## 10 Conclusions and Further Steps  
In this paper, the modeling of a morphing architecture aimed at altering the original twist of a blade of the main rotor is presented. The architecture was conceived to be modular, that is to say, constituted by different structural elements, called cells, connected to each other towards the span direction to form a blade segment. This approach was implemented to define two models destined for wind tunnel and whirl tower tests, respectively. At first, the definition of the requirements was addressed. In this phase, an attempt was made to conciliate the restrictions of the test facilities with some requirements typical of a real application. This work led to an architecture not applicable for flight but with room for improvement. To cite an example, the current stiffness, even if similar in order of magnitude to that of the real blade, is about 20% of it. This choice allowed the required twist with a stress level compliant with the restrictions of the facilities. Higher rigidities and, thus, more robust structures would have required a higher authority of the SMA elements, still obtainable by increasing their radius. However, the pre-load would have needed the application of greater forces, making the integration process more challenging from a safety point of view. After having faced the requirement task, the layout was defined. Some aspects were particularly considered. First is the structure's capability to absorb the typical loads acting on a blade, keeping a stable configuration from the inertia point of view. Second, its specific compliance to the twist actuation within the safety prescription. Third, the possibility of measuring the current shape through a dedicated sensor network. All these primary aspects concurred with the identification of the architecture described in the first part of the work. The layout is constituted by the main solid metallic structure absorbing loads through a couple of shaped spars. Their location, the placement of the SMA element and of the heating coil between them, and the presence of additional interior masses on the leading-edge region contributed to moving forward the center of gravity. Truss-like ribs, robust but at the same time, do not significantly alter the mass distribution and assure an adequate transmission of the twist along the chord. Plate elements were then integrated between the ribs of each cell, very close to the trailing edge, where the displacements due to the twist were amplified. The strain measurements at specific stations of these plates, suitably elaborated by a dedicated logic of shape reconstruction, can give precious information regarding the type of morphing (flap bending and/or twist) and magnitude. After having assessed the layout, its behavior was investigated. At first, the focus was on the structural performance and the twist transmitted by the SMA elements, assuming the constraint conditions and the most severe load sets foreseen in the test campaigns. The specific nature of the SMA required the adoption of dedicated tools capable of simulating the constitutive law of the alloy, jointly involving both the temperature and the stress level. Nonlinear static analyses were implemented, describing, at first, the pretwist of the SMA and the integration within the structure and, then, the activation of the alloy through heating. The results were expressed in terms of stress level within the structure, strain estimated at the sensor plates, and transmitted twist. After having critically examined the results and having tracked a comparison between the WT and WhT configurations,the estimate of the power supplied to heat the SMAs was addressed. Attention was paid to the minimum power needed to fully and uniformly activate the SMAs, respecting the restriction of the facilities. A logic of control was judged necessary jointly to fuse within the power supply circuit to avoid any overheating. Another critical aspect was represented by the level of activation against the temperature profile.