A shell-inspired double-arrow honeycomb enabling decoupled tuning of dual plateau strain intervals and the second plateau stress

The double-arrow honeycomb (DAH) is a representative auxetic structure characterized by low density and high specific strength. Nevertheless, its nominal stress–strain curve typically exhibits a single stress plateau, which restricts energy absorption efficiency at large deformations and limits adaptability to complex loading conditions. In this study, a shell-inspired double arrow honeycomb (SDAH) with a tunable second plateau stress is proposed. Moreover, by regulating the strain distribution among different deformation stages, the SDAH enables multistage load-bearing behavior and enhanced adaptability under complex loading scenarios. The in-plane crushing behavior and energy absorption performance of the SDAH are systematically investigated, and the optimal geometric parameter combination is identified by taking specific energy absorption (SEA) as the optimization objective. The results show that the SDAH undergoes a two-step deformation mode, characterized by initial buckling followed by progressive contraction. This deformation sequence gives rise to a stable double-plateau stress response. Parametric analyses reveal that the wall thicknesses of the middle and lower inclined struts independently control the second plateau stress level, while the heights of the upper and middle inclined struts predominantly determine the extents of the first and second plateau strain intervals, respectively, enabling decoupled regulation of plateau stresses and strain ranges. The optimized SDAH exhibits a 102.55% increase in SEA compared with the initial design and outperforms conventional honeycomb structures in both plateau stress levels and energy absorption capability. These features, namely adjustable plateau strain intervals and a tunable second plateau stress, provide an effective design strategy for double-plateau mechanical metamaterials and multistage energy-absorbing structures.