Optical Fiber Sensors for Organic Matrix Composite Material Cure Monitoring. Phase 1

The report describes experiments that were conducted to demonstrate the feasibility of a novel optical fiber based composite cure monitoring technique. Preliminary investigations were conducted using a fast cure, industrial grade epoxy in a neat resin environment. Neat resin tests were demonstrated using a more common composite resin, Hercules' 3501-6 material. A neat resin cure monitoring station, which allowed repeatable cure monitoring results, was developed. A cure monitor assembly which addressed practical feasibility issues, was also developed. This assembly made it possible to interface the relatively fragile resin fiber elements with standard all-silica lead fibers without requiring micro-positioning equipment for alignment. In order to simplify the data acquisition process during the cure monitoring cycle, a PC-Basic routine was written which allowed continuous retrieval of data from a multi-channel optical meter as well as conventional thermocouples. This routine was used to perform cure monitoring measurements on Hercules 3501-6/AS4 composite coupons. Normalized Transmitted Power as a function of cure was monitored and showed correlation to the neat resin experiments conducted earlier.