Monitoring of epoxy composite cure process with fiber optic pefractive index sensors

Although using fiber optic refractive index sensor to monitor the resin cure process has long been known as a kind of novel and promising method, there is no further report of the investigation on the in-situ monitoring of composite manufacture process. In this presentation, a kind of fiber optic refractive index sensor is developed and a portable instrument for the optic emission, signal receiving and interrogation are integrated to meet the requirements of on-site application. With it the cure process of resin and fiber reinforced prepreg is monitored. Tests of resin cure process monitoring are carried out with both resin that should be cured under room temperature and resin that should be cured under high temperature. The results of tests with resin cure under temperature are compared with the results of Michelson interferometer tests under similar circumstance, which are in good consistency. Tests are also carried out during composite manufacture, in which the fiber optic refractive index sensors are embedded in prepreg during the cure process. It is proved with the method the key information of the cure process can be extracted out during the process and be used in on-line intelligent control. In conclusion, this technique can be used not only in the establishment of the cure routine but also the in-situ monitoring and control of the composite manufacture process.