Chemical and physical changes occur during the processing of toughened thermosetting resins. A number of properties are related to the type and sequence of these changes. There is a need for the development of in-situ real-time sensors to follow these changes. Once these sensors are developed, they can be used to preferentially select networks and/or morphologies by feedback-controlled "intelligent" processing. A practical, durable, inexpensive Fourier Transform NearInfrared (FTNIR) fiber optic sensor was developed and the cure of a model toughened cyanate as well as a commercial paste adhesive was followed with this sensor In the near-infrared. The design was suitable for many applications. A mold was designed to incorporate the fiber sensor for composite applications. The growth of the normalized triazine (crosslink) peak appeared to follow second order kinetics. The normalized peak reflected chemical as well as physical changes. Analysis of the individual peaks showed significant physical effects. Conversion based on triazine concentration did not follow second order kinetics. / Ph. D.