Piezo-Aeroelastic modeling and flutter prediction of flexible composite wings

The design of structural components with enhanced flexibility led to research new solutions to control the arising structural instabilities. For this purpose a reasonable compromise between control effectiveness and added weight have to be reached. The solution proposed in this paper reflect this attempt, of finding an optimal configuration without any substantial weight penalty. The discussion is here furthermore restricted, among the various aeroelastic phenomena, to the conventional flutter condition only. Aeroelastic flutter of wings and structures is typically considered a dangerous self-starting instability phenomenon that must be avoided by properly designing the mass, stiffness, and inertia properties of structures and by restricting the flight envelope of the aircraft. A reduced order model, including only three degrees of freedom in edgewise, flap-wise and torsion, of a thin-walled composite beam has been proposed to study the flutter phenomenon of a such wing configuration. Besides, the possibility of acting on the restriction of the flight envelope, postponing the flutter instabilities onset, have been investigated by adding to the composite beam a piezoelectric (PZT) passive circuit. The governing equations of the expanded structural element, beam and PZT, have been matched with an aerodynamic model for incompressible unsteady flow. The effect of composite bending/torsion couplings terms have been analyzed as well as the optimum electrical load value and bending stiffness as a function of the model flutter speed. The analysis show the possibility to identify an optimum setting, in terms of structural stiffness and resistive load, in order to conciliate the goals of postponing the flutter onset and of power generation.