REDUCTION IN ENERGY-RELEASE RATE FOR MODE-I FRACTURE OF A FIBER WITH A CRACKED COATING LAYER DUE TO SMALL-SCALE INTERFACIAL DEBONDING

In order to predict the effect of small-scale interfacial debonding on the energy release rate at a crack tip for mode I fracture of a fibre with a cracked coating layer, an approximate calculation method has b een presented. The relation of debonding length, thickness of the coat ing layer and ratio of elastic modulus of the coating layer to that of the fibre, to the energy release rate of the fibre was calculated for some examples. It was demonstrated that small-scale debonding reduces the energy release rate and, therefore, effectively prevents reductio n in fibre strength.