Research on Design Routes of Steel/ VT ‐ CFRP Hybrid Laminates Under Out‐of‐Plane Crashworthiness Constraint

Hybrid metal/fiber‐reinforced polymer (FRP) structures have emerged as an effective solution to balance the safety and lightweight design of battery pack protective structures, and the variable‐thickness FRP (VT‐FRP) offers more potentials. However, the damage and energy absorption behaviors of variable‐thickness carbon‐fiber‐reinforced polymer (VT‐CFRP) under out‐of‐plane impact attract limited attention, and the influence of transition zone parameters on impact damage evolution also lacks systematic research, which leads to implementable workflows for metal/VT‐CFRP hybrid structures targeting lightweight and low‐cost design under performance constraints to be still absent. Therefore, this study investigated the out‐of‐plane impact resistance of steel/VT‐CFRP hybrid laminates. First, a numerical model of the steel/CFRP hybrid laminate was constructed and validated. Next, the influence of design parameters on the crashworthiness and energy absorption mechanisms was explored, followed by a sensitivity analysis. The results indicate that increasing the metal thickness t and the number of plies in the thick region n can significantly enhance the impact resistance of the hybrid laminate and their respective energy absorption proportions. The stacking sequence θ not only exerts a certain influence on crashworthiness indicators and energy absorptions but also significantly affects the distribution and propagation of impact damage. Finally, two implementable design routes for the steel/VT‐CFRP hybrid laminate were proposed.