## 1 Introduction
In the same program, the project \"Smart High Lift Devices for Next Generation Wings\" (SADE) [16] considered the development of high lift morphing systems characterized by a smooth geometry prone to the preservation of the laminar flow. In the next framework, the project \"Smart Intelligent Aircraft Structures\" (SARISTU) [17] addressed the problem of the integration of morphing devices within aircraft. Then, at the European level, Clean-Sky, a public-private partnership between the European Commission and the European aeronautic industry, was constituted [18]. Within this partnership and its extensions, Clean Sky 2 [19] and Clean Aviation [20], different projects were funded with the specific scope of maturing and demonstrating, in relevant environments, the most promising technologies to bring them in flight and pave the way towards industrialization. Among the different projects framed in these programs, one recalls: \"JTI-Clean Sky 1-Green Regional Aircraft-Integrated Technology Demonstrator\" [21], pointing to weight reduction, energy saving, and aerodynamic efficiency increase through break-through technologies as morphing wings; \"AIRGEEN2\" [22] focusing on the maturation and demonstration of laminar flow, high lift and load control, wing morphing, and turbulator strategies to mitigate the environmental impact of the aircraft. Also, \"Hybrid Electric Regional Wing Integration Novel Green Technologies\" (HERWINGT) [23] fostered the decarbonization of aviation systems using new technologies as morphing. Within this scenario and with a specific focus on blade morphing, the Program Horizon 2020 funded SABRE's research project: \"Shape Adaptive Blades for Rotocrraft Efficiency\" (2017-2021) [24]. The ambition of this project was to mitigate the environmental impact of the rotorcraft, implementing innovative morphing architectures on the main rotor of the Bo105 rotorcraft, predicting their impact through dedicated tools, and finally demonstrating them in a representative environment, such as a wind tunnel and whirl tower. The developed concepts involved the adaptive variation of twist [25], chord, and curvature [26; 27; 28]. Still, within the same theme, Bell Helicopter presented, at the Heli-Expo in Dallas in 2017, the FCX-001 aircraft, including, among others, innovative systems for blade morphing, highlighting the growing interest of the aerospace industry in the topic [29]. Still speaking of research programs and some years before, in 2009, within the DARPA research program, NASA demonstrated the possibility of reducing hub noise and vibration in relevant environments through advanced adaptive systems based on smart materials [30]. The growing interest in blade morphing is also evidenced by the number of scientific publications on its use in the blades of highly integrated actuation architectures. Among the most recent ones are the study of SMA-based skins for blade chamber variation [31], the strength analysis of the blade region for the later integration of an SMA actuator [32], and the active vibration control of rotating blades using piezoelectric actuators [33]. Still on the blade morphing topic, but with a focus on renewable energy production, one recalls INWIND \"Innovative Wind Conversion Systems (10-20 MW) For Offshore Applications\" (2012-2017), funded within the 7 th Framework program and targeting the conceptual design and development of innovative off-shore concepts and their demonstration [34]. These systems proved their capability to reduce the levelized cost of energy dramatically. Another example in the sector is the project \"Morphing Blades: New-Concept Tidal Turbine Blades for Unsteady Load Mitigation\", funded by the Engineering and Physical Sciences Research Council and focusing on the demonstration, at a scale level, of innovative systems able to mitigate the unsteady loading of tidal turbines and reduce their levelized cost of energy [35; 36].