Development Of A High Strength Laminate Repair System

Composite manufacturing often requires repairs at some point during the life of the part. Working with LM Wind Power, the Chemical and Mechanical Engineering Departments at the University of North Dakota worked to develop a new laminate repair system to be used in composite repairs. Both chemical and mechanical test methods were explored to analyze various resins in an attempt to increase the interface toughness between the parent laminate and repair laminate. A total of six resins from four suppliers were tested. Differential scanning calorimetry and dynamic mechanical rheological testing were performed to analyze the curing kinetics of each resin tested. Static double cantilever beam and tension-tension fatigue tests were performed to measure the mechanical performance of each resin. All specimens were prepared to mimic that of a large-scale wind turbine blade. Each resin tested was compared to the current repair resin system to determine which choice was best to meet the requirements set for by LM Wind Power for repair laminate improvement. The results indicated that toughened resin performance is superior to that of the current resin system. Along with the analysis of new repair resins, an initiator study was performed. The initiator study was done on the blade resin used for vacuum assisted resin transfer molding (VARTM). Four initiators were tested and compared to the current initiator. Methods included differential scanning calorimetry and rheology. The goal with testing these initiators was to see if changing the initiator would increase the working time while decreasing the overall curing time. To achieve this, the initial viscosity of the resin needed to remain low to ensure a full wet out of the part and once wet out was complete a sharp increase in viscosity would indicate a fast cure. Of the initiators tested, Pulcat from Syrgis Performance Initiators performed better than the others. However, without testing it in production, it is unclear whether or not it is superior to the current initiator MCP-75