Crashworthiness analysis and optimization of multi-functional gradient foam-aluminum filled hierarchical thin-walled structures

The combination of metallic thin-walled structures and foam aluminum with lightweight characteristics and high energy absorption can further improve the crashworthiness of hollow homogenized structures. A novel tri-functional gradient (TFG) hierarchical thin-walled structure to simultaneously improve lightweight and crashworthiness is proposed, which is an aluminum-foam-filled hierarchical structure with functional gradient strength and thickness properties. Three characterized indices including the thickness index m, density index n, and strength index p are introduced to analyze the crashworthiness of TFG structure. The experimental results show that the crashworthiness of the TFG structure is superior to the uniform functional gradient (UFG) structure. The peak crushing force (PCF) and specific energy absorption (SEA) of TFG structure can reach 133kN and 19.903 kJ/kg, SEA is improved by 13.71% and PCF is reduced by 40.36%. Besides, the thickness and strength of the external tube is the primary factor affecting the PCF. The crashworthiness of the TFG structure is highly dependent on the synergistic combination of three gradient indices. When the combination of (m, n, p) is (0.25, 0.25, 0.25), the maximum SEA is 21.206 kJ/kg. The thickness and strength indices m, n have a large effect on SEA and PCF, yet the density index n has barely any effect on SEA and PCF. Furthermore, the non-dominated sorting genetic algorithm II (NSGA-II) is employed to build the optimal Pareto frontier aim at this TFG structure to realize a coupled material-function-structure multi-objective optimal design.