CONTROL OF INTERFACIAL PROPERTIES THROUGH FIBER COATINGS - MONAZITE COATINGS IN OXIDE-OXIDE COMPOSITES

Fiber pushout tests were used to quantify the effects of fiber coating thickness on the mechanical properties of two model composite systems : a monazite-coated (LaPO4-coated) alumina (Al2O3) fiber in an Al2O3 m atrix and a LaPO2-coated yttrium aluminum garnet (YAG) fiber in an Al2 O3 matrix, Interface properties were quantified using the Liang and Hu tchinson (LH) pushout model and mechanistically rationalized by consid ering the change in residual thermal stresses with changes in the coat ing thickness. Measures of the pure Mode II interfacial fracture energ y, the coefficient of friction, and a radial clamping pressure are ext racted by fitting the LH equations to the experimental results, Using the approach that has been developed herein, a methodology is availabl e for measuring the interfacial properties, predicting the effect of c oating thickness, and selecting the coating thickness to alter the int erfacial properties.