Intrinsic strength and non-hookean behaviour of carbon fibres
1971; Elsevier BV; Volume: 9; Issue: 5 Linguagem: Inglês
10.1016/0008-6223(71)90087-x
ISSN1873-3891
AutoresWilliam‐Philip Jones, Jeremiah Johnson,
Tópico(s)Carbon Nanotubes in Composites
ResumoThe achievement of higher strengths for carbon fibres depends on the elimination of internal and surface flaws which are responsible for the current limit on tensile strength and the wide dispersion about the mean value. Meanwhile to determine the strength of the material between flaws, small volume tests have been conducted using the elastica method. These tests for PAN based 1000°C fibre have indicated that this strength would be in the neighbourhood of 106 psi in the absence of gross flaws. The material is elastic to fracture and shows no marked change in Young's modulus with strain. Similar tests on 2800°C fibre exhibit marked non-elastic effects with a decrease in Young's modulus with increase in strain as is found for cellulose based fibres. The phenomenon sets in above heat-treatment temperatures of about 1500–1600°C for PAN. The cause of the non-Hookean behaviour in PAN based fibres has been shown to be structural failure in the fibre within the compressive region under the action of the high compressive forces set up in it due to bending and its own great structural anisotropy. This mechanism of failure is different from that found to occur for cellulose based carbon.
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