The Effect of Processing Conditions on the Properties of Carbon Fiber-LaRC TPI Composites Made by Suspension Prepregging

Abstract

Unidirectional carbon fiber-LaRC TPI composites were made by prepreg ging carbon fiber tow with particles of LaRC TPI suspended in aqueous solutions of the ammonium salt of LaRC TPI polyamic acid. The prepregging was followed by drying and consolidation steps designed to facilitate water removal. The effects of processing condi tions on composite properties were investigated. The processing conditions included the degree of overlap of the fiber bundle in the prepreg, the fiber tension during prepregging, and the use of vacuum during the consolidation step. It was found that fiber volume % in creased with increasing fiber tension and that consolidation under vacuum resulted in composites with void content as low as 0.14 volume %. Fourier transform infrared spec troscopy and thermogravimetric analysis coupled with mass spectroscopy established that most of the water was removed from the prepreg and most of the polyamic acid was con verted to polyimide prior to consolidation. The properties of the resulting unidirectional laminates were quite reproducible. Shear moduli were comparable to those for graphite fiber/epoxy and graphite-fiber/PEEK laminates.