Models for the strain energy release rate in crack extension and tunnelling are taken from the literature with minor modification to take account of the compressive stresses in multi-layer ceramic tubes or composites. These models are applied to predict the potential for crack development in co-extruded tubes fabricated from combinations of alumina, zirconia (fully and partially stabilized) and zirconia toughened alumina. Experimental results show that the models predict the failure in the composites closely and thus form useful tools in the design of such structures. The main aspect of the predictive capacity is in the selection of the layer numbers and the layer thicknesses to prevent failure. The significance of crack-free layers is improved mechanical properties, in particular strength, and potential improvement in fracture toughness and device performance.