The development of wind-turbine blades requires advanced materials. With a demand for low weight and high strength, the wind industry is constantly seeing new and innovative technologies in blades. The advanced composites market is set to reach over $15 billion by 2020, with wind energy accounting for about 60% of its growth. Currently, a few materials stand out in blade development.
Graphene has great promise in composites because it could make turbine blades, longer and lighter, but only if scientists can get it to stick to resins. Graphene is highly inert which makes it difficult to bond with or disperse within other materials. Conventional methods for treating or functionalizing graphene involve thermal and chemical shocking agents. Although they allow for scalable production, the treatments can cause significant damage to the material’s structure and defects in the final product.
Recent research suggests that graphene nanoplatelets significantly improve the nano-reinforcement of resin. The research also reports significant strength improvements in toughened epoxy composites, such as a greater than two-fold increase in tensile strength and modulus of an epoxy composite using a number of graphene nanoplatelets. This resulted in strength increases of over 125% and toughness improvements of 100% over that of similarly cured, unreinforced material.
One fiberglass producer announced its production of a glass material to fill the cost and performance gap between traditional E-Glass products and higher performance fiberglasses. The glass was developed primarily for the wind energy market with input from blade and turbine manufactures. The company says the glass is mechanically superior to E-Glass, but much less expensive than extremely high-end fiberglasses, making it ideal for composite manufacturers.
Carbon fiber, of course, also works well in turbine blades. When compared with traditional materials, carbon fiber allows for thinner, longer, stronger, stiffer and lighter turbine blades. The result has been larger swept areas and more energy output. However, new demands to lower manufacturing costs without sacrificing quality have designers searching for ways to improve carbon fiber.
A common method of applying carbon fiber in a turbine blade is with epoxy prepregs. The product is rolled out on the spar cap or structural member of the blade, then layered one over another to reach the needed thickness. The prepreg is then cured or hardened on the production floor. Although the process yields excellent structural properties, prepregs require cool storage and have a limited shelf life. Also, uni-directional fabrics present challenges in obtaining complete infusion.
A solution, suggested by one developer, is to build thicker-ply carbon fiber prepregs that require fewer layers of material per blade. This cuts throughput time off each part and saves resources. Another way compresses the production line through proprietary prepreg installation tools. The developer provides design support and the specialized tools for efficient carbon-fiber installation.
By Nic Abraham, Managing Editor, Windpower Engineering & Development
Filed Under: Components, Featured, Turbines