Mechanical Behavior of Hexagonal Tubes Reinforced with Circular Inner Ribs under Axial Load

Inspired by the gradient layered structure of bamboo, a series of hexagonal hierarchical multicellular tubes (HHMT) with circular reinforcement are proposed. This design integrates circular reinforcement into traditional hexagonal tubes and applies a hierarchical concept to enhance structural performance. A finite element model of the structure is developed using Abaqus/Explicit, and the crashworthiness of the HHMT with a hierarchical structure is systematically investigated. The results indicate that higher-order HHMTs exhibit superior energy absorption capacity and impact force efficiency compared to lower-order configurations under both identical thickness and mass conditions. Notably, the B-structure of 3rd-order HHMT (HHMT-3B) demonstrates energy absorption rates that are 23.30 times greater than those of the conventional hexagonal tube under the same wall thickness conditions, with a significantly faster increase in the initial peak force. The findings suggest that augmenting the thickness of the second-order circular reinforcing ribs effectively enhances the crashworthiness of the structure, particularly in terms of energy absorption capacity per unit mass and load stability, as compared to 3rd-order HHMT with the same wall thickness. Finally, a comparative analysis with other multicellular tubes is conducted to illustrate the superiority of the proposed hexagonal layered multicellular tube with circular reinforcing ribs.