Ultraductile Bar with Bioinspired Helical Strands

Abstract

Through natural selection, living systems have evolved elegant hierarchical structures with excellent mechanical properties and efficient biological functions. The helical tendrils of climbing plants are known for their intriguing geometry and superior deformability. Many engineering materials are vulnerable to plastic strain localization, and the efficiency of material usage can be significantly improved by suppressing strain localization. Inspired by plant tendrils, a novel structural design of ultraductile engineering materials is proposed in this work. A cylindrical metallic bar is considered as an example. In the proposed design, a number of strands are wound spirally about and bonded to the bar. The effectiveness of the design in improving the deformation capacity of the metallic bar is demonstrated by numerical simulations and experimental tests. In the postnecking process, the maximum principal strain in the composite bar is distributed more evenly than that in the bare bar. This work provides a way for improving the deformability and ductility of a diversity of engineering materials, which can prevent these materials from failing under excessive deformation.