Paper number 1224

COMPOSITE MATERIAL PROCESSING IN A SINGLE MODE CAVITY WITH VARIABLE FREQUENCY MICROWAVES

Yunchang Qiu and Martin C. Hawley

Department of Chemical Engineering
Michigan State University
East Lansing, MI 48824

Summary

A computer controlled microwave processing system for polymers and composites is presented. The microwave circuit of the system comprises a variable frequency microwave power source and a single mode cavity. A computer data acquisition and control system has been developed to improve the heating uniformity and curing temperature stability by intelligently adjusting the frequency and power. Variable frequency mode switching technique was applied to achieve uniform heating. A parabolic power control algorithm was used to maintain the curing temperature so as to avoid thermal runaway. Heating results demonstrated the efficacy and stability of the control system. Flexural tests on samples heated for 90 minutes showed improved product quality resulted from decreased temperature gradients.

Keywords

microwaves, variable frequency, single mode cavity, computer control, uniform heating, graphite/epoxy.