Development of Morphing Fairing for Semi-Aeroelastic Hinge winglets

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In recent years, increasing emphasis has been placed on reducing aircraft emissions. One of the well-understood approaches to reduce emissions in civil aircraft is to increase the wingspan. This reduces the induced drag of the wing, hence, the fuel consumed. Two major constraints in the way of this approach are (1) the limited airport gate sizes and (2) the increased structural requirement of a longer wing.The Semi-Aeroelastic Hinge concept is aimed at circumventing the above-mentioned two challenges by having a folding wingtip where the folding axis is at a flare angle outward to the freestream direction. The folding of the wingtip allows the aircraft to shorten the wing before approaching the airport gate and the flare angle allows the wing to reduce the maximum gust load on the wing root. Previous research in the literature has shown that the best gust load alleviation is achieved for wingtips with low folding stiffness, damping and mass along with a high flare angle.One of the challenges in the physical realisation of such a device is the discontinuity of the wing skin between the inboard wing and the wingtip. This discontinuity of the surface is prone to the generation of vortices and the subsequent flow separation which erodes some of the aerodynamic benefits of the foldable wingtip. A compliant fairing around the joint will close the gap while allowing for the folding of the wingtip. This fairing could be an integrated primary structure that also acts as the joint; or a secondary skin around a hinge joint, which only carries the aerodynamic load. The choice of the latter is based on space efficiency and minimising the folding stiffness for better gust load alleviation.This research project focuses on (1) studying the behaviour of the skin on a folding wing geometry and identifying the properties of the skin which optimise the desired characteristics, (2) identifying the architecture of skins that has the desired properties and (3) implementation of the identified skin architecture on a folding wingtip device.In summary, the overarching research question could be summarised as "What benefits can compliance-based, stiffness tailored, morphing fairings provide to full-scale commercial airliners with Semi-Aeroelastic Hinge winglets?".