Unsteady aero-elastic analysis of a composite wing containing an edge crack

Abstract

This paper deals with the investigation of the influence of edge surface crack on the flutter behavior of unidirectional fiber-reinforced composite wing subjected to unsteady aerodynamic loads. The cracked wing is modeled as a two-interconnected Euler–Bernoulli beam at the crack location, where the related crack is modeled using continuity conditions and the local flexibility matrix concept. The components of this matrix are extracted from the theory of linear fracture mechanics. The formulation takes into account the effects of bending-torsion coupling due to the unbalanced laminates and offset of the center of gravity inherent to composite structures. The fundamental modes of intact and cracked cantilevered beams, derived from the free vibration analysis by the dynamic stiffness matrix, are used in Galerkin's method. The modified shape functions are developed to reflect the crack effect in the aeroelastic analysis, wherein an unsteady aerodynamic model based on strip theory is employed. By a combination of structure and aerodynamic formulations and using the modified mode shapes and applying a new iteration algorithm, the flutter boundary is determined. Also, the procedure has been evaluated by solving the number of problems available in the literature. Then effects of various parameters, such as the fiber angle, the crack location, the crack length, and the aerodynamic model, on the flutter boundary are analyzed and a detailed discussion will be addressed. It was found that these parameters can have a positive or negative influence on the flutter behavior of the structure.