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New Plastics and the Automobile
Why now?
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The Tele Aid and telephone antennae of the new Mercedes-Benz CL500 are in its composite trunk lid.
The grille opening reinforcement of the Ford Focus consists of a plastic/metal composite that is 40% lighter than an equivalent all-metal part.
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Legislative actions such as the Clean Air Act Amendment, the National Energy Policy Act, and potential new corporate average fuel economy (CAFE) standards have resulted in increased emphasis on electric, hybrid, and alternative-fuel vehicles, as well as improved fuel economy of conventional vehicles. The Lightweight Materials Program at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) in Oak Ridge, TN, is aimed at developing new, cost-effective, environmentally sound materials and process technologies to enable the U.S. transportation industry to be more energy efficient through vehicle weight reduction. According to ORNL, 75% of a vehicle's energy consumption is directly related to factors associated with vehicle weight, and it identifies as critical the need to produce safe and cost-effective lightweight vehicles.
The Partnership for a New Generation of Vehicles (PNGV) was established in 1993 by the U.S. government, Chrysler, Ford, and GM to achieve three goals:
- Explore technologies that reduce the time and cost to design and manufacture vehicles.
- Apply innovations, when commercially viable, to conventional vehicles.
- Develop a mid-size vehicle with a fuel efficiency of 2.94 L/100 km (80 mpg) while achieving improved recyclability and maintaining performance, utility, safety, and cost of ownership comparable to a mid-size vehicle of 1994.
Through PNGV, the three automakers are pursuing a variety of advanced powertrain options, such as fuel cells and various hybrid combinations, to meet the fuel efficiency goal in a pre-production vehicle by 2004. According to the U.S. Council for Automotive Research (USCAR), one of the challenges in integrating these powertrains into vehicles is overcoming their increased weight and complexity as compared to conventional powertrains. To compensate for the increased weight, the weight of other vehicle components must be reduced by approximately 40% to meet the fuel efficiency targets.
There has been much research involving material options for vehicle bodies, such as steel, aluminum, and a variety of composites. However, every component and part must be analyzed for potential weight reduction. While the PNGV partners have decades of experience with lightweight body component designs (the Chevrolet Corvette has been made of fiberglass body components since the early 1950s), the most difficult challenges are reducing the actual cost of materials and manufacturing the lightweight parts affordably. According to the DOE's Office of Transportation Technologies (OTT), current materials can reduce vehicle weight by more than 60%. However, OTT believes the cost of these materials, the capability to design with them, and the associated manufacturing processes presently are inadequate to produce safe, durable, recyclable, and affordable cars.
The DOE announced in January that it is funding a $1.8 million project at Virginia Tech and Clemson University aimed at the development of low-cost carbon fiber for use in making lightweight automotive parts. The approach to reducing cost is to develop a new polymer (or plastic) to serve as a precursor for the carbon fiber. The new polymer would have to be processed more cheaply than existing polymers and contain a higher percentage of carbon in the final fiber. Carbon fibers are currently produced through a process called pyrolysis, in which a precursor material such as tar-like pitch is chemically changed by heating and subsequently pre-tensioned, or stretched, to obtain the desired properties. The fibers are then ready to be made into a carbon-fiber composite. Currently, carbon fiber suitable for automotive use costs around $8 per pound. The research team hopes to develop a carbon fiber that can be produced for less than $5 per pound.
Designers have moved away from plastics as just a direct replacement material, and have begun integrating plastics at the design stage to meet weight reduction requirements while improving safety, performance, corrosion resistance, and fuel economy; exploring new styling potentials; and reducing maintenance. Following are the more innovative examples of how plastics are changing, and have changed, the design of the automobile.
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