Aeroelastic Stability Analysis of Damaged HALE Aircraft Wings

Hanif S. Hoseini

Nonlinear aeroelastic analysis of damaged High-Altitude-Long-Endurance aircraft composite wings is considered. The structural model consists of full three-dimensional finite elements continuum model for the damaged area, which is a small localized area of the wing, and a geometrically exact one-dimensional displacement-based finite elements beam model for the undamaged part of the wing. The solid and the beam parts are then rigorously combined using a transformation between the joined nodes of the two models at their intersection. The transformation is derived using the recovery equations of variational asymptotic beam model and employed to eliminate the six degrees-of-freedom of the single joined node of the beam. The validity and efficiency of the method is demonstrated using test cases involving cracks and delaminations in the solid part. It is shown that although the accuracy remains virtually the same between the full three-dimensional model and the joined one-dimensional/three-dimensional model, the computational cost is considerably lower for the latter. Finite-state induced flow theory of Peters is exploited as the unsteady aerodynamic model to compute aerodynamic forces and moments acting on the wing. Combining the structural and aerodynamic models, a dynamic nonlinear aeroelastic element is developed for the time simulation of the dynamic responses of composite high aspect-ratio wings. The model can be conveniently used for analyzing flutter characteristics and time responses to external excitations, as well as synthesizing passive and active flutter suppression control systems. Numerical results verifying the validity of the method are presented and the results are discussed.

The proposed joined model will enables the High-Altitude-Long-Endurance aircraft designers to tackle the problem of aeroelasticity in a computationally efficient manner, without sacrificing accuracy with regard to full three-dimensional models, hence reducing the overall time and cost of the design process.