Researchers developing a tougher and lighter wind turbine blade

A Case Western Reserve University researcher has built a prototype blade that is substantially lighter and more durable compared to materials currently used in blades of wind turbines. He came up with a polyurethane blade reinforced with carbon nanotubes, which make the material eight times tougher compared to other materials which are currently used as wind turbine blades.

The heavier the blades, the more wind is needed to turn the rotor. That means less energy is captured. And the more the blades flex in the wind, the more they lose the optimal shape for catching moving air, so, even less energy is captured. Marcio Loos, a post-doctoral researcher in the Department of Macromolecular Science and Engineering, went to the lab on weekends and built the prototype by using a small commercial blade as a template. He manufactured a 29-inch blade that is substantially lighter, more rigid and tougher.

He is conducting his research in the Professor Ica Manas-Zloczower lab, where she and Chemical Engineering Professor Donald L. Feke, a vice provost at the university, serve as advisors on the project. Investigators from Bayer MaterialScience in Pittsburgh, and Molded Fiber Glass Co. in Ashtabula, Ohio, helped him compare the properties of new materials with the current standards used in blade manufacturing.

“Results of mechanical testing for the carbon nanotube reinforced polyurethane show that this material outperforms the currently used resins for wind blades applications”, said Manas-Zloczower, Professor of Department of Macromolecular Science and Engineering and associate dean in the Case School of Engineering.

In a comparison of reinforcing materials, the researchers found carbon nanotubes are lighter per unit of volume than carbon fiber and aluminum and had more than 5 times the tensile strength of carbon fiber and more than 60 times that of aluminum. Fatigue testing showed the reinforced polyurethane composite lasts about eight times longer than epoxy reinforced with fiberglass. The new material was also about eight times tougher in delamination fracture tests.

The performance in each test was even better when compared to vinyl ester reinforced with fiberglass, another material used to make blades. The new composite also has shown fracture growth rates at a fraction of the rates found for traditional epoxy and vinyl ester composites.

Although the results already look promising, Loos and the rest of the team are conducting tests in order to find optimal conditions for the stable dispersion of nanotubes, the best distribution within the polyurethane and methods to make that happen.