Interfaces in composites: Relations between structure and properties

The toughness of ceramic composites is mainly governed by the mechanical behavior of the interfaces between the ceramic matrix and the ductile particle or the strong fiber/whisker reinforcements. The toughening can be described by a bridging zone mechanism. In the crack bridging models, debonding of the reinforcement at the interface plays an important role. The status of present understanding is reviewed. Transmission electron microscopy has been used to study the interfacial structure and behavior of ductile particles and fiber/whisker reinforced composites. Furthermore, model systems of ceramic/ceramic and metal/ceramic interfaces have been investigated. The atomic structure of such interfaces can be determined by a quantitative analysis of high resolution micrographs. Chemical reaction products and structural defects at the interface can be identified by analytical electron microscopy. The results of such studies will help to tailor the interfaces in composites.