Critical Aeroelastic Behaviour of Slender Composite Wings in an Incompressible Flow

The design of highly flexible aircraft, such as high-altitude long endurance (HALE) configurations, must include phenomena that are not usually considered in traditional aircraft design. Wing flexibility, coupled with long wing span can lead to large deflections during normal flight operation with aeroelastic instabilities quite different from their rigid counterparts. A proper beam model, capable of describing the structural flight deflections, should be adopted. It includes the evaluation of the equivalent stiffness both in the case of isotropic configuration and in simple/thin-walled laminated sections emphasizing different coupling effects. Consequently, the flutter analysis has to be performed considering the deflected state as a reference point. The resulting equations are derived by the extended Hamilton's principle and are valid to second order for long, slender, composite beams undergoing moderate to large displacements. The structural model has been coupled with an unsteady aerodynamic model for an incompressible flow field, based on the Wagner aerodynamic indicial function, in order to obtain a nonlinear aeroelastic model. Using Galerkin's method and a mode summation technique, the governing equations will be solved by introducing a simple numerical method that enables one to expedite the calculation process during the preliminary design phase. In order to assess the accuracy of the prediction, the results obtained in a test case are compared with a FEM model showing a good correlation. The effect of typical parameters on critical boundaries, including stiffness ratios, ply layup, deflection amplitude, as well as the wing aspect ratio, are investigated. Analytical/Experimental comparisons are presented both in the linear case and in the non-linear derivation. A test model identification procedure is also reported, based on similarity theory, for the development of a wind-tunnel component suitable for experimental test campaign © 2011 Nova Science Publishers, Inc. All rights reserved.