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Rex Features |
Nonmetal cars have been with us for a while, but with the exception of vehicles considered substandard - such as the former East Germany's Trabant - these autos have usually been high-end items, such as the UK's Aston Martin or US-based Chevrolet's Corvette. And while fiberglass and other nonmetals were used on the bodies, the frames were still metal. Recently, however, two of the best-known luxury automakers have turned to carbon composite fibers for more structural and interior body parts.
In April, carbon parts maker SGL Group and car company BMW, both German, announced that their joint venture, US-based SGL Automotive Carbon Fibers, would build a $100m ( 75m) carbon fiber-reinforced plastics (CFRP) manufacturing facility.
These fibers are earmarked exclusively for BMW's new electric Megacity Vehicle, due to be released between 2013 and 2015. "We will be able to produce carbon fiber-enhanced components in large volumes at competitive costs for the first time," said Friedrich Eichiner, member of the board of management, finance, for BMW, during a press conference.
In May, German automaker Daimler signed a joint development agreement with Japan-based Toray Industries to develop auto parts from CFRP. Toray will use its proprietary high cycle resin transfer molding system to create the parts, and Daimler will create a method to join the pieces together.
In 2007, Toray declared it would be the first company to mass produce carbon fiber auto parts, especially targeting the chassis and body applications, and invested yen 20bn ($170m) in research.
According to the US Department of Energy's Oak Ridge National Laboratory, for most auto applications, carbon fibers are aligned into a preform, which is placed into a mold in which resin is then injected and heated. The heat activates and cures the resin, gluing together the carbon fibers, creating great strength.
While SGL/BMW's and Toray/Daimler's plans - if successful - would be a great leap forward for automotive engineering, BMW and Mercedes vehicles are, however, still not considered affordable by most people.
BUILT FOR SPEED
Consumers really do not care what their cars are made of, notes Jay Baron, CEO and president of the US-based Center for Automotive Research (CAR). The potential US customer is "looking for a more European design, with a maximum of materials that are optimally designed based on cost and performance," he says. "If cost were not an issue, you'd make your cars out of carbon fiber, and they'd look like Formula One racing cars, and be very safe and light."
Ten years ago, carbon fiber cost $150/lb. While costs have decreased to about $10-15/lb, steel is still roughly $0.50-1.00/lb, according to CAR.
"You can make a very safe car out of carbon fiber - you just can't afford to buy it," says Bruce Harrison, director, North American Automotive Group, for US-based consultancy IHS Global Insight.
Many factors, including the drive for innovation and higher fuel efficiency requirements, are expected to result in increased use of plastics in cars, says trade body the American Chemistry Council (ACC).
In 40 years, the use of lightweight plastics in US automobiles grew from an average of 60lb (27kg) per vehicle to approximately 330lb (150kg) per vehicle in 2007.
"More than 50% of a typical vehicle's volume is composed of plastics and polymer composites, but these materials only account for approximately 10% of total vehicle weight," says Keith Christman, the ACC's managing director, plastics markets.
Meanwhile, in emerging countries where new capacity is being built, "we see companies [taking another look] at the value of plastics versus traditional materials when the system costs are similar," says Greg Adams, vice president, automotive, at US-based SABIC Innovative Plastics (IP).
SABIC IP has supplied polymer material to US auto firm General Motors' forthcoming all-electric Volt, and the QarmaQ from South Korea's Hyundai.
The chassis tends to be a high-weight section of a vehicle, and "the challenge the plastic industry will have is with the chassis," says Dagmar van Heur, vice president at Styron Automotive, a division of US-based Dow Chemical.
In March, Dow agreed to sell its Styron business to compatriot private equity firm Bain Capital for $1.63bn.
Additionally, the large battery pack needed by electric vehicles "is a huge opportunity," says van Heur. "These cars will need to reduce weight to get any type of range that the end-consumer would like to see."
SABIC IP sees the industry ready to finally make a change to using polycarbonate (PC) for windows. "The technology has been in development for over 10 years, and is ready for mass adoption," says Adams. "The weight can be reduced by up to 50% where current windows are heavy above the car's center of gravity."
CAFE SOCIETY
Earlier this year, the US Corporate Average Fuel Economy (CAFE) standards were made more stringent. The average fuel economy for cars must improve by 37% from the current 27.5 mpg, where it has been since 1990, to 37.8 mpg by 2016. The truck standard has increased by 23% from 23.5 mpg to 28.8 mpg.
According to Styron, a 10% reduction in vehicle weight - about 200lb - offers 5-7% fuel savings, provided the vehicle's powertrain is also downsized. If the powertrain is not reduced, a 3-4% fuel saving is achieved. Either way, for each pound of reduced weight, carbon dioxide emissions are reduced by 25.3lb over the life of the vehicle.
Cars have not become lighter over the past 10 to 20 years because weight has been added via more exotic electronics and bigger engines. "But with CAFE laws, they are going to have to stop doing that," says Baron. "They are going to have to get weight out of the car, and leave it out."
Regarding the new CAFE regulations, "there is a desire to improve fuel efficiency through using lightweight materials, but there is some discussion that the lighter the vehicle, the less safe it is," and that is also the broader public perception, notes Harrison.
"So the US Department of Transportation [DOT] and the National Highway Traffic Safety Administration [NHTSA] find themselves with competing agendas - one to provide the safest vehicle possible, and the other to provide the most efficient vehicle possible. And the two may not be complementary."
CAFE will influence manufacturers to reduce weight, but along with the cost, "the big issue with plastics and composites is ensuring comparable safety," says James deVries, chairman of the automotive composite consortium for the US Council of Automotive Research (USCAR). "Metal is considered the strongest material, and thus considered the safest."
On average, Baron points out, companies are willing to spend $2 to save 1lb of weight, passing on the cost to consumers who have demonstrated that they are willing to pick up the extra cost, especially when it accompanies something considered eco-friendly or fuel-saving.
However, he warns: "You cannot just take out a steel part and replace it with a plastic or composite - the whole system will need to be redesigned. Material substitution oversimplifies the complexity of lightweighting the car."
And it will not be just one material that will provide the desired weight loss. "It is a potpourri of materials that gets you to lightweight," says deVries.
Too often observers think in terms of "all-aluminum," "all-magnesium," or "only plastic," but that is not realistic, he notes. "You need to look at a cadre of lightweight technologies, especially if you are mass-producing a vehicle."
It is a misconception that plastics are the only lightweight replacement, deVries says. "There is aluminum, magnesium and other lightweight metals - all of which challenge conventional composites for weight savings."
However, neither the composites nor other lightweight providers are as in tune with the automotive manufacturers when compared with the manufacturers of steel. "The steel industry has been catering to the auto industry for nearly a century," says deVries.
"There is an installed base for current traditional material applications that will take time to replace," agrees Adams.
"Steel and aluminum are currently the incumbent and dominant materials in the vehicle world," explains Baron. "So they are somewhat defensive, and are trying to keep the other material suppliers from nipping at their market share."
MOLDED FOR THE ROAD
Plastic's advantage is that it is molded - instead of stamped, as metal is, points out Baron. The molding process is longer, though - a stamp press cycle time for metal is about six seconds - a plastic mold takes about 45 seconds.
Molded parts tend to be on smaller, niche vehicles that are exactly the types of cars buyers are now trending towards. "This is good for plastics," he adds.
"Molds can be a complex shape - something that is difficult to create with stamped steel, but relatively easy with molten polymer in a mold." Meanwhile, multiple parts can be made at one time with a mold, "so the slower molding speed is made up for," says Baron.
"Our vision is that by 2020, the automotive industry and society will recognize plastics as a preferred material solution that meets - and, in many cases, sets - automotive performance and sustainability requirements," says Christman.
Many of today's plastics would enjoy increased use as automakers strive to reduce weight, postulates the ACC.
Polymers found in vehicles include polypropylene (PP), including homopolymer, copolymer and impact-modified; polyurethane (PU); nylon; thermoset and thermoplastic polyester; PC; polybutylene terephthalate (PBT); and acrylonitrile-butadiene-styrene (ABS).
The ACC sees higher heat resistance becoming more important, since newer advanced powertrains have higher operating temperatures.
FIRST AROUND THE BLOCK
The first plastic car was introduced by Henry Ford in August 1941. Designed by Ford's protege Robert Allen Boyer, the vehicle was made from plastic that was 70% cellulose.
Looking like any other of Ford's models that year, the car was much lighter - the plastic reducing the weight from 3,000lb (1,360kg) to 2,000lb. The US's participation in World War II ceased nonmilitary auto production, and post-war cheap steel and inexpensive gasoline made a plastic car superfluous.
