EFFECT OF FIBER ARCHITECTURE ON MECHANICAL BEHAVIOR OF SiC(f)/SiC COMPOSITES

摘要

We evaluated mechanical properties (first matrix cracking stress, strength, and work-of-fracture) of Nicalon-fiber-reinforced silicon carbide matrix composites with three different fiber lay-up sequences (0 deg /20 deg/60 deg, 0 deg/40 deg/60 deg, and 0 deg/45 deg) at various temperatures from room to 1300 deg C. Up to 1200 deg C, ultimate strength and work-of-fracture for the 0 deg/40 deg/60 deg and 0 deg/45 deg composites increased, but then declined at 1300 deg C. The decreases were correlated to in-situ Nicalon fiber strength and fiber/matrix interface degradation. However, for the 0 deg /20 deg/60 deg composites, ultimate strength and work-of-fracture reached their a minima at 1200 deg C. These measured ultimate strengths at room and 1300 deg C were correlated to the predictions made with an analytical model and to in-situ fiber strength characteristics. The large difference in room-temperature ultimate strengths between the three sets of composites is attributed to the relative contributions of the off-axis fibers to the load-bearing capacity of each composite.