Calculation of J-integrals using experimental and numerical data: Influences of ratio (a/W) and the 3D structure

Contrary to J-integral values calculated from the 2D numerical model, calculated J-integrals [1] from 3D specimen in the numerical and experimental cases are not very close with J-integral used in the literature and two distinct points are present. The first one is according to (a/W) and can be reduced, when this ratio is inferior to 0.2. The second is a structure problem and can be explain by local three-dimensional effects surrounding the crack tip. Two applications using polymer materials for large and minor deformations are experimented. A grid method is used to experimentally determine the in-plane displacement fields around a crack tip in a Single-Edge-Notch (SEN) tensile polyurethane and PMMA specimens. This indirect method composed of experimental in-plane displacement fields and of two theoretical formulations, allows the experimental J-integral to be determined and the results obtained by the numerical simulations to be confirmed.