Deformation behaviors and energy absorption characteristics of a hollow re-entrant auxetic lattice metamaterial

Designing innovative architected metamaterials with enhanced energy absorption is a long-term pursuit to provide impact protection capacity for human beings and crucial structural components. Numerous natural materials prove that hollow structures present unique combinations of mechanical properties and functionalities with minimal weight cost. Therefore, a novel 3D hollow re-entrant auxetic (HRA) lattice metamaterial is proposed to improve the energy absorption capacity. To investigate the mechanical properties of the HRA lattices, an analytical model based on plastica theory is established to predict the crushing force. The energy absorption behaviors of the HRA lattices under quasi-static crushing load are studied based on finite element method, and the analytical predictions are in good agreement with the numerical simulation results. The analytical model can be used to optimize the appropriate design parameters of the HRA lattice and explain the simulation results in the parametric studies. Compared with the solid re-entrant auxetic (SRA) lattice with the same density, specific energy absorption of the HRA lattice can be improved by up to 27.43%. Finally, a parametric investigation is carried out to comprehend the influences of the length-to-height ratio, the re-entrant angle, the width-to-height ratio, and the wall thickness-to-height ratio on the energy absorption capacity of the HRA lattices. According to various energy absorption demands, the HRA lattices with different energy absorption properties can be designed by tuning these design parameters. This concept of building hollow auxetic lattice metamaterials can open up a new solution to design metamaterials with negative Poisson's ratio effects and enhanced energy absorption for potential engineering applications.