Mechanical characterization of advanced polyacrylonitrile derived carbon fibers reinforced with carbon nanotubes
This research focused on the mechanical characterization of individual carbon fibers reinforced with carbon nanotubes (CNTs) which were dispersed in the polyacrylonitrile (PAN) precursor. The carbon nanofibers were obtained from the Georgia Institute of Technology and were fabricated in bundles by the “islands-in-a-sea” method. The fiber test specimens, with roughly 1 µm in diameter and 50 or 100 µm in gauge length, were tested in tension by specially designed MEMS devices that provided independent measurement of fiber force and extension with the aid of digital image correlation (DIC). The fiber extension and force data were used to derive stress vs. strain plots for a large number of individual fibers. The two parameter Weibull distribution was used to analyze the mechanical strength data. Due to variability in the fiber cross-section and the two different gauge lengths, a volume corrected Weibull analysis was applied. Fibers isolated from three different bundles, all subject to the same manufacturing conditions, were tested. The first fiber bundle yielded an average tensile strength of 3.41±0.93 GPa, Young's modulus of 228±45 GPa, and Weibull characteristic strength of 4.3 GPa. The second data set, comprised of fibers from the third bundle, resulted in average tensile strength of 4.55±1.35 GPa, Young's modulus of 254±36 GPa, and Weibull characteristic strength of 5.07 GPa. A third data set was generated with carbon fibers from bundles #2 and #3 by using compliant gripping that prevented failure at the specimen grips resulted in an average tensile strength of 5.59±1.24 GPa. The strongest fibers from the first, second and third data sets had tensile strengths 5.66 GPa, 7.24 GPa, and 7.31 GPa, respectively. All fiber bundles provided strength values that were significantly higher than those reported for the control carbon fiber manufactured under the same conditions but without CNTs.
Polyacrylonitrile, Carbon nanotubes, Pan Reinforced with Nanotubes, Carbon Fiber Isolation, Microelectromechanical Systems (MEMS), Microscale Testing
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign