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Model for Toughness Curves in Two‐Phase Ceramics: II, Microstructural Variables
Author(s) -
Padture Nitin P.,
Runyan Julie L.,
Bennison Stephen J.,
Braun Linda M.,
Lawn Brian R.
Publication year - 1993
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.1151-2916.1993.tb07760.x
Subject(s) - materials science , volume fraction , indentation , coalescence (physics) , composite material , toughness , ceramic , fracture toughness , fracture mechanics , physics , astrobiology
The fracture mechanics analysis of Part I is here extended to consider the effects of volume fraction and scale of second‐phase particles on the toughness‐curve properties of ceramic‐matrix composites. Increasing these variables enhances the flaw tolerance of the material, but only up to certain limits, beyond which bulk microcracking occurs. These limits define domains of damage accumulation and potential strength degradation by microcrack coalescence. In the familiar approximation of elliptical crack‐wall profiles, we show that the principal effects of increasing volume fraction (or expansion mismatch) and particle size is to enhance the slope and scale of the T ‐curve, respectively. We also derive expressions for the microcracking limits and use these expressions to construct a simple design diagram for characterizing the effects of microstructural variation on mechanical behavior. Indentation‐strength data on Al 2 O 3 l Al 2 TiO 5 composites over a range of volume fractions and particles sizes are used to demonstrate the severe loss in mechanical integrity that can be suffered on entering the microcracking domains.