A Comparison of Surface Preparation Techniques for Wind Turbine Field Repairs

Wind turbine service lifetimes can exceed 20 years. This extreme operational demand necessitates reliable and consistent field repairs; however, the effects of current wind turbine field repair surface preparation techniques are not well-documented and are thus not well-understood. This leads to reliance on technician experience rather than scientific data for repair procedures, which causes variability in the quality of repairs. Solvent wiping is a common procedure for contaminant removal after damaged material is removed from a wind turbine blade, but it was unknown if solvent wiping reduced the surface energy and consequently the likelihood of a durable repair. The goal of this study was to quantify the effects that various surface preparation techniques have on the overall strength and reliability of wind turbine repairs. Type of reagent-grade solvent, fiber direction, matrix, and adhesive were varied for contact angle, lap shear, Double Cantilever Beam (DCB), and End-Notch Flexure (ENF) testing. The type of solvent used did not affect surface energy, maximum lap shear stress, or modes I and II fracture toughness values. However matrix-adhesive combinations significantly affected maximum lap shear stress and fracture toughness values.