Fatigue behaviour of polymer-based composites and life prediction methods

A general introduction to the problems of defining and studying the fatigue behaviour of composite materials is presented, with specific reference to the high-performance carbon-, glass-, and aramidfibre-reinforced thermosets that are of current interest to the aerospace industry. A description is also given of the overall patterns of fatigue response of composites, with particular emphasis on materials of unidirectional and [(±45,0 2 ) 2 ] s lay-up, with reference to plain and hybrid systems, and including consideration of damage accumulation and the effects of damage on residual properties. A method of analysis of data in terms of constant-life diagrams for life prediction purposes is presented, together with an indication of the level of success that may be achieved in prediction and prevention of the potential hazards. Some consideration is also given to statistical aspects of data analysis. Mention will be made of the problem of variable-stress testing and the difficulties of analysis of the data from such tests and the paper concludes with a brief discussion of the use of artificial neural networks for life prediction purposes.