FRACTURE-MECHANICS AND CAVITATION IN RUBBER-LIKE SOLIDS

Conditions for propagation of a pressurized crack within a rubber-like solid are derived in terms of the elastic properties of rubber, the fracture energy G(c) and the initial radius r(o) of the crack. A previously proposed criterion, that the critical internal pressure P(c) for crack growth is given by 5E/6, where E is the tensile (Young) modulus of elasticity, is shown to be inadequate both for small cracks, when the stiffening of rubber at high strains must be taken into account, and for large cracks, when the critical degree of inflation is so small that the assumptions leading to P(c) = 5E/6 do not apply. However, this simple criterion is found to remain a useful guide for cracks having initial radii lying in an intermediate range, such that r(o)E/G(c) lies between about 0.0005 and 1. For representative rubber-like solids, this corresponds to the range r(o) = 0.5-mu-m to 1 mm.