Geometrically nonlinear beam analysis of composite wind turbine blades based on quadrature element method

A new nonlinear beam theory is proposed for the analysis of composite wind turbine blades. The beam theory is developed by extending classical Euler-Bernoulli beam theory to a generalized Timoshenko beam. Mechanics-based variables are used to describe finite rotation such that the problems of the sequence dependence or spatially discontinuity of rotational variables can be avoided. Furthermore, nonlinear beam theory is implemented using the weak-form quadrature element method. Numerical examples of both non-rotating and rotating beams are given and the comparison with analytical and finite element results shows high computational accuracy and efficiency of the proposed nonlinear quadrature element. A simple parametric study of a virtual 5-MW wind turbine blade shows that bend-twist coupling due to both material anisotropy and geometrical nonlinearity affects the dynamic performance of the blade significantly.