The effect of fiber angle on the natural frequencies of orthotropic composite pre-twisted blades

The eigenvalue problem of a tapered pre-twisted orthotropic composite blade is formulated by employing the differential quadrature method (DQM). The Euler–Bernoulli beam model is used to characterize the pre-twisted orthotropic composite blade. The Kelvin–Voigt internal and linear external damping coefficients are employed and determined for the orthotropic composite blade. The DQM is used to transform the partial differential equations of a tapered pre-twisted orthotropic composite blade into a discrete eigenvalue problem. The Chebyshev–Gauss–Lobatto sample point equation is used to select the sample points. In this study, the effects of the fiber orientation, internal damping, external damping, inclined angle and the rotation speed on the natural frequencies for a tapered pre-twisted orthotropic composite blade are investigated. 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 pre-twisted orthotropic composite blade formulation.