HIGH-TEMPERATURE TOUGHNESS AND TENSILE-STRENGTH OF WHISKER-REINFORCED SILICON-NITRIDE

The R-curve behavior of hot-pressed silicon nitride reinforced with silicon carbide whiskers is investigated from room temperature to 1300-degrees-C using the chevron-notch bend test. The bridging stress, estimated from increment of fracture resistance in the rising R-curve, is discussed in relation to tensile strength measured with various displacement rates at 1300-degrees-C. The reinforcing whiskers provide most of the tensile strength in the creep-deformation range at 1300-degrees-C. The whiskers appear to bear a great deal of the applied tensile stress during slow crack growth.