Letter | Published:

Tensile Strengths of Carbon Fibres

Naturevolume 247pages360361 (1974) | Download Citation



THE strength of carbon fibres prepared from commercially available polyacrylonitrile (PAN) fibres depends on the heat treatment temperature (HTT) and normally decreases1 from a maximum after a HTT of about 1,500° C. Moreton2 found that after all heat treatment temperatures (1,000–3,000° C) the strength is dependent on the gauge length indicative of a random distribution of flaws. Johnson3 and Thorne4 demonstrated that both surface and internal flaws are present, the latter due to foreign particles in the PAN precursor fibre reacting with the fibre during high temperature processing. Sharp and Burnay5 subsequently used high voltage electron microscopy to examine carbon fibres directly and concluded that, when the HTT is raised above about 1,800° C, inclusions react and volatilise to form voids. This results in the formation of misoriented three-dimensional graphite on the walls of the voids and decreases the strengths of the fibres.

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  1. 1

    Moreton, R., Watt, W., and Johnson, W., Nature, 213, 690 (1967).

  2. 2

    Moreton, R., Fibre Sci. Technol., 1, 4, 273 (1969).

  3. 3

    Johnson, J. W., Appl. Poly. Symposia, No. 9, 215 (Interscience, 1969).

  4. 4

    Thorne, D. J., Third Conf. on Industrial Carbon and Graphite (Society of Chemical Industry, London, 1970).

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    Sharp, J. V., and Burnay, S. G., Plastics and Polymers Conf., Suppl.5 (Plastics Institute, London, 1971).

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    Whitney, E., and Kimmel, R. M., Nature phys. Sci., 237, 93 (1972).

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    Coyle, R. A., Gillin, L. M., and Wicks, B. J., Nature, 226, 257 (1970).

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    Le Maistre, C. W., and Diefendorf, R. J., Tenth Biennial Carbon Conf. (Lehigh University, 1971).

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    Cooper, G. A., and Mayer, R. M., J. Mat. Sci., 6, 60 (1971).

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    Watt, W., Proc. R. Soc., A 319, 5 (1970).

  11. 11

    Reynolds, W. N., and Sharp, J. V. (in the press).

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  1. Royal Aircraft Establishment, Farnborough, Hampshire

    • R. MORETON
    •  & W. WATT


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