Specimen size effects on tensile properties of 2D/3D SiC/SiC composites

Miniaturization of tensile specimen is investigated as one of the important methods to evaluate tensile properties of ceramic matrix composites such as SiC/SiC composites, which are attractive materials for fusion applications. For the establishment of small specimen test techniques, specimen size effects on the tensile properties for P/W, S/W and 3-D SiC/SiC composites were investigated. For 3-D composites, whose failure was characteristic in the sequences of statistical fiber fractures, tensile properties were significantly dependent on specimen size. Decreases of tensile strength due to the weakest link concept, the ratio of damage area, and stress concentration due to the local load sharing theory could be observed. For 2-D SiC/SiC composites, dependencies of tensile properties on specimen size were dissimilar to that for 3-D ones and much smaller, because they failed with another failure mode due to the structural restrictions by weaving fiber bundles, and hence this made it difficult to show fiber strength sufficiently.