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Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4’-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC). The changes in physical properties indicating increasing conversion are followed by shifts in glass transition temperature determined by DSC and temperature-modulated DSC (TMDSC), thermomechanical (TMA) and dynamic mechanical (DMA) analysis and thermally stimulated depolarization (TSD). Changes in viscosity, also indicative of degree of conversion, are monitored by DMA. Thermal stability as a function of degree of cure is monitored by thermogravimetric analysis (TGA). The parameters of the general kinetic equations, including activation energy and rate constant, are explained and used to compare results of various techniques. The utilities of the kinetic descriptions are demonstrated in the construction of a useful time-temperature-transformation (TTT) diagram for rapid determination of processing parameters in the processing of prepregs. Copyright is held by the author, unless otherwise noted. All rights reserved. Files: Thesis.pdf Special Conditions

Thesis (Elec.E)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Huan Lim Lee. / Elec.E

The state of cure of epoxies is an important issue in the manufacture of graphite epoxy composites used in aerospace structures. Variations in the initial state and process used to cure the epoxy resin in a composite material lead to variations in the mechanical properties of the part manufactured from the composite._[12] Control of these variation can be accomplished by monitoring the bulk and shear moduli of the epoxy resin as it cures. The moduli properties of the resin determine the acoustic properties of the epoxy._{[12],[13],[14]} Hence measurement of the acoustic longitudinal velocity and attenuation of the epoxy during its cure cycle provides a good indicator of the state of cure. Optical fiber waveguides can be embedded within a host material and used to detect longitudinal acoustic waves._[15],[16] Herein, the mechanisms allowing the detection of ultrasound with optical fiber are presented. An analysis of optical fiber waveguides and optical fiber based interferometric detection methods is performed in detail. The interaction of radial strain fields, induced by longitudinal acoustic waves, with singlemode optical fibers is described. Experimental results obtained in epoxy cure monitoring, using an optical fiber based method for acoustic detection, are compared with results obtained using conventional piezoelectric based acoustic detection methods. / Master of Science

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