Initial exploration of a compliance-based morphing fairing concept for hinged aerodynamic surfaces

Discontinuity on aerodynamic surfaces leads to notable aerodynamic penalties which could be avoided with compliant fairings. This paper introduces a novel design for a compliant fairing to eliminate the gaps present on hinged aerodynamic surfaces such as hinged wingtips. The fairing is designed to provide a smooth, continuous change in shape between the surfaces on either side of the hinge as they rotate relative to each other. While the concept is generally applicable to any folding surface, including trailing edge flaps, this work focuses on applying it to the Semi-Aeroelastic Hinge (SAH) wingtip concept, which consists of a hinged outer wing panel mounted at a flare angle to the incoming flow. The design aims to minimise the strain on the skin and the rotational stiffness of the fairing while maintaining a smooth and robust outer aerodynamic surface. The skin is attached to the underlying joint structure via a novel pivoting-rib solution which alleviates skin strains over the +90/-20 degree operating rotation range of the joint. This paper introduces the concept and motivates the design constraints underlying it. A simplified analytical model of the fairing mechanism is presented and the effects of changing the design variables are explored. The results show the benefit of the pivoting ribs over fixed ribs in minimising the strain on the skin and the folding stiffness of the joint. Further arguments are drawn to emphasise the need for a higher fidelity model to account for the geometric and out-of-plane deformation effects of the fairing.