Structural design and analysis of an anisotropic, bi-axially morphing skin concept

Abstract

Morphing skins as structural component in shape adaptive wings are still in their early development phase, as they need to combine contradicting requirements, such as extreme anisotropic mechanical behaviour, low structural thickness and air-tightness. Various morphing skin approaches have been designed for confined problems such as camber morphing and low load scenarios. However, to expand the applicability of morphing wings, a morphing skin with full in-plane deformability and an out-of-plane stiffness suitable for manned aircraft is necessary. In this work, a novel, elastomer free layered morphing skin is designed, manufactured, applied to a camber morphing transition region for small aircraft and analysed. The layered morphing skin is based on stacked, stiff platelets contributing to the out-of-plane stiffness, while compliant ligaments connecting the platelets provide in-plane compliance. Therefore, the layered morphing skin shows extreme orthotropy and can independently deform in both in-plane directions with an initial modulus of 198 kPa. Deformation analysis of the layered morphing skin on the camber morphing transition region confirms the bi-axial deformability and shows strains in span and chord up to 10% and 16%, respectively. Conducted pressure tests indicate an out-of-plane stiffness high enough for small aircraft, despite the demonstrator being manufactured from a polymer. The layered morphing skin concept is a promising base for bi-directionally deformable morphing skins.