Carbon—carbon composites unidirectionally reinforced with carbon and graphite fibers

Abstract

A study was performed on unidirectional fiber reinforced composites, prepared by the wet-winding technique using thermosetting resins or pitch as binder. In the case of pitch binder, gas pressure was applied during the baking process for obtaining higher coking values at fast heating rates. Usually, as a result of the shrinkage of the thermosetting resin during carbonization, the structural integrity of a composite is damaged. It is demonstrated that such damage can be avoided by the use of binder materials exhibiting a wide temperature range of plasticity. Carbon—carbon composites reinforced by Thornel 50 graphite fibers were prepared with pitch as matrix precursor. Superior mechanical properties as compared with those of the multiple impregnated carbon—carbon composites made with resin were already found without impregnation, even at bulk densities below 1·3 g/cm 3. A subsequent pitch impregnation and recarbonization resulted in an increase of the flexural and interlaminar shear strength. With 36 per cent Thornel 50 fiber and two pitch impregnations, a carbon-carbon composite of 1·48 g/cm 3 bulk density with flexural strength of 79 × 10 3 psi and interlaminar shear strength of 3.1 × 10 3 psi was obtained.