Ceramic Matrices

A partial answer to the first question has been provided by a theoretical treatment (1,2) that examines the conditions under which a matrix crack will deflect along the iaterface betweea the matrix and the reinforcement. This fracture—mechanics analysis links the condition for crack deflection to both the relative fracture resistance of the iaterface and the bridge and to the relative elastic mismatch between the reinforcement and the matrix. The calculations iadicate that, for any elastic mismatch, iaterface failure will occur whea the fracture resistance of the bridge is at least four times greater than that of the iaterface. For specific degrees of elastic mismatch, this coaditioa can be a conservative lower estimate. This condition provides a guide for iaterfacial desiga of ceramic matrix composites. 

Various combiaations of ceramic—matrix composites have been manufactured at the research level. Their properties are given ia Table 1 for oxide-based matrices and ia Table 2 for aoaoxide matrices. Some commercial products are ideatifted for information only. Such identification does not imply recommendation or endorsement by NIST, nor does it imply that the products are the best available for the purpose. 

Type Amount, vol % Strength, MPa Toughness, MFai/in Modulus, GFa Density, g/cm or % td Referer 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Subscripts denote reinforcement morphology p = particulate, 1 = platelet, w = whisker, f = fiber, i = interlayer between reinforcement and matrix. Strength as measured in a four-point flexure test (modulus of mpture) to convert MPa to psi, multiply by 145. 

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