INTERFACIAL BEHAVIOR IN HIGH-TEMPERATURE CURED CARBON FIBRE/EPOXY RESIN MODEL COMPOSITE

The interfacial shear strength of carbon fibre/epoxy resin model composites cured either at room temperature or at 80 degrees C has been evaluated by using both the conventional fragmentation test and Raman spectroscopy. It was found using both techniques that the composite cured at high temperature showed a significantly higher interfacial shear strength. This increase in interfacial shear strength can be explained by the existence of a radial pressure at the interface resulting from thermal expansion coefficient mismatch between the fibre and the matrix during cooling from the curing temperature. Raman spectroscopy has also been used to determine the axial compressive strain in the fibres after high temperature curing and to monitor fibre compressive failure. It was also observed that the level of debonding during fragmentation in the hot-cured composite was greatly reduced at a given strain level, and it was found that the frictional shear stress in the debonded region in a hot-cured composite was higher than that for the cold-cured composite.