Energy Absorption Mechanisms in Layer-to-Layer 3D Woven Composites

3D woven composites provide improved out-of-plane performance over their two-dimensional counterparts. This sort of reinforced through thickness behaviour is desirable in crashworthiness applications where energy absorption can be increased by the composite material's resistance to delamination. The behaviour of these 3D materials in not well understood and fundamental data that can be used to validate and improve material models is not yet sufficiently comprehensive. Here we demonstrate that a modified layer-to-layer type 3D woven architecture can be effectively used in energy absorbing elements to produce repeatable and predictable progressive failure under axial crush conditions. Specific energy absorption (SEA) values in glass and carbon coupons of up to 62J/g and 95J/g respectively are achieved in the quasi-static regime; values up 93J/g to were achieved in the dynamic regime when carbon coupons are tested. Carbon specimens displayed uncharacteristic mixed mode failure with elements of ductile and brittle failure. The addition of a toughening agent showed mixed results in this study, providing quasi-static improvements (+8%) in SEA but significant diminishment in dynamic SEA (-22%). The failure modes present in all cases are explored in depth and the suitability of this material for industry crash applications is investigated.