Investigation of failure modes in impact damaged steered fibre laminates

Continuous Tow Shearing (CTS) is a novel form of fibre steering technology which can produce optimised laminated composite structures with improved buckling capacity and lower mass. The distribution of fibre orientation and mass across the width of these laminates that results from optimisation produces regions of high stress near supports. These regions, which are vital to the integrity of the CTS laminate, are at risk of reduction in compressive strength as a consequence of Barely Visible Impact Damage (BVID). In this paper straight fibre coupons, representing the high stiffness regions of the CTS laminate, are subject to compression testing to shed light on the intra-ply failure seen in the compression after impact testing of CTS laminates. A Tsai-Wu first ply failure analysis predicts experimental failure stress to within 14% for an undamaged coupon. This increases to 41% for damaged coupons where damage has seeded intra-ply cracking.