It’s a materials race to produce a more lightweight carAP File Photo
Car shoppers in the not-too-distant future will be looking at vehicles that are more lightweight and burn less fuel. A critical component will be the materials that are used to make cars.
Thanks to tough new federal fuel-efficiency rules, automakers must meet a fleet average of 54.5 mpg by 2025. More efficient engines and electric powertrains can’t carry the whole load, so carmakers and the federal government are pouring resources into “lightweighting” auto platforms to meet the Corporate Average Fuel Economy, or CAFE, standards.
The Energy Department says that reducing a car’s weight by only 10 percent can improve fuel economy by 6 to 8 percent. Three technologies that show promise in lightening vehicles are high-strength steel, carbon fiber composites and aluminum. All of them are supported by $8 million in development awards that the department has doled out to the likes of General Motors, Ford and Caterpillar, as well as to two federal laboratories.
Drivers worried about running into older, heavier sport utility vehicles on the road might be reassured that these new materials are exceptionally stiff and strong, and will have to pass muster, including crash tests, with the National Highway Traffic Safety Administration.
Alan Hall, a technology spokesman for Ford, said it was too early to tell which of the materials would become dominant in carmaking. Ford has used carbon fiber in certain niche applications, like an inner-engine hatch cover for the Ford GT supercar and a hood for the Shelby GT500KR. Earlier this year, the company announced that it was collaborating with Dow Automotive Systems to develop lower-cost carbon fiber composites for mass production. It estimated that 750-pound weight reductions were possible.
Not surprisingly, the steel industry is looking to retain its pre-eminent position in the business.
Ronald P. Krupitzer, vice president of automotive applications at a division of the American Iron and Steel Institute, said about 60 percent of the average car by weight “is steel in one form or another.” Since 2000, the industry has doubled the available grades of steel and increased strength levels by 50 to 100 percent. “The steel available for car companies now is up to five times stronger than the steel used 10 years ago,” he said. “A part that weighed 100 pounds is being replaced by one that’s 75 pounds, with no price increase.”
Krupitzer acknowledged that steel did not yet offer the same weight savings as aluminum, another material in longtime use, but he said it was close and significantly cheaper. He pointed to a recent FutureSteelVehicle study, which found that high-strength steel had the potential to reduce mass by more than 35 percent compared with older steel cars. That contrasts with what Krupitzer said was an estimated 40 percent mass reduction for aluminum.
While aluminum has been used for a century to build lightweight cars, Randall Scheps, director of ground transportation at Alcoa, acknowledged that it cost $600 to $800 more using aluminum to produce what automakers call a body in white — the car’s basic structure before moving parts like doors and engines are installed.
Scheps also said it was difficult for automakers to give up accepted industry practices. “They’ve had 100 years of working with steel,” he said. “It’s a very comfortable material for them.” But he offered a long list of advantages that he said should persuade carmakers with an eye on the CAFE standards to switch to aluminum.
“It performs as well as steel in accidents, and it absorbs twice the crash energy per pound of mild steel,” or older steel, Scheps said. “An aluminum crash rail folds up like an accordion, which is exactly what you want it to do.” He said aluminum also had advantages in corrosion, handling and braking.
He pointed to cars like the 2013 Range Rover, whose all-aluminum body is up to 39 percent lighter than older models, the company has said. The new Cadillac ATS uses many aluminum components, including the engine, hood and wheels. Scheps said the higher cost of aluminum was offset by lighter cars that required smaller engines, suspension and braking components.
That argument is also used in favor of carbon fiber, which is very light and strong but remains expensive. The BMW i3, a battery electric car designed for urban use, has an upper body structure of carbon-fiber-reinforced plastic sitting on an aluminum chassis. It is scheduled to appear in late 2013. Although limited-edition supercars like the SRT Viper use carbon fiber, a BMW spokesman, Dave Buchko, said the i3 was “the first volume-produced vehicle that uses carbon fiber for the full body structure.”
Greg Rucks, a transportation consultant to the Rocky Mountain Institute, a Colorado-based environmental research group, said that carbon fiber offered “unparalleled performance advantages,” but estimated that replacing a steel “body in white” with carbon fiber would cost $1,200 per unit. Another hurdle for carbon fiber is a slower production process.
Despite all that, Rucks nonetheless sees a business case for using carbon fiber today, because it offers lower tooling costs and manufacturing processes, and significant fuel savings for the customer.
For those weighing the energy costs of producing alternatives, Rucks said the fuel savings from switching to lightweight carbon fiber composites would “far outweigh the energy intensity of producing the fiber, even with today’s relatively immature processing technology.”
It’s safe to say that carmakers will increase their use of all three materials — advanced steel, aluminum and carbon fiber — and creatively blend them into future cars. All offer big weight savings, and that’s critical in the countdown to 54.5 mpg in 2025.
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