Development and validation of an equivalent honeycomb model

Abstract

Due to their low density, high strength and high specific energy absorption, honeycombs have been widely employed as excellent energy-absorbing structures in crashworthiness design. However, the computational cost of detailed finite element (FE) models of honeycombs is prohibitively high, due to the small size and large number of elements involved. Therefore, to reduce computational time while ensuring accuracy, equivalent modeling methods for honeycombs are of particular interest to researchers. In this study, tests were conducted on aluminum honeycombs to investigate anisotropy, strain rate effects and tearing effects. The results indicated that the compressive strength decreased with increasing off-axis angles and increased with rising strain rates, and it was enhanced due to the tearing force. Based on the test results, the basic mechanical parameters, including elastic modulus, plateau stress, densification strain, and densification modulus, were obtained. More importantly, a continuous solid equivalent honeycomb model was developed, in which a modified Hill48 yield criterion and a segmented linearity rate-dependent hardening model were adopted to describe the anisotropic properties and strain rate effect of the honeycomb, and beam elements with failure criteria were utilized to characterize the tearing effect. The developed equivalent constitutive model was implemented into LS-DYNA via user material subroutine (UMAT) for numerical simulation. The simulation results were highly consistent with the test results, demonstrating the reliability of this equivalent honeycomb model.