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

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, was 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 kJm⁻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.