Mechanical properties of thin pyrolitic carbon interphase SiC-matrix composites reinforced with near-stoichiometric SiC fibers

Tensile properties of Tyranno™-SA near-stoichiometric silicon carbide (SiC)-fiber-reinforced chemically vapor-infiltrated SiC-matrix composites with pyrolytic carbon interphases were experimentally studied. The influence of interphase thickness in a range of 60-300 nm on the tensile properties of the materials appeared to be generally minor. Thin interphase (<100 nm) did not have a significant deteriorating effect on composite properties, which has commonly been reported for conventional SiC-fiber composites. For very thin interphase (<60 nm) composites, a slight decrease in fracture strain and a substantial increase in interfacial sliding stress were noted. Increases in ultimate tensile strength and fracture strain were observed at a much thicker interphase (>600 nm) at the expense of composite stiffness.