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. Guided by similarity theory, spiral shell specimens were selected to analyze structural characteristics along macro-oriented directions, with mechanical tests conducted using a universal testing machine. Transverse compression tests revealed that the lateral compressive strength correlates with aperture thickness and overall height, with a Young's modulus ranging from 10 to 15 GPa. Axial compression tests indicated a progressive fracture pattern during shell failure accompanied by nonlinear deformation. A mathematical 3D model of the conch was developed based on geometric formulas, complemented by scanner-based sample digitization and reverse reconstruction. Cross-validation among theoretical models, reconstructed digital models, and physical specimens confirmed the accuracy of the conch's geometric formulations. Multiphysics simulation tools enabled optimization of key conch topology parameters (α、β、r0、a、b), while response surface modeling quantified parameter-energy absorption correlations. The optimized structural parameters were determined as α=86.6、β=12.2、r0=92.5、a=27.5、b=37.5. 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. .