Tensile Creep and Creep‐Strain Recovery Behavior of Silicon Carbide Fiber/Calcium Aluminosilicate Matrix Ceramic Composites

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Abstract
The tensile creep and creep strain recovery behavior of 0° and 0°/90° Nicalon‐fiber/calcium aluminosilicate matrix composites was investigated at 1200°C in high‐purity argon. For the 0° composite, the 100‐h creep rate ranged from approximately 4.6 × 10−9 s−1 at 60 MPa to 2.2 × 10−8 s−1 at 200 MPa. At 60 MPa, the creep rate of the 0°/90° composite was approximately the same as that found for the 0° composite, even though the 0°/90° composite had only one‐half the number of fibers in the loading direction. Upon unloading, the composites exhibited viscous strain recovery. For a loading history involving 100 h of creep at 60 MPa, followed by 100 h of recovery at 2 MPa, approximately 27% of the prior creep strain was recovered for the 0° composite and 49% for the 0°/90° composite. At low stresses (60 and 120 MPa), cavities formed in the matrix, but there was no significant fiber or matrix damage. For moderate stresses (200 MPa), periodic fiber rupture occurred. At high stresses (250 MPa), matrix fracture and rupture of the highly stressed bridging fibers limited the creep life to under 70 min.