Deformation Mechanisms and Crashworthiness of Gradient Star-Shaped Re-entrant Auxetic Honeycombs

Abstract

In the crash safety design of new energy vehicles (NEVs), anti-collision beams and energy-absorbing boxes play a crucial role in reducing impact loads and improving passive safety. Auxetic honeycomb structures, characterized by a negative Poisson’s ratio, exhibit excellent mechanical properties and strong potential for energy absorption. To investigate how gradient design affects energy absorption performance, a graded star-shaped re-entrant auxetic honeycomb (SRAH) structure is proposed. The structural gradient is achieved by tailoring the cell-wall thickness. Experimental specimens are fabricated and subjected to tensile and quasi-static compression tests, and a finite element model is developed and validated against the experimental results. An equivalent mechanical model is established to explain the experimental results. The effects of the gradient sequence, wall-thickness distribution, and loading velocity on the structure's compressive behavior are systematically investigated. The results demonstrate that the gradient design effectively regulates the deformation mode, induces a multistage plateau-stress response, and reduces the initial peak stress by 75.7% compared with U-SRAH. The specific energy absorption (SEA) of PG-SRAH-2 is 53.2% higher than that of U-SRAH. Moreover, NG-SRAH exhibits more pronounced auxetic behavior. This study provides theoretical guidance for the application of graded auxetic structures in energy-absorbing components for NEVs.