Abstract
In pursuit of the goal to produce ultra-lightweight fuel efficient vehicles, there has been great excitement during the last few years about the potential for using carbon fiber reinforced composites in high volume applications. Currently, the greatest hurdle that inhibits wider implementation of carbon fiber composites in transportation is the high cost of carbon fiber when compared to other candidate materials. As part of the US DOE´s FreedomCAR initiative, significant research is being conducted to develop lower cost, high volume technologies for producing carbon fiber. This paper will highlight the ongoing research in this area.
Through Department of Energy sponsorship, Oak Ridge National Laboratory (ORNL) and its partners have been working with the US Automotive Composites Consortium (ACC) to develop technologies that would enable the production of a carbon fiber at less than $5 per pound. That cost goal would allow the introduction of carbon fiber based composites into a greater number of applications for future vehicles. The approach has necessitated the development of both (i) alternative precursors and (ii) alternative production methods.
Alternative precursors under investigation include textile grade polyacrylonitrile (PAN) fibers and fibers from lignin-based feedstocks. Previously, as part of the research programme, Hexcel Corporation developed the science necessary to allow textile grade PAN to be used as a precursor rather than typical carbon fiber grade precursors. UKbased PAN producers are collaborating in this work. Efforts have also been continuing to develop carbon fiber precursors from lignin-based feedstocks. ORNL and its partners are working on this effort with domestic wood and paper producers.
In terms of alternative production methods, ORNL has developed a microwave-based carbonization unit that can process pre-oxidized fiber at over 250 inches per minute. They have developed a new method of high speed oxidation, and are defining new methods for precursor stabilization. Additionally, novel methods of activating carbon fiber surfaces have been developed which allow atomic oxygen concentrations as high as 25-30% to be achieved rather than the more typical 4-8% achieved by ozone treatment.