Model-Based Analysis of Cure-Induced Stresses for a Short Fiber-Reinforced Epoxy Adhesive Used in Wind Turbine Rotor Blades

As a climate-neutral energy source, wind energy plays a key role in the global energy transition to mitigate climate change. Ensuring a reliable and affordable supply of wind energy requires a deep understanding of materials, structures, and processes both for existing wind turbines and for the future development of ever larger turbines.
Bond line cracks in rotor blades often initiate structural blade damage as they propagate into the surrounding laminate. Adhesive shrinkage during cure results in a pre-stressed bond line due to residual stresses which affects the mechanical performance by promoting adhesive cracking. This work generates comprehensive insights into the formation mechanisms of residual stresses in bond lines during cure and their effects on the bond line strength. An analytical residual stress model is developed on an experimental basis, taking into account the relevant adhesive properties and manufacturing boundary conditions. The findings contribute to an improved understanding of the curing process of adhesives and its influence on the mechanical strength of bond lines. The application of this knowledge improves the reliability of wind turbine rotor blades.