In-Plane Dynamic Crushing Behaviors of a Vertex-Based Hierarchical Auxetic Honeycomb

Auxetic metamaterials, which exhibit the negative Poisson’s ratio (NPR) effect, have found wide applications in many engineering fields. However, their high porosity inevitably weakens their bearing capacity and impact resistance. To improve the energy absorption efficiency of auxetic honeycombs, a novel vertex-based hierarchical star-shaped honeycomb (VSH) is designed by replacing each vertex in the classical star-shaped honeycomb (SSH) with a newly added self-similar sub-cell. An analytical model is built to investigate the Young’s modulus of VSH, which shows good agreement with experimental results and numerical simulations. The in-plane dynamic crushing behaviors of VSH at three different crushing velocities are investigated, and empirical formulas for the densification strain and plateau stress are deduced. Numerical results reveal more stable deformation modes for VSH, attributed to the addition of self-similar star-shaped sub-cells. Moreover, compared with SSH under the same relative densities, VSH exhibits better specific energy absorption and higher plateau stresses. Therefore, VSH is verified to be a better candidate for energy absorption while maintaining the auxetic effect. This study is expected to provide a new design strategy for auxetic honeycombs.