Fatigue damage mechanisms in carbon-epoxy multi-fibre model composites

Abstract

Polarised-light microscopy was used to investigate the influence of stress level and fibre/matrix adhesion on the fatigue failure process in carbon-epoxy multi-fibre model composites. It was shown that the fatigue stress has a strong influence on the damage accumulation process in such model composites. Increasing levels of tension-tension fatigue stress resulted in an increase in total number of fibre breaks, stronger fibre-fibre interaction, i.e. fibre failure due to stress concentrations caused by a fractured adjacent fibre, and more interfacial damage. An increase in fibre-matrix adhesion was also found to result in more fibre-fibre interactions, whereas in the case of poor fibre/matrix adhesion extensive debonding takes place. Finally, the experimental observations were interpreted using a 3-D finite element analysis of the model composites.