Damage monitoring in hybrid composites under projectile impact loading

This study investigates the high-velocity impact mechanics in correlation with piezo-resistance damage sensing characteristics of glass/carbon hybrid composites under projectile impact loading. Inter-ply and Intra-ply hybrid composites consisting of different ply orientations, stacking sequences, and liquid metal (LM) compositions (1 and 2 wt%) are considered for this study. An in-house one-stage gas gun setup is used to conduct projectile impact loading experiments. A novel circumferential four probes electrical resistivity method is employed to investigate the damage-sensing capability of hybrid composites. Two different projectile shapes (cone end projectile and stepped cone end projectile) are considered and investigated their effect on the composites’ ballistic limit, impact energy absorption, damage area, and piezo-resistance response. Projectile shape significantly influences ballistic limit and energy absorption, whereas a stepped cone end projectile demonstrates higher amount of energy absorption of about 42% and peak piezo-resistance change of around 60% compared to cone end projectile. The addition of LM improved the ballistic limit by about 20% and the amount of energy absorption by around 50% but reduced damage-sensing sensitivity due to improved electrical conductivity with its presence. Moreover, the intra-ply hybrid composites exhibited lower ballistic limits owing to weaker fiber strength, while inter-ply hybrids showed better energy absorption capabilities, resulting in higher ballistic limits. Thermal imaging technique is adopted in post-mortem analysis of the damaged area, and it revealed delamination inside the intra-ply hybrid composites.