Energy absorption characteristic of auxetic metamaterials honeycombs and lattices with negative thermal expansion

Designing lightweight mechanical metamaterials with high energy absorption capacity is of crucial importance for ensuring human safety and protecting delicate instruments during impact events. Porous lattice structures with auxetic properties are widely prevalent in the field of energy absorption due to their lightweight nature and contraction behavior when subjected to compression. Based on previous research on planar metamaterials, both planar honeycombs and three-dimensional metamaterial lattices are constructed for energy absorption purposes. Four honeycomb samples made from a single material were subjected to compression tests to verify the accuracy of numerical finite element models. The numerical results indicate that the negative thermal expansion effect can mitigate the increasing rate of initial compression load, while conventional positive thermal expansion inevitably leads to a sudden surge in initial thermal load. However, the negative thermal expansion behavior associated with small deformations has minimal impact on energy absorption capacity involving large deformations. Moreover, these four metamaterials possess high effective elastic modulus and strength, along with low quasi-isotropic thermal expansion and Poisson's ratio. One type of planar or three-dimensional metamaterial displays higher energy absorption capacity due to its high plateau stress and stable compression process resulting from auxeticity. Their high specific energy absorption effectively characterizes them as buffer devices capable of protecting personnel and precision equipment from impacts.