Aeroelasticity and Dynamic Analysis of Cracked Composite Wings Using Spectral Finite Element Method

Abstract

In this paper, a spectral finite element model (SFEM) is developed to conduct aeroelastic and dynamic analyses of composite wings. The governing equations are derived based on the extension-bending-torsion beam dynamic model, in which warping effects are included. The unsteady aerodynamic model is employed in order to conduct aeroelasticity predictions. The SFEM is formulated in the frequency domain based on the exact solutions of the governing equations. In order to investigate the effect an edge surface crack has on a composite wing’s performance, a local flexibility matrix is introduced to model the open crack, which is in terms of crack depth and crack location on the wing. The local flexibility matrix is based on Castigliano's theorem and the laws of fracture mechanics. By applying force compatibility conditions at each crack location, we can assemble the spectral finite elements and conduct aeroelastic and dynamic predictions on the composite wings. Flutter and bending-torsion beam frequency results available from various sources are used to validate our predictions. In summary, an accurate and efficient approach is developed to predict the flutter speed and natural frequency of composite wings both with and without edge surface cracks. Physical insights can be collected from our simulation results to advance design analysis and health monitoring for composite wings.