INTERFACIAL STRESS MEASUREMENTS ON CERAMIC-MATRIX COMPOSITES

A recently published method of quantitative interfacial friction stress analysis was used to characterise the interfaces of a number of composite types, including Pyrex-Nicalon, calcium aluminosilicate (CAS)-Nicalon and barium osumulite (BMAS)-Nicalon. The test involved the compression of a polished slice of the composite cut normal to its reinforcement. The bottom surface of the slice was compressed at constant strain, by being placed on a flat polished silicon carbide plate, while the top surface of the slice was compressed at constant stress. The compressive force led to debonding of the fibres which protruded into the aluminium leaving indentations on its surface. On relaxation, the fibres partially relaxed back into the matrix. The depth of the indentations and height of residual protrusions, calculated from scanning electron micrographs, were then used to calculate the interfacial frictional stress. Several samples were studied, including CAS-Nicalon and BMAS-Nicalon after heat treatment in air. The data calculated, along with information collected from transmission electron microscopy and energy dispersive X-ray spectrometry, were used to establish a relationship between interface microstructure and interface properties. (C) 1993 The Institute of Materials.