness of engineering composites by incorporating high volume fractions of natural fibres.

A Transparent, Skin‐Inspired Composite Film with Outstanding Tear Resistance Based on Flat Silk Cocoon

“…Specifically, the tensile strength and modulus of the composite could be increased by 300% and 612%, respectively. Compared with previously reported studies based on silk fibers, [29,37,44,46,49] our research achieved the most significant reinforcing effect with the lowest fiber content of 1 wt% (Figure 2c,d).…”

“…[19,20] Among them, the silk fiber is widely used as the reinforcing phase because of its low density, outstanding mechanical advantage, and sustainability. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Besides its high strength and toughness, another intriguing but less studied mechanical property of skin is its remarkable tear resistance, resulting from the rearrangement of skin collagen fibers in the tensile-loading direction. [39] In this work, we show that this stress redistribution mechanism can be utilized to construct fiber-reinforced supporting substrates with excellent tear resistance.…”

“…[38,43] The mechanical reinforcing effect of the silk fibers has been verified in many studies, including both natural and synthetic polymers, such as regenerated silk protein, [44,45] gelatin, [46] polylactic acid, [47,48] polycaprolactone, [49] polypropylene, [50] and some thermosets. [29,37,51,52] In this study, we selected a flat silk cocoon and a flexible matrix to construct a transparent composite, focusing on its tear resistance. On the material property side, different from the conventional silk-based composites where strength and toughness were the main focus, we applied silk fiber networks in an attempt to improve the tear resistance, which is critically important for the emerging flexible electronic devices but has been rarely reported.…”

“…[48] With increasing loading force, the polymer matrix begins to damage, followed by fiber rupture, and finally, the failure of the whole material. Unlike the commonly used stiff and brittle polymer matrices with relatively low fracture strain, [37,51] the flexible resin in this study could resist a larger deformation. As mentioned above, the tear resistance of skin originates from the rearrangement of the collagen fibrils during tensile loading.…”

“…As mentioned above, the tear resistance of skin originates from the rearrangement of the collagen fibrils during tensile loading. [39] Similarly, the loosely arranged fibers in the flat silk cocoon can also better disperse the loading stress, and [44], [46], [49], and [29,37], respectively. therefore inhibit fast crack growth at the notch tip.…”