Vibration characteristics of a rotating pre-twisted composite laminated blade

A new dynamic model based on the shell theory is presented to investigate the vibration behavior of a rotating composite laminated blade with a pre-twisted angle. The effects of the Coriolis and centrifugal forces due to the rotation motion of the blade are considered in the formulation. Based on the Rayleigh-Ritz method and continuous algebraic polynomial functions satisfying the boundary conditions of a cantilever, the natural frequencies and mode shapes of a rotating pre-twisted blade are obtained. The convergence analysis is performed and the accuracy of the proposed model is verified by comparing the non-dimensional frequencies obtained by the present method with those in literature. The frequency loci veering and crossing phenomena along with the corresponding mode shape variations are presented and discussed in detail. A comprehensive parameter investigation of the effects of aspect ratio, pre-twisted angle, stagger angle, rotation velocity and hub radius on variations of the modal characteristics of the blade is conducted. It is demonstrated through the results of this paper that the developed model is effective to evaluate the dynamic behavior of rotating pre-twisted blades, which would be useful for improvement in design and optimization of the material and geometry dimension of the blades.