THE EFFECT OF SURFACE-LIMITED MICROCRACKS ON THE EFFECTIVE YOUNGS MODULUS OF CERAMICS .1. ANALYSIS

Two types of composite layer model were used to characterize the surface-limited microcrack damage: (i) a dynamic modulus model and (ii) a rule-of-mixtures model. Each model can be applied to either one or two microcracked surface layers for all physically meaningful values of the relative thickness of the layer(s) and all physically meaningful values of the microcrack damage severity states. The microcrack severity can be described in terms of known functions of microcrack size, number density and orientation. A second paper will deal with the details of applying the models to microcracks of a particular geometry, while a third paper deals with experimental tests of the models presented here.