COMPRESSION FAILURE MECHANISMS IN UNIDIRECTIONAL COMPOSITES

The compressive failure of unidirectional fibre composites has been examined. Four mechanisms of failure have been identified: fibre failure, elastic microbuckling, matrix failure, and plastic microbuckling. Theoretical models to predict the onset of these mechanisms have been reviewed and validated using both model materials and data from the literature. Plastic microbuckling is identified as the dominant compressive failure mechanism in polymeric matrix composites; for this failure mode compressive strength is dictated by the shear yield strength of the matrix and the misalignment of the fibres. Preliminary work has been undertaken to compare predicted and measured distributions of fibre waviness in a carbon AS4/PEEK composite. Weibull statistics have been used successfully to characterise the compressive failure of unidirectional AS4/PEEK composite.