Mechanisms of failure in the static indentation resistance of auxetic carbon fibre laminates

Carbon fibre laminates were produced with matched through-the-thickness modulus, but with negative (auxetic), positive and near zero through-the-thickness Poisson's ratios. These were indented with noses of diameter 2, 12.7 and 20 mm. Enhancements in indentation resistance were seen for the auxetic laminates with smaller, more localized damage areas for the two larger diameter indentors where delamination was the dominant failure mechanism. Little difference was seen in mechanical properties for the 2 mm diameter indentor where fibre breakage was the dominant failure mechanism, though smaller damage areas are still obtained in this case due to delamination growth suppression.