Biaxial crushing of honeycombs - Part I: Experiments

The in-plane compression and crushing of honeycombs is known to be closely related to the crushing behavior of the broader class of space filling cellular solids. Previously, the authors conducted an extensive study of uniaxial crushing of a polycarbonate honeycomb with circular cells. In this paper the same honeycomb is crushed biaxially. The crushing was performed in a custom testing facility between rigid platens which can be moved independently in two orthogonal directions. The facility allows testing at various biaxiality ratios and volume reductions as high as 95%. The facility was used to conduct several series of biaxial crushing experiments on nearly square honeycomb specimens (18 x 21 cells). In; each experiment we recorded the true stress-displacement responses in the x- and y-directions as well as full field views of the deformation using a video camera. Biaxial crushing is quite complex and the prevalent mechanisms of collapse depend on the biaxiality ratio (gamma). As is the case in uniaxial crushing, the onset of collapse involves localized instabilities, however, the extent of localized deformation varies with gamma. The energy absorption capacity of the material depends on gamma. The highest energy is required when the specimen is crushed at the same rates in the two directions. (C) 1999 Elsevier Science Ltd. All rights reserved.