EFFECTS OF THE INTERFACE ON THE MECHANICAL RESPONSE OF CF EP MICROCOMPOSITES AND MACROCOMPOSITES

The aim of this study was to investigate the effects of the interfacial bond quality on the mechanical response of composite laminates, for example an epoxy matrix reinforced by continuous carbon fibres of varying surface coating. The fibre/matrix adhesion was characterized by determining the interfacial shear strength tau(i) in single-fibre fragmentation and microdroplet pull-off tests. The failure mechanisms were deduced from the stress birefringent patterns (fragmentation test) and from fractographic analysis in a scanning electron microscope (microdroplet pull-off test). Selected interface-relevant properties were evaluated in mechanical tests on laminates. The present paper highlights the problems related to the micromechanical characterization and the interface relevance of data resulting from transverse tensile, transverse flexure and interlaminar shear tests. Furthermore, the effects of the interface on the impact performance of unidirectional and cross-ply laminates were studied. Attempts were made to correlate the macroscopic mechanical response with the interface-related characteristics (tau(i) and failure mechanisms).