Energy absorption characteristics of bio-inspired hierarchical multi-cell square tubes under axial crushing

In this study, the dynamic crushing behaviour and energy absorption characteristics of a novel bio-inspired hier-archical multi-cell square (BHMS) tubes were numerically and theoretically investigated. The proposed structures were constructed mimicking the gradient distribution of cell sizes in the biological structures such as bone and bamboo. A series of compression tests were numerically carried out for the BHMS structures with different hier-archical orders and mass of the structures. The results indicated that the specific energy absorption ( SEA ) of the 3rd order BHMS tube is 178.4% higher than that of the 0th order BHMS tube. Comparing with the conventional square and multi-cell square tube, the maximum increment of the SEA of the BHMS tube reaches up to 173.7% and 128.1%, respectively. Moreover, the undulation of the load-carrying capacity (ULC) used for evaluating the stability of the BHMS tubes under dynamic crushing was also considered. The ULC of the 3rd order BHMS tube reduces up to 88.8% and 85.7% compared to the square and multi-cell tubes. It indicates that the BHMS tube has a larger potential to improve energy absorption than the square tube and conventional multi-cell square tube. Finally, a theoretical study for the mean crushing force (MCF) was developed for the proposed tubes, which was in good agreement with the numerical results. This study provides an effective guide for the design of a multi-cell energy absorber with excellent energy absorption efficiency.