Comparison of different cross-sectional approaches for the structural design and optimization of composite wind turbine blades based on beam models

Abstract

During the preliminary multidisciplinary design phase of wind turbine blades the evaluation of many design candidates plays an important role. Computationally efficient methods for the structural analysis are needed to cover the required effects, e.g., correct prediction of stiffness matrix entries including the (bend-twist) coupling terms. The present paper provides an extended overview of available approaches and shows their ability to fulfill the requirements for the composite design of rotor blades. Three cross-sectional theories are selected and implemented to compare the cross-sectional coupling stiffness terms and the stress distribution based on different multi-cell test cross-sections. The cross-sectional results are compared with the 2D finite element code BECAS and discussed in the context of accuracy and computational efficiency. The most promising approach achieved a better resolution of the stress distribution compared to BECAS and an order of a magnitude less computation time when the same discretization is used. The deviations of the stress distributions are below 10 percent for the most test cases. The results can serve as a basis for the beam-based design of wind turbine rotor blades.