Stiffness Degradation Modeling for Composite Wind Turbine Blades Based on Full-Scale Fatigue Testing

In order to provide more insights into the damage propagation composite wind turbine blades (blade) under cyclic fatigue loading, a stiffness degradation model for blade is proposed based on the full-scale fatigue testing of a blade. A novel non-linear fatigue damage accumulation model is proposed using the damage assessment theories of composite laminates for the first time. Then, a stiffness degradation model is established based on the correlation of fatigue damage and residual stiffness of the composite laminates. Finally, a stiffness degradation model for the blade is presented based on the full-scale fatigue testing. The scientific rationale of the proposed stiffness model of blade is verified by using full-scale fatigue test data of blade with a total length of 52.5 m. The results indicate that the proposed stiffness degradation model of the blade agrees well with the fatigue testing results of this blade. This work provides a basis for evaluating the fatigue damage and lifetime of blade under cyclic fatigue loading.