Research project: 3D Imaging Of The Tensile Failure Mechanisms Of Carbon Fibre Composites

Carbon fibre/epoxy composites offer superior properties for structural applications, including high specific stiffness and strength, good fatigue behaviour, and excellent corrosion resistance. The use of these materials as replacements for their traditional metal counterparts has increased considerably over the last couple of decades. However, the optimal design of a composite structure is often not achieved, due to uncertainties surrounding the prediction of failure.

The tensile strength of continuous fibre FRPS is controlled by the fibre properties, and more specifically the stress transfer mechanisms surrounding broken fibres. The failure process of a composite undergoing tensile failure has two distinguishing features (1) multiple failure sites, distributed through the structure and (2) a sequential progression of failure as a function of increasing load or time duration under applied load. Failure occurs due to the accumulation and interaction of individual fibre breaks, which develop as the material is loaded until a group of interacting breaks reaches a critical size and the specimen fails catastrophically. The strength of a specific structure ultimately depends on the chance dispersion or clustering of failure sites. The understanding of this damage initiation and propagation in composites, and the role of the material parameters in the transition from subcritical to critical damage is vital in material development and design applications.