Fracture toughness and failure mechanism of graphene based epoxy composites

The present study investigates the effect of addition of three different types on carbon nano-fillers on fracture toughness (KIC) and failure mechanism of epoxy based polymer nano-composites. The carbon nano-fillers were dispersed in the epoxy matrix using a three-roll mill and the three nano-fillers used for this experiment were (i) thermally reduced graphene oxide (TRGO); (ii) graphite nano-platelets (GNP); and (iii) multi-wall carbon nano-tubes (MWCNT). The fracture toughness was measured as a function of weight percentage of the filler using single edge notch three-point-bending tests. The toughening effect of TRGO was most significant resulting in 40% increase in KIC for 0.5 wt% of filler. On the other hand, the enhancements in toughness were 25% for GNP/epoxy and 8% for MWCNT/epoxy. Investigations on fracture surface revealed that crack pinning or bi-furcation by TRGO and crack face separation initiated from TRGO contributed to enhance the fracture toughness. Based on the observations, a schematic explaining the crack propagation in graphene/epoxy composite and the interaction of crack front with graphene particles was proposed.