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Lightweight materials pave the road for energy-efficient vehicles



A key component of vehicle lightweighting is to ensure that safety is not compromised. Extensive numerical simulations of the vehicle with the Next Generation Frame were performed to ensure that a 5-Star Rating -- the government's highest ratingówould be achieved. Photo courtesy of DaimlerChrysler.

In efforts to shorten the long road to fuel efficiency, researchers at Pacific Northwest National Laboratory are working to develop cost-effective, high-strength, lightweight materials that will reduce vehicle weight without compromising cost, performance or safety.

A key component of vehicle lightweighting is to ensure that safety is not compromised. Extensive numerical simulations of the vehicle with the Next Generation Frame were performed to ensure that a 5-Star Rating--the government's highest rating -- would be achieved. Photo courtesy of DaimlerChrysler.

PNNL is assisting the Department of Energy's Office of FreedomCAR and Vehicle Technologies by performing materials research with auto and truck manufacturers and suppliers in the transportation industry. The primary focus is the development of lightweight, fuel-efficient cars and trucks, and pursuing research in the development and characterization of new methods for joining dissimilar materials.

In 2006, PNNL partnered with MeadWestvaco, a major player in the paper and specialty chemicals business, to investigate lowering the cost of carbon fiber composites through the processing of lignin-based precursors.

"A by-product of the papermaking process called kraft-based lignin seems to offer the best opportunity to meet the FreedomCAR carbon fiber cost goals," said Mark Smith, who leads the Energy Materials group for PNNL.

Carbon-fiber composites weigh about one-fifth as much as steel but are comparable in terms of stiffness and strength, depending on fiber grade and orientation. They have the potential to reduce vehicle weight by as much as 60 percent, significantly increasing fuel economy.

All of these benefits come with no sacrifice in safety. Computer crash simulations performed at Oak Ridge National Laboratory indicate that cars made with some carbon fiber composites would be just as safe -- if not safer -- than today's cars.

The problem with carbon-fiber composites is that they cost at least 20 times as much as steel, and the automobile industry is not interested in using them until the price drops dramatically.

"The number one goal of the FreedomCAR Program is to develop and produce low-cost carbon fiber that would be in the $3- to $5-per-pound range compared to today's cost of $8 to $10 per pound," Smith said.

Because the purification and control of impurity levels in kraft-based lignin are the keys to reliable carbon fiber, MeadWestvaco is developing the concept for a cost-effective purification process. The proposed process has the potential to be low-cost, efficient, environmentally friendly and compatible with existing paper plant layout.

Researchers at PNNL are also continuing work in other areas to reduce manufacturing costs and develop new lightweight materials that are economical for manufacturers. PNNL in partnership with DaimlerChrysler; DOE's Office of Heavy Vehicle Technologies; and Alcoa, the world's largest aluminum producer; completed a project that involved developing three prototype lightweight vehicle frames. The prototypes, which are steel and aluminum hybrids, were tested on the chassis of a 2002 Dodge Durango earlier this year.

"The test results exceeded everyone's expectations, successful to the point that we have initiated a more challenging follow-on program called the Next Generation Frame," Smith said.

The Next Generation Frame prototype abandoned the steel portion of the frame, focusing entirely on an aluminum frame. The aluminum frame resulted in a weight savings exceeding 40 percent, and is now being tested on the latest model of the Dodge Durango.

Finally, PNNL is continuing to work with Northwest heavy-duty truck manufacturers to reduce the weight of tractor-trailer combinations by 20 percent. "We are working on a variety of projects addressing this goal including new materials and manufacturing for a lightweight door with PACCAR, and the production of lightweight hybrid composites for body applications with Freightliner," Smith said.

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