Design diagram for linear SMA actuators integrated in a morphing wing structure

Shape memory alloy (SMA) actuators can be used effectively as active elements coupled with the passive elastic structure of a morphing wing, given their exceptional power density characteristics. Upon heating, SMA deforms the elastic envelope of the wing, while during cooling, the wing restores the energy accumulated during the actuation period, thus ensuring the SMA actuators are reset. The shape-changing behavior of the morphing structure depends on a series of parameters which can be grouped as follows: SMA characteristics, elastic structure properties and the assembly conditions between the SMA and the elastic structure. For an SMA of a given composition, its recovery stress-strain characteristics are determined by the alloy’s thermomechanical history. This paper focuses on the development of a design methodology leading to an optimum selection of a thermomechanical SMA treatment and assembly conditions according to the requirements imposed by the application in terms of the required forcedisplacement characteristic and number of cycles of operation. A minimum-weight optimization case study is presented.