Minimizing the in-plane damage of Z-pinned composite laminates via a pre-hole pin insertion process

The present work focuses on an experimental investigation on the efficiency of the Z-pin pre-hole insertion technique in minimizing the in-plane damage while improving the delamination resistance of quasi-isotropic carbon fibre/epoxy laminates. The results indicate that the Z-pin pre-hole insertion causes much less crimped and/or broken fibres leading to a minimal strength reduction of 3.50% in tension and 4.80% in compression respectively for composite laminates containing 1 vol.% of carbon Z-pins. The Mode-I fracture toughnesses of the composites reinforced with ~1 vol.% carbon and Kevlar Z-pins are about 12 times higher than that of the control samples, suggesting an efficient crack arrest mechanism by the implanted pins. The substantially enhanced through-thickness properties together with the minimal reduction in in-plane performance warrant the pre-hole insertion technique as a practical method in mitigating the delamination in fibre reinforced laminates.