Fracture Toughness of Carbon-Graphene/Epoxy Hybrid Nanocomposites

Plain strain fracture toughness (KIC) of graphene-epoxy (G-Ep) and carbon-graphene-epoxy (C-G-Ep) hybrid nanocomposites have been evaluated using single-edge-notch bending (SENB) specimens. The effects of graphene concentrations on KIC have been examined. G-Ep nanocomposites were prepared using a combination of mechanical mixing, magnetic stirring, sonication and high shear mixing. The hybrid nanocomposites (C-G-Ep) were processed using manual layup techniques and vacuum assistance during curing process. The dispersion morphology and fracture surface of all specimens were evaluated using scanning electron microscopy (SEM) analysis. The results show significant improvement in fracture toughness of both G-Ep and C-G-Ep nanocomposites in comparison to neat epoxy and conventional carbon-epoxy composites. The SEM images show evidence of slight graphene agglomeration, but reasonably effective graphene dispersion is observed throughout epoxy matrix. The toughening mechanisms such as crack deflection, crack pinning, debonding, fiber bridging and pull-out are possibly contributed to enhancing fracture toughness in G-Ep and C-G-Ep nanocomposites.