Kirigami-inspired TI–6AL–4V titanium alloy truncated cone for high-efficiency energy absorption via brittle fracture

In thin-walled energy absorbers, ductile metals are generally preferred because they dissipate energy through stable progressive plastic deformation, whereas brittle materials are typically avoided due to unstable crushing behavior induced by fracture. This study proposes a kirigami-inspired truncated cone (TC) that promotes progressive plastic hinge formation and sequential fracture evolution during axial crushing. The proposed design enables the effective utilization of the high-specific-stiffness Ti–6Al–4 V alloy in thin-walled energy absorbers while maintaining stable progressive collapse. Quasi-static compression experiments, finite-element simulations, and low-velocity impact tests were conducted to investigate the crushing behavior of the TC and compare it with conventional hierarchical cellular (HC) and multicell configurations (MC). Under quasi-static loading, the AM 316 L TC exhibited an 11% increase in specific energy absorption (SEA) compared with the AM 316 L HC. More importantly, the SEA of the AM Ti–6Al–4 V TC was approximately three times that of the AM 316 L TC, preserving a stable near-rectangular crushing response. Low-velocity impact tests further demonstrated that the TC maintained deformation modes highly consistent with quasi-static crushing behavior, exhibiting lower initial peak crushing force (IPCF), smoother force responses, and improved deformation stability compared with the HC and MC structures. For the Ti–6Al–4 V specimens, the IPCF of the TC was reduced to 31% and 34% of those of the HC and MC structures, respectively. Combined experimental and numerical analyses, together with a simplified mechanical model, indicate that the foot-like supporting units provide a height-dependent structural constraint arising from the gradual increase in their second moment of area along the structural height, thereby promoting the sequential formation of plastic hinges and top-to-bottom sequential damage evolution during progressive collapse. The proposed mechanism provides a pathway for integrating brittle, high-specific-stiffness materials into crashworthy thin-walled structures by enabling progressive deformation and sequential fracture evolution.