Model experiments on pure oxide composites

A promising approach to develop composites with long time stability at high temperatures even in oxidising atmospheres is the use of oxide materials both for the matrix and for the reinforcing elements. Ceramic composites of alumina and mullite can be formed through conventional powder metallurgical processing using the reaction bonding technique, developed at TUHH. Continuous filaments of single crystal alumina (sapphire fibres) serve as model reinforcement. Single fibre samples are used to investigate the basic interfacial behaviour in these composite systems by observations of crack deflection and crack propagation, and by high temperature push-out measurements. Despite the interesting results of these tests, the micromechanical mechanisms in these pure oxide composites are not fully resolved yet. It is demonstrated that the most commonly accepted models for the description of the interfacial behaviour do not seem to be applicable to this class of material. In the following, the most recent experience in pure oxide composites based on Reaction Bonded Aluminium Oxide (RBAO) is described with special emphasis on the requirements for further modelling.