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.