Experimental and numerical investigation on in-plane impact behaviour of chiral auxetic structure

Abstract

This paper presents an experimental study on impact behaviour and plastic evolution of chiral structure subjected to in-plane impact loading using a Split Hopkinson pressure bar (SHPB). The finite element (FE) model developed in ABAQUS/Explicit was validated and utilized for parametric study, and further developed as an extension of experimental work. The impact scenarios from both structure itself and external input are considered, including relative density, topology parameter r/R and initial impact energy. Results indicate that chiral structure exhibits three critical failure modes corresponding to various impact velocities ranging from 5 m/s to 50 m/s. Interestingly, chiral structure occurs with two densification stages induced by ligaments-dominated and nodes-dominated crushing deformation, respectively, proving the capability of independent energy management mechanism. Increasing the value of relative density from 0.19 to 0.39 contributes to a maximum of 250% increase in the specific energy absorption (SEA). Although increasing the value of r/R from 0.04 to 0.2 can dramatically decrease Poisson’s ratio (PR) from 0.07 to − 0.63 (significant negative PR), high strain-rate dependence of PR is also observed. In addition, the impact displacement is mostly influenced by initial impact energy but not by impact velocity and mass. The obtained results of this study provide a new insight into the impact performance of chiral structure, which contributes to the optimal design of auxetic crashworthiness system.