Journal of Materials Science

, Volume 11, Issue 1, pp 97–110 | Cite as

The mechanics of stretch-graphitization of glassy carbon fibres

  • H. M. Hawthorne
Papers

Abstract

The mechanics of stretch-graphitization of glassy carbon fibres made from two pitch precursors was studied by determining the plastic deformation characteristics of monofilaments during their elongation to 50% strain in a continuous apparatus. By monitoring fibre tension under various processing conditions and analysing deformation profiles quenched into extending fibres, the temperature and strain-rate dependence of induced fibre stresses has been obtained. Over the temperature range 2200 to 3000° C and strainrate range 3.0×10−4 to 2.5×10−1 sec−1, tensile stresses in the glassy carbon fibres ranged from 7000 to 50 000 psi. The deformation can be described by the empirical equation \(\dot \varepsilon = A\sigma ^n \) exp (− ΔH/RT), where A is a constant, n=8.6±1 and ΔH ∼ 290±50 kcal mole−1, independent of temperature and strain-rate, for both fibre types. The apparent activation energy is consistent with the controlling operation of a microfibrillar reorientation process, accompanied by atomic diffusion (ordering). The high strain-rate stress dependence, indicating an apparent activation volume ∼ 4000 Å3, also suggests a molecular-scale rate-limiting process. Results are compared with those of various high temperature processes in carbonaceous solids and deformation in organic polymers and it is suggested that stretch-graphitization can be considered analogous to the affine drawing of amorphous polymer fibres.

Keywords

Carbon Fibre Glassy Carbon Stress Exponent Fibre Tension High Temperature Plastic Deformation 

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Copyright information

© Chapman and Hall Ltd. 1976

Authors and Affiliations

  • H. M. Hawthorne
    • 1
  1. 1.Centre for Materials ResearchThe University of British ColumbiaVancouver, B.C.Canada

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