# Design and Optimization of a Compliant Morphing Trailing Edge for High-Lift Generation
## 1 Introduction
Finally, the next phases of the already-cited programs of Electric Aircraft Propulsion, phases 2-5 (2015-2025), and Continuous Lower Energy, Emissions, and Noise, phases 3-4 (2020-2030), at the U.S. level and the Clean Aviation program (2022-2028) [38] at the EU level are part of the third-wave actions and generally concern the extension of the selected technologies to full-sized structures for a pre-industrial or industrial use. The Project Hybrid Electric Regional Wing Integration Novel Wing Technologies (HERWINGT), given in ref. [39], is supported by the above-mentioned Clean Aviation Joint Undertaking Programme. HERWINGT will validate, down-select, mature, and demonstrate the concept, the architecture, the design, and the key technologies for addressing an innovative wing design of a hybrid electric regional aircraft (HER) with a maximum capacity of 100 seats and a range from 500 to 1000 km. The aim is a reduction in CO\({}_{2}\) and other greenhouse (GHG) emissions by improving the aerodynamic efficiency and reducing the weight of the wings of future aircrafts. The development of a morphing trailing edge represents a significant advancement in aerodynamics and aircraft performance, particularly during critical phases of flight, such as take-off and landing [40]. HERWINGT [41], amongst others, pursues the objective of enabling the activation of wing camber morphing to generate high lift during the take-off and landing phases. To achieve that, a compliant morphing architecture capable of generating high lift when activated and reducing drag owing to the absence of steps and gaps in clean configuration [42] has been properly conceived. This is assured by a dedicated design and integration of a continuous skin that ensures the optimal aerodynamic shapes are maintained while adhering to certification regulations. The use of a continuous surface minimizes turbulence and drag and, at the same time, maximizes lift, contributing to overall aerodynamic efficiency [43]. Another aim relevant to the proposed morphing trailing edge technology is the integration of electro-mechanical actuation (EMA) systems, capable of robustly withstanding sizing loads without compromising performance or safety. Finally, the design, manufacturing, and ground testing of a true-scale segment of the compliant device are other essential objectives. The proposed architecture will replace an inner flap spanning 3.8 m and an outer tapered flap spanning 6.6 m. In addition, a single-bay assembly with a limited span of 0.5 m is also foreseen for the mentioned ground demo purposes. Different configurations were investigated for the above-mentioned compliant morphing trailing edge. This paper focuses on a specific layout derived from lessons learned by the architectures previously explored. The final scope of the activities described in what follows is the design of the morphing-compliant training edge segment prototype with a span of 0.5 m.  
First, the requirements at aircraft level are presented, highlighting their impact on the investigated device. This process ends with the translation of these requirements into specifications for the specific technology. On this basis, the layout of the system is identified, also considering the lessons learned from two previous architectures. After freezing the layout comes the design task. To this scope, a genetic approach was implemented, trying to determine the best compromise amongst different, often conflicting requirements approaching the target morphed shape, the structural integrity, the compliance with actuation capabilities, and the weight. A light finite-element model of the system was realized to reduce the computational effort related to the evaluation of several configurations. This model was conceived to quickly address static, buckling, and modal analyses by altering some critical design parameters, such as the skin thickness distribution, the topology of the architecture, and the transmission features of the actuation chain.