Forward Flight Simulation of Composite Rotor Blades with Matrix Cracking and Uncertainties

摘要

This study is focused on the stochastic analysis of composite rotor blades with matrix cracking in forwardrnflight condition. The effect of matrix cracking and uncertainties are introduced to aeroelastic analysisrnthrough the cross-sectional stiffness properties obtained using thin walled beam formulation, which isrnbased on a mixed force and displacement method. Forward flight analysis is carried out using an aeroelasticrnanalysis methodology developed for composite rotor blades based on the finite element method in spacernand time. The effects of matrix cracking are introduced through the changes in the extension, extensionbendingrnand bending matrices of composites whereas the effect of uncertainties are introduced through thernstochastic properties obtained from previous experimental and analytical studies. The stochastic behavior ofrnhelicopter hub loads, blade root forces and blade tip responses are obtained for different crack densities.rnFurther, assuming the behavior of progressive damage in same beam is measurable as compared to itsrnundamaged state, the stochastic behaviors of delta values of various measurements are studied. From thernstochastic analysis forward flight behavior of composite rotor blades at various matrix cracking levels, it isrnobserved that the histograms of these behaviors get mixed due to uncertainties. This analysis brings out thernparameters which can be used for effective prediction of matrix cracking level under various uncertainties.rnThe behavior is useful for development of realistic online matrix crack prediction system. Instead ofrnintroducing the white noise in the simulated data for testing the robustness of damage prediction algorithm,rna systematic approach is developed to model uncertainties along with damage in forward flight simulation.