Optimization and integration of shape memory alloy (SMA)-based elastic actuators within a morphing flap architecture

Aircraft morphing architectures are currently worldwide investigated to enhance performance while reducing weights, volumes and costs. A 3-flap wing, for instance, shall pay a penalty up to 100% due to the insertion of mechanical devices in its body. Moreover, the insertion of cover nacelles disturbs the wing aerodynamics itself. In addition, flapped wings are noisy: deformable, instead of slotted and flapped wings, may lead to significant enhancement also in this field. Within Joint European Initiative on Green Regional Aircraft frame, in cooperation with the University of Naples, Department of Aerospace Engineering, the authors with their colleagues came to the definition of dedicated morphing architectures. This paper focuses on the design and optimization of a morphing architecture based on Shape Memory Alloy (SMA) technology, aimed at increasing airfoil trailing edge curvature. The deformable rib system is constituted of four elastic elements. The aerodynamic loads were computed through a classical panel method for the most severe flight condition. The descriptive finite element model underwent an optimization process performed through a proprietary code, based on a genetic selection strategy. Resulting values, from the optimization study were different for the variables referring to each subsystem: plate thickness, depth and length, relative orientation, SMA ribbons thickness, depth and location. Trailing edge vertical displacement was assumed as target. The main features of the 4 elastic elements are presented in the body of the document. As expected, the more rearward is the element position, the less is the weight and size; decreasing values of the aerodynamic load led towards lighter solutions.