Open-Access Database Covers Wind Blade Composites

The new report from Sandia National Laboratories, called "MSU/DOE Fatigue Database for Composite Materials" shares data from 17 years of accumulated 10,000 results on about 150 different composite materials. It is compiled by John Mandell, Dan Samborsky and students at Montana State University (MSU).

According to the government laboratory, the database is one of the world's largest open-access libraries on wind turbine materials, the largest in the U.S. Most importantly, the data is being made available to the public.

Wind turbine blades are composed of combinations of fiberglass, carbon fiber, and resin, states a press release from MSU. With modern blades reaching lengths of up to 200 feet and weights of up to 50,000 pounds, they may spin half a billion times or more in their hoped-for 20-plus-year life spans. But no one is willing to wait 20 years to see if a particular composite material for a blade holds up or not. That's where Mandell, Samborsky, and scores of students come in.

In 1989, Sandia National Laboratories offered to fund Mandell, a professor of materials science in MSU's department of chemical and biological engineering, Mandell's work is essentially about cheating time, or compressing it. He plugs his lab data into various models and tries to predict how a particular composite material will hold up over years or decades from the tug of gravity and the stress of wind.

"A lot of effort has gone into these tests so that the data mean something," Mandell said. "We've had to invent methods ourselves. It has been a great deal of work." Current materials last much longer in the tests and are stronger compared with the more primitive materials in early years of the study.

U. S. blade manufacturers and materials suppliers send Mandell materials for testing. He also creates his own composites with resin and cuttings from bolts of fiberglass and carbon fiber cloth. Over time, interest has shifted from fiberglass to carbon fiber. Though carbon fiber is stronger and lighter, it's also more expensive.

"In the 1980s and 1990s, wind was a boom or bust research technology, and putting up wind turbines depended strongly on subsidies," Mandell said. "In 1987, wind cost 10 cents per kilowatt hour to produce. Now, it's down to about 4 cents." That price makes wind competitive with new natural gas and coal-fired power plants, he added.

"The United States has the best wind resources of any county in the world and Montana has the fifth-best wind resources of any state," Mandell said. "The technology is efficient enough that huge areas from the Rocky Mountain front in Montana and Wyoming, across the Dakotas, are developable."

"I think they look great compared to smoke stacks. These big turbines rotate slowly. They remind me of sail boats," Mandell said. "They are relatively quiet; they just turn in the wind and keep the lights on. I wouldn't mind if they were put on the hills behind my house."