Interface Design in Brittle-Brittle Systems
In brittle matrix composites both ceramic, intermetallic, and cement-based, design of the fiber-matrix interface is key to achieving high composite toughness. In this paper we explore first, a method for accurately determining interfacial properties and second, the influence of physical and chemical aspects of the fiber-matrix interface which influence fracture toughness of the composite. A modified fiber pullout technique has been developed which allows direct experimental evaluation of the force-displacement relation for a crack bridging fiber. The technique allows continuous, accurate measurement of stable, progressive debonding and frictional sliding. Coupled with an appropriate analysis, the test provides a quantitative determination of interfacial properties relevant to the toughening of brittle materials. Among the parameters of influence in determining interfacial properties, and consequently, composite toughness, are interface toughness, surface roughness, residual stress state, and coefficient of friction. Each of these can be altered by use of coatings or surface modifications. Examples of each will be reviewed in a variety of brittle systems.
© 1994 ASM International. Funding for this work has been provided by the Advanced Research Projects Agency through the Office of Naval Research, Grant No. N00014-90-J-4020.