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Author

Colin Scott

Date of Award

10-2001

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Materials Engineering

Supervisor

P.S. Nicholson

Abstract

Ceramics have material properties that make them useful for many industrial applications. They are strong, hard, and chemically inert. Their refractoriness gives them an advantage over metals and polymers for use at high temperature. Unfortunately, the inherent brittleness of ceramics limits their use in structural applications.

One way to improve the toughness of ceramics is to combine them with other materials to make composites. The correct combination of materials can lead to synergism, and a significant improvement in properties. In this work, brittle laminates that contain weak interlayers are considered. The weak interlayers lead to crack deflection, and can result in non-catastrophic failure of the material. The requirements for consistent crack deflection and non-catastrophic failure are not fully understood.

This work is an attempt to explain the observed fracture behaviour in brittle laminar composites that contain weak interlayers. A combination of experimental work, fracture mechanics modeling and finite element modeling has been used to predict the requirements necessary for non-catastrophic failure.

The work shows the size of flaws in the surface of the composite, in the weak interlayer, and in subsequent strong layers in the material, all play an important role in the fracture behaviour. Control and understanding of the effect of the various flaw sizes can be used to achieve non-catastrophic failure and increased work of fracture in these composites.

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