A ZrB2 ceramic containing continuous BN-coated SiC fibers was produced
and characterized. TEM was used to examine the microstructure
at the nanoscale level inside fiber, fiber coating and at the fiber/matrix
interface. The use of a BN-coating for Hi-Nicalon fiber was effective in
hindering fiber degradation during processing. However, themeasured
fracture toughness values were similar to monolithic ZrB2 ceramics
owing to an unfavorable ratio between Young's modulus of the matrix
and the fibers,which did not allowefficient load transfer fromthe brittle
matrix to the high strength fibers. Nonetheless, the use of the BN-coated
long continuous fibers resulted in a more damage tolerant composite
compared with monolithic ZrB2 or ZrB2 reinforced by particles or
short fibers. The composite containing the continuous fibers exhibited
inelastic WOF values that were more than 3 times higher than those
for the short fiber composites demonstrating the enhanced controlled
failure behavior of the continuous fiber composites.