Energy Absorption Characteristics Analysis of Fractal Hierarchical Honeycomb with Tree‐Like Fractal under Out‐of‐Plane Impact

This study explores the design and crashworthiness of a fractal hierarchical honeycomb (FHH) inspired by the branching structure of a tree. The FHH consists of tree‐like fractal hierarchical double‐tube cell structures, combining the advantageous properties of both hierarchical fractals and double‐tube structures. A validated finite element model is employed to investigate the crashworthiness of the FHH, with a focus on the impact of wall thickness, bifurcation factor, and bifurcation angle. The findings reveal that wall thickness has the most significant influence on crashworthiness. Increasing the wall thickness not only enhances the specific energy absorption of the FHH but also leads to a higher initial peak impact force. Notably, FHHs with a 90° bifurcation angle exhibit superior impact resistance, and both FHH‐II and FHH‐III demonstrate enhanced impact resistance with a bifurcation factor ξ of 2/3. These results provide valuable insights for the further advancement of hierarchical honeycombs incorporating tree‐fractured double‐tube cells.