Carbon fibers are important engineering materials for lightweight structures due to their high specific stiffness and strength. It has been demonstrated that carbon fibers play an important role in civil engineering construction, aerospace field, automotive systems, athletic equipment, etc. Using carbon fiber composites to replace metals used in core structures of body shells in passenger automobiles can reduce vehicle weight by as much as 60%. This can result in fuel savings and less carbon dioxide emissions, having positive impacts on energy consumption and the environment. However, carbon fibers have not been widely used in various systems, especially automotive systems. The largest obstacle is the high cost of carbon fiber manufacturing. This award supports fundamental research on a new manufacturing process for fabricating carbon fibers with low cost. Compared with the current carbon fiber manufacturing process, the new process can potentially dramatically shorten the process time, achieve high-energy efficiency, lower manufacturing cost, and improve properties of carbon fibers. Results from this research will enable the wider use of carbon fibers as lightweight and strong engineering materials in broad applications.
The new manufacturing process for fabricating carbon fibers uses laser processing to convert stabilized polyacrylonitrile precursor fibers to carbon fibers (carbonization) and carbon fibers to graphite fibers (graphitization). The research objective is to understand the effects of laser processing parameters (laser wavelength, power, mode, scan speed, and beam profile) on fiber microstructure and mechanical properties. To achieve this objective, experiments will be conducted using a CO2 laser with wavelength of 10.6 micrometer and a solid-state laser with wavelength of 532 nm. Laser power (less than 5 W), laser mode (continuous or pulsed), and scan speed (up to 25 cm/s) will be varied. Laser beam profile will be adjusted to introduce preheating and control temperature distribution in the fiber. The typical length of the fibers will be within 30 cm, and typical diameter around 7 micrometer. Fiber microstructure will be observed by using electron microscopy and evaluated in terms of bonding status (measured by FTIR and Raman microscopy) and crystallinity (by X-ray diffraction). Mechanical properties (tensile strength, modulus, and failure strain) of fibers will be measured by dynamic mechanical analyzer.
