Cohesive Zone Models identification using an inverse homogenization method

International audienceA major challenge when using cohesive zone models (CZMs) in numerical damageand fracture simulations (e.g. cohesive-volumetric finite element method with CZMsembedded between each volumetric elements) lies in the appropriate identification oftheir parameters. Such a calibration has to be able to predict the response of thestudied material and also to handle the mesh-dependency issue.In order to avoid the usual cumbersome numerical-experimental fitting of CZMs, wepropose an original and practical method for the CZMs parameters calibration. Theformulation is based on a micromechanical approach and consists in deriving explicitrelationships between the local cohesive parameters, the bulk properties, the meshcharacteristics and the applied loading triaxiality rate.The main ingredient of this approach is the introduction of a cohesive ‘matrixinclusion’composite as an equivalent representation of a continuum medium withembedded cohesive zones: the matrix has the same behavior as the bulk elementsof the finite element discretization whereas the inclusions follow a surface damagebehavior corresponding to the traction-separation CZM law. The effective behavior ofthis medium can be then bounded or estimated using advanced non-linearhomogenization methods.Since the effective cohesive-volumetric behavior is obtained, practical criteria for thecalibration of the CZMs parameters are obtained through an inverse analysis. Theoriginality of this calibration lies in its ability to be applied for the case of brittle asductile damage and hence to be used whatever the cohesive law shape. Moreover, itexhibits the dependence of the cohesive parameters on the triaxiality rate of theapplied loading for the case of ductile behaviors and allows to properly avoid theinherent mesh-sensitivity problem. The proposed micromechanical model providesaccurate predictions of the overall material response