Progressive Failure Analysis of Wind Turbine Blades Based on a Thin-Wall Beam Finite Element Model

Abstract

The implementation of a Progressive Failure Analysis (PFA) onto a Thin-Wall Beam (TWB) Finite Element (FE) model is presented. The developed TWB model has been based primarily on the work by Librescu, Lee and others, and has been specialized here for the case of a generic wind turbine blade. The selected model provides analytical expressions for arbitrary crosssection’s stiffness, thus bridging the gap between “damaged” (i.e. degraded) material properties and displacement-based FE solutions. In addition, it allows the straightforward modelling of material anisotropy, arbitrary laminate layups and shear deformability, thus being able to represent fundamental structural behaviour of more complex 3D shell or solid FE models with reasonably good accuracy. Moreover, as the stress/strain field can be recovered for individual layers based solely on nodal FE displacement solutions, PFA allows tracking damage at any layer and position of the structure. The failure criteria implemented on the TWB model are those used in GENOA, a commercial software specialized on composite material failure analysis. The developed damage and structural models were tested via a detailed numerical model of a commercial wind turbine blade comprised of multiple airfoils and material layups. Good results agreement was obtained when compared against those yielded by a 3D shell FE model built in GENOA. These results indicate that the proposed PFA-TWB is a feasible and economic approach for a preliminary aeroelastic wind turbine blade’s structural design.