Energy-Absorbing Properties of Thin-Walled Bionic Gradient Layered Bellows under Axial Compression

Inspired by the layered structure of human vertebrae and spider webs, a thin-walled bionic gradient layered bellows (TBLB) was proposed by integrating layered design and gradient-designed filling structures into traditional bellow configurations. This structure enhances energy absorption while effectively reducing the initial peak crushing force (IPCF). A combined experimental and numerical simulation approach was employed to comparatively analyze the energy absorption performance of 0-2 Layer TBLB and traditional multicellular tube (TMT) under axial loading. Results demonstrate that increasing the layered number stabilizes deformation and strengthens energy absorption. Specifically, the specific energy absorption (SEA) of 1-Layer and 2-Layer TBLB significantly improved by 108 and 154%, respectively, compared to 0-Layer TBLB. While 2-Layer TBLB exhibited comparable energy absorption to TMT, its IPCF was 44.1% lower than that of TMT. Additionally, positive-gradient bellow structures outperformed negative-gradient counterparts in energy absorption capability. The effects of multi-layered corrugated cores with different cross-sections and impact velocity (V) on TBLB’s energy absorption were further investigated. Hexagonal multi-layered corrugated cores demonstrated superior energy absorption to circular counterparts, achieving 10% higher SEA and 36.2% improvement in compression force efficiency (CFE). Moreover, the SEA of TBLB increased with rising V, indicating that higher V enhances the energy absorption advantages of TBLB. These findings highlight the critical role of layered design, gradient configuration, and cross-sectional geometry in optimizing crashworthiness performance.