U-Type Honeycomb Based on Super-Elastic Shape-Memory Alloy for One-Dimensional Large Wing Morphing

Flexible skin is an important part of morphing wings, which must comply with the altered geometry during wing morphing. Especially for some applications of one-dimensional large morphing wing such as chord-change, flexible skin is demanded to be capable of large deformation. In this paper, we present a U-type honeycomb structure of shape-memory alloy (SMA) for flexible skin that can undergo large deformation owing to the super-elastic Nickel Titanium (NiTi)-SMA, and the mechanical properties are studied by numerical and experimental methods. In the stage of linear elasticity, U-type honeycomb structure is analyzed theoretically based on the virtual work principle, and its mechanical behavior in the stage of large deformation is studied by finite element method with considering geometric and material nonlinearity. In-plane tensile tests and out-of-plane load-bearing tests are performed, and the experimental results agree well with the numerical results. The experimental results have proved that the U-type honeycomb structure based on NiTi-SMA has large deformation capability, of which the recoverable global strain can reach at least 60%, and has great potential in the application of morphing wings.