Study of three-dimensional crack fronts under plane stress using a phase field model

The shape of a crack front propagating through a thin sample is studied using a phase field model. The model is shown to have a well defined sharp interface limit. The crack front is found to be an ellipse with large axis the width of the sample and small axis a function of the Poisson ratio and the width of the sample. Numerical results also indicate that the front shape is independent of the crack speed and of the sample extension perpendicular to its width.