Cure monitoring of epoxy resin via use of FBG

In order to monitor curing process of epoxy resin in real time, the system for cure monitoring is established based on Fiber Bragg Grating. First, a bare FBG, a FBG packaged with quartz capillary and an accurate resistance thermometer are closely stacked into a special mould. Then the mould is filled with mixture of epoxy resin and curing agent. Finally they are heated and cured together in the temperature-controlled cabinet. The changes of temperature inside epoxy resin are detected by resistance thermometer. Meanwhile, the reflection wavelengths of two Fiber Bragg Gratings are measured by spectrum analyzer. Experimental results indicate that the temperature evolution monitored by FBG packaged with quartz capillary is the same as measurement results of resistance thermometer. During curing process, inner strain changes of epoxy resin can be taken in by the variation of wavelength difference of two FBGs. At the beginning of polymerization reaction, the strain inside epoxy resin quickly increases, and then gradually trends to constant value. When the curing process ends, the inner strain is -945 με. When the temperature drops down to room temperature, it is - 2953 με. The temperature and shrinkage strain monitor of epoxy resin has been implemented via using two FBGs. It is a new approach to monitor curing process of polymer materials.