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Posted in | Carbon Nanotubes

Carbon Nanotubes Improve Fracture Toughness of Polyurethane Composites for Wind Turbine Blades

Published on February 22, 2012 at 6:38 PM

As demand for renewable energy increases, wind turbine blades are increasing in size, leading to longer blades that can achieve larger swept areas. Yet, gravity-induced bending loads on blades create dramatic increases in dynamic stress, heightening market demand for a material that reduces blade mass while retaining strength.

Current materials aren't designed to withstand these increased demands. Lighter weight composite materials with increased stiffness and enhanced fatigue endurance properties offer a promising solution. Bayer MaterialScience LLC's newly developed class of polyurethane systems offer stronger, tougher systems ideal for producing polyurethane composites materials suitable for manufacture of large parts by vacuum infusion.

Bayer's new Baydur polyurethane system possesses low-viscosity and long-gelling properties. When compared with epoxy- and vinyl ester-based composites, the Baydur polyurethane system provides several key advantages, including,

  • Ultra-low volatile organic compounds (VOCs);
  • Faster infusion time;
  • Superior tensile fatigue, interlaminar fracture toughness and fatigue crack growth;
  • Use of sustainable raw materials from renewable resources.

Bayer principal scientist Dr. Usama Younes will share the results of a recent study, funded in part by a Department of Energy (DOE) grant that details the development of this new Baydur polyurethane system. His presentation, "New Generation Polyurethane-based Fiber-reinforced Composites for Vacuum Infusion and the Effect of Multi-Walled Carbon Nanotubes on their Performance," will take place during Composites 2012, held Feb. 21-23, in Las Vegas. The paper is co-authored by Dr. Serkan Unal.

As part of his presentation, Dr. Younes will explain tests they conducted comparing properties of incumbent epoxy and vinyl ester resin systems with a polyurethane resin system. The testing included two sets of long flow, vacuum-infusion experiments designed to compare the flow rates of the different resins. It also studied the effect of multi-walled carbon nanotubes on fiber-reinforced composite properties. Results showed a clear trend toward improvement in the fracture toughness of the composites from the presence of multi-walled carbon nanotubes.
"Incorporation of a small amount of multi-walled carbon nanotubes improves the fracture of both polyurethane and epoxy composites by as much as 48 percent," says Younes. "The addition of carbon nanotubes is a viable option to improve the strength of wind turbine blades."

Development of the Baydur polyurethane system is the result of a two-part DOE grant (DOE award number DE-EE0001361) for the development of new, stronger composite materials for wind blades. The grant also will help fund additional research comparing the performance of new polyurethane resins systems with those of traditional epoxy and vinyl ester resins used for wind blades. The grant's scope includes investigating the effect of carbon nanotubes on the performance of polyurethane, epoxy and vinyl ester composites.

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