Mechanical Property Evaluation of Si-SiC Matrix C/C Composite with the Use of Complex Rules

Si-SiC matrix C/C composites are known to be synthesized through the following process. With the C/C composite having a yarn-like structure of carbon fibers as a base material, the Si-SiC matrix C/C composite is obtained by synthesizing a trunk Si-SiC matrix after impregnating Si into the clearances between yarns and then synthesizing a branch Si-SiC matrix which stretches from the trunk Si-SiC to the inside of the C/C composite. Compressive strength of the Si-SiC matrix C/C composite is increased up to about twice as large as that of the base material C/C composite. However, the tensile strength of this composite is decreased to about one fourth of that of the base material C/C composite, and the bending strength is decreased to about a half of that of the base material C/C composite. This paper reports that 1) degradation of tensile/bending strength caused on the Si-SiC matrix C/C composite is an unavoidable phenomenon and 2) a technique for forming only a part of the base material C/C composite into the Si-SiC matrix structure is an effective means of structural component design by increasing compressive strength of the base material C/C composite and restraining degradation of tensile/bending strength.