CERAMIC COMPOSITE INTERFACES sliding resistance, and residual stress state determines the loac cement response. Each of these components is expounded upon below Interface Toughn Conditions for fiber pullout in a fiber-reinforced material first require that a propagating crack deflects along the interface rather than penetrates the fiber uch conditions have been aptly described by He Hutchison(7, 8). They evaluated the relative energy release rate for a crack deflecting along an interface and for the crack penetrating the interface. The competition between crack growth along the interface and penetration through a fiber was found to depend upon the ratio of the fracture energy of the interface Gic and that of the adjoining material Gc, in this case the fiber. In a system where the modulus and fiber have identical moduli, the interface toughness Gic must be less than one quarte of the matrix toughness G. This finding now serves as the basis of interface design. Shown in Figure I is a contour separating regions of crack deflection 0.5 -0.5 0.5 Dundurs' Parameter a Figure I Debonding map showing crack penetration and crack deflection regimes as a function of Dundurs' parameter(after 7, 8)P1: ARK/MBL/rkc P2: MBL/vks QC: MBL/agr T1: MBL May 16, 1997 13:47 Annual Reviews AR034-16 CERAMIC COMPOSITE INTERFACES 501 sliding resistance, and residual stress state determines the load displacement response. Each of these components is expounded upon below. Interface Toughness Conditions for fiber pullout in a fiber-reinforced material first require that a propagating crack deflects along the interface rather than penetrates the fiber. Such conditions have been aptly described by He & Hutchison (7, 8). They evaluated the relative energy release rate for a crack deflecting along an interface and for the crack penetrating the interface. The competition between crack growth along the interface and penetration through a fiber was found to depend upon the ratio of the fracture energy of the interface Gic and that of the adjoining material Gc, in this case the fiber. In a system where the modulus and fiber have identical moduli, the interface toughness Gic must be less than one quarter of the matrix toughness Gc. This finding now serves as the basis of interface design. Shown in Figure 1 is a contour separating regions of crack deflection Figure 1 Debonding map showing crack penetration and crack deflection regimes as a function of Dundurs’ parameter (after 7, 8)