A Novel Method for Aeroelastic Analysis of Curved Composite Rotor Blades in Forward Flight Based on Geometrically Exact Beam Theory

The composite rotor blades with initial curvatures such as single swept, double swept and so on have excellent aerodynamic performance, but also have complex aeroelastic performance which depends on the composite laminate layup. Currently, there is no good method for dealing with the aeroelastic problem. In this paper, a novel method for aeroelastic analysis of curved composite rotor blades in forward flight based on the geometrically exact beam theory with the updated V ABS for the structural modeling of curved composite rotor blades has been presented. The effect of blade initial curvatures on the blade cross-sectional properties and one-dimensional blade deformations are both considered. The formulations for calculating the transformation matrix, position and length of curved composite rotor blades are developed. The Peters finite state airloads theory and the Peters-He finite state dynamic inflow model are combined to calculate the three-dimensional unsteady airloads. Auto-pilot trim scheme is used to determine the blade pitch controls to meet the trim requirements. The time domain method based on the finite element spatial discretization, Newmark numerical integration and Newton-Raphson methods is developed to calculate the geometrically exact steady-state responses of composite rotor blades in forward flight. The proposed geometrically exact aeroelastic response analysis method is validated by correlation with SA349/2 flight test data. It is found that the blade initial curvatures significantly affect the aeroelastic responses of composite rotor blades. The investigations highlight the importance of the coupled effect of blade initial curvatures and elastic couplings on the reduction of the vibratory hub loads.