FAILURE MICROMECHANISMS IN CONTINUOUS CARBON-FIBER EPOXY-RESIN COMPOSITES

This study is concerned with the influence of the strength of the fibr e/matrix interface on the strength and failure process in uniaxial arr ays of carbon fibres in an epoxy resin. A batch of high-strength carbo n fibres has been supplied with several levels of an oxidative surface treatment to produce composites with various interface strengths. Ten sile tests have been conducted on single fibres, on loose bundles and on tows impregnated with an epoxy resin. Further tests have been condu cted to estimate the interface strength. A hybrid-tow test configurati on has then been used to follow the sequence of failure within a singl e tow of the carbon fibre in a uniaxial composite. The results indicat e that the fibre strength is affected only slightly by the surface tre atment, the strength of impregnated tows is reduced, and their mode of failure and that of the hybrid tows is affected significantly.