Design and crashworthiness analysis of novel gradient hashtag-shaped fractal thin-walled structure

• Hashtag-shaped fractal thin-walled structure (#-FS) was proposed inspired by organisms. • Crashworthiness performances of #-FS are investigated by numerical simulation. • #-FS has better energy absorption capacity than conventional square tube under the same mass. • Hashtag-shaped gradient fractal core structure (#-GFS- k -SW) was constructed by adding the inner and outer tubes on #-FS. • Effects of structural parameters on the crashworthiness performance of #-FS and #-GFS- k -SW are systematically studied. Inspired by the fractal and hierarchical features of organisms, a novel hashtag-shaped fractal structure (#-FS) was proposed, and its crashworthiness performance was analyzed using finite element simulations. The results show that the proposed #-FS exhibits superior energy-absorbing capacity compared to the conventional square tube under the same mass condition. Compared with conventional square tube, the energy absorption of #-FS with 3rd level increases by 216.36 % and its peak crush force (PCF) decreases by 0.24 % at the same mass. Finally, the effects of the wall thickness gradient ( k ) on the crashworthiness performance of #-FS and the hashtag-shaped gradient fractal core structure (#-GFS- k -SW) were systematically investigated.