A comparison of the predictive capabilities of current failure theories for composite laminates, judged against experimental evidence

This paper draws together the results from a co-ordinated study, known as the World-Wide Failure Exercise, whereby 12 of the leading theories for predicting failure in composite laminates have been tested against experimental evidence. The comparison has been effected through 14 carefully selected test cases, which include biaxial strength envelopes for a range of unidirectional and multi-directional laminates, and stress-strain curves for a range of multi-directional laminates, loaded under uniaxial or biaxial conditions. The predictions were provided by the originators of the theories, not by third parties, and were made without access to the experimental results beforehand. The predictions and experimental data have been compared in a systematic and detailed manner, to identify the strengths and weaknesses of each theory, together with a ranking of the overall effectiveness of each theory. Careful reading of this analysis and study of the figures provided will inform the reader when selecting an appropriate failure theory for use in a given design situation. It will also provide a qualitative assessment of the likely accuracy and reliability of the prediction in a given circumstance. (C) QinetiQ Ltd 2002.