Application of a stress-corrosion-cracking model to an analysis of the durability of glass/epoxy composites in wet environments

A stress-corrosion-cracking (S.C.C.) model has been applied to an analysis of the flexural fatigue behaviour of water-aged unidirectional glass/epoxy composites. The approach has been restricted to the initial stages of the fatigue life, i.e. when the damage consists mainly in the accumulation of broken glass fibres at the microscopic level. The fatigue behaviour of the aged material has been investigated at different strain levels, frequencies and strain ratios. The results demonstrate that the stiffness loss exhibits some of the main characteristic features which can be deduced from the delayed failure of a statistical population of glass fibres by a S.C.C. mechanism. This approach was supported by microscope observations which revealed that, within the investigated time range, the stiffness loss is proportional to the density of broken fibres in the vicinity of the loading point.