Fatigue damage of carbon–epoxy laminates with embedded optical fibres

The present paper is concerned with the fatigue behaviour ofcarbon-epoxy laminates with embedded optical fibres subjected to bending loads. The main goal of this investigation was to evaluate quantitatively the effect of the presence of optical fibres within the host structure on its whole fatigue behaviour. Two optical fibre positions were investigated: in the mid-plane of the laminate and near the surface subjected to loading. Two distinct geometries of the ply stacking sequence were also considered, namely unidirectional and crossply. In order to evaluate the fatigue life and the fatigue damage, two different loading levels were used, both at 6 Hz frequency, room temperature and R = 0.1. Fatigue damage was monitored using dynamic stiffness decay and acoustic emission techniques. Failure mechanisms were analysed by means of optical and scanning microscopy. The results obtained lead to the conclusion that the embedding of optical fibres markedly prejudices the fatigue performance of the material only for certain configurations. It was also possible to speculate on the fatigue failure mechanisms, and to relate them with relevant experimental parameters, such as the lay-up geometry and optical fibre position.