An instrument has been developed for monitoring cure processes under microwave heating conditions. The main function of the instrument was a calorimeter for performing microwave thermal analysis. A single model resonant cavity was used as the heating cell in the microwave calorimeter. Thermal analysis measurements were obtained by monitoring the variation in the microwave power that was required to maintain controlled heating of the sample. The microwave thermal analysis data were analogous to conventional differential scanning calorimetry measurements. The dielectric properties of the sample, as a function of the extent of cure, have been obtained using perturbation theory from the changes in resonant frequency and quality factor of the microwave cavity during heating. Additionally, remote sensing fibre-optic probes have been employed to measure real time in situ infrared spectra of the sample during the cure reaction. In this paper, we describe the design and operation of the microwave calorimeter. Examples of experimental results are also presented.

The deployment of optical fibre based sensor systems for process monitoring of advanced fibre reinforced organic matrix composites is reviewed. The focus is on thermosetting resins and the various optical and spectroscopy-based techniques that can be used to monitor the processing of these materials. Following brief consideration of the manufacturing methods commonly used in the production of thermoset based composites, a discussion is presented on sensor systems that can be used to facilitate real-time chemical process monitoring. Although the focus is on thermosets, the techniques described can be adapted for chemical monitoring of organic species in general. Glossary of terms usedAFRC advanced fibre reinforced composites ATIR attenuated total internal reflectance ATR attenuated total reflectance CCD charged coupled device CRL charge recombination luminescence DDM diaminophenylmethane DDS diaminophenylsulphone DGEBA diglycidyl ether of bisphenol-A DICY dicyandiamide DMA dynamic mechanical analysis DMTA dynamic mechanical thermal analysis DRS diffuse reflectance spectroscopy DSC differential scanning calorimetry DTA differential thermal analysis EFPI extrinsic Fabry-Perot interferometric FBG fibre Bragg grating FTIR Fourier transform infrared HMGF heavy metal glass fibre IR infrared LED light emitting diode MCVD modified chemical vapour deposition MEA monoethylamine NA numerical aperture NIR near infrared NMR nuclear magnetic resonance OD outer diameter PCS plastic-clad silica PEEK polyether ether ketone PTFE polytetrafluoroethylene SLD super-luminescent diode SMA standard sub-miniature adaptor TGA thermogravimetric analysis TGDDM tetraglycidyl-4,49-diaminophenyl methane (also TGMDA) TMA thermomechanical analysis UV ultraviolet VNA vector network analyser

Although the deployment of sensor systems for process and "health" monitoring of AFRCs and similar materials is currently highly fashionable, there are genuine production and end-user-related reasons for wanting to monitor the production process. Some of these requirements are Cure kinetics: This term relates to the rates of reaction of the components in AbstractThis article presents a review of optical-fiber-based process-monitoring techniques that can be used to track the chemical reactions that take place during the processing of materials, with specific reference to thermosetting resins. The techniques covered include quantitative process-monitoring methods based on near-and mid-infrared, Raman, UV-visible, evanescent wave, and fluorescence spectroscopy. The basis for refractive-index-based process monitoring using optical fibers is also presented. The techniques described here can be readily applied to other classes of materials and other areas of interest such as aging and degradation. Recent advances in noncontact process monitoring are also presented.

This article reports on the design and development of two fiber optic sensing systems that facilitate the cure monitoring of an epoxy/amine thermoset in a microwave oven. First, the design, construction, and evaluation of a fiber optic probe were necessary so that noncontact diffuse reflectance spectra could be obtained during the curing of the resin in a microwave oven. Second, a low-cost, disposable fiber optic temperature sensor had to be developed for use in the microwave oven because the use of conventional metal-based thermocouples was not possible. The deployment of the two sensor systems was demonstrated successfully.