A Sustained High-Strength and Anti-Collapse Slender Tube Enabled by Bionic Taper Design with Progressively Enhanced Fold Deformation Mode

Abstract

Slender tubes are in high demand owing to their lightweight and outstanding mechanical behaviors. However, most conventional slender tubes are mechanically unstable and prone to catastrophic failure such as Euler’s buckling under axial load due to their large slenderness radio. Interestingly, the growing bamboos in nature overcome the similar dilemma by a unique tapered intine in the internodes, which endows them with excellent axial mechanical performance. Inspired by this finding, a bionic inner-tapered tube (BITT) was designed to enhance the mechanical performance of slender tubes under axial load. The mechanical behaviors and energy absorption capacities were evaluated by quasi-static axial crushing test. Then, theoretical calculation and finite element analysis are carried out to analyze the axial mechanical mechanisms of BITT. The results reveal that the taper of inner wall induces a progressively enhanced fold deformation mode for BITT, which not only prevents buckling failure and decreases initial peak crushing load but also improves the energy absorption efficiency by improving the effective utilization of materials. Nylon is selected as the base material by contrast tests, and the influences of taper and length-diameter ratio on the axial mechanical properties of BITT are explored. Finally, the bionic square array (BSA) and bionic hexagon array (BHA) are fabricated by taking BITT as the basic structural unit, both of them show excellent axial mechanical properties, indicating the universality of bionic design inspired by tapered intine of growing bamboo. The bionic design in this work offers an effective strategy to improving axial mechanical properties of slender tubes as energy absorbers.

Keywords: slender tubes, inner-tapered, bionic design, axial crushing, energy absorption