Fibre Content in Graphite Reinforced Composites

Abstract

EFFECTIVE evaluation of the properties associated with graphite fibre reinforced plastics requires an uncomplicated, accurate measure of the weight fraction of reinforcement^1–3. Two principal techniques are used to determine fibre content: those which involve pyrolysis of the specimen⁴ and those which use selective solvent extraction of the polymer from the specimen⁵. The former, as applied to graphite fibre composites, is usually a thermogravimetric type of chemical analysis carried out in a non-oxidizing atmosphere. This procedure necessitates the use of very small samples having large surface areas. Use of such small specimens, however, may not be truly representative of the original composite. In contrast, the selective solvent extraction procedure requires that the specimens be in powder form, and all the ground powder must be collected to give an adequate specimen. The total volume of reinforcement in the specimen must also be recovered after the selective extraction of the polymer, otherwise the results will be inaccurate.