SiC fiber-reinforced barium aluminosilicate glass-ceramic matrix composites

Unidirectional CVD SiC (SCS-6) monofilament reinforced BaO-Al2O3-2SiO(2) (BAS) glass-ceramic matrix composites have been fabricated by a tape lay-up method followed by hot pressing. The glass matrix flows around fibers during hot pressing resulting in nearly fully dense (95-98%) composites. Strong and tough composites having first matrix cracking stress of 250-300 MPa and ultimate flexural strength as high as 900 MPa have been obtained. Composite fracture surfaces showed fiber pullout with no chemical reaction at the fiber/matrix interface. From fiber push out, the fiber/matrix interfacial debond strength and the sliding frictional stress were determined to be 5.9 +/- 1.2 MPa and 4.8 +/- 0.9 MPa, respectively. The fracture surface of an uncoated SiCf(SCS-0)/BAS composite also showed fiber/matrix debonding, fiber pullout, and crack deflection around the fibers implying that the SiC fibers may need no surface coating for reinforcement of the BAS glass-ceramic. Applicability of micromechanical models in predicting the first matrix cracking stress and the ultimate strength of these composites has also been examined.