The expression of the energetic parameter J proposed by Andrews is re-examined and the influence of finite dimensions is introduced, leading to a general expression of the form
In this work, fracture tests have been performed on an EPDM based polymer, using two kinds of specimen geometry.
The different terms of this expression are identified using two different approaches:- the first one is based upon a compliance method; - the second one is an energy separation procedure we have developed. Interesting results have been pointed out in this work: - In first, SENT and CCT specimen leads to a similar function k(W0) which is clearly depending on both the non linear behaviour of the material and of conditions of loading. - Secondly, when considering CCT specimen, the calibration factor F(a/w), derived from the second method, is in good agreement with the Linear Elastic Fracture Mechanics (LEFM) equivalent one. - At least, concerning the deeply cracked specimens, the J estimation using the above mentioned multiplicative form and the direct evaluation from the energy rate dU*/dA give quite concordant results.