PhDCeramic materials have considerable attraction for use in applications where the service
temperatures are high and where fire performance and non-combustibility are important.
Unfortunately most monolithic ceramic materials are extremely brittle which limits their
use for structural applications. The development of fibre and particulate reinforced
ceramic composites provides a route to achieving increased toughness in the materials,
although this is often at the expense of ultimate strengths and/or the process-ability of the
materials. Many reinforcing fibres used with ceramics are inherently expensive and
manufacturing routes to produce fibre reinforced materials can involve high processing
temperatures and are consequently expensive. A key goal of this research therefore is to
develop a new type of ceramic matrix composites that combine toughness, strength and
process-ability to provide a cost effective structural material.
The research described in this thesis has been concerned with the development and
characterisation of a series of ceramic compounds that can be moulded at modest
temperatures( 130-160" C) and pressures in a manufacturing system that replicates dough
moulding compounds (DMC) as used for polymeric matrix composites. The conventional
polyester matrix of polymeric DMC has been replaced by a soluble inorganic system
which is compounded with fibres, fillers and hardening agents to produce a paste-like or
doughy substance The handle-ability of the material is determined by the viscosity of the
matrix and the type or amount of fillers and additives present.
The research has involved a careful set of experiments in which the formulation of the
ceramic DMC has been systematically varied in order to achieve an optimum viscosity for
storage and handling together with a further series of experiments studying the hardening
and cure of the compounds. The mechanical properties of the compounds have been
measured and additional formulation changes have been introduced to maintain desirable
processing characteristics while improving mechanical properties, and in particular the
impact resistance using instrumented falling weight impact machines. Finally the fire
properties of the compounds have been studied using cone calorimetry and indicative
furnace testing.
The structure of the compound has been studied throughout the programme with various
microscopic techniques and thermal analysis systems used to characterise the materials,
their dispersion and changes that occurred during processing and after high temperature
exposure.
The final result of the programme has been the identification of a range of material
formulations that can provide a tough moulding compound, capable of high temperature
service use, that possesses useful structural properties and which can be processed
cheaply at modest temperatures using low cost materials
