Crushing behavior of crash boxes with hybrid honeycomb–auxetic fillers: Effects of architecture, geometry, and material behaviors

Abstract

Additively manufactured (AM) fillers provide new opportunities to tailor the crushing response and energy absorption of thin-walled metallic crash boxes. This study presents a combined experimental–numerical investigation of hexagonal AA6063-T4 crash boxes filled with architected structures, i.e., honeycomb, auxetic-reentrant, and hybrid honeycomb–auxetic topology. The hybrid configuration, which integrates cells with positive and negative Poisson's ratios, triggers coordinated mechanisms (that enhance folding behavior and collapse control) unattainable via single topology. Quasi-static axial compression tests were conducted to characterize force–displacement curves, deformation mechanisms, energy absorption (EA), and specific energy absorption (SEA). Finite element models developed in the explicit solver LS-DYNA were employed to characterize mechanical responses through parametric studies. The effects of filler architecture, geometry (i.e., cell thickness), and material behaviors were systematically studied using the models. Results show that fillers have minimal influence on initial peak force but significantly improve progressive folding stability and mean crushing force. We found that the filler's material properties have more influence on the crushing response than topology and geometric effects. This work is expected to contribute to revealing the stiffness–mass trade-off and overall crashworthiness performance of the filled crash box.