STRUCTURE-COMPRESSIONAL PROPERTY RELATIONS IN CARBON-FIBERS

Microstructural features of carbon fibres based on both polyacrylonitrile (PAN) acid mesophase pitch (MP) are discussed in relation to their compressional performance estimated by the recoil test. The compressive strength of carbon fibres is influenced by a combination of various structural features and not by any single feature. In particular, the compressive failure strength increases linearly with increasing amounts of both inter- and intracrystalline disorder. For a given amount of disorder, the more recently developed PAN-based fibres exhibited much higher compressive failure stresses than older PAN- and MP-based carbon fibres; this is due to the more homogeneous distribution of microstructural features. In order to promote compressive strength it is suggested that all crystallite dimensions should be limited to below 5 nm whilst maintaining good orientation.