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Effect of a Boron Nitride Interphase That Debonds between the Interphase and the Matrix in SiC/SiC Composites
Author(s) -
Morscher Gregory N.,
Yun Hee Mann,
DiCarlo James A.,
ThomasOgbuji Linus
Publication year - 2004
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.1551-2916.2004.00104.x
Subject(s) - interphase , composite material , materials science , ultimate tensile strength , boron nitride , ceramic matrix composite , composite number , residual stress , fiber , fabrication , medicine , alternative medicine , genetics , pathology , biology
Typically, the debonding and sliding interface enabling fiber pullout for SiC‐fiber‐reinforced SiC‐matrix composites with BN‐based interphases occurs between the fiber and the interphase. Recently, composites have been fabricated where interface debonding and sliding occur between the BN interphase and the matrix. This results in two major improvements in mechanical properties. First, significantly higher failure strains were attained due to the lower interfacial shear strength with no loss in ultimate strength properties of the composites. Second, significantly longer stress‐rupture times at higher stresses were observed in air at 815°3C. In addition, no loss in mechanical properties was observed for composites that did not possess a thin carbon layer between the fiber and the interphase when subjected to burner‐rig exposure. Two primary factors were hypothesized for the occurrence of debonding and sliding between the BN interphase and the SiC matrix: a weaker interface at the BN/matrix interface than the fiber/BN interface and a residual tensile/shear stress‐state at the BN/matrix interface of melt‐infiltrated composites. Also, the occurrence of outside debonding was believed to occur during composite fabrication, i.e., on cooldown after molten silicon infiltration.