Flexural behavior of three-axis woven carbon/carbon composites

Abstract

This work examines the processing characteristics and flexural behavior of 3D woven carbon/carbon composites. Two types of the composites have been made, both having 3-axis orthogonal structures. The first combines solid rods along the axial direction. The rod, 1 mm in diameter, is composed of unidirectional carbon fibers and a phenolic resin. The second is a conventional type composed of carbon yarns in all axes. Both preforms were then impregnated by the phenolic resin. Matched molds were used to enhance fiber packing and to cure the resin under a hot press. The green composites were then heat-treated at various temperatures ranging from 200° through 1000° C. The second set of specimens was made by applying multi-cycle impregnation and carbonization. Flexural tests were carried out for these two sets of specimens. Their responses to the load and the induced damage behavior have been examined. The use of rods enhances fiber packing and reduces fiber crimp, leading to higher material performance. Decomposition of the resin due to the heat-treatment results in weak interfacial bonding and compressive failure in axial yarns. The efficiency of densification has been examined. The induced damage configurations vary significantly in these specimens, as a result of the processing. Some unique modes associated with the 3D structure are discussed.