Buckling and progressive crushing of laterally loaded honeycomb

This paper presents a comprehensive study of the lateral compressive response of hexagonal honeycomb panels from the initial elastic regime to a fully crushed state. Expanded aluminum alloy honeycomb panels with a cell size of 9.53 mm, a relative density of 0.026, and a height of 15.9 mm are laterally compressed quasi statically between rigid platens under displacement control. The cells buckle elastically and collapse at a higher stress due to inelastic action. Deformation then first localizes at mid-height and the cells crush by progressive formation of folds; associated with each fold family is a stress undulation. The response densifies when the whole panel height is consumed by folds. The buckling and crushing events are simulated numerically using finite element models involving periodic domains of a single or several characteristic cells. The models idealize the microstructure as hexagonal, with double walls in one direction. The nonlinear behavior is initiated by elastic buckling while inelastic collapse that leads to the localization observed in the experiments occurs at a significantly higher load. The collapse stress is found to be mildly sensitive to various problem imperfections. The subsequent folding can be reproduced numerically using periodic domains but requires a fine mesh capable of capturing the complexity of the folds. The calculated crushing response is shown to better resemble measured ones when a 4 × 4 cell domain is used. However, the average crushing stress can be captured with engineering accuracy even from a single cell domain.