For a tensile test specimen made of a short fibre-reinforced composite with the fibres oriented in the direction of force, a model was developed to describe the onset and propagation of microcracks, which finally lead to macroscopic failure of the specimen. The crack propagation theory used is based on a standard fracture mechanics method and was applied to the microstructure of the specimen by the finite element method. The results appear qualitatively correct. The micromechanical method applied gives a deeper insight into the fracture processes within short fibre-reinforced composites.