Identification of mode-I cohesive parameters for bonded interfaces based on DCB test

An inverse procedure is developed for computing the material parameters of the class of intrinsic cohesive-zone models for the analysis of structural adhesive joints presented in [Valoroso N, Champaney L. A damage-mechanics-based approach for modeling decohesion in adhesively bonded assemblies, Engng Fract Mech 2006;73:2774-801.]. In particular, using the same experimental data recorded as of ISO 25217 test protocol and Double Cantilever Beam bonded specimens, a deterministic identification that overcomes the usual limitations and difficulties of ISO 25217 is proposed to estimate the mode-I cohesive parameters. The driving rationale for our approach to identification is to set up an inverse procedure based on one single experimental test that uses the measured load-deflection curve and crack length as data set. A finite element model updating scheme is used that renders extensions to more general situations such as different geometries, large displacements and nonlinearities in the bulk material, possible with minor modifications. Experiments are conducted for symmetric DCB specimens under pure mode-I bending and an optimization problem is solved to find a suitable agreement between experimental data and finite element computations. Identification results are presented and the key role played by the crack progression in the identification is discussed to assess the effectiveness of the proposed approach.