New Crushing Strength Formula of Aluminum Honeycomb with Thinning Cell Wall

An aluminum honeycomb which has etched cell wall is used as a shock absorbent material for the offset frontal collision test and the side collision test of automobile. In this study, based on the analyses of the shock absorption mechanism, a new crushing strength formula is proposed. Firstly, load-displacement curves obtained from compression tests in quasi-static condition showed almost linear relation between a thinning rate of cell walls R and a crushing strength. Secondly, based on Wierzbicki's theory, a new formula was proposed, which can estimate a crushing strength of honeycomb material with thinning wall. Thirdly, parametric analyses were carried out with FEM model which can simulate a delamination between cell walls. The results which were obtained from theory and FEM almost corresponded to each other for a wide range of core ratio. The proposed formula works well for R <70%. Impact tests were carried out, in which the weight was dropped freely at the speed used for automobile tests. Those results almost agreed well with the sum of the theoretical crush strength and the inside air pressure.