STP1409

    Crack Deflection Toughening Mechanism in Brittle Materials

    Published: Jan 2002


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    Abstract

    Toughening mechanisms in polycrystalline ceramics and ceramic-based composites were discussed based on Griffith's energy equilibrium and classified into three groups: (A) the frontal process-zone toughening mechanism, (B) the crack-bridging mechanism, and (C) the macroscopic crack-deflection mechanism. The increase in fracture toughness caused by enforced macroscopic crack-deflection was estimated using the energy equilibrium between the energy-release rate and the fracture-energy rate. The analytical results revealed that the fracture toughness under Mode I loading was enhanced by twice the normal value when the crack propagates in the direction 90° from its original plane. Under Mode II loading the fracture toughness is increased 1.2 times the normal value when the crack propagates in its original plane. Crack-deflection tests were carried out by using wooden, thin rectangular plates with a central crack. The increase in the fracture toughness caused by crack deflection was confirmed and the experimental data was coincident with the calculated results.

    Keywords:

    toughening mechanism, crack deflection, self-remforced ceramics, Griffith criterion, multilayered composites


    Author Information:

    Awaji, H
    Professor, and graduate students, Nagoya Institute of Technology, Nagoya,

    Ebisudani, M
    Professor, and graduate students, Nagoya Institute of Technology, Nagoya,

    Choi, S-M
    Professor, and graduate students, Nagoya Institute of Technology, Nagoya,

    Ohashi, T
    Professor, and graduate students, Nagoya Institute of Technology, Nagoya,


    Paper ID: STP10476S

    Committee/Subcommittee: C28.01

    DOI: 10.1520/STP10476S


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