Mechanics of Failure of High Temperature Metal Matrix Composites

摘要

Results of a three-year research effort aimed at developing an understanding ofthe factors controlling transverse strength and failure of intermetallic composites are presented. Experiments were conducted involving several aluminide matrix composites; two types of fibers were used in order to allow for large as well as small residual stresses. On the basis of the in situ observations and with the aid of high resolution strain mapping, the relevant damage mechanisms were identified. The experimental effort coupled with analytical models led to a number of conclusions that are important for the proper design of such composites. Among the important properties are the strength and sliding resistances of the interface, residual stresses, and fiber spacing. Therefore optimum strength is achieved with either strongly bonded interfaces, or interfaces that debond easily but have large resistance to circumferential sliding. The latter condition could also be compatible with the requirement of debonding and relatively easy frictional sliding for maximum benefit from fiber reinforcement in longitudinal properties. The results suggest a potential benefit from having anisotropic interfacial properties, perhaps obtained through morphology, to allow easy sliding in the axial direction and more strongly resisted sliding in the circumferential direction.