Issue 39

M. A. Lepore et alii, Frattura ed Integrità Strutturale, 39 (2017) 191-201; DOI: 10.3221/IGF-ESIS.39.19 191 From test data to FE code: a straightforward strategy for modelling the structural bonding interface M. A. Lepore, M. Perrella Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II, 132 - 84084 - Fisciano (SA), Italy malepore@unisa.it , mperrella@unisa.it A BSTRACT . A straightforward methodology for modelling the cohesive zone (CZM) of an adhesively bonded joint is developed, by using a commercial finite element code and experimental outcomes from standard fracture tests, without defining a damage law explicitly. The in-house developed algorithm implements a linear interpolated cohesive relationship, obtained from literature data, and calculates the damage at each step increment. The algorithm is applicable both to dominant mode I or dominant mode II debonding simulations. The hypothesis of unloading stages occurrence is also considered employing an irreversible behaviour with elastic damaged reloading. A case study for validation is presented, implementing the algorithm in the commercial finite element method (FEM) software Abaqus®. Numerical simulation of dominant mode I fracture loading provides with satisfactory results. K EYWORDS . Finite element method; Mode I crack; Fracture toughness; Cohesive law; Adhesive bonding. Citation: Lepore, M. A., Perrella, M., From test data to FE code: a straightforward strategy for modelling the structural bonding interface, Frattura ed Integrità Strutturale, 39 (2017) 191-201. Received: 10.06.2016 Accepted: 10.10.2016 Published: 01.01.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION owadays, structural bonding is widely used as joining technique in many engineering fields. Safety requirements are often to be satisfied, as for example in civil applications where FRP laminates are anchored to beams for strengthening purposes and seismic retrofitting [1]; in superconducting systems where insulating composite wraps are bonded to superconducting cables subjected to Lorentz forces [2]; in aeronautical and automotive structures for repairing process [3]. There are numerous advantages with respect to traditional mechanical fastening methods: homogeneous distribution of stresses throughout the union, reduction of the joint weight, sealing function and protection against corrosion, excellent fatigue strength, free design of the joint, and so on. However, the application of this technique to high-technology industry requires the satisfaction of a large number of requirements especially about the adhesive joining durability and reliability. Thus, a proper description of mechanical behaviour, and the prediction of fracture propagation at the interface is necessary in order to realize a correct design phase of adhesively bonded structures. Continuum damage mechanics (CDM) offers suitable tools for facing this issue, in coupling with the FE methodology. Using such approach the proper definition of a representative volume element (RVE) is crucial because its dimension relates the relevant scales in which the fracture process and the softening behaviour take place. A careful choice of the N