Reusable multilevel bioinspired tapered tubes for bimodal energy absorption and shape-recoverable crashworthiness

Achieving thin-walled impact absorbers that combine high energy absorption, stable progressive collapse, and reusability remains challenging. Here, we develop a reusable multilevel bio-inspired thin-walled tapered tube (MBTTT) through additive manufacturing of shape-memory polymers. By integrating bamboo-inspired segmentation, barnacle-inspired corrugated walls, and Victoria cruziana –inspired fractal venation networks into a tapered thin-walled architecture, the proposed design coordinates axial load transfer, lateral support, and sequential collapse to enable multistage energy dissipation. The results show that outward-convex MBTTTs suppress global instability and promote stable progressive crushing, increasing energy absorption and specific energy absorption by 26.7% and 7.2%, respectively, relative to inward-concave counterparts. Benefiting from the sequential activation of the upper and lower structural subunits, the structure exhibits a bimodal energy-absorption response. Further tuning of the generatrix angle enhances the compressive crushing resistance and load-bearing capacity of the structure, leading to a 19.1% increase in peak crushing force (PCF), along with improvements of 18.0% and 8.2% in energy absorption (EA) and specific energy absorption (SEA), respectively. This enables a balanced trade-off between load-bearing capability and energy-absorption. In addition, the introduction of barnacle-inspired corrugated features improves compressive stability by increasing the sectional moment of inertia, thereby rendering the energy-absorption process more stable and reliable. Impact tests further demonstrate that the structure can still maintain effective energy-absorption capability under a high strain rate corresponding to an impact energy of 80 J. Moreover, benefiting from the shape-memory effect, the optimized BV-1 tube retains 89.5% shape recovery and 60.1% of its initial energy absorption after five reuse cycles. These findings establish a lightweight crashworthy architecture that integrates progressive crushing stability and cyclic shape recovery.