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This paper dealing with the fracture of rubber-like materials is a continuation of our previous works (Ait Hocine et al., 1996, 1998). Single specimen methods for measuring the J-integral and, so, its critical value J c (fracture surface energy) are investigated combining experimental data and finite elements analysis. It shown that the formula of J established by Rivlin et al. in the case of the SENT geometry can be extended to the DENT specimen containing small crack lengths (a/w≤0.3). Moreover, considering DENT and pure-shear (PS) specimens, alternative expressions of this parameter, based on the η factor, are proposed and a good agreement is obtained between the numerical calculations and the experimental data whenever available. The critical values of J are found constant for the two tested materials. Finally, it's pointed out that, at the onset of crack growth, the strain energy density along the crack axis is independent on both the crack length and the specimen geometry.

In this paper, we have verified the validity of some formulations allowing the determination of the fracture surface energy in the case of rubber-like materials. The J-integral is chosen as a fracture characterizing parameter which is experimentally determined by considering a multiplying form that; numerically evaluated using a finite element method. The numerical results are compared to the experimental data and a good agreement has been pointed out for the deeply cracked specimen (a/w≥0.5). Below this limit, a significant divergence is observed which is attributed to a lack of accuracy of the experimental data processing.