Design and mechanical testing of a variable stiffness morphing trailing edge flap

Morphing structures that are both lightweight and conformal to the aerofoil are currently being considered as promising candidates for the next generation of aircraft high-lift systems. Utilizing spatially variable stiffness materials in morphing structures leads to a possible reduction in the actuation energy requirement and also enables geometric control over the deformed shape of the morphing structure, resulting in enhanced aerodynamic and aeroacoustic performance. In this study, a design optimization methodology has been developed to identify the required material stiffness variations of a morphing structure for target optimal deformed shapes. In the optimization scheme, a layer-wise sandwich beam model is used to predict the structural behaviour of the flap with a specific material stiffness variation. Two-dimensional fluid/structure static aeroelastic interaction analysis is performed in the design optimization. Finite element analysis and mechanical tests were also carried out for a chosen optimization result to study the actuation requirements and the capability of control over the deformed shape of the morphing trailing edge. Numerical and experimental results confirm the feasibility of the proposed optimization methodology for identifying the required stiffness variation in the core and also ways of using rapid prototyped honeycomb core to realize the honeycomb core stiffness variations are discussed.