Monitoring Based Fatigue Damage Prognosis of Wind Turbine Composite Blades under Uncertain Wind Loads

Lifecycle assessment of wind turbines is essential to improve their design and to optimum maintenance plans for preventing failures during the design life. A critical element of wind turbines is the composite blade due to uncertain cyclic wind loads with relatively high frequency and amplitude in offshore environments. It is critical to detect the wind fatigue damage evolution in composite blades before they fail catastrophically and destroy the entire wind turbines. This study presents a methodology for analysing the fatigue failure probability of a wind turbine composite blade by using monitoring stochastic deterioration modelling. On the basis of 5 minutes mean wind speed measurements, the internal stresses can be accurately obtained from finite element analysis, and failure probabilities are predicted by stochastic gamma process fatigue damage model in design service life. A numerical example of a wind turbine composite blade is investigated to show the applicability of the proposed model. The results show that the stochastic fatigue damage model can give reliable results for time-dependent reliability analysis for composite blades of wind turbines.