Mechanical analysis and layup optimization of simulating specimen for composite rotor blades based on Rayleigh-Ritz method

Composite rotor blade becomes one of the important components in the aerospace and energy industries, owing to its advantages of lightweight, high specific strength and modulus, and tunable mechanical properties. Determining the effects of material parameters and layup on structural load-bearing capacity is valuable for engineering application. With energy method, a theoretical model for strength evaluation, stiffness analysis, and layup optimization of this structure are proposed. Based on Rayleigh-Ritz method, theoretical models about the simulating specimen for composite rotor blade under different loading conditions are established, including the blade solely under centrifugal force and the blade under combined centrifugal force and uniform pressure. The theoretical model is verified by the finite element method (FEM). And a higher order of the trial function induces higher prediction accuracy of the model. Finally, the effects of different layups on the strength and stiffness of the rotor blade simulator with ply drops are evaluated with this model. The results show that the prediction error of the theoretical model in radial deformation is lower than 6%. And for transverse deformation prediction, the error is no higher than 15%. The theoretical analysis aligns well with simulation results in predicting stress distribution. Besides, it shows that the layup significantly influence the mechanical performance of the structure. The deformation in x-direction of the structure with [0]_n layup is the smallest, followed by the structure with [0/90]_ns layup and [±30]_ns layup. The deformation in x-direction of the structure with [±45]_ns layup is the largest. The increase in proportion of 0° plies improves the structural stiffness. As for stress along the principal material axes, the structures with [0]_n, [±30]_ns and [±45]_ns layups have similar magnitude, which are smaller than that of the structure with [0/90]_ns layup. The theorical model proposed in this paper provides a method for efficiently evaluating the mechanical properties of the composite rotor blade. Compared to traditional method, this model can shorten the design period and improve the efficiency, which is helpful for optimal design of composite power components.