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Morphing promises to enhance the performance of wing-like structures by allowing for operating optimally in a wide range of flying conditions. Yet, a key unresolved problem is the realization of a skin capable of concurrently carrying bending and shear loads, as well as allowing for significant levels of in-plane stretching. In this article, a novel concept exhibiting these desirable characteristics is introduced by means of a double walled structure hereafter called double corrugation. Numerical results show that the double corrugation is capable of offering a high bending stiffness while achieving, with low applied forces, a 20% in-plane stretching. The numerically obtained results are validated with experimental tests, showing the feasibility of the concept. Furthermore, the structural characteristics of the double corrugation are optimized for different material constructions. Nonlinear optimization results concurrently considering strength, bending stiffness, axial compliance and weight show the capabilities of this concept to potentially address the conflicting requirements of morphing skins.

In this article, a compliant morphing wing featuring an innovative load-carrying, highly anisotropic, doubly corrugated morphing skin is introduced. A multi-disciplinary design methodology is used to optimally generate the compliant structure with the aim of maximising the produced rolling moment, while minimising mass and drag. The design tool considers the three-dimensional, aeroelastic behaviour and structural constraints. In particular, a parametric metamodel is used to identify the best morphing skin design. The results show that the wing can achieve high levels of control authority and has a lower or equivalent weight compared to conventional wings. A wing demonstrator is manufactured and its aeroelastic performance is tested. The measurements of the displacement field show an appreciable deformation without shape discontinuities. Low-speed wind tunnel tests indicate that the designed wing can produce roll moments that are sufficient for replacing conventional ailerons. Moreover, the obtained changes in shape have a negligible effect on the zero-lift drag, thus demonstrating the aerodynamic efficiency of profile changes achieved through morphing. An effective solution for covering the used corrugation while allowing for shape changes is also introduced and tested.

Morphing wings have a high potential for improving the performance and reducing the fuel consumption of modern aircraft. Thanks to its simplicity, the compliant belt-rib concept is regarded by the authors as a promising solution. Using the compliant rib designed by Hasse and Campanile as a starting point, a compliant morphing wing made of composite materials is designed. Innovative methods for optimal placing of the actuation and for the quantification of the morphing are used. The performance of the compliant morphing wing in terms of three-dimensional (3D) structural behaviour and aerodynamic properties, both two- and three-dimensional, is presented and discussed. The fundamental importance of considering 3D coupling effects in the determination of the performance of morphing aerofoils is shown.

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Because of their anisotropic properties, corrugated panels are good candidates for morphing skin applications. Their non-smoothness, however, might result in disadvantageous aerodynamic effects. In this work, we suggest the use of electro-bonded laminates (EBL) to realize a smooth corrugated skin. The EBL is applied to a double corrugation (DCo) design, which offers greater structural performance than conventional corrugations. Experimental tests indicate that the electrical adhesion force is sufficient for the intended application. The electrical bonding is also shown to improve the dissipative properties of the skin, which help to counteract vibrations arising from the high axial compliance. The behavior can be modified by varying the applied voltage, thus resulting in a tunable system.

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The aerodynamic performance of wing structures is directly related to their external geometry. The idea of seamless shape adaptation of the wing geometry (or morphing) has emerged to provide the capability of operating optimally in a wide range of conditions. Of particular importance to realize the potential of morphing is the ability of the wing skin to conform to the different geometrical contours. Several concepts for morphing skins have been presented to address this design challenge, each presenting peculiar strengths and weaknesses depending on the chosen combination of material and structural arrangement. This paper investigates the generic structural properties of a passive morphing skin design to allow for optimal shape adaptation through cambering. The properties of the morphing skin are included among the design variables to identify their optimal value; multi-objective optimizations are used to obtain parametric results. The results indicate the need for a high anisotropy, both between membrane and bending properties and between the skin's principal directions. The impact of the skin weight on the wing design is also shown.