In-plane dynamic crushing of honeycomb. Part II: application to impact

Abstract

Finite element simulations were employed to analyse in-plane dynamic crushing of two different hexagonal honeycombs (slenderness ratios L/ t=38 and 167). The response of the honeycomb with the smaller slenderness ratio was studied for impact speeds up to 40.0 m/s which corresponds to a nominal strain rate for the specimen of 500 s −1 . Total plastically dissipated energy was used to quantify the effects of increasing strain-rate, since other measures showed a strong dependence on details of the finite element model. The simulations revealed a strong increase of total dissipated energy with increasing impact speed for velocities larger than the critical speed for wave trapping, v cr . One reason was a higher percent of cells collapsing in a symmetric crush mode (IV). Another reason for the larger total dissipation at higher crushing speeds was the greater irregularity in the folding pattern that developed. Experimental and calculated global force-time curves were compared for the honeycomb with the larger slenderness ratio at impact speeds 3.0 and 7.2 m/s and a satisfactory agreement was found. At these low impact speeds there was no increase of initial collapse or plateau stresses. A comparison of sequences of deformed mesh plots and high speed photos showed good correlation of the general distribution and modes of crushing.