Variable-stiffness skin concept for camber-morphing airfoils

Morphing airfoils promise advances in performance and efficiency when compared to conventional designs. However, the conflict of requirements between compliance and stiffness, which is characteristic of shape-adaptable structures, often leads to compromise-driven solutions. This article presents the concept of a variable-camber airfoil with adjustable stiffness. Smart elements in the airfoil skin permit to adapt the structural rigidity to the system’s operational states, resulting in more efficient morphing and potentially lighter designs. It is shown by a numerical study that with respect to a reference configuration, the actuation energy is reduced by up to 97% and the structural mass can be lowered by up to two thirds. Furthermore, experiments on a scaled airfoil structure with a variable-stiffness skin based on electro-bonded laminates demonstrate effectivity and integrability of the proposed structural concept, which permit changes in cambering stiffness by a factor of at least 70.