Fracture under point loading of brittle fibres in a ductile matrix

Abstract

An elementary wear event occurring during the abrasion of metal matrix composite materials has been studied by modelling the interaction between a single grit particle and an isolated fibre. Point loads were applied to glass fibres supported in a transparent ductile acrylic resin matrix. The load was applied by a hardness indenter. Transverse cracks appeared in the fibre above a critical load, and the distances between these cracks, and the loads at which they formed, were measured. Good agreement was found between these measured quantities and the predictions of a simple theoretical model. The transverse fractures, which delimit the length of fibre likely to be removed in wear, result from tensile stresses on the upper surface of the fibre. The distance between the cracks is proportional to the fibre diameter, and also to the square root of its fracture stress divided by the hardness of the matrix.