High modulus (M40) and high strength (T300) carbon fibers have been surface treated by argon and oxygen plasma to modify the fibre surfaces. The etching process and the effects of plasma gases on the carbon fibers are discussed. ESCA analyses of treated fiber surfaces show abnormal functionality changes during the plasma treatments. A clear picture of the removal of the outermost structure by plasma etching is given by the coupled evidence of SEM and ESCA analysis.
