Crushing mechanism of hierarchical lattice structure

Hierarchy greatly enhances anti-crushing behavior of thin-walled tubular structures. To reveal the energy-absorbing mechanism, hierarchical triangular lattice structures with lattice-core sandwich walls were designed. Crushing experiments were carried out to reveal the progressive collapse modes and folding mechanisms. Compared with single-cell and multi-cell lattice structures, hierarchical structures possess greater mean crushing forces (MCFs), three to four times higher. Three mechanisms, including hierarchical folding, shortening wave length and enlarging plastic bending moment of sandwich wall, help hierarchical structure greatly enhance its anti-crushing behavior. Folding styles turning from single fold, multi-fold, hierarchical fold to single sandwich-fold when increasing micro-cells in the wall were revealed by numerical simulation to propose optimized hierarchical lattice structure possessing the best specific energy absorption (SEA). Based on progressive folding mechanism, global bending mechanism and hybrid folding mechanism, theoretical models were built to predict the MCF. The predictions are reasonable.