Alumina and Zirconia Based Layered Composites: Part 2 Fracture Response

Abstract

Laminated materials are used for special applications where combination of properties of two components is needed. Ceramics is inherently brittle and above all superior properties (wear resistance, temperature durability, stiffness, low density and others) the brittleness is limiting factor for massive implementation in wide range applications. The laminated structure can be capable to overcome this handicap. Electrophoretic deposition (EPD) is the technique able to prepare ceramic laminated structures having strong interface between layers [1]. It is possible to prepare dense and crack free materials with tailored residual stresses controlled by layer thickness and deposition conditions by this technique. Crack propagation through layered composites based on Al2O3 and ZrO2 was studied. Cracks, produced by an indentation technique, propagated in direction to layer interfaces deflected towards the interface in the compressed layers and away from the interface in the layers containing tension stress [2,3]. Changes in the direction of crack propagation for the whole range of angles of incidence (0° - 90°) were described. The biggest change in the crack propagation was observed for the angle of incidence 45° for A/Z systems and was ca. 15°. The change in the crack propagation was independent on the level of residual stresses in the layers. Behaviour of indentation cracks observed in laminates under investigation was compared with the results obtained on standard SEVNB specimens having inclined the fracture plane with respect to the composite lamellar structure. This model condition helps to understand crack propagation in bulk material. All experimental work was supported by fractographical techniques enabling explanation of fracture micromechanism.