Repeated impact behaviour of inter-ply hybrid aramid/S2-glass epoxy laminates

This paper presents an experimental study on the repeated low-velocity impact behaviour of inter-ply hybrid composites of aramid/S2-glass/epoxy. The impacts were performed using a drop-tower apparatus following ASTM D7136 Standard. Two energies (19 and 37 J) were chosen for the study with up to twenty and five repeated impacts, respectively. A double exponential empirical model is proposed to describe the degradation due to the repeated impacts, considering the hybridization ratio. The impact response and progressive damage are presented and discussed for different laminates: single-fibre, and asymmetric or symmetric hybrids. The results show that hybridization may lead to the mitigation of repeated impact degradation. For asymmetric hybrids, impact on S2-glass showed a combination of higher impact stiffness and lower degradation rate, outperforming single-fibre laminates.