CRACK INITIATION AND GROWTH-CHARACTERISTICS IN SIC SIC UNDER INDENTATION TEST/

The mechanical behavior of ceramic matrix composites (CMC) is known to be strongly influenced by fiber-matrix interfacial properties and the re have been many efforts to clarify the interfacial characteristics. To understand the fracture mechanism of the materials it is necessary to clarify how the cracks initiate and propagate among fibers, interph ase (coating) and matrix. The objective of this study is to investigat e crack initiation and growth characteristics in SiC/SiC composites wi th Variations in coating thickness and coating methods by means of mic ro-indentation technique. Micro-indentation tests and hardness tests w ere carried out on SiC/SiC composites produced by the chemical vapour infiltration (CVI) process. The intrinsic catastrophic mode of failure of the brittle composite was prevented by application of single carbo n and multiple coatings on fibers. Thinner coatings are sensitive to m ake fibers debonded and may improve the toughness of the composites. ( C) 1998 Elsevier Science B.V. All rights reserved.