Particulate/whisker-filled ceramic matrix composites

Note that for the asymptotic equations of Eqns. (2) and (3) to be valid, r

characteristic length, and is normally the crack length or the remaining ligament, whichever is the smaller, of a fracture specimen. Also, the above asymptotic equations are not valid for an orthotropic elastic continuum, such as a ceramic fiber/ceramic matrix composite. While the static crack tip state for an orthotropic elastic continuum has been derived, to the author s knowledge, no dynamic counterpart is available to date. Nevertheless, the above crack tip state should be applicable to particulate/whisker-filled ceramic matrix composites which macroscopically behave like an isotropic homogeneous continuum. 

Again, the above crack kinking and branching criteria are limited to isotropic homogeneous material, which for all practical purposes will include particulate/whisker-filled ceramic matrix composites. No equivalent criterion exists for orthotropic/inhomogeneous material. Limited experimental results show that self-similar crack extension is a rare phenomenon in fracture of fiber-reinforced ceramic matrix composites and thus the kinking and branching criterion, if developed, must necessarily be a three-dimensional one. 

The composites can be classified on the basis of the form of their structural components fibrous (composed of fibers in a matrix), laminar (composed of layers of materials), and particulate (composed of particles in a matrix). The particulate class can be further subdivided into flake (flat flakes in a matrix) or skeletal (composed of a continuous skeletal matrix filled by a second material). In general, the reinforcing agent can be either fibrous, powdered, spherical, crystalline, or whiskered and either an organic, inorganic, metallic, or ceramic material. 

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