A Variable Camber Piezocomposite Trailing-Edge for Subsonic Aircraft: Multidisciplinary Design Optimization

A continuous-surface morphing airfoil is desirable for commercial aircraft in order to improve fuel efficiency, and due to the potential to morph the wing into a high-lift configuration for take-off and landing. Piezocomposite actuators have shown to be a feasible strategy for camber morphing in small unmanned fixed-wing aircraft with a Reynold’s number in the range of 50,000 to 250,000. As an extension, this paper presents a theoretical framework and results for morphing in single and multi-segment natural laminar flow airfoils with a maximum Reynold’s number of 825,000. The airfoils presented employ a continuous inextensible surface. To achieve morphing, piezocomposite actuating elements are applied on the suction and pressure surfaces of the airfoils. The geometric properties of the airfoils are determined using a genetic algorithm optimization method with a migration strategy in order to maintain population diversity. The algorithm optimizes independently the substrate thicknesses for the nominal airfoil, the leading edge, and the piezocomposite bonded surfaces. In addition, positions and voltages for each piezocomposite actuators are optimized. The genetic algorithm uses an objective function to maximize the change in coefficient of lift to morph the airfoil from its baseline (i.e. cruise) state to the high-lift state. Analysis is performed using a coupled fluid-structure interaction method assuming static aero-elastic behavior. Optimization is followed by a parametric analysis to examine lift, drag, and lift-to-drag ratio of the airfoils over their full operational range. The optimization is performed on a symmetric, asymmetric, and the aft element of a slotted multi-segment airfoil to examine the capabilities of induced-strain actuation at high dynamic pressures.