Optical Fiber Methods for Autoclave and Epoxy Cure Monitoring

Abstract

The fabrication process of recently developed advanced technology hybrid structures has placed a demand on methods to monitor the state of cure of resins and epoxies commonly used in composite materials. Such monitoring allows in-situ process control insuring homogeneous structural integrity. Furthermore, fabrication costs can be reduced by avoiding the need to over cure“ the composite specimens. Existing techniques such as differential scanning calorimetry (DSC), optical spectroscopy, and dielectric spectroscopy lack the in-situ capabilities required to monitor localized cure state. Other methods, including ultrasonic wave monitoring, are absolute in nature, require frequent calibration, and involve complex measurement systems for monitoring localized cure state [1–3]. We propose to expand upon a principle recently suggested by M. A. Afromowitz, in which optical waveguides made out of the hybrid resin material itself are embedded within the specimen to be monitored [4]. Such implementation exploits some of the advantages of fiber optic sensing techniques, while avoiding the incorporation of “foreign materials” which might cause inhomogeneities in the composite structure.