Static and dynamic response of shape memory alloy improved auxetic honeycomb structures

Protective structures are widely employed in aerospace, marine, automotive, and biomedical systems. Honeycomb architectures are favored for their combination of high specific energy absorption and mechanical robustness, yet structures made from conventional materials generally deform irreversibly after impact. Leveraging the recoverability of NiTi shape memory alloys and the high strength-to-weight benefits of auxetic (negative Poisson’s ratio) honeycombs, we design and fabricate two improved variants derived from canonical concave and double-arrow configurations. Quasi-static compression, cyclic loading–unloading, and drop-hammer impact tests are conducted to evaluate energy-absorption performance and deformation modes. Compared with their baselines, the improved lattices exhibit enhanced quasi-static energy absorption and more stable deformation evolution. Under drop-hammer impact, ICHS shows reduced peak displacement and a more compact collapse mode, although with a tradeoff in conventional SEA, whereas IDHS exhibits a slight SEA improvement over DHS. Finite-element predictions are in satisfactory agreement with the experimental observations. The lattices also demonstrate thermally assisted shape recovery and short-term repeatable recoverable functionality over three compression cycles. These findings provide experimental support and design guidance for lightweight, reusable protective systems.