Monitoring damage state of fiber reinforced composites using an FBG network for failure prediction

A structural health monitoring (SHM) study of biaxial glass fiber reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using Fiber Bragg Grating (FBG) optical sensors embedded in composites at various locations to monitor the evolution of local strains thereby understanding damage mechanisms. Concurrently, the temperature changes of the samples during the fatigue test have also been monitored at the same locations. Close to fracture, significant variations in local temperatures and strains are observed and it is shown that the variations in temperature and strain can be used to predict imminent fracture. It is noted that the latter information cannot be obtained using external strain gages, which underlines the importance of tracking of local strains internally