Graphene/epoxy interleaves for delamination toughening and monitoring of crack damage in carbon fibre/epoxy composite laminates

Functionalized graphene sheets were fabricated by a simple thermal reduction method in air at 700 °C and used to prepare graphene/epoxy (G/E) composites. The incorporation of 1.0 wt% of graphene into epoxy was found to significantly improve the matrix fracture energy by ∼150% and reduce the thermal expansion coefficient by ∼30%. When these partially cured G/E composites were used as interleaves in carbon fiber/epoxy (CF/E) composites and co-cured, a remarkable 140% increase in mode I interlaminar fracture energy was achieved. Detailed toughening mechanisms of the graphene sheets in both G/E and CF/E composites were studied. Moreover, the damage sensing capacity of the graphene interleaved CF/E composites with a simple electrical response method was demonstrated, where the electrical resistance change increased almost linearly with crack increment.