Enhancing the repair performances of glass/epoxy wind turbine blades using a novel resistance-welding approach

Abstract

Commercial wind turbine (WT) blades that are now being operational globally, are primarily made of glass-reinforced composites using epoxy or polyester matrix systems, mainly epoxy. The industry is rapidly growing (2100 TWh currently; 17% growth annually) with a forecast of 7400 TWh by 2030. The average lifespan of a WT is 20-25 years, which signifies the importance of repairing the damaged blades. Amongst the methods that have been exploited so far, resistance welding shows eminent potential, due to its ease of operation, promptness of the repair process, and cost effectiveness. Resistance welding was exploited previously for repairing thermoplastic composites. But in this project, repair of thermoset composites was evaluated using thermoplastic welding medium. The project focused on parametric optimisation of resistance welding, evaluation of welding via single lap shear strength, and COMSOL multiphysics modelling to examine the homogeneity of heat-distribution across the welding region. Stainless steel mesh and carbon nonwoven sheet were used as heating elements, while polymethyl methacrylate and thermoplastic polyurethane were used as welding medium. The highest single lap shear strength was shown as 6.4 MPa when nonwoven carbon sheet was used along with thermoplastic polyurethane. COMSOL modelling with a custom-designed heating element showed improvement in thermal homogeneity; however, further modifications will be required to better optimisation of welding.