An elongation-shortening strategy modifying the deformation mechanism of cellular structure for excellent energy absorption

Due to the excellent specific energy absorption and high specific strength, cellular materials are widely used in impact protection fields. Higher energy absorption efficiency has always been pursued through designing various structures. According to the bio-inspired design from the growth of ticks and bamboo, this study proposes an easy-to-operate elongation-shortening strategy to improve the mechanical properties of Schwarz Primitive (P) and Schoen Gyroid (G) cells. After that, a gradient design is achieved by combining unit cells with different mechanical properties. The mechanical properties, deformation modes, deformation mechanisms and cyclic response behaviours of the proposed novel cellular materials are investigated by conducting compression testing and finite element analysis. The results show that the elongation-shortening strategy effectively adjusts the configuration of the unit cell, thereby altering the deformation model and optimising energy storage and energy dissipation. Specifically, tensile unit cells exhibit superior energy storage capability. The impact of the elongation-shortening ratio on energy absorption varies across different relative densities. Gradient structures with various elongation-shortening ratios facilitate steady and gradual energy absorption, akin to density-gradient structures. This approach enhances performance by altering the deformation mechanism and expands design possibilities for controlling energy absorption, providing a promising new direction for cellular material design.