Fiber reinforced carbon-carbon composites for enhanced fire retardancy and electrical and thermal conductivities
Telagamsetti, Murali Krishna Sai
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The aim of this study is to manufacture carbon-carbon composites in desired shapes (2D or 3D) for lightning strike, EMI shielding, and other high temperature and space applications. Carbon - carbon composites are being used in various fields such as defense, aviation, energy and electronics for their enhanced properties, including high temperature resistivity, electrical and thermal conductivities, low coefficient of thermal expansion, high elastic modulus, etc. Polyacrylonitrile (PAN) powder was dissolved in dimethylformamide (DMF) solution, and carbon fibers with desired concentrations (20-80wt%) were immersed into this solution prior to the evaporation and solidification. Vacuuming at 25 in Hg during the processing has reduced the air and voids in carbon fiber composites. The PAN/ fiber systems were then stabilized at 250-270 °C for 60 minutes in air and carbonized at 650, 750 and 850 °C (or higher) for 120 minutes in presence of Argon (Ar) gas to receive carbon-carbon composites in desired shapes. Several tests have been conducted on the samples with different weight concentrations (20-80wt%), such as stress and strain tests, FTIR, water contact angle, electrical and thermal conductivity tests. The change in the properties of the manufactured composites have been verified using confocal microscopy. The tensile test indicated that the actual sample was far superior compared to the oxidized and carbonized samples as it withstood a load of 2160.06 Lbf and had an ultimate stress of 57628.26 psi (0.397 GPa). The TGA tests on the samples indicated that the carbonized sample has a little weight loss of 2.5%, while other samples had more weight losses. The results of the water contact angle had shown that the carbonized surface was more hydrophobic compared to the other samples due to the presence of carbon and surface texture changes. The results of FTIR spectroscopy revealed several peaks for actual sample indicating the presence of different functional groups of polyacrylonitrile prior to the oxidation and carbonization, but most of them disappeared then.
Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Mechanical Engineering