Microwave Curing of Composites.

Abstract

Models were developed which describe the interaction between linearly polarized transverse electromagnetic waves or isotropic electromagnetic wave and continuous fiber-reinforced organic matrix composites, and which simulate the microwave curing of such composites. On the basis of the models, a computer code was developed which provides the reflectance, transmittance, total absorbed energy, and absorbed energy distribution inside the composite. The computer code also yields the temperature distribution, the resin viscosity, and the degree of cure of resin during microwave curing of flat plate composites. In addition, the computer code gives the amount of resin flow out of the composite and the resin contents of the composite and the bleeder. Tests were performed using a waveguide measuring the reflectances and transmittances of Fiberite S2/9134B glass epoxy and Hercules AS/3501-6 graphite epoxy composites. Tests were also conducted using a microwave oven measuring the temperature distribution inside Fiberite S2/9134B glass epoxy composites, and the temperature distribution inside and resin flow out of Hercules AS/3501-6 graphite epoxy composites. The data were compared with the results calculated by the computer code. Good agreements were found between the experimental data and the numerical results. A parametric study was performed which show the dependence of the reflectance, transmittance, and absorbed energy on the characteristics of the incident electromagnetic wave, the geometry (composite and coating thicknesses and ply orientation), and the properties of the composite. A parametric study was also made to illustrate how the models and the associated computer code can be used to determine the microwave cure cycle which results in a composite which is cured uniformly in the shortest amount of time.