Structural transverse cracking mechanisms of trailing edge regions in composite wind turbine blades

Macro-scale crack transverse to the blade length direction is one of the typical damage types observed in the trailing edge regions of wind turbine rotor blades. In this work, the mechanisms of such transverse cracks and their failure characteristics under ultimate static loading are investigated numerically by high-fidelity three-dimensional finite element modelling. Composite failure, foam crushing, and adhesive tunnelling crack are captured in the finite element model. The effects of load directions, material properties of foam cores and adhesives on the formation and development of transverse cracks, as well as longitudinal cracks along the intersection between spar cap and sandwich panels are examined in detail under ultimate static loading. We find that under static loading, the formation of macro-scale transverse cracks is a buckling-driven process. The transverse cracks occur in load directions that can result in severe buckling deformation when the trailing edge is dominated by compressive loading. The buckling resistance can be increased by replacing low stiffness foam cores in sandwich panels with high stiffness ones so that the transverse cracking process is mitigated. The effects of adhesive materials on the buckling resistance are minor and thus the formation of transverse cracks is not affected by the material properties of adhesive materials.