Tailored energy absorption for a novel auxetic honeycomb structure under large deformation

Abstract

In comparison to conventional hexagonal honeycomb structures, auxetic metamaterials with re-entrant configurations have exhibited superior mechanical properties in terms of energy absorption. To further enhance the energy absorption capacity of these materials, a novel re-entrant honeycomb configuration, named novel auxetic re-entrant honeycomb (NARH), is developed by incorporating “<>”-shaped cell walls into the conventional auxetic re-entrant honeycomb (ARH). Two analytical models for the plateau stress are formulated to consider the plastic deformation of NARH during quasi-static compression and the dynamic impact using the linear momentum theorem. Quasi-static compression tests on 3D printed NARH honeycomb specimens and finite element simulations are performed to verify the effectiveness of the theoretical models. NARH exhibits higher plateau stresses compared with ARH during compression, which can be attributed to the presence of more plastic hinges formed in NARH. These hinges, the embedded parts with inclined cell walls, not only improve stability by forming stable triangles during compression but also enhance the energy absorption capacity. A parametric study is conducted to analyze the effect of impact velocity, thickness, and incline angle of cell walls on crashworthiness. Numerical simulations demonstrate higher sensitivity of the mechanical properties to impact velocity and cell wall thickness. Adding ribs to the “<>”-shaped cell walls in NARH further reduces the initial peak force during dynamic crushing while maintaining high energy absorption. The research provides valuable guidelines for the design of energy absorption metamaterials.