Implementation of a continuous-inextensible-surface piezocomposite airfoil

The theoretical and experimental evaluation of a variable-camber airfoil which employs a continuous inextensible surface and surface bonded piezoelectric actuators is presented. The partially-active surface is designed to have sufficient bending stiffness in the chordwise direction to sustain chordwise shape under aerodynamic loading. In contrast, the in-plane stiffness is relatively high; however the necessary deformations that are required to change the aerodynamic response can still be attained while maintaining the surface perimeter constant. Coupled with two carefully selected boundary conditions, the proposed piezocomposite airfoil can achieve significant change in aerodynamic response. The surface geometry properties are determined using a Genetic Algorithm optimization method. The optimization is conducted to achieve maximum change of lift-output-per-square-root-of-drag which is the difference in the aerodynamic response for the airfoil at maximum excitation (asymmetric) and zero excitation (symmetric). A coupled analysis of the fluid-structure interaction is employed assuming static-aeroelastic behavior which allows the realization of a design that can sustain aerodynamic loads. The theoretical response is supplemented with extensive bench top and wind tunnel experiments on a representative prototype. The experimental results are compared to the theoretical predictions, highlighting agreements and discrepancies.