This work presents the design, optimization and testing of a novel lattice-structure based morphing wing. The lattice-structure concept spans a large design space, including the possibility to vary among others material, number, distribution and the orientation of the lattice rods. The used parametrization scheme considers both the positioning of the Carbon Fiber Reinforced Polymer (CFRP) rods and their orientation in spherical coordinates within the wing, thus allowing to appropriately cover the design space, while reducing the set of variables during the design optimization procedure. The morphing deformations are relying on electromechanical servomotors. Design objectives include weight minimization and structural requirements, while achieving sufficient roll control.
The local deformation induced by the electromechanical actuators is distributed by an internal skeleton structure across the rear section of the wing. An extensible skin is ensuring a smooth cambering and minimizes the required actuation energy. The in-house developed and validated simulation environment couples the aerodynamic pressure and the structural deformations, to accurately predict the aeroelastic response of the wing to aerodynamic and actuation forces, considering large deformations. In addition to the lattice structure, the aeroelastic optimization also considers the actuation layout, and the layup-thickness of the wing skin. Planform and airfoil shape are fixed to a NACA0012 airfoil with 80 cm span, and 30 cm chord.
The structural and morphing behavior was evaluated on a technology demonstrator. The demonstrator provides large continuous shape changes, improving the aerodynamic performance and achieving large deflections and high rolling moment coefficients. This is mainly achieved by exploiting the interaction of the tailored internal structure and the actuation system. Since the deformation is distributed over a large portion of the wing, local stress concentrations are minimized, and actuation forces are reduced. Wing-up bending tests have been carried out, confirming the simulation results, respectively the load-carrying capability of the presented concept. Furthermore, actuation tests resulted in peak-to-peak trailing edge deflections of 31mm, respectively a rolling moment coefficient of 0.062, which are consistent with the simulation results and guarantee sufficient roll control.