Honeycomb integrated re-entrant auxetic lattice: A topology-driven energy absorption enhancement

Auxetic structures are well known for their enhanced mechanical properties, yet conventional re-entrant (CR) lattices offer limited scope for further improvement without added mass. This study proposes the Honeycomb Integrated Re-entrant (HIR) structure, formed by integrating half-split honeycomb ribs into a CR lattice, motivated by potential applications in stroke-constrained energy-absorbing systems. The mechanical response of HIR and CR, modelled in LS-DYNA with the lattice assigned the properties of aluminum AL6060-T4, was investigated under quasi-static, dynamic, and oblique compression. HIR increases specific energy absorption (SEA) at densification strain by 142% and at mid-range strain by 53%, while plateau stress, initial stress, and effective Young’s modulus increase by 124%, 147%, and 48%, respectively. These gains arise from a transitional region in which the integrated ribs engage and lock against the re-entrant wall. Further benchmarking was conducted against the underlying honeycomb and CR baseline. A parametric study shows rib thickness governs stiffness and mass contribution, while rib spacing and length control the onset and progression of the transitional plateau. Under dynamic compression, HIR sustains SEA improvements of 118% and 50% over CR at 20 and 40 m/s. Under oblique impact at 5°, 10°, and 15°, HIR consistently outperforms CR and reaches complete densification within a fixed stroke across all tested conditions, whereas CR often fails to densify at higher angles, a critical advantage for stroke-limited buffer applications. Crashworthiness indices, Peak, Mean, and Crushing Force Efficiency (PCF, MCF, CFE), further show HIR achieving substantially higher CFE than CR under oblique loading, indicating more efficient force transmission despite a higher peak load.