A customized shear traction separation law for cohesive zone modelling of creep loaded ENF adhesive joints

Considering the creep behavior of bonded joints is of paramount importance since a constant service load can significantly change the properties of adhesives. Several models have been proposed to analyze the creep response of adhesive joints. However, none of them considers the cohesive zone modelling (CZM) as a robust damage analysis approach. The aim of the current work is to present a customized CZM based approach to predict the creep behavior of adhesives subjected to pure shear loading conditions using end notched flexure (ENF) samples. To achieve this a triangular shape cohesive law was used and the variation in cohesive properties of the adhesive was addressed through the proposition of two developed equations, one for the mode II fracture energy and the other for the shear traction. A family of numerical curves can be obtained for each creep condition, thus, the best numerical curve was achieved through a statistical analysis. The effects of the model on the cohesive parameters were also evaluated. The model was validated by an additional creep test. The numerical results were compared to the experimental data obtained in previous work and a good agreement was observed.