INFLUENCE OF FIBER VOLUME FRACTION ON MECHANICAL-BEHAVIOR OF CVD SIC FIBER SRAL2SI2O8 GLASS-CERAMIC MATRIX COMPOSITES/

Unidirectional CVD SiCf(SCS-6) fiber-reinforced strontium aluminosilic ate (SAS) glass-ceramic matrix composites containing various volume fr actions, similar to 16 to 40%, of fibers were fabricated by hot pressi ng. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase for med, with complete absence of the undesired hexacelsian phase in the m atrix. Room temperature mechanical properties were measured in three-p oint flexure. The matrix microcracking stress and the ultimate strengt h increased with increase in fiber volume fraction, reached maximum va lues for V-f 0.35, and degraded at higher fiber contents. This degrada tion in mechanical properties is related to the change in failure mode , form tensile at lower V-f to interlaminar shear at higher fiber cont ents. The extent of fiber loading did not have a noticeable effect on either fiber-matrix debonding stress or frictional sliding stress at t he interface. The applicability of currently available micromechanical models in predicting the mechanical properties of the composites was also examined.