Impact resistance of foam-filled hybrid-chiral honeycomb beam under localized impulse loading

•Comparative impact tests of novel FHCB were performed.•Foam filling enhances impact resistance.•Gradient design can optimize foam energy absorption. Auxetic structures have attracted a lot of attention as they can meet the requirements of impact resistance and lightweight performance of protective structures in aerospace and defense industries. To enhance the impact resistance and improve the capacity of energy absorption of auxetic structures, foam-filled hybrid-chiral honeycomb beams (FHCB) were designed and fabricated through SLM (Selective laser melting) printing method and foaming method. The localized impulse loading was generated through the impact from foam projectile, accelerated by light gas gun. The dynamic responses of EHCB (empty hybrid-chiral honeycomb beam) and FHCB were compared. In the experimental results, FHCB showed enhanced impact resistance and higher SEA (specific energy absorption) value than EHCB. A validate finite element model was used to study the influence of cell-wall thickness on the impact resistance of EHCB and FHCB. Results indicated that by changing the cell-wall thickness, the potential energy absorption capacity of the filled foam can be fully utilized. Furthermore, the impact resistance of FHCB can be effectively improved by using a gradient cell-wall thickness arrangement. This study can provide reference for the optimal design of blast mitigation and impact resistant structures.