Probabilistic structural reliability analysis of a horizontal axis tidal turbine blade by considering the moisture effects on the blade material

Abstract

The use of composite materials in marine structures like the horizontal axis tidal turbine blade introduces inherent uncertainties in the material properties of the blade. Further, the blade material ages because of the absorption of seawater into the material. Hence, whilst performing the static structural analysis of the blade, the probabilistic nature of the material properties, as well as its degradation due to ageing, must be considered. In this study, the probabilistic structural response of a 0.5 m blade was estimated by considering the experimentally determined statistical distributions of the dry and aged material properties. The polynomial chaos expansion (PCE) method was used to build a surrogate model to mimic the static analysis of the blade, which was used in conjunction with the Monte Carlo simulation to estimate the distributions of the structural response of the blade and the probability of failure of the dry and aged blade. Stochastic convergence was used to check the accuracy of the surrogate model built via the PCE method. The study revealed a statistically significant increase in the probability of failure of the blade due to the ageing induced degradation of the blade material. Further, the need for a probabilistic structural analysis was also established.