The effect of nanostructure upon the deformation micromechanics of carbon fibres |
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Affiliation: | 1. School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK;2. Department of Aerospace Engineering, Tohoku University, 6-6-01 Aoba-yama, Aoba-ku, Sendai, Japan;3. Composite Materials Research Laboratories, TORAY Industries, Inc., 1515 Tsutsui, Masaki-cho, Iyo-gun, Ehime, Japan;1. Beijing National Laboratory of Molecular Science, Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China;2. University of the Chinese Academy of Sciences, Beijing 100049, PR China;3. School of Materials Science and Engineering, Beihang University, Beijing 100191, PR China;1. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA;2. L.A. Giannuzzi & Associates LLC, 12580 Walden Run Dr, Fort Myers, FL 33913, USA;3. George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA;1. National Carbon Fiber Engineering Research Center, Beijing 100029, China;;2. Beijing University of Chemical Technology, Beijing 100029, China |
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Abstract: | We have used the Mori–Tanaka theory to develop a new micromechanical model to predict the Young’s modulus for carbon fibres, taking into account both the crystallites and amorphous components of the fibre structure. In order to follow the dependence of the mechanical properties of the fibres upon nanostructure, we prepared five different types of PAN-based fibres, with Young’s moduli in the range 200–500 GPa. The axial elastic constants of the bulk carbon fibres were measured directly by X-ray diffraction and an axial shear modulus of about 20 GPa was calculated. The elastic constants of the amorphous carbon in the fibres and the volume fractions of crystallites were estimated. It was found that the amorphous modulus was approximately 200 GPa and the volume fractions of crystallites were 0.4–0.8, depending upon the nanostructure of the carbon fibres. Also, as it is known that the Raman G band shift rate per unit strain is related to the crystallite modulus, the data indicated a nearly constant value of 1.1 TPa. The results show clearly that the behavior of carbon fibres can be expressed through a composite mechanical model that assumes they consist of both crystalline and amorphous carbon components. |
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