Effects of local stress fields around broken fibres on the longitudinal failure of composite materials

An in-depth analysis of the stress fields that surround a broken fibre in fibre reinforced composites is performed and the effects of different material properties are analysed. The stress fields obtained using a spring element model with a random distribution are compared with analytical formulations present in the literature, within a progressive failure model framework. This analysis is then extended to clusters of broken fibres with different sizes and the evolution of the stress fields are analysed. Finally, material macro behaviour and cluster formation is analysed using the spring element model and the progressive failure model framework. The authors found that while for the spring element model the stress redistribution and material behaviour changes with the main material parameters, the same was not found to be true using the analytical formulations for stress concentration and ineffective length. Furthermore, it was found that the current definition for a cluster of broken fibres can lead to erroneous results, depending on the material system.