EFFECTS OF AN INTERFACIAL REGION ON THE TRANSVERSE BEHAVIOR OF METAL-MATRIX COMPOSITES - A FINITE-ELEMENT ANALYSIS

An interfacial region (i.e. an interface coating or a reaction product ) between the fiber and matrix is known to exist in most metal-matrix composites. Since the load transfer between the fiber and matrix depen ds on the properties and conditions of this interfacial region, :he me chanical behavior of the composites is strongly affected by its charac teristics. In this study, finite element analysis has been used to inv estigate the distribution of residual thermal stresses in the interfac ial region, characteristics of interfacial crack initiation and propag ation, and mechanical response of the composites under transverse tens ile loading. The matrix material is taken to be Ti-6A1-4V (wt%) and be haves elasto-plastically, while the SiC-fiber is assumed to be elastic . The interface is treated as a thin layer with a finite thickness bet ween the fiber and matrix. Three separate interfacial conditions (i.e. a graded carbon coating, a Y2O3 coating and an uncoated interface) ha ve been considered to evaluate the influence of the (independent) ther mal and mechanical properties of the interfacial region. For compariso n, an infinitely strong bond al the interface is also assessed. The re sults indicate that the properties of the interfacial region affect th e stress distribution, the interfacial crack initiation and propagatio n, and the mechanical response of the composites. Based on these resul ts, the thermal and mechanical properties of the coating for improved performance of the composites under transverse loading conditions are proposed.