New class of PU-based composite systems for large windmill blades

The results of the studies and development of the low-viscosity, long-gelling polyurethane systems are detailed in a technical paper: “Polyurethane Composites for Wind Turbine Blades,” authored by Dr. Usama Younes, principal scientist with Bayer MaterialScience LLC, and Frank Bradish, a researcher with Molded Fiber Glass Research Company.

Glass-reinforced polyurethane composites have been used for many years to make various parts used in agricultural equipment, heavy-duty construction equipment and watercraft. However, these polyurethane systems were designed for fast throughput equipment and are known for fast gelling and fast demould properties. As such, these polyurethane systems were not suitable for making very large windmill blades, which require polyurethane systems with lower viscosities and longer gel times. However, the studies performed by Younes and Bradish demonstrated that new polyurethane systems have been developed and adapted to current large blade manufacturing processes and retrofitted into existing designs at minimal cost.

According to the results of the research, the new polyurethane-based composite systems outperformed the epoxy and vinyl ester samples in tensile fatigue, interlaminar fracture toughness testing and fatigue crack growth testing. According to the authors, “These urethane systems showed much improved fatigue and fracture toughness properties as well as faster demould than resins currently used in wind turbine blade manufacture.”

Furthermore, the polyurethane systems are environmentally friendly, as they contain low-to-no volatile organic compounds and use sustainable raw materials from renewable resources.