Transverse single-fibre test for interfacial debonding in composites: 1. Experimental observations

Micromechanical methods for studies of interfacial debonding in fibre composites provide the possibility of comparing different materials. Since most previous composite studies focus on shear loading of the fibre matrix interface, the debonding process in single-fibre glass fibre/epoxy composites was studied in situ by optical microscopy during transverse tensile loading. Specimens had cylindrical debond cracks of known dimensions created in fragmentation tests. Mechanisms for debond growth were described for two materials where the difference was in glass fibre surface treatment. As the debonds reached a critical size in the arc (circumferential) direction, unstable debond growth occurred in the fibre direction. The debond angle at instability was fairly similar for both materials, although the material based on glass fibre treated with a coupling agent reached twice as high stress before instability.