Control of strength and toughness of ceramic/metal laminates using interface design

The fracture strength and toughness of alumina can be increased by lamination with strategically placed nickel layers and by controlling the geometry of the interfaces. This paper describes the interface design of a ceramic/metal bonded system produced by changing the surface topography of the interface between the metal and ceramic layers in order to vary the strength of bonding. The tortuosity of the interface is described quantitatively using fractal geometry. Experiments and models of single ductile layer laminates show that the work of fracture of ductile layers which contribute to the increment of toughness of ceramic/metal laminates is dependent on the tortuosity of the interface. The more tortuous the interface, the stronger the laminate; the smoother the interface, the tougher the laminate. The results are used to design a ceramic/metal multilayer composite. The strength and toughness of the laminates can be controlled by the tortuosity of the interface and characterized using the fractal dimension.