Mechanical properties and energy absorption characteristics of the self-similar structure in spiral shells

The multi-scale hierarchical structure of the conch shell exhibits exceptional mechanical properties, earning it the reputation as nature's natural armor. Based on structural bionics, this study investigates the self-similar three-dimensional structure of conch shells and analyzes their effects on energy absorption (EA). The universal testing machine results demonstrate that the shell specimens exhibit distinct mechanical properties under different loading conditions. Under transverse compression testing, the gastropod shells showed an average peak load of 442.55 N, compressive strength of 110.62 MPa, and Young's modulus of 13.36 GPa. In axial compression tests, the shells displayed an average peak load of 412.16 N with a mean crushing force of 219.79 N. A mathematical 3D model of the conch was developed based on geometric formulas, complemented by scanner-based sample digitization and reverse reconstruction. Multiphysics simulation tools enabled optimization of key conch topology parameters (<i>α</i>,<i>β</i>,<i>r</i>₀,<i>a</i>,<i>b</i>), while response surface modeling quantified parameter-EA correlations. The optimized structural parameters were determined as<i>α</i>= 86.6,<i>β</i>= 12.2,<i>r</i>₀= 92.5,<i>a</i>= 27.5,<i>b</i>= 37.5.The performance metrics of this structure are as follows: SEA_optim= 13.38 J g^-1, MCF_optim= 13.08 kN, CFE_optim= 0.45, and ULC_optim= 0.33.Our findings establish that energy dissipation performance in conch shells is fundamentally linked to their fractal-like self-similar organization. These findings provide crucial theoretical foundations and experimental references for the optimized design of bio-inspired energy-absorbing structures.