A material system with dorsal-ventral bending asymmetry
Thomas Siegmund (Purdue University), Somesh Khandelwal (Purdue), Zhwei Wu (Purdue)
Materials Design and Biomimetic Material Concepts
Tue 2:40 - 4:00
Barus-Holley 158
Insect wings have been demonstrated to possess strong dorsal-ventral bending asymmetry (Combs and Daniels, 2003). The understanding of this phenomenon is of relevance as the elastic response of insect wings directly determines the aerodynamic characteristics of insect flight. Furthermore, insect flight often serves as the bioinspiration for micro-UAV systems. Combs and Daniels suggest that one-way hinges could be responsible for dorsal-ventral bending asymmetry. Following that suggestion we explore the design, manufacture and characterization of a material system with a pronounced one-way hinge characteristic. This material system is created by the ordered, dense packed assembly of a layer of tetrahedra. Each tetrahedron is surrounded by four adjacent tetrahedra such that its motion is constraint. Furthermore, elastic strings (tendons) are interwoven into the tetrahedra layer such that a load carrying structural assembly is obtained. We employ both full as well as truncated tetrahedra in the assembly. The mechanical characterization of the material system reveals that the structural assembly is non-linear strain hardening, and that the dorsal-ventral bending asymmetry depends on the degree of tetrahedra truncation and the assembly structure. We develop a structural mechanics model that can well describe the non-linear elastic response and the stiffness asymmetry. If the elastic strings are substituted by shape memory wires, the structural assembly can be controlled in shape. With this development we contribute to the development of multifunctional materials for morphing flight structures. The authors gratefully acknowledge the support provided for this