Mechanical and curing behavior of epoxy composites reinforced with polystyrene-graphene oxide (PS-GO) core-shell particles

Abstract

Epoxy is a high performance yet brittle thermosetting resin. To deem epoxy fit for aircraft applications, its mechanical properties, especially fracture toughness, must be improved. In this work, epoxy resin was reinforced with 0.1, 0.5 and 1.0 wt.% polystyrene-graphene oxide (PS-GO) core-shell nano-particles to enhance its fracture toughness. Styrene monomer (oil phase) was polymerized in situ using aqueous GO dispersion (water phase) to obtain PS-GO core-shell nano-particles, which appeared as wrinkled spheres under the electron microscope, confirming that the PS particles were wrapped by the GO sheets. The effect of PS-GO and GO on the curing of epoxy resin was studied and compared. The fracture tests of the cured composites revealed 28% and 26% improvements in the fracture toughness (KIC) and fracture energy (GIC) values for the 1.0 wt.% PS-GO epoxy composite, respectively. Toughening in the composites majorly occurred due to filler debonding accompanied by void formation, crack deflection and blunting and strong filler matrix interaction. The compressive strength and strain at failure improved by 25% and 52% for the 0.1 wt.% PS-GO epoxy composite, respectively. Dynamic mechanical analysis (DMA) revealed that epoxy's stiffness improved slightly after PS-GO addition while the Tg remained almost constant. Finally, the FTIR analysis of cured epoxy composites in agreement with the curing studies ascertained that, irrespective of the filler loading, the amount of hardener used was adequate to achieve complete curing of the epoxy.