Physiochemical Characterization of Composites and Quality Control of Raw Materials

Abstract

A review is given of several methods for determining the chemical and physical (not mechanical) properties of advanced composites. This discussion is not all-inclusive; rather, it is restricted to composites with thermoset matrices, usually epoxies, and to methods that have gained some acceptance among researchers in the composites field. Strictly speaking, mechanical testing is a form of physical characterization but because the subject is amply covered in published literature, it will not be discussed here. Specifically, three steps are discussed of physiochemical characterization of composites: screening and quality control of the raw materials, determining the degree of cure, and characterizing the cured composite. In addition to wet chemical analysis, infrared spectroscopy, nuclear magnetic resonance, and liquid chromatography are recommended for quality control. For cure cycle monitoring, infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, dielectrometry, and torsional braid analysis are reviewed. In addition, the versatility of thermal analysis and the applicability of Raman spectroscopy and infrared spectroscopy are discussed for characterizing cured composites. Finally, we stress the need for standard procedures for screening and quality control of raw materials as well as the need for innovative testing to relate properties of the cured composite to specific service conditions. We alsomore » point out the pitfalls of the methods reviewed.« less