Prolonging structural integrity—Fatigue of scarf repairs for wind turbine blade shell applications

The influence of scarf repair variables on the mechanical properties of glass fiber reinforced polymer sandwich structures is examined for the application of wind turbine blade shell repairs. Reference shell specimens are tested under fully-reversed cyclic loading to understand the fatigue behavior of the sub-component structure within a range of in-service loads, to which shell specimens with a scarf joint repair are compared. A fatigue-superior repair material is shown to improve the fatigue behavior of the repaired structures compared to the reference specimens. In separating layup and geometry, damage development is examined on the sub-component scale for a structural understanding of a scarf repair using in-situ digital image correlation-based strain field measurements as well as passive thermography. Within scarf repair variables, the geometry is shown to play a larger role than layup in the fatigue performance of the repaired structure.