A Study of the Mechanical Properties of Naturally-Inspired Tubular Structures Designed for Lightweight Applications

Inspired by the macro/microstructures of starfish and beetle elytra, a series of bio-inspired structures (BSs) with improved comprehensive mechanical performance were proposed and fabricated. In the BS design, the principle of the branching structure of starfish was borrowed and each arm was endowed with calcified exoskeletons that can bend autonomously, enabling the starfish to move flexibly and adapt to changing shapes. At the same time, inspiration was taken from the concave-convex structure design principle of beetle elytra to enhance the internal complexity and mechanical performance of the BS. By increasing the number of polygons inside the thin-walled tubes, the performance of the BS in torsion and three-point bending was effectively improved. To evaluate the mechanical properties of the BS, finite element models were constructed using ANSYS and verified through experimental measurements. Universal testing machines and electronic torsion testers controlled by a microcomputer were used to study the compression, bending, and torsion properties of the BS. The results indicated that the differences in maximum compressive load-bearing capacity between each BS were small, and their lightweight compression values (LWN-C) remained unchanged, around 310 N/g. Increasing the number of polygons inside the thin-walled tubes effectively improved the performance of the BS in torsion and three-point bending. Moreover, the crashworthiness behaviors of the bio-inspired lightweight tube were also studied using a drop hammer impact tester. These findings have significant implications for the development of bio-inspired designs, particularly in the fields of machine arms, vehicle shafts, and bumpers, where lightweight yet high-strength structures are highly desirable.