A probabilistic approach for strength and stability evaluation of wind turbine rotor blades in ultimate loading

Reliability assessment of strength and elastic stability of a composite rotor blade designed according to IEC 61400-1 ed. 3 was performed. Calculations were carried out at the ply level of the laminates where material properties are also measured and certified. Stress analysis was performed using a thick-shell 3D finite element formulation. The mechanical properties of the material and the extreme loads were considered as stochastic variables taking into account both the physical and statistical uncertainty. Loading of the blade was derived from aero-elastic simulations in which the rotor blades are modeled using beam element formulation. A procedure was developed to properly represent the stochastic nature of the extreme loading that has to be applied on the 3D shell-finite element model based on the aero elastic beam results. Reliability analysis was performed by means of a response surface method combined with crude Monte Carlo simulation.