The Effects of Resin Thermal Degradation on Thermostructural Response of Carbon-Phenolic Composites and the Manufacturing Process of Carbon-Carbon Composites

Abstract

Research in the effects of thermal degradation of phenolic resins on the anomalous behaviors in the thermostructural response of carbon-phenolic composites and in the manufacturing process of carbon-carbon composites was reviewed. Remarkable progress has been made in understanding the macroscopic fracture behavior of the composites, and in elucidating the interrelationships between thermal degradation, gas permeation, resin shrinkage, and composite expansion. Recent efforts have been focused on the fundamental understanding of the processing and property characteristics of the phenolic and carbon composites. However, some problems have been encountered in establishing a comprehensive, systematic understanding on the reactive mechanisms of those anomalous events. This paper begins by reviewing the occurrence of these anomalous behaviors in both processes. The restrained thermal growth (RTG) testing results are used to describe the complex thermostructural response of a phenolic composite in response to a heating environment, and to investigate the conditions for the anomalous events. Then, the effects of resin shrinkage, composite expansion, material microcracking, and gas permeation on the thermostructural response are presented. These are followed by a model framework on thermal degradation process of phenolic resins, and a micromechanical analysis of fracture mechanisms. Finally, this paper presents a brief discussion on the needs for the design of the optimum fiber-resin-filler interactions and concludes by pointing out future research directions in process modeling and expert system for the design of phenolic composites for thermal protection applications of carbon-phenolic composites and for the preparation of the carbon-carbon composites from the carbon-phenolic composites.