Effect of fiber architecture on mechanical behavior of SiC(f)/SiC composites

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{degrees}/20{degrees}/60{degrees}, 0{degrees}/40{degrees}/60{degrees}, and 0{degrees}/45{degrees}) at various temperatures from room to 1300{degrees}C. Up to 1200{degrees}C, ultimate strength and work-of-fracture for the 0{degrees}/40{degrees}/60{degrees} and 0{degrees}/45{degrees} composites increased, but then declined at 1300{degrees}C. The decreases were correlated to in-situ Nicalon fiber strength and fiber/matrix interface degradation. However, for the 0{degrees}/20{degrees}/60{degrees} composites, ultimate strength and work-of-fracture reached their a minima at 1200{degrees}C. These measured ultimate strengths at room and 1300{degrees}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