Silicon Carbide Monofilament-Reinforced Silicon Nitride or Silicon Carbide Matrix Composites |
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Authors: | Hironori Kodama Hiroshi Sakamoto Tadahiko Miyoshi |
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Affiliation: | Hitachi Research Laboratory, Hitachi, Ltd., 4026 Kuji-cho, Hitachi-shi, Ibaraki-ken 319-12, Japan |
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Abstract: | SiC-monofilament-reinforced SiC or Si3N4 matrix composites were fabricated by hot-pressing, and their mechanical properties and effects of filaments and filament coating layers were studied. Relationships between frictional stress of filament/matrix interface and fracture toughness of SiC monofilament/Si3N4 matrix composites were also investigated. As a result, it was confirmed experimentally that in the case of composites fractured with filament pullout, the fracture toughness increased as the frictional stress increased. On the other hand, when frictional stress was too large (>about 80 MPa) for the filament to be pulled out, fracture toughnesses of the composites were almost the same and not so much improved over that of Si3N4 monolithic ceramics. The filament coating layers were found to have a significant effect on the frictional stress of the SiC monofilament/Si3N4 matrix interface and consequently the fracture toughness of the composites. Also the crack propagation behavior in the SiC monofilament/Si3N4 matrix composites was observed during flexural loading and cyclic loading tests by an in situ observation apparatus consisting of an SEM and a bending machine. The filament effect which obstructed crack propagation was clearly observed. Fatigue crack growth was not detected after 300 cyclic load applications. |
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Keywords: | composites silicon carbide silicon nitride mechanical properties fracture toughness |
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