Transmission electron microscopic study of three-dimensional polyacrylonitrile fibre-mesophase pitch matrix carbon-carbon composite

Conventional and high resolution transmission electron microscopy performed in this study provides some detailed microstructural information of a polyacrylonitrile (PAN) fibremesophase pitch matrix carbon-carbon composite which has not been published in open literature. The PAN fibre in this composite possesses a turbostratic structure throughout the fibre. The structure of the mesophase pitch matrix is graphitic and anisotropic. Near-fibre matrix crystallites are aligned roughly parallel to the fibre surface, exhibiting a flow-type morphology. The fibre-matrix interface in this composite is microfissured. Numerous microcracks exist both within the matrix and along partially bonded interfaces. The irregularly shaped interfacial microcracks readily expose the fibre surface topography. Microcracks within the matrix are formed between, and parallel to, the basal planes of the graphitic platelets. Such submicron-sized matrix cracks appear smaller and denser near the fibre-matrix interface.