Abstract
Fiber Bragg grating (FBG) sensor can be used to monitor the mechanical behavior of composite. The internal strain of composite during a constant stress amplitude fatigue testing process was monitored with FBG sensors in this paper. FBG sensor as a fatigue indicator can reveal the decrease of Young's modulus of the specimen, which is a direct index of damage. FBG sensor can not only be embedded in composite laminates to detect fatigue damage, but also has excellent durability compared with other sensors such as electric strain gauge. After 1 million cycles, the FBG sensor can still keep good sensibility. FBG sensor as a fatigue indicator is a novel sensor to monitor, evaluate and give crash alert for the health state of composite during its whole service life. And also, a new and simple model of stiffness degradation was developed. This model can be used to predict the fatigue life of composite material.