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Effect of Bridged Boron Nitride Coatings on the Flexure Behavior of a Unidirectional Ceramic‐Fiber Ceramic‐Matrix Composite
Author(s) -
Jessen Todd L.,
Bender Barry A.,
Greenhut Victor A.
Publication year - 2000
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2000.tb01715.x
Subject(s) - materials science , boron nitride , composite material , ceramic , ribbon , mullite , composite number , toughness , ceramic matrix composite , amorphous solid , coating , fiber , fracture toughness , crystallography , chemistry
A series of 50 vol/% unidirectional Nicalon™ fiber/zirconium titanate matrix composites were fabricated by alkoxide infiltration of the fiber tows. The fibers had a thin, amorphous boron nitride coating that was either heavily or lightly bridged. The bridged coatings were a result of localized excess boron nitride deposits and had the effect of binding adjacent fibers at boron nitride nodules during the immersion process. The resultant composites contained matrix‐rich ribbons, which exhibited laminate‐like mechanical behavior reported previously. Highest strength was obtained when the composites were loaded parallel to the ribbon orientation, and highest toughness (WOF) was obtained when the composites were loaded perpendicular to the ribbons. The ribbon orientation had a more pronounced effect on composite behavior than the presence or lack of bridging boron nitride nodules. However, the bridging nodules altered the relative orientation of the matrix‐rich ribbons during fabrication and, thus, the direction of optimal strength or toughness.