Energy absorption characteristics of bio-inspired multi-corner CFRP tubes under axial quasi-static and dynamic loading.

• A bio-inspired CFRP tube was designed by mimicking the ceiba pentandra. • Quasi-static and dynamic axial crushing responses were studied. • Mesoscale failure mechanisms were explored by the scanning electron microscope. • Bio-inspired tube exhibited superior quasi-static and dynamic SEA than square tube. The multi-corner design approach can effectively enhance the energy absorption capacity of thin-walled metallic tubes under axial quasi-static and dynamic loading conditions. However, its efficacy in augmenting the crashworthiness performance of carbon fiber reinforced plastic (CFRP) tubes remains inconclusive, particularly due to the different failure mechanisms and pronounced strain rate effects inherent to CFRP materials compared to their metallic counterparts. Therefore, a type of bio-inspired multi-corner CFRP tube structure was designed by mimicking the non-convex cross-sectional shape of the root of ceiba pentandra tree, and its axial crushing responses were studied experimentally and numerically. Quasi-static compression and dynamic impact tests were conducted to compare the energy absorption capabilities of square and bio-inspired tubes with the same mass. The results showed that the specific energy absorption (S E A) of the square CFRP tube increased after adopting the bio-inspired design; however, different percentages of increase in S E A values were found under quasi-static and dynamic crush conditions, 13.5 % and 4 %, respectively. With the aid of finite element analysis and electron scanning technologies, the energy absorption mechanisms of bio-inspired tubes were further studied. It was found that the increase in S E A values was attributable to the increased number of axial splitting and secondary squeezing effects between internal fronds in the crushed tubes. Moreover, most of the fibers at the corner in a tube failed in tensile fracture mode during quasi-static testing, whereas they failed in both tensile and shearing fracture mode in dynamic testing, thereby leading to a reduction of energy absorption. Finally, two novel multi-corner tubes based on bio-inspired design and corner fractal design methods were proposed and they showed higher SEA values than initial one under dynamic impact. [ABSTRACT FROM AUTHOR]