Damage evolution in unidirectional and cross-ply flax/epoxy laminates subjected to low velocity impact loading

With the resurgence of natural fibers as a viable alternative to synthetic fibers, there is a need to study their mechanical behaviour under different modes of loading. In this research, flax/epoxy composite laminates were manufactured and tested under low velocity impact loading to study the damage development on the laminates and assess their capability for low velocity impact applications. The laminates were tested using a pendulum-type impact apparatus. Two composite laminate configurations were tested: a symmetric unidirectional flax/epoxy laminate with stacking sequence [0]8S and a symmetric cross-ply flax/epoxy laminate with stacking sequence [0/90]4S. The unidirectional laminate exhibited poor and brittle behaviour under impact loading, with an energy penetration threshold of 10 J and an impact toughness of 34 kJ/m2. On the other hand, the cross-ply laminate showed better impact performance, with its energy penetration threshold and impact toughness being three and 2.5 times higher than that of the unidirectional laminate, respectively.