Modelling delamination of a DCB test by using non-linear truss interface elements and plate elements with assumed shear strain

Fracture resistance of structural adhesive joints is key for their application in the industry. Mode-I adhesive joint delamination is the most severe type of fracture and the possibility of this outcome should be avoided whenever possible. In this work we are investigating mode-I delamination of plate-like specimens, where the width is comparable to the length. In such cases anticlastic bending of the plates takes place on the debonded part and the crack front is a curve rather than a straight line. We model the interface by means of discrete non-linear truss elements with embedded exponential traction-separation law [1]. Such choice is justified because in this test, only pure mode-I (opening) displacements occur at the interface, which in our case will cause axial elongation of the truss elements. The plates are modelled using 4-node plate finite elements derived by the assumed shear strain approach that pass the general constant-bending patch test [2]. Cohesive-zone interface parameter identification is performed by a direct method (J-integral) [3] and by virtual experiments regression. Numerical tests have been performed and the exponential cohesive-zone interface model compared against the bi-linear in terms of precision, robustness and computing time. The results confirm the experimentally observed behaviour with anticlastic bending of the arms and the curved crack front.