Interlaminar Fracture Toughness of Carbon Fibre-Reinforced Polymer Laminates With Nano- and Micro-Fillers

Vapour growth carbon nanofibres (CNF) and lead zirconate titanate (PZT) piezoelectric particles were added in the matrix of carbon fibre-reinforced polymer laminates. The fracture toughness of the modified composites was measured under mode I and mode II loading and compared with plain epoxy carbon fibre-reinforced composites. The mode I fracture toughness of the composites improved with the incorporation of the carbon nanofibres and deteriorated with the incorporation of PZT piezoelectric particles. When both fillers were added in the composite matrix, the mode I fracture toughness improved but to a lesser extend. The mode II fracture toughness of the modified composites was improved in all three cases. The aforementioned behaviour was attributed to competing fracture mechanisms instigated by the different fillers, and backed by fractographic evidence from the failed composite coupons; during the tests, the acoustic emission activity of the coupons was monitored and classified in three major energy absorbing mechanisms which were attributed to the failure of distinct composite phases.