Continuum damage model for the polyurethane coating of wind turbine blades

Leading edge erosion of polyurethane (PU) coatings, driven by repeated high-speed raindroplet impacts, is a critical issue that limits the operational longevity of wind turbine blades. To investigate the degradation behavior of PU coatings, this study employs a numerical model integrating continuum damage mechanics (CDM) with finite element analysis. The model is specifically developed to track the progression of micro-scale damage in PU coatings subjected to cyclic, high-speed raindroplet impact pressures. Results demonstrate that the transient pressure from raindroplet impacts is the primary driver of degradation, creating localized high-stress regions that rapidly accelerate damage accumulation at subsurface levels. With repetitive impacts, this localized damage propagates downward and upward from the impact zone, reaching the surface. The analysis confirms a direct correlation between peak damage and maximum impact pressure, quantifying the cumulative effect of repeated raindroplet strikes on coating.