# Design and Optimization of a Compliant Morphing Trailing Edge for High-Lift Generation
## 3 The Proposed Architecture  
The compliant trailing edge investigated in this work is constituted by an upper and lower skin panel with a stepwise variable thickness. As shown in the bottom scheme of  
Figure 4: Lift coefficient vs. AoA for clean configuration (2D computation). Figure 5, a web element connects these two panels for cooperation in absorbing loads. The thickness distribution of the skin parts and the web and the position of the web itself is the result of a good compromise among different requirements in terms of structural integrity, lightness, shape preservation under the external actions, and approaching the target morphed shape shown in Figure 2.  
The actuation subsystem comprises a linear actuator hinged on the front edge and connected on the other edge to the lower skin through a flange. The pulling action of the actuator is transmitted to the lower skin, whose retraction determines the bending of the trailing edge. Starting from the definition of the requirements discussed in the previous section, an initial 2D aerodynamic assessment was carried out to obtain aerodynamic shapes and loads. The aerodynamic data were concurrently used as input for two distinct configurations, designated as C\({}_{1}\) and C\({}_{2}\), which were designed and evaluated as structural layouts with actuation systems through industrial collaboration with Collins concerning the actuation elements. This thorough concept selection drove the creation of a new third configuration, C\({}_{3}\), integrating the best features of the previous ones. For all three configurations, a compliant architecture was chosen to enable wing morphing capabilities. This decision was driven by the inherent advantages of compliant morphing devices, capable of exhibiting precise deformation of sub-components to seamlessly alter the overall shape of the assembly. The structural stiffness is carefully designed to provide the necessary compliance for substantial deformations while ensuring adequate robustness to maintain a defined shape under external aerodynamic pressures. As mentioned, the first architecture investigated, namely C\({}_{1}\) (Figure 5, top left), is a truss rib configuration composed of a one-piece composite morphing skin and equipped with a lower strip portion capable of sliding in the chordwise direction under the action of a linear actuation system [46]. Two morphing ribs, with selective stiffness truss elements  
Figure 5: Evolution of the configuration design of the morphing trailing edge: truss rib configuration, C\({}_{1}\), X-Rib configuration, C\({}_{2}\), and hybrid configuration, C\({}_{3}\). properly attached to the skin, allow the morphed-down activation under the actuation loads action. The second layout, namely C\({}_{2}\), accounts for an X-Rib configuration (Figure 5, top right). It was conceived to optimize the number of linear actuators from two to one through genetic algorithms. The morphed-down shape is achieved through a push-and-pull linear actuation system [46]. Both these architectures proved their ability in approaching the target morphed shape. Despite this capability, efforts were spent to arrive at an architecture characterized by a simplified layout to achieve easier integration and maintenance processes and implement the lesson learned from the previous architectures in terms of load absorption. The final configuration, C\({}_{3}\), or hybrid configuration (Figure 5, bottom), is equipped with two external linear actuators (heritage from C\({}_{1}\)) in line with the left and right border rib planes; a vertical web (heritage from C\({}_{2}\))was inserted to guarantee torsional absorption. The demonstrator version spanning 0.5 m is, however, equipped with only one actuator at mid-span performing the same action of the above-mentioned two external lateral ones. As mentioned above, this architecture is driven by ease of integration and maintenance. The inner structure is cut to the bone with a unique web reinforcing the upper and lower skin panels and driving their relative motion.