Enhancing crashworthiness through corner element Densification: Novel hierarchical tubes

The pursuit of ultra-lightweight energy absorbers is constrained by the limited efficiency of conventional cross-sectional configurations. This paper presents a topology-optimization strategy inspired by the microscopic configurations of snowflakes, integrating dual-tube hierarchy with fractal branching. Combined experimental, theoretical and numerical analyses reveal a unique energy absorption mechanism driven by the synergistic coupling of the hierarchical skeleton and branching network. Detailed stress analysis demonstrates that this topology enforces a volumetric stress saturation mode, transforming to highly stable, short-wavelength progressive folding. Through comprehensive parametric optimization and COPRAS evaluation, the structure achieves a specific energy absorption of 43.65 kJ/kg. This represents a distinct 147.68% performance improvement over the traditional hexagonal dual-tube baseline. These results confirm that the snowflake-inspired design offers a mechanically superior, distinct topology for space-constrained energy absorption systems.