Design of cellular based structures in sandwiched morphing skin via topology optimization

Sandwiched morphing skin, composed of cellular based structure and flexible face-sheets, is one of the most promising concepts which can be used for morphing aircraft. Apparently, cellular based structure, with ability to endure aerodynamic pressure and morphing capability, is the most critical component of sandwiched morphing skin. This paper presents a design process for optimal topologies of cellular based structures for two-dimensional morphing skins, and this design procedure is effortless to be adjusted to be applied under different sets of boundary and loading conditions. The topology optimization problem formulation is established based on the simplified isotropic material with penalization (SIMP) interpolation method coupled with the method of moving asymptotes (MMA), meanwhile, Heaviside filter is adopted for reducing the occurrence of transition elements. After several iterations, various optimized topologies of unit cell are calculated corresponding to different morphing applications such as span morphing, sweep morphing and two-dimensional morphing. The mechanical properties of cellular topologies are investigated by comparing with conventional regular honeycomb structure and zero Poisson’s ratio structure via simulation after establishing 3D models of topologies. Results indicate that the design method using topology optimization technique is entirely feasible and optimal topologies of cellular based structure appear to provide superior performance.