Simulation and Analysis of Stiffened Auxetic Honeycombs Having Enhanced High Impact Velocity Response

This study investigates the ballistic performance of two aluminum‐based re‐entrant auxetic honeycomb configurations: classic and stiffened structures. Finite element analysis was conducted using ANSYS Explicit Dynamics to evaluate the in‐plane response under high‐velocity impact conditions. The effects of key geometric parameters, including horizontal cell wall length, wall thickness, and cell wall angle, were examined. The numerical model was validated against published data and showed good agreement. Simulations were performed for impacts in two orthogonal directions, revealing that the X ‐direction provides higher ballistic resistance. A total of 64 configurations were analyzed under a bullet impact velocity of 450 m/s and rotational speed of 11,771 rad/s. Results showed that increasing horizontal wall thickness significantly enhances ballistic resistance and energy absorption, while reducing wall length further improves impact performance. Cell wall angle exhibited minimal influence on ballistic time. Additionally, incorporating vertical and horizontal stiffening ribs significantly enhanced the ballistic performance, increasing the energy absorption efficiency by up to 119.45% and the projectile velocity reduction by up to 281.36% relative to the baseline specimen, that is, weakest unstiffened structure. The enhanced performance is attributed to structural reinforcement and auxetic‐induced densification near the impact zone, which increases local resistance and energy dissipation.