Quasi-static compression and dynamic crushing behaviors of novel hybrid re-entrant auxetic metamaterials with enhanced energy-absorption

Auxetic metamaterials with excellent mechanical properties have attracted considerable attention for use in various applications, especially for energy-absorption. In this work, novel vertical strut combined auxetic met-amaterials are proposed to enhance their energy-absorption performances. Specifically, a vertical strut and hexagon combined structure (VSHCS) is developed by overlapping the two convex corners of a hexagonal unit with two concave corners of a vertical strut combined structure (VSCS). The finite element model (FEM) is validated by employing the quasi-static compression experiment of 3D-printed VSCS honeycomb samples. The quasi-static compression and dynamic crushing behaviors of VSHCS are investigated through simulation and theoretical analysis. To clarify the deformation mechanisms, the deformation modes, structure effect, stress-strain curves, and energy-absorption ability are comprehensively examined under different velocities. The VSHCS exhibits a hierarchical deformation mode, corresponding to two-stage stress-strain curves with double-plateau stresses. The results indicate that the VSHCS possesses higher mean plateau stress and specific energy-absorption (SEA) than re-entrant, VSCS, and non-auxetic hexagonal structures. The enhancement can be attributed to the novel structural design, unique two-order deformation modes, and plastic hinge dissipation.