Study of composite cure real time sensing using fiber optic sensor

A new sort of fiber optic sensor is designed, which measures the variation of refractive index of the resin surrounding the embedded fiber optic by measuring the speckle spatial spectrum at the end-face of the fiber optic. The normalized speckle spatial spectrum which depends upon the variation of the refractive index through the resin cure process is calculated, and the approximate relation between refractive index and cutoff frequency is given. The resin cure experiment results measured by the fiber optic sensor are presented. This sort of fiber optic sensor is found to be able to detect the gel point and the end point of the cure process. For the fiber optic maintains wave guide performance after cure sensing, it was pointed out that this sensor could also be used to sense the factors such as temperature and vibration which perturb the structures.