Coal-tar pitch as a matrix precursor for 2-D C/C composites Original Research Article

Four coal-tar pitches were used in conjunction with a woven carbon fibre cloth to produce carbon/carbon (C/C) composites in order to study the effect of the nature of the pitch, as matrix precursor, on the properties of fully-processed composites. The nature of the pitch had little effect on the density, porosity, flexural modulus or inter-lamellar shear strength of the composites. However, the flexural strength of the composites decreased as the quinoline insolubles (QI) content of the precursor pitch increased. Two structural features of the composites also varied with the pitch QI content: the amount of granular carbon in inter-layer positions and the mean length of bundle voids, i.e. those oriented perpendicular to the cloth layers. The flexural strength could be related to void parameters using an equation developed from the Knudsen equation.