A bio-inspired foam-filled multi-cell structural configuration for energy absorption

Bio-inspired thin-walled structures have gained growing interests attributed to their excellent performance of energy absorption and lightweight. This study proposes a novel energy absorber by mimicking the structural characteristics of animal long bone, namely bio-inspired multi-cell tube (BIMCT), which comprises laterally-graded multi-cell configuration and the axially-graded aluminum foam. The BIMCTs were respectively fabricated with steel and aluminum for quasi-static crushing tests to explore the corresponding deformation mechanisms, force-displacement curves and interactive effects between tube wall and foam filler. The experimental tests indicated that the steel BIMCT generated a more stable and more regular deformation mode, presenting noticeably higher specific energy absorption (SEA). Furthermore, a numerical modeling study was conducted on the steel BIMCT to analyze the energy absorption mechanism, effects of thickness gradient kt, foam density gradient ktf and average density ρ‾avg of foam on the force-displacement curves, energy absorption (EA), peak crush force (PCF), SEA and the interactive effects between the tube wall and graded metallic foam. Finally, a theoretical model was developed based upon the so-called simplified super folding element method to predict the mean crushing force of BIMCT analytically. The comparative analysis results indicated that the proposed theoretical model is applicable of both the BIMCT and its empty counterpart. This study is anticipated to demonstrate a new way for developing a superior bio-inspired structure for energy absorption.