Fatigue life prediction of wind turbine rotor blade composites considering the combined effects of stress amplitude and mean stress

To predict fatigue life of wind turbine rotor blade composites under random loads, the combined effects of stress amplitude and mean stress are considered. First, the generalized sigma-N curved surface is introduced to characterize the fatigue properties of composites under constant amplitude cyclic load. Then, a modified Miner's rule is developed to reveal the evolution process of fatigue damage under variable amplitude cyclic loads. Finally, a fatigue life prediction model is presented based on the total probability formula and the modified Miner's rule, which can reflect the combined effects of stress amplitude and mean stress on fatigue life. The experimental data of wind turbine rotor blade composites are used to illustrate the specific process of the proposed method; the results indicate that the prediction values of the developed method are reasonable and effective.