Parametric Studies of Flexible Sandwich Panels As a Compliant Fairing for Folding Wingtip Joints

This paper presents a parametric study into the design space of morphing fairings for the Semi-Aeroelastic Hinged (SAH) folding wing concept. The fairing will cover the angled hinge region of the wingtip with a smooth and continuous skin surface to reduce drag. It is made from flexible sandwich panels employing the Geometrically Anisotropic ThermOplastic Rubber (GATOR) morphing skin concept, with a chevron-based cellular core covered in elastomeric facesheets. A parametrically defined finite element analysis framework is established and used to explore the mechanical response of a three-dimensional wing fairing. The two design objectives are minimising torsional stiffness and out-of-plane deformation during the rotation of the underlying wingtip joint. A parameter sweep is used to establish correlations between the design variables and the competing objectives. Notable correlations were identified for the chevron wall angle, core thickness, facesheet thickness, fairing span, pre-strain and flare angle. Pre-straining the facesheets is found to delay the onset of large changes in surface curvature and the subsequent softening of stiffness. However, it also leads to higher levels of torque at large rotation angles. Overall, this study helps to elucidate the design trends for compliant fairings while also reducing the design space in preparation for further studies.