CARBON FIBER: THE AUTOMOTIVE MATERIAL OF THE TWENTY-FIRST CENTURY STARTS FULFILLING THE PROMISE

For more than forty years since its introduction, carbon fiber composites have remained an elusive material in the automotive industry. Proven in jet fighters and high-end race cars for over 20 years, there is little doubt about its ability to build lighter, more durable vehicles. Offering a weight savings of 75 percent over steel, carbon fiber gives sports cars a real advantage in acceleration and top speed, and enables all automobiles to achieve improved fuel economy. Commercialization continues to be hindered by high material and processing costs and slow production rates. In spite of these obstacles, more than 25 series production vehicles will feature carbon fiber composites in 2004, fueled by advances in manufacturing technology, new material forms and steadily declining material costs. This paper presents the current state of carbon fiber use in automobiles in Europe, North America and Japan, ranging from the exotic “supercars” to niche producers and the major automobile manufacturers. Carbon fiber applications include body panels, structure and functional components. Advances in processing techniques will be reviewed, with a focus on what is being done today and what still needs to occur to economically move beyond volumes of a few thousand parts per year and into more mainstream vehicles. Background The selection of a material for an automotive application requires the evaluation of a number of specific criteria, including styling needs, performance demands, anticipated volumes, and ultimately, cost. Does each factor contribute positively to the business case for the vehicle? Can the preferred material and its associated manufacturing process be justified? What skepticism will have to be overcome via a thorough development and validation effort? Can we get this past the upper level decision makers? Will the consumer pay for it if it costs more to implement? One material for which these questions have become increasingly relevant is carbon fiber. With over 40 years of use in military applications, and over 20 in high performance sporting goods, its appeal to automotive designers is stronger than ever. In the 2004 model year, over 25 vehicles will be offered for sale worldwide with OEM carbon fiber content. Does this mean carbon fiber has finally “arrived” as a viable material of construction for production automobiles? The Promise For several decades, producers of carbon fiber have attempted to get the material specified as a mainstream material for production vehicles. The raw fiber has a tensile modulus equal to steel at less than one-fourth the specific gravity. New developments in pitch-based fiber, produced from scrap material from the oil refining process, had the potential to yield fiber for less than several dollars per pound, the producers advertised. Spurred by the OPEC crisis of 1978, Ford built prototypes of the LTD, demonstrating weight savings of 544kg (1,200 lb) compared to the steel production model. With a manufacturing cost equal to that of a private airplane and a production process able to make one or two per day, the likelihood of this vehicle hitting the showroom floor was non-existent. Fiber producers achieved moderate success in the 1980’s with filament wound and pultruded drive shafts, but the economics did not justify widespread adoption. Pitch technology failed to deliver a low cost fiber, but significant advancements were made in lowering the cost of higher strength polyacrylonitrile, or PAN fibers, with the potential to get to below $5.00/lb for large volume commercial applications widely promoted. The price of carbon fiber in 2003, while not quite yet to $5.00, has reached a point where it has become a viable option for some vehicles. Mass Savings Potential Approximately 16% of the new 555 passenger Airbus A380 jumbo aircraft will be carbon fiber composites. Boeing has announced the fuselage and wings of the 7E7 under development will be carbon intensive to save weight. The use of carbon fiber in place of aerospace aluminum alloys is driven by the need to save weight in commercial aircraft, which translates to lower operating costs.