Enhanced Energy Absorption of Auxetic Square Tubes Filled with Hollow Spherical Cells

To enhance the energy dissipation capacity and structural stability of conventional thin‐walled energy absorbers, auxetic square tubes (ASTs) filled with hollow spherical cells (HSCs) are proposed in this study. The composite design leverages the negative‐Poisson‐ratio deformation of the tube and the structural synergy with the HSC to realize the enhanced energy absorption and overall stability. First, the HSC, empty ASTs, and HSC‐filled ASTs are manufactured using 3D printing. Quasistatic axial compression tests are conducted to obtain load‐displacement responses, deformation modes, and energy absorption characteristics. Finite element simulations show good agreement with experimental results. The validated FE model is subsequently employed to conduct a parametric study on the effects of the tube wall thickness, structural height, and the thickness of spherical cells. The results show that the HSC‐filled ASTs exhibit a pronounced enhancement in energy absorption by 28.7%–44.8% compared to the sum of their individual components, revealing a synergistic reinforcement effect. Increasing the thickness of the tube wall and HSC can effectively enhance the specific energy absorption, whereas the tube height mainly affects the total absorbed energy with only a minor influence on the specific energy absorption. This study provides new insights for the design of high‐performance lightweight energy‐absorbing structures.