Numerical investigation of a star-shaped auxetic structure under different impact velocities

Abstract

Auxetic structures are a class of mechanical metamaterials characterized by a negative Poisson’s ratio and enhanced energy absorption capabilities under impact loading. In this study, the influence of impact velocity on the mechanical response of a star-shaped auxetic (SSA) structure is investigated using the finite element method implemented in ANSYS Workbench LS-DYNA. A cellular structure composed of a 6×6 arrangement of SSA unit cells was subjected to compressive impact loading at velocities of 1 m/s, 10 m/s, and 100 m/s. The deformation mechanisms, force displacement response, kinetic and internal energy histories, and energy absorption characteristics were analyzed. The results show that the deformation patterns obtained at 1 m/s and 10 m/s are nearly identical, exhibiting the characteristic elastic, plateau, and densification stages of cellular structures. Furthermore, the quasi-static condition was satisfied for these loading velocities, as the kinetic energy remained significantly lower than the internal energy throughout the simulations. In contrast, the response at 100 m/s was dominated by dynamic effects, resulting in non-uniform deformation, increased impact forces, and significantly higher energy absorption. The findings provide insight into the influence of impact velocity on the mechanical behavior of star-shaped auxetic structures and may contribute to their application in energy absorbing systems.