THE RELEVANCE OF THE SURFACE-STRUCTURE AND SURFACE-CHEMISTRY OF CARBON-FIBERS IN THEIR ADHESION TO HIGH-TEMPERATURE THERMOPLASTICS .3. INTERFACE ADHESION AND REINFORCEMENT EFFECTS

This paper has three principle thrusts: (i) the fabrication of unidire ctionally reinforced composites made from carbon fibres subjected to d ifferent surface treatments in combination with various (polycarbonate , polyethersulphone and epoxy) matrices, (ii) a study of some of the m echanical properties (that is, the interlaminar-shear strength (ILSS) and the failure behaviour) of these composites; and (iii) determinatio n of the correlations between the adhesion of the matrix polymers as m easured by the ILSS and the surface structure as well as the surface c hemistry of the various fibres. It will be shown that the surface stru cture of the fibres has a minor effect, while the surface chemistry ap pears to have an extraordinarily great influence on the adhesion of th e fibres to high-temperature thermoplastics. The data clearly show tha t, depending on the processing temperature during the fabrication of t he composites, chemical bonds can be formed at the fibre-polymer inter face. This bond formation is initiated by the decomposition of carboxy lic groups and, as a consequence, dangling carbon atoms are free to re act with the functional groups of the polymer.