Balanced electrical, thermal and mechanical properties of epoxy composites filled with chemically reduced graphene oxide and rubber nanoparticles

Epoxy composites filled with 2D chemically reduced graphene oxide (CRGO) sheets and preformed 3D powdered rubber (PR) nanoparticles were fabricated to investigate the effect of hybrid nanofillers on the electrical, thermal and mechanical properties as well as fracture toughness. As expected, the presence of CRGO sheets endows epoxy with electrical conductivity and enhances its thermal properties, stiffness and toughness; while the addition of PR results in significant reductions in thermal stability and stiffness, but produces dramatic improvements in fracture toughness. Compared with the binary composites, the ternary composites containing hybrid 2D CRGO and 3D PR fillers provide a good balance among electrical conductivity, thermal stability, glass transition temperature, stiffness, strength and fracture toughness, which cannot be achieved by independent single-phase fillers. Based on the morphologies of the fracture surfaces and damage zones around the crack tip, various toughening mechanisms such as crack-bridging by GO sheets, sheet/sheet delamination and sheet/matrix debonding, rubber cavitation and matrix shear banding, were identified and correlated with the fracture toughness of the hybrid composites studied. Results obtained disclosed suppression of deformation and/or cavitation of the PR nanoparticles after the incorporation of CRGO, which explained the moderate improvement in fracture toughness of the hybrid composites.