Investigation of microwave energy to cure carbon fiber reinforced phenylethynyl-terminated polyimide composites, PETI-5/IM7

The application of microwave energy to the processing of carbon fiber reinforced phenylethynyl-terminated polyimide composites (PETI-S/IM7) was investigated and evaluated with a variable-frequency microwave furnace. The thermal and physical properties of the composites were measured by dynamic mechanical thermal analysis, thermogravimetric analysis, thermomechanical analysis, and density and composition tests. The mechanical properties were determined by 3-point-bending and short-beam-shear tests at both room temperature and 177 degrees C. The shear failure surfaces of both microwave- and thermally cured composites were detected with environmental scanning electron microscopy. A comparison of the thermal and microwave processes was conducted to evaluate the advantage of the micro wave process, Microwave-cured composites, fabricated under various pressures at the fixed process temperatures, also were investigated. From these studies, it was concluded that microwave energy successfully was used to fabricate PETI-5/IM7 composites with higher glass-transition temperatures (by 11-16 degrees C) and higher retention in flexural strength, flexural modulus, and shear strength at 177 degrees C than those fabricated by the thermal process. Furthermore, the microwave processes required only half the time used for the standard thermal process. (C) 1999 John Wiley & Sons, Inc.