As early wind farms approach the end of design life, further attention is being given to the opportunity of delaying the decommissioning phase, helping to decrease the LCOE of a farm. To do so, operators need to ensure that the risk of failure within the structure remains sufficiently low. The risk arises due to fatigue failure, and as such, designers use fatigue design curves to help mitigate the risks. The fatigue design curve is conservative in nature to account for variations in the structure such as material properties, microstructural defects, welding geometry and residual stresses. This research aims to develop a framework to virtually test components and samples with varying properties to allow for a better understanding on how these variations can effect the fatigue life. The model was constructed using a phase-field model for fracture which is extended to account for fatigue damage.