Raman spectroscopy study of HM carbon fibres: effect of plasma treatment on the interfacial properties of single fibre/epoxy composites

Abstract

The effect of an oxygen plasma treatment upon the structural and morphological properties of high-modulus carbon fibres has been studied by means of several characterisation techniques. Scanning electron microscopy showed that there were only minor changes of the morphology of the fibres following treatment. X-ray diffraction traces revealed that there were differences in structural parameters between the untreated fibres but no further modifications in the crystalline structure were detected after the plasma oxidation. Raman spectroscopy was used to follow the changes on the fibre surface structure following treatment. The peak positions and widths of the four main Raman bands (D, G, D′ and G′) were determined, with no significant changes observed after the surface treatment. A relationship between the width of the G band and the crystal parameter d 002 was found, with the magnitudes of both decreasing as the fibre modulus increased. A reference order parameter I D/( I D+ I G) ratio was calculated from the intensities of D and G bands. The treated fibres exhibited a more highly disordered surface structure that the untreated ones, as revealed by the increase of I D/( I D+ I G) after the plasma oxidation.