Crashworthiness of bionic tree-shaped hexagonal hierarchical gradient structures under oblique crushing conditions

To improve the energy absorption characteristics of thin-walled structures under oblique loads, a new hexagon hierarchical gradient structure (HHGS) was designed in this work, which was inspired by the fractal structure of tree gradient in nature. The crashworthiness of the structure under oblique loads was systematically studied by numerical simulation method. The force-displacement curve of this structure under oblique loads is different from that of conventional thin-walled tubes under axial loads. Crashworthiness comparisons show that gradient structure can significantly reduce initial peak forces and maintain good deformation patterns and energy absorption advantages compared to other structures under oblique loads, at 15° load, the specific energy absorption of the third-order structure was increased by 59.20% at the highest level, at the same time, the initial peak force was reduced by 94.23%. At 30° load, the specific energy absorption of the third-order structure was increased by 32.30% and the initial peak force was reduced by 84.45%.