Out-of-plane crushing performances of cell-based hierarchical honeycombs based on the evaluation criteria for ideal energy absorption

A cell-based hierarchical strategy was introduced in the preparation of traditional honeycombs to design a novel structure, known as cell-based quadrangular hierarchical honeycombs (CQHHs). The out-of-plane crashworthiness of CQHHs was investigated using experimental, numerical, and analytical methods. The criteria of ideal energy absorption were employed to evaluate the crushing performance. Then, the effects of a hierarchical strategy and geometric parameters, including the cell densities of macrocells and microcells, the relative density, and the thickness coefficient, on the crushing performance of the CQHHs were tested. Consequently, the optimal hierarchical strategy, namely, the completely ordered arrangement (COA) was identified, and a parameter analysis demonstrated that the cell density and thickness coefficient effectively improved the energy absorption efficiency of the CQHHs. Based on the combination of the COA strategy and optimal parameters, an improvement of 74.45% in energy absorption efficiency was observed, compared with a traditional honeycomb with 3 x 3 cells. The mean crushing force (MCF) reached 96.24% of the full plastic strength of the matrix, indicating that the ideal energy absorption could be closely approached by the cell-based hierarchical honeycomb. These achievements provide an effective way for developing lightweight energy absorbers and achieving ideal energy absorption.