Recent advances in studies of carbon fibre structure

Carbon fibre structure is usually characterized by means of X-ray diffraction measurement and electron microscope observation. The meaning of the most important parameters is discussed in terms of the structures revealed by high resolution transmission electron microscopy. Recently, dark-field electron microscopy and electron diffraction of selected areas has been used to reveal and characterize skin-core and sheath—core heterogeneity in type I (2500 °C) polyacrylonitrile (PAN)-based carbon fibres. Lattice-fringe electron microscopy has given some insight into the nature of the surface layers in type I, type II (1500 °C) and type A (1000 °C) fibres. The skin regions of type I fibres are seen to contain misorientated crystallites interlinked in a complex manner; these are flaws that will limit the intrinsic tensile strength of the material.