Physical and Chemical Heterogeneity of Carbon Fibre

Abstract

Carbon fibre composites have been employed commercially for more than 50 years and their use is growing rapidly in the aerospace and automotive industries. In spite of its commercial success the relationship between the fibre structure and its physical properties are still poorly understood. This paper utilises a range of physical and chemical techniques to characterise both polyacrylonitrile and pitch based carbon fibre and highlights the heterogeneity of the fibre. Physical methods include nano-mechanical indentation whilst the use of focussed ion beam (FIB) milling for the preparation of flat surfaces for nano-indentation experiments has also been investigated. Chemical analysis involves inverse gas chromatography under finite concentration conditions and confocal Raman spectroscopy. The later includes both depth profiling showing the variation in structure from the surface to the core of the fibre and high spatial resolution (0.5 μm) mapping of the surface of the fibres.