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Crack opening behavior in ceramic matrix composites
Author(s) -
Sevener Kathleen M.,
Tracy Jared M.,
Chen Zhe,
Kiser James D.,
Daly Samantha
Publication year - 2017
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/jace.14976
Subject(s) - materials science , composite material , digital image correlation , ceramic matrix composite , scanning electron microscope , ceramic , cracking , matrix (chemical analysis) , stress (linguistics) , tension (geology) , composite number , stress relaxation , relaxation (psychology) , creep , compression (physics) , psychology , social psychology , philosophy , linguistics
The evolution of matrix cracks in a melt‐infiltrated SiC/SiC ceramic matrix composite ( CMC ) under uniaxial tension was examined using scanning electron microscopy ( SEM ) combined with digital image correlation ( DIC ) and manual crack opening displacement ( COD ) measurements. CMC modeling and life prediction strongly depend a thorough understanding of when matrix cracks occur, the extent of cracking for given conditions (time‐temperature‐environment‐stress), and the interactions of matrix cracks with fibers and interfaces. In this work, strain relaxation due to matrix cracking, the relationship between COD s and applied stress, and damage evolution at stresses below the proportional limit were assessed. Direct experimental observation of strain relaxation adjacent to regions of matrix cracking is presented and discussed. Additionally, crack openings were found to increase linearly with increasing applied stress, and no crack was found to pass fully through the gage cross‐section. This calls into question the modeling assumption of through‐cracks for all loading conditions and fiber architectures, which can obscure oxidation mechanisms that are active in realistic cracking conditions. Finally, the combination of SEM with DIC is demonstrated throughout to be a powerful means for damage identification and quantification in CMC s at stresses well below the proportional limit.