Structural integrity of offshore wind turbine blade under extreme gust and normal operating conditions

• the size of a blade increases, its power output increases. • Larger sized turbine blades are more susceptible to deflection and stress, resulting in a significant reduction in its load-carrying capacity. • We propose an improved finite element (FE) simulation-based methodology of to evaluate the structural integrity of a large sized composite wind turbine blade under various loads during extreme wind gusts and normal operation. • We conducted a geometrically nonlinear analysis using a three-dimensional model and composite failure criterion to investigate blade deformations and high stress concentrations comprehensively. • The results indicate that the maximum load-carrying capacity of the blade is governed by a coupled local buckling and de-bonding phenomenon under extreme loading. The power output of a turbine blade is proportional to its size. As the size of a blade increases, its power output increases. However, larger size of a blade also makes it more susceptible to deflection and stress, resulting in a significant reduction in its load-carrying capacity. In order to efficiently evaluate the structural integrity and stability of large blades, we propose an improved finite element (FE) based methodology of a 53-meter-long composite wind turbine blade. 3D non-linear FE simulations, employing the composite failure criterion, are performed to examine the deformations of blades under extreme wind gusts and normal operational conditions. The results obtained from simulations revels that high compressive stresses are experienced by the suction side (SS) of the blade, leading to localized skin buckling and de-bonding at the skin-spar interface. Under normal operating conditions, gravity loads dominate the aerodynamic loads, and an edgewise bending is observed from the leading to the trailing edge of the blade. Under extreme loading condition, the maximum load-carrying capacity of the blade is governed by a coupled local buckling and de-bonding phenomenon. The analysis methodology proposed in our current work can make a basis for the development of reliable and cost-effective computational procedures to investigate the structural strength of large turbine blades under extreme and normal loadings, potentially reducing expensive experimental testing.