Tensile fatigue life prediction of adhesively bonded structures based on CZM technique and a modified degradation approach

Due to their inherent advantages, the use of adhesive joints is widely increasing in advanced industrial sectors such as automotive and aircraft structures, where the lightweight components play a significant role in the efficiency of the products. These structural adhesively bonded connections mostly experience cyclic stress conditions during their service life. One of the most critical fatigue loading conditions for adhesive joints is the tensile cyclic loading. To design against tensile fatigue conditions recently a cohesive zone modelling (CZM) technique combined with a degradation approach was proposed in the literature. However, to apply this degradation method on cohesive elements, the total fatigue life of the joints should be known before the analysis. The aim of the current work is to improve this degradation approach to calculate the fatigue life automatically. To achieve this, a combination of Paris law and degradation model were considered in a numerical procedure. Using the Paris law and the experimental results obtained out of the fatigue crack propagation tests of DCB (double cantilever beam) specimens, the tensile fatigue life of each integration point (IP) during the analysis is estimated automatically. The model was validated and calibrated by experimental data.