Finite element analysis and failure prediction of adhesive joints in wind turbine rotor blades

Wind turbines have been growing in size significantly during the past years. As a consequence, the mechanical loads acting on the wind turbine components increase as well. This gives rise to the need to develop new or to enhance existing methodologies for failure analyses of wind turbine components. This paper deals with the finite element analysis of adhesive joints in wind turbine rotor blades and addresses both ultimate and fatigue load analyses. For ultimate loading, an equivalent stress approach is utilized. In fatigue, wind turbines experience high amplitudes and very high cycle numbers. Hence, an appropriate fatigue analysis framework is of utmost importance. In this paper a critical plane approach is employed. The model captures multiaxial stress states as required by current design guidelines and takes into account non-proportional stress histories. The paper focuses on the trailing edge adhesive joints, as they are highly stressed in longitudinal direction and shear. Representative numerical examples show that a multiaxial strength analysis for ultimate and fatigue loads is extraordinarily important to design reliable adhesive joints. The necessity to account for non-proportionality in the stress histories is also demonstrated.