Morphing Airfoil with Thermally Activated SMA Actuators

In this paper we study a type of design of Shape Memory Alloy (SMA) wire actuated morphing airfoil having discontinuous skin by targeting trailing edge deflection and changing camber. The design aims at airfoils to have optimal directional stiffness and relaxed shear constraint to allow the required change to create a conformal target shape. The trailing edge deflection of the morphing airfoil structure is produced by the electrical actuation via Joule heating of the actuators placed in the airfoil in various different configurations. Actuation response is tested under quasi-static loading and partial loading–unloading cycles applied to the actuators. Deformation characteristics are analyzed for these actuation schemes. Response time for various actuation rates and also the functional fatigue of SMA actuators due to variable stiffness conditions are investigated. Aerodynamic characteristics of this design are analyzed under a simulated free-stream flow velocity of up to 20 m/s and up to aerodynamic stall. For a maximum trailing edge rotation of 9°, a 150% increase in the coefficient of lift is observed. These results are further compared with wind tunnel test results which show promising outcome. Various aspects of aerodynamic performance enhancement and possibilities to realize it with distributed dynamic control via morphing structures are discussed.