Fiber optic sensor for composite cure monitoring

The fiber/resin interface is critical to the final mechanical properties of a fiber reinforced composite material. To directly study this region, Robello siloxane (RBS) was grafted to glass surfaces. RBS contains a dimethylaminonitrostilbene fluorophore tethered to a isocyanatopropyltriethoxysilane coupling agent. Silane coupling agent chemistry was used to deposit small amounts of RBS to glass surfaces in a mixed silane layer with a diluting coupling agent. The fluorescence response of grafted RBS was sensitive to the chemical functionality of the diluting coupling agent. A blue shift in fluorescence from the grafted RBS dye can be followed during cure of an epoxy resin over layer, giving the technique potential to monitor cure in the interfacial region.