Quasi-static and dynamic compression behaviors of a novel auxetic structure

Auxetic materials exhibit interesting mechanical properties. In this work, a novel auxetic unit cell was proposed with an aim to improve the strength and energy absorption of the auxetic structure constituting these unit cells. In the developed unit cell, the vertical member of a conventional re-entrant unit cell was replaced by a diamond. The corresponding structure was named re-entrant diamond structure. Specimens were fabricated using Multi-Jet Fusion (MJF) technique and experimentally tested to investigate their mechanical performance under uniaxial quasi-static and dynamic compression. Finite element model was also developed in ABAQUS/Explicit and validated using experimental results. Moreover, in order to improve stiffness of the diamonds, a cross-link member was introduced in each diamond. Subsequently, a parametric study was conducted to study the influence of diamond angle (theta(2)) and length ratio (L-2/L-1) on the deformation mode, stress-strain curve, Poisson's ratio, and energy absorption of the re-entrant diamond structures with and without cross-links. This study revealed that larger diamond angle (theta(2)) and smaller length ratio (L-2/L-1) are desirable for high strength. Furthermore, the re-entrant diamond structures with and without cross-links were compared with the conventional re-entrant and hexagonal honeycombs in terms of strength and energy absorption.