Wind-Tunnel Testing of Shape Memory Alloys Actuators as Morphing Wing Driving Systems

A morphing wing, composed of flexible extrados, rigid intrados and a Shape Memory Alloys (SMA) actuator group located inside the wing box, is used to adapt an airfoil profile to variable flight conditions. The SMA actuator group developed for the morphing wing prototype consists of three main subsystems: the SMA active element, the transmission system, and the passive bias element. The functional requirements for the actuator group were determined using a coupled fluid-structure model of the flexible extrados. An original design approach was applied to determine the geometry and assembly conditions of the SMA active elements. For validation purposes, the morphing wing powered by SMA actuators was tested in a wind tunnel under subsonic flight conditions (Mach = 0.2 to 0.3 and α = −1 to 2°). The ability of the actuator group to move the flexible extrados up to 8 mm of vertical displacement and to bring it back to the initial profile has been successfully proven for all of the wind tunnel testing conditions. During the repetitive actuation, the force, displacement and temperature of the SMA active elements were measured and the results obtained in the force-displacement-temperature space were used to validate the SMA performances predicted during the design phase.