Dynamic Characteristics of Composite Helicopter Blade Solved by Using the Differential Quadrature Method

Abstract

The dynamic characteristics of nonlinear composite helicoper blades are solved by using the differential quadrature method (DQM). The bending-torsion coupled beam model is proposed to characterize the composite blade. The Kelvin-Voigt internal and linear external damping coefficients are also employed. The DQM is used to transform the partial differential equations of a composite rotor blade into a discrete eigenvalue problem. The Chebyshev-Gauss-Lobatto sample point equation is used to select the sample points. Numerical results indicate that even nine sample points can provide the convergent results by employing this DQM for the blade analysis. The difference between the responses derived from the linear and the nonlinear models have been compared to illustrate the significance of the nonlinear effect in this case. The transitional dynamic responses of the derived systems are calculated by using Newmark method. In this study, the effects of the fiber orientation, internal damping, external damping, pre-twisted angle and the rotation speed on the dynamic behavior for a composite beam are studied. The effect of the number of sample points on the accuracy of the calculated natural frequencies is also discussed. The integrity and computational efficiency of the DQM in this problem will be demonstrated through a number of case studies. Numerical results indicated that the DQM is valid and efficient for a composite blade formulation.