Improvement in the Crushing Behavior of Auxetic Tubular Structures through Rotational Kinematics-driven Stiffness Modulation

This study focuses on design improvements for auxetic tubular structures to enhance stiffness and energy absorption under sudden shock loads. Auxetic tubes have good energy absorption but face challenges of low stiffness and instability that limit their structural applications. Conventional reinforcement using foams or struts improves stiffness but compromises the lightweight advantage by adding extra mass. To overcome this, two geometric strategies are proposed for elliptical-hole auxetic tubes. First, the major axis of the hole is optimized to reduce rigid-strut rotation and improve rigidity. Second, solid ribs are added inside the hole to prevent early wall collapse under oblique loading. The approach is validated using additively manufactured specimens and FE simulations. Results show that auxetic contraction is governed by strut rotation, causing lateral shrinkage and stress redistribution during deformation. Geometric modifications increase yield strength and peak load by up to 500% in axial compression and improve energy absorption (by 72%) and plastic dissipation (by 87%) at 20[Formula: see text]mm compression. Under inclined loading, rib-reinforced tubes achieve higher stiffness and peak strength, though they later fail due to excessive shear. The findings provide useful guidelines for designing impact-resistant structures.