Interfacial Shear Stresses in SiC and Al_2O_3 Fiber-Reinforced Glasses

Single fiber pullout tests were performed on silicon carbide and sapphire filaments embedded in glass matrices to determine the interfacial shear strengths both as a function of residual stress and as a function of fiber coating. The effect of residual stress on the interfacial shear stress was studied by altering the glass matrix composition, and hence, the thermal mismatch between fiber and matrix. The interfacial shear strength exhibits a maximum with increasing thermal mismatch after which it drops precipitously and levels off. The presence of a carbon coating on sapphire is sufficient to reduce the interfacial shear stress to measurable levels, while excess carbon at the SiC/glass interface increases the interfacial shear stress. In the silicon carbide-reinforced systems, the interfacial shear strengths are also shown to be stressing-rate dependent.