Monitoring the composite curing process with a fluorescence‐based fiber‐optic sensor

Abstract A novel cure sensor, based on the combination of fiber‐optic fluorometry and the viscosity/degree‐of‐cure dependence of the epoxy resin fluorescence, was developed to provide a reliable low‐cost cure‐monitoring sensor for control of composite manufacturing. The capability of the first‐generation sensor to monitor chemorheological changes that occur during the autoclave cure of carbon‐epoxy laminates was successfully demonstrated. An improved second‐generation sensor, which simultaneously monitors the changes in the epoxy fluorescence intensity and the wavelength of maximum emission, was also developed. The changes in the sensor intensity and wavelength signals, as a function of cure time, provide characteristic profiles that reveal the main chemorheological events of the cure cycle; these signals follow the changes in the degree‐of‐cure to completion. The configuration of the optrode‐laminate interface strongly affects the signal profiles and their reproducibility. A “resin cavity” optrode‐laminate interface, which improves reproducibility, was developed and tested.