Structural Integrity of Composite Rotor Blades with Service and Ballistic Damage

A general computational approach is developed to understand and quantify the effect of damage in composite rotor blades on their structural integrity. The approach is based on multi-scale non-linear finite element analysis (FEA) to capture the complexity of blade designs and to provide efficient engineering solutions. A generalized parametric model of blade section is developed with artificial damage in the form of circular or elliptical holes within the pocket region of the blade. These damage entities represent possible results of numerous service and ballistic conditions. Their characteristics such as size, location, shape, type, aspect ratio, and orientation are considered as variable parameters of the analysis. Stress-based criteria for composite skin are applied for evaluation of blade structural integrity. Computational implementation of the approach is performed on examples of a representative composite main rotor blade. The robust nature of numerical non-linear solutions is demonstrated. Important trends with respect to the damage characteristics are observed and quantified. Generated results may help to develop more advanced repair criteria and reduce over-conservatism of existing repair methodologies for the pocket region of the blades.