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This paper summarizes the results of the design study and provides a description of three morphing wing devices developed for a turboprop regional aircraft in the framework of the Clean Sky 2 REG-IADP Airgreen 2 project. In sinergy with a natural laminar flow wing, morphing wing technologies are investigated to improve both high-lift performance and aerodynamic efficiency in off-design conditions of the aircraft, by demonstrating also load control and alleviation capabilities over the flight envelope. The combined use of a deformable droop nose and a multifunctional morphing flap, designed by PoliMi and UniNA respectively, is able to meet the minimum high-lift performance requirement of the AG2-NLF aircraft for both take-off and landing conditions. The controlled flap is deployed during take-off by using a fairingless concept, totally hosted in the wing, that offers additional benefits on structural weight and aerodynamic efficiency at high speed. The flap camber is then morphed to gain the extra lift required for landing operations. An adaptive winglet concept, designed by CIRA, is also presented to further enhance aircraft aerodynamic efficiency also in climb/descent conditions by lowering at the same time wing-bending moments due to aircraft maneuvers. Such a mechanical system is characterized by two movable surfaces aimed at performing variable camber and differential tab settings depending on the flight conditions. Both aerodynamic performance and benefits of the three morphing devices are assessed by ONERA on the natural laminar flow wing.

The advantages of using shape memory alloys (SMAs) in aeronautical applications are various (compactness, lightness, etc.). Some of the most interesting aeronautical applications involving SMAs are briefly examined with a focus on wing morphing, propulsion systems, and noise reduction. In particular, the potential of SMAs to realize adaptive flaps according to two different architectures, compliant and kinematic, is discussed, examining the pros and cons.

Winglets are introduced into modern aircraft to reduce wing aerodynamic drag and to consequently optimize the fuel burn per mission. In order to be aerodynamically effective, these devices are installed at the wing tip section; this wing region is generally characterized by relevant oscillations induced by flights maneuvers and gust. The present work is focused on the validation of a continuous monitoring system based on fiber Bragg grating sensors and frequency domain analysis to detect physical condition of a skin-spar bonding failure in a composite winglet for in-service purposes. Optical fibers are used as deformation sensors. Short Time Fast Fourier Transform (STFT) analysis is applied to analyze the occurrence of structural response deviations on the base of strain data. Obtained results showed high accuracy in estimating static and dynamic deformations and great potentials in detecting structural failure occurrences.

A major difficulty in the design of morphing devices for aircraft wings is to reach an adequate compromise between high load-carrying capacity to withstand aerodynamic loads and sufficient flexibility to achieve better aerodynamic performance. Such counteracting and demanding targets lead to an increased structural complexity whose experimental characterization is a matter of high priority prior to the ultimate physical integration into the aircraft structure. Compared to the passive counterpart, morphing devices enable augmented capabilities by locally adapting wing shape and lift distribution through either a quasistatic or dynamic deflection, with excursions ranging into a few units of degrees, positive and negative.This chapter provides an overview of the verification approaches suitable for morphing devices ranging from the basic concepts applicable to individual subsystems up to the global experimental analysis of the integrated system. A number of test objectives are illustrated at both component and system level, providing practical tips for the experimental analysis of morphing structures combining both compliant structural systems and multibox self-contained actuation mechanisms.

Nature teaches that the flight of the birds succeeds perfectly since they are able to change the shape of their wings in a continuous manner. The careful observation of this phenomenon has re-introduced in the recent research topics the study of “metamorphic” wing structures; these innovative architectures allow for the controlled wing shape adaptation to different flight conditions with the ultimate goal of getting desirable improvements such as the increase of aerodynamic efficiency or load control effectiveness. In this framework, the European research project SARISTU aimed at combining morphing and smart ideas to the leading edge, the trailing edge and the winglet of a large commercial airplane (EASA CS25 category) while assessing integrated technologies validation through high-speed wind tunnel test on a true scale outer wing segment. The design process of the adaptive trailing edge (ATED) addressed by SARISTU is here outlined, from the conceptual definition of the camber-morphing architecture up to the assessment of the device executive layout. Rational design criteria were implemented in order to preliminarily define ATED structural layout and the general configuration of the embedded mechanisms enabling morphing under the action of aerodynamic loads. Advanced FE analyses were then carried out and the robustness of adopted structural arrangements was proven in compliance with applicable airworthiness requirements.

In the field of European and International morphing structures projects, the CRIAQ MD0-505 enables collaboration among Italian and Canadian research centers and industries paying particular attention to the development of innovative design in the area of adaptive technologies. The main project goals involve the design of a wing trailing edge device capable to improve aerodynamic efficiency in all the flight envelope leading to fuel consumption reduction with positive impact on aircraft weight. This paper deals with the design and modeling of a novel actuation system of a full scale morphing aileron for a regional aircraft wing. The proposed aileron architecture is characterized by segmented adaptive ribs. Each rib is composed of two movable blocks connected by means of rotational hinges in which are housed bearings and bushing in a finger-like mechanism. Rib actuation is guaranteed by an actuation system composed of a dedicated kinematic chain derived from a quick-return mechanism. In order to achieve the aileron target shapes, the system is driven by a set of servo-rotary electro mechanical actuators that permit a highly integrated design which lays the groundwork for the technological transition from the torque shaft to the distributed actuation architecture.

The development of elastomeric materials for adaptive wings focuses on the elasticity at -55 °C to ensure morphing at cruise altitudes. FEM simulations and mechanical tests are carried out to optimize fatigue and aging properties of this new multi-material device. Two large skin panels are manufactured and successfully assembled into a true-scale wind tunnel demonstrator for the experimental validation of adaptive trailing edge device functionality in simulated operative conditions.

Morphing Wings Technologies: Large Commercial Aircraft and Civil Helicopters offers a fresh look at current research on morphing aircraft, including industry design, real manufactured prototypes and certification. This is an invaluable reference for students in the aeronautics and aerospace fields who need an introduction to the morphing discipline, as well as senior professionals seeking exposure to morphing potentialities. Practical applications of morphing devices are presented-from the challenge of conceptual design incorporating both structural and aerodynamic studies, to the most promising and potentially flyable solutions aimed at improving the performance of commercial aircraft and UAVs. Morphing aircraft are multi-role aircraft that change their external shape substantially to adapt to a changing mission environment during flight. The book consists of eight sections as well as an appendix which contains both updates on main systems evolution (skin, structure, actuator, sensor, and control systems) and a survey on the most significant achievements of integrated systems for large commercial aircraft. Provides current worldwide status of morphing technologies, the industrial development expectations, and what is already available in terms of flying systems Offers new perspectives on wing structure design and a new approach to general structural design Discusses hot topics such as multifunctional materials and auxetic materials Presents practical applications of morphing devices. © 2018 Elsevier Ltd. All rights reserved.

The development of aircraft structural morphing devices involves the integration of complex and different systems, interacting and modifying their uncoupled characteristics. In detail, when adaptive skins, designed to afford the exceptional deformations needed to achieve morphing capabilities, are integrated into the actuation structural system, mass, stiffness and damping aspects are highly affected. This fact can have relevant impacts for the design process either from the static (load-bearing capabilities) and the dynamic (aeroelastic response, mainly), point of view. In order to properly characterise these important aspects, the manufacture of intermediate demonstrators was decided, not implementing all the design solutions yet but giving emphasis at certain subsystems. A mock-up was initially manufactured, whose structural properties (ability to carry out loads) were simply guaranteed by the elastic skin. The structural characteristics of the second one were insuured by the actuator system, only. The final one integrated both the concepts. The comparison of the results among the three allowed giving hints on the behaviour of the single and coupled subcomponents. In this paper, experimental modal analysis results are discussed, specifically addressed at characterising the damping coefficient, so important for aeroelasticity aspects.

A conceptual design of an active device able to attenuate the tonal vibrations of a mounting bracket for automotive gearboxes is addressed in this paper. A preloaded piezo stack actuator is used to counteract the unbalanced vibrations of the component by monitoring its operational deformations. Firstly, a numerical modal analysis is carried out to characterize the normal modes in the frequency range of interest. The piezo stack is simulated by a rod element and its effect is numerically characterized. The upper and lower faces of the stack are mechanically coupled with the bracket structure, whereas the active control deals with the relative displacement of two points of the bracket. The primary disturbance was simulated by a shaker to control the vibrations in correspondence of the second bending mode (around 1.6 kHz). A 20 Hz narrow band was additionally selected as the control window. Then, this frequency range was enlarged around the resonance peak in order to optimize the control effect, till 80 Hz to investigate the resulting effects. Finally, focus is given to the structural damping by assessing its impact on the control forces and phases to cancel the deformation along the contact direction. The description of the experimental results concludes this work by generally confirming the numerical expectations.

In the framework of Clean Sky 2 Airgreen 2 GRA ITD project, this paper deals with the design process of a morphing winglet for a regional aircraft. By improving A/C aerodynamic efficiency in off-design flight conditions, the morphing winglet is expected to operate during long (cruise) and short (climb and descent) mission phases to reduce aircraft drag and optimize lift distribution, while providing augmented roll and yaw control capability. The mechanical system is designed to face different flight situations by a proper action on the movable parts represented by two independent and asynchronous control surfaces with variable camber and differential settings. A set of suitable electromechanical actuators are integrated within the limited space inside the winglet loft-line, capable of holding prescribed deflections for long time operations. Such a solution mitigates the risks associated with critical failure cases (jamming, loss of WL control) with beneficial impacts on A/C safety. Numerical details on the system architecture and ability to cope with the typical mission loads profiles are given, along with a description of the conceptual analysis and the expected system performance according to a suitable metric.

In an innovative system, it is essential to keep under control the crucial development phases, which should consider several aspects involving, for instance, the modeling or the assessment of suitable analytical representations. Aiming to pursue a final demonstration to verify the actual capability of an engineering idea, however, some fundamental elements may have been partially considered. Many projects state the initial and final technology readiness level based on the famous scale introduced by the US National and Aeronautics Space Administration (NASA) many years ago and now widespread in many fields of technology innovation. Its nine-step definition provides a high-level indication of the maturity of the observed innovative system. Trivially, the resolution of that macroscopic meter is not made for catching advancement details, but it rather provides comprehensive information on the examined technology. It is, therefore, necessary to refer to more sophisticated analysis tools that can show a more accurate picture of the development stage and helps designers to highlight points that deserve further attention and deeper analysis. The risk is to perform a very good demonstration test that can miss generality and remain confined only to that specific experimental campaign. Moving on to these assumptions, the authors expose three realizations of theirs concerning aeronautic morphing systems, to the analysis of a well-assessed Technology Readiness Level instrument. The aim is to define the aspects to be further assessed, the aspect to be considered fully mature, and even aspects that could miss some elementary point to attain full maturation. Such studies are not so frequent in the literature, and the authors believe to give a valuable, yet preliminary, contribution to the engineering of breakthrough systems. Without losing generality, the paper refers to the 2.2 version of a tool set up by the US Air Force Research Laboratory (AFRL), and NASA, with the aim to standardize the evaluation process of the mentioned nine-step TRL.

SARISTU was a big cooperation project granted by the European Commission, 7th Framework Programme, carried out between 2011 and 2015. It dealt with smart aeronautic structures, both morphing and sensored; its main target was to demonstrate the feasibility of designing, manufacturing and operating in representative environment, instrumented structures. Till now, it represents the major effort carried out within the European Union on the development of adaptive architectures for air systems. Inside that big activity, the realization of an Adaptive Trailing Edge Device (ATED) for wing camber adaptations aimed at compensating the weight reduction following the fuel consumption during cruise was addressed. It made the core of investigations target variable geometry aircraft components together with two other analyses concerning the development of shape-changing winglet and droop nose. ATED activities were conducted by the Italian Aerospace Research Centre (CIRA) in tight cooperation with the University of Napoli, “Federico II”, who coordinated a group of 12 different partners from 8 different nations (France, Germany, Greece, the Netherlands, Israel, Spain, Turkey, and Italy). In this paper, an integral synthesis of that work is reported, with a focus on the definition and realization of the components of the presented device. The publication is in fact meant as the first part of a series that is aimed at overviewing the whole adaptive trailing edge development, till wind tunnel tests execution. Such a concise report is a critical and harmonized review of what have been performed by many colleagues spread all over Europe, all of which are duly recalled in the reported bibliography where the reader may access more detailed information and descriptions. In detail, the paper starts with a general introduction of the concept and its aims, to move to the specs definition immediately after. Then, it deals with a short but comprehensive description of the main ATED components: structural skeleton, skin, actuation and sensing systems. It is worth remarking that the paragraph dedicated to the body frame includes some discussion about aeroelastic assessment and manufacture, seen as complementation for a complete assessment of the design constraints.

Magneto-rheological fluids, or MRF, have been known for a long time in the technological and scientific community [...]

This paper offers an overview of the Project of AIRGREEN2 (AG2, Clean Sky 2), in terms of main targets, technology development and maturation path, current achievements and further steps and perspective. Starting from the industrial and scientific scenario in which AG2 was conceived, outlining the specific way it meets the current market and environmental requirements, the general structure is illustrated, paying attention to the specific validation gates and demonstration test campaigns. The paper then continues with an overview of the last achievements, encompassing the ground tests of an adaptive winglet and of an innovative wingtip, the finalization of a wind tunnel campaign for aeroelastic validation and the realization of morphing device models, for the upcoming wind tunnel tests on a flexible and laminar wing model. Finally, the next steps of the research are introduced, with specific reference to the ground test of a multifunctional flap, the execution of the just mentioned wind tunnel demonstration on a laminar, flexible and morphing wing, and the final flight demonstration of the winglet and of the wingtip.

In a previous paper, the authors dealt with the current showstoppers for morphing systems and with the reasons that have inhibited their commercial applicability. In this work, the authors ex-press a critical vision of the current status of the proposed architectures and the needs that should be accomplished to make them viable for installation onboard of commercial aircraft. The distinc-tion is essential because military and civil issues and necessities are very different, and both the solutions and difficulties to be overcome are widely diverse. Yet, still remaining in the civil seg-ment, there can be other differences, depending on the size of the aircraft, from large jets to com-muters or general aviation, in turn classifiable in tourism, acrobatic, ultralight and so on, each with their own peculiarities. Therefore, the paper wants to try to trace a common technology de-nominator, if possible, and envisage a future perspective of actual applications.

This paper deals with the actuation system design of a full-scale morphing aileron for regional aircraft. The aileron is allowed to smoothly change its geometrical configuration and perform the in-flight transition from a baseline shape to a set of optimal morphed ones pre-defined on the basis of aerodynamic requirements. The design of such innovative aileron is aimed not only at substituting the conventional aileron installed on a real aircraft but also to provide additional functionality. The aileron is free to rotate around its main hinge axis and it is also allowed to smoothly modify camber with two independent actuation systems. In such manner it can be used also during cruise with a symmetric deflection between the two half wings in order to reduce drag in off design condition. To accomplish variable aileron shape, a rigid-body mechanism was designed. The proposed aileron architecture is characterised by segmented adaptive ribs rigidly linked each other with spanwise reinforcements such as spars and stringers in a multi-box arrangement. Each rib is split into two movable plates connected by means of rotational hinges in a finger-like mechanism. The mechanism is driven by a load-bearing actuator by means of a kinematic chain opportunely tied based on the structural requirements in terms of shape to be matched and load to be withstood. The proposed device is an innovative arrangement of the quick-return mechanism composed of a beam leverage, commercial linear guides and a crank. The actuator shaft is directly inserted in the crank, which transmits the rotation to the linear guide that slide along a rail moving upward or downward the beam thus resulting in a camber variation. The entire aileron is moved by three leverages internally contained and distributed along the first two bays while the most external ribs are considered passive and their movement slaved. Two actuation layouts are analytically and numerically studied, the analytical theory is presented and validated by means of a multi-body simulation. Moreover, a linear static analysis was carried out under the hypothesis of glued contact between linear guides components simulating a jamming condition. This assumption has been formulated because it represents the most severe condition that envelop all the operative loads to which the actuation system is subjected. The analyses conducted are preliminarily aimed to verify that no failure occur under the imposed loads. In this first design loop, the vertical static force acting on the linear carriage exceeded allowable value and then a new configuration with double-sided linear guides was then investigated.

International audience; Aircraft winglets are well-established devices that improve aircraft fuel efficiency by enabling a higher lift over drag ratios and lower induced drag. Retrofitting winglets to existing aircraft also increases aircraft payload/range by the same order of the fuel burn savings, although the additional loads and moments imparted to the wing may impact structural interfaces, adding more weight to the wing. Winglet installation on aircraft wing influences numerous design parameters and requires a proper balance between aerodynamics and weight efficiency. Advanced dynamic aeroelastic analyses of the wing/winglet structure are also crucial for this assessment. Within the scope of the Clean Sky 2 REG IADP Airgreen 2 project, targeting novel technologies for next-generation regional aircraft, this paper deals with the integrated design of a full-scale morphing winglet for the purpose of improving aircraft aerodynamic efficiency in off-design flight conditions, lowering wing-bending moments due to maneuvers and increasing aircraft flight stability through morphing technology. A fault-tolerant morphing winglet architecture, based on two independent and asynchronous control surfaces with variable camber and differential settings, is presented. The system is designed to face different flight situations by a proper action on the movable control tabs. The potential for reducing wing and winglet loads by means of the winglet control surfaces is numerically assessed, along with the expected aerodynamic performance and the actuation systems' integration in the winglet surface geometry. Such a device was designed by CIRA for regional aircraft installation, whereas the aerodynamic benefits and performance were estimated by ONERA on the natural laminar flow wing. An active load controller was developed by PoliMI and UniNA performed aeroelastic trade-offs and flutter calculations due to the coupling of winglet movable harmonics and aircraft wing bending and torsion.

Morphing is an increasingly investigated topic in aeronautics due to the performance improvements brought by aerodynamic shapes adaptivity on large aircraft. Being aerodynamics mainly driven by geometry, a structure that can modify its shape may achieve tremendous capability enhancement, especially if its operating scenario is wide. However, the implementation of morphing structures leads to many issues that still need to be properly solved to make the technology fully operative in real application scenarios. For instance, additional DOFs generate systems with increased modal density and then with more complex aeroelastic behaviour, and premature onset of dynamic instabilities. The authors of the present paper have dealt with this problem in other publications, in cooperation with several colleagues, and interesting results are available in literature, to some extent. In this general framework, there are peculiar aspects that only recently have started to catch the attention of the scientific community. Among those, a particular one is the objective of the present work, referring to the numerical simulation strategy of adaptive devices. The kinematic system at the basis of a wide class of morphing structures is driven by an actuation chain, which gives an important contribution to the already cited aeroelastic behaviour. For safety-critical embedded subsystems, it is crucial to detect potential failures and predict their impacts since the early design stages. Now, kinematic components significantly affecting the structural dynamics, as torsion bars and bearings, are assumed rigid in the traditional simulation strategy. If such a concept may be supposed valid for standard layouts (as in the case of flap, ailerons and other moveable systems), it cannot be held for architectures integrating hundreds of those mechanical parts. This work addresses preliminary investigations on systematic analyses carried out on detailed simulations of selected components of aircraft morphing structures, trying to evaluate the effects of elasticity of bearings and hinged connections on the global dynamic response.

A new wing-tip concept with morphing upper surface and interchangeable conventional and morphing ailerons was designed, manufactured, bench and wind-tunnel tested. The development of this wing-tip model was performed in the frame of an international CRIAQ project, and the purpose was to demonstrate the wing upper surface and aileron morphing capabilities in improving the wing-tip aerodynamic performances. During numerical optimisation with ‘in-house’ genetic algorithm software, and during wind-tunnel experimental tests, it was demonstrated that the air-flow laminarity over the wing skin was promoted, and the laminar flow was extended with up to 9% of the chord. Drag coefficient reduction of up to 9% was obtained when the morphing aileron was introduced.

The actuation mechanism is a crucial aspect in the design of morphing structures due to the very stringent requirements involving actuation torque, consumed power, and allowable size and weight.In the framework of the CRIAQ MD0-505 project, novel design strategies are investigated to enable morphing of aeronautical structures. This paper deals with the design of a morphing aileron with the main focus on the actuation technology. The morphing aileron consists of segmented 'finger-like' ribs capable of changing the aerofoil camber in order to match target aerodynamic shapes. In this work, lightweight and compact actuation kinematics driven by electromechanical actuators are investigated to actuate the morphing device. An unshafted distributed servo-electromechanical actuation arrangement is employed to realise the transition from the baseline configuration to a set of target aerodynamic shapes by also withstanding the aerodynamics loads. Numerical investigations are detailed to identify the optimal actuation architecture matching as well as the system integratability and structural compactness.