Spray deposition of graphene nano-platelets for modifying interleaves in carbon fibre reinforced polymer laminates

Abstract This study describes a novel and versatile method of incorporating graphene nano-platelets (GNP) into composite laminates to investigate its effect on mode I and mode II interlaminar fracture toughness (ILFT). Non-woven thermoplastic veil interleaves have been modified by spray deposition with a GNP dispersion to give either a continuous or strip-patterned distribution. The coated interleaves were used to modify the interlaminar region of carbon fibre reinforced polymer (CFRP) laminates. The fracture surfaces were characterised by scanning electron and optical microscopy. The continuous GNP distribution in mode I prevented the formation of carbon fibre bridging, resulting in similar initiation and propagation values. In mode II, the increased thickness of the interlaminar region, coupled with the uneven fracture surface showed the highest increase in the mode II ILFT for the continuous GNP distribution. The strip-patterned GNP distribution showed reduced carbon fibre bridging compared to the baseline CFRP and thermoplastic interleave laminates. This may be due to small scale fibre bridging between the deposited GNP-strips which also lead to peaks and troughs in the load-displacement response. In mode II, it is suggested that the deposited GNP-strips were sufficiently tough to re-direct the propagating crack from the modified interlaminar region to the adjacent ply.