Design of tough ceramic laminates by residual stresses control

Design of tough ceramic laminates by residual stresses control 

N ORLOVSKAYA, Drexel University, USA, M L U G O V Y, Institute for Problems of Materials Science, Ukraine, J KUEBLER, EMPA, Lab for High Performance Ceramics, Switzerland, S YARMOLENKO and J S A N K A R, North Carolina A T State University, USA 

A number of articles on the design of ceramic laminates leading to a significant increase of their mechanical properties were published in the past [15-19]. Our work is based on the control of thermal residual stresses by optimization of the layered structure [20, 21], The proposed approach targets the fracture toughness increase of laminate ceramic composites and is based on the preliminary results both from our work [22, 23] and from the work of others [24-26], 

A schematic presentation of a general case of two-component multilayered sample is shown in Fig. 7.1, where q is the thickness of the Ah layer, ivis the total thickness of the specimen, b is the width, and TV is the total number of layers. Often the two-component brittle layered composites with symmetric macrostructure are only considered. In this case the layers consisting of different components alternate one after another and the external layers consist of the same component. The total number of layers TVin such a composite sample is odd. Often the layer of each component has some constant thickness, and the layers of same component have identical thickness. In this case all 

The compressive residual stress crrl in the outside layers of a laminate shields natural and artificial cracks in the layer. Therefore, the effective (apparent) fracture toughness of such a structure increases. The more compressive residual stress induced, the more shielding occurs. Another important factor that contributes to the apparent fracture toughness increase 

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