Directional dependence of fracture toughness in hot-Pressed SiC-whisker reinforced alumina at room and elevated temperatures

Andrew A. Wereszczak, Mattison K. Ferber, Azar Parvizi-Majidi

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

The directional dependence of fracture toughness was investigated in commercially available hot-pressed SiC-whisker reinforced alumina composites at room and elevated temperatures. Whisker orientation was transversely isotropic with respect to the pressing axis in these composites. Composite bend bars were chevron-notched and loaded in four-point bending to induce stable crack propagation in two different crack systems: defined here as a combination of crack plane and direction with reference to the pressing axis. The average fracture toughness, K1c, was found to be approximately 30% less for a crack system with its crack plane parallel and crack direction perpendicular to the pressing axis compared to a crack system with both its crack plane and direction parallel to the pressing axis through 1200°C. The crack systems with the lower fracture toughness exhibited a characteristic high concentration of whiskers aligned parallel to the crack direction within the crack plane; this appeared to be associated with decreased or unpromoted crack deflection. This fracture mechanism evidently dominated the fracture process through 1200°C because measured fracture toughnesses were independent of temperature; crack-wake toughening mechanisms, whose efficiency is a function of the residual thermal stresses, are expected to be temperature-dependent.

Original languageEnglish
Pages (from-to)1905-1919
Number of pages15
JournalJournal of Composite Materials
Volume31
Issue number19
DOIs
StatePublished - 1997

Keywords

  • Ceramic composite
  • Crack deflection
  • Elevated temperatures
  • Fracture toughness
  • Whisker

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