Insight into the negative Poisson's ratio effect of metallic auxetic reentrant honeycomb under dynamic compression

This paper presented a detailed study of the negative Poisson's ratio (NPR) effect on shrinkage deformation and crushing stress of metallic auxetic reentrant honeycomb under low, medium and high-velocity compressions. Instead of the traditional calculating method for the crushing stress of auxetic honeycomb, the new theoretical formula considering the NPR effect was proposed. The theoretical and finite element (FE) results showed that the crushing stress of reentrant honeycomb had been underestimated according to the traditional nominal stress-strain curve. Not only had that, but also the theoretical results showed that the NPR effect could enhance the inertial effect during dynamic compression. Subsequently, under the medium and high-velocity compressions, the dynamic deformations of reentrant honeycomb were obviously different from that under low-velocity compression and those of metallic cellular materials with positive Poisson's ratio (such as Al foam and traditional hexagonal honeycomb) under medium or high-velocity compressions. In view of these differences, a new shrinkage deformation mechanism of reentrant honeycomb was proposed and a characterization parameter in contrast to the Poisson's ratio was presented to describe its dynamic shrinkage deformation capacity.