The development of composite carbon fibres of large diameter—macro fibres
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This paper describes the development of a process for manufacturing carbon fibres of larger diameter than those normally available from the “RAE process”  or other routes which have so far been described (e.g. the hot-stretching of pitch  or cellulose-based  fibres). The method consists of impregnating a bundle of carbon fibres or their precursors with resin and after curing, subjecting the composite fibre to a controlled carbonization. The end-product is a thin rod or fibre of carbon-fibre reinforced carbon, which can, in principle, have any desired cross-sectional shape or area .
Experiments have been conducted to discover the effect of various processing variables on the properties of the composite fibre. Having chosen a suitable resin for impregnation the principal variables are (a) the degrees of pyrolysis of the initial fibre before impregnation, (b) the rate of cure of the resin to form the “intermediate” and (c) the rate of temperature rise and the maximum temperature during the carbonization process.
Fibres of reasonable properties (Young's modulus 76.8 GN m−2 and ultimate tensile strength of 267 MN m−2) have been produced but improvements should be obtainable by optimization of this basic process as fibres with strengths up to 400 MN m−2 have been observed.
KeywordsTensile Strength Pyrolysis Carbon Fibre Temperature Rise Processing Variable
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