A novel star auxetic honeycomb with enhanced in-plane crushing strength

摘要

Auxetic honeycombs exhibit low weight, shear stiffness, and excellent energy absorption capacity and thus have great potential for achieving the requirements of crashworthiness and lightweight in automotive fields. This work presents a novel auxetic structure called the star-triangular honeycomb (STH), in which the horizontal and vertical ligaments of the star honeycombs (SH) are replaced with triangular structures. The dynamic crushing behaviors of the STH under three different crushing velocities were investigated using 1D shock theory. The results show that the STH has a more obvious negative Poisson's ratio effect than the SH and that transverse contraction mainly occurs in the first plateau stage. Theoretical models were deduced based on the collapse mechanism of the typical unit revealed by numerical simulation for STH crushing strength prediction. The theoretical predictions agreed well with the simulation results, and two different plateau stresses appeared under low-velocity crushing. In addition, the influences of the STH geometric parameters and crushing velocity on the energy-absorbing capacity and densification strain were systematically explored. The parameter analysis indicated that the effects of the cell-wall thickness and incline angle on the dynamic response and energy absorption capacity of the STH under low-and medium-velocity crushing are more significant than those under high-velocity crushing. Moreover, the STH showed better energy absorption capacity than the SH. Thus, this design is expected to provide a novel means of improving the mechanical properties of honeycombs.