Effects of fiber coating properties on the crack deflection and penetration in fiber-reinforced ceramic composites

A finite element technique is used to study the effects of coating properties on the deflection and penetration of cracks which terminate perpendicular to the fiber-coating or coating-matrix interfaces. Four types of coatings are considered for the SCS6 (fiber)-Zircon (matrix) composites. The hoop and tangential stresses and the energy release rates are analyzed for the various coatings. The effects of the thickness of coatings on these parameters are also studied. In general, no significant changes are found in stress ratio (ratio of hoop stresses along the crack and at the interface) and energy release rate ratio (ratio of energy release rates for the crack penetration and crack deflection), but the magnitudes of the stresses and energy release change substantially with the change in the coating thickness. Also, the effects of the coating properties on various stresses (except on the crack opening stress at the interface) and energy release rates are found to be the same irrespective of the relative modulus of the fiber and matrix. (C) 1997 Acta Metallurgica Inc.