Metallic lattice structures are focused on as excellent energy absorption materials. The mechanical properties strongly depend on the cell structure. Rigid cell structure consisting of stretching-dominated unit cells shows high strength and low energy absorption efficiency. On the other hand, flexible cell structure consisting of bending-dominated unit cells shows low strength and high energy absorption efficiency. Three types of cellular aluminum alloy specimens are manufactured through additive manufacturing process. Flexible cell structure has a rhombic dodecahedron unit cell. Rigid cell structure has a rhombic dodecahedron unit cell with braces. Bimodal cell structure has both flexible and rigid unit cells. Compression tests clarified that the bimodal cell structure managed both high strength and high energy absorption efficiency. FE analysis showed the bending and stretching modes in bimodal cell structure. Proposed bimodal cell structures have a potential as novel energy absorbing materials.
Kosaka et al. (Tue,) studied this question.