The importance of translaminar fracture toughness for the penetration impact behaviour of woven carbon/glass hybrid composites

The impact resistance of fibre-reinforced composites is vital in many applications, and can be improved by exploiting synergies in fibre-hybridisation. These effects are however not sufficiently well understood in the literature. Penetration impact tests were hence performed on carbon/glass hybrids, and the results were linked to the flexural behaviour and translaminar fracture toughness. The results revealed large synergetic effects of up to 40% compared to the linear rule-of-mixtures. The results are also the first to reveal that creating a translaminar fracture surface can strongly contribute to the energy absorbed during penetration impact: 56% for an all-carbon fibre composite and 13% for an all-glass fibre composite. These results prove that strategies for maximising the translaminar fracture toughness can also be exploited to maximise the penetration impact resistance of fibre-hybrids. In carbon fibre composites in particular, ply blocking, using larger yarns and introducing micro-cuts should therefore increase the penetration impact resistance.