Dynamic crushing response of novel re-entrant circular auxetic honeycombs: Numerical simulation and theoretical analysis

Abstract

Auxetic honeycombs have a variety of potential applications in aerospace engineering due to their excellent mechanical and multidisciplinary properties. A novel class of auxetic honeycombs have been invented recently named as Re-entrant circular (REC) honeycombs. The REC honeycombs can be obtained by replacing the sloped cell walls of the well-known re-entrant (RE) unit honeycombs with double circular arc walls to dissipate more energy. This study aims to investigate the in-plane dynamic crushing responses of the novel REC honeycombs through numerical simulations and theoretical analyses. LS-DYNA based numerical simulations revealed the “X” and “I” combined deformation mode of the REC honeycomb under low velocity crushing, and the “I” mode under high velocity loading. The geometric parameters of unit cell and the crushing velocity were both found to have great effects on the proximal end crushing stress of the REC honeycomb. It was also shown that the REC honeycomb presents obvious negative Poisson's ratio (NPR) effect, attributed to its re-entrant characteristic. Based on the meso-scale deformation mechanisms of the representative unit cell, theoretical models have been established to predict the plateau stress of the REC honeycomb under different crushing velocities. The theoretical predictions were in good agreement with the numerical simulation results. Moreover, the dynamic sensitivity index and the deformation mode map of the REC honeycomb were obtained to evaluate its dynamic response sensitivity to the loading velocity. Finally, the in-plane crushing characteristics of the REC and the RE honeycombs were compared. The REC honeycomb was found to show higher specific energy absorption (SEA) and penetration resistance than its RE counterpart, due to the more plastic hinges formed during the dynamic crushing process.