Strong and tough Hi-Nicalon-fiber-reinforced celsian-matrix composites

Strong, tough, and almost fully dense BN/SiC-coated Hi-Nicalon-fiber-reinforced celsian-matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from a mixed oxide precursor. The unidirectional composites having ∼42 vol% of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature. Values of stress and strain at the proportional limit were 435 ± 35 MPa and 0.27 ± 0.01%, respectively, and an apparent ultimate strength of 900 ± 60 MPa was observed. Young's modulus of the composites was 165 ± 5 GPa