Numerical analysis of mixed-mode fatigue crack growth of adhesive joints nusing CZM

With the increased use of adhesive joints in industrial environments, the need for improvement of this bonding technology arises. Namely, a reliable fatigue life estimation is essential to prevent catastrophic failure in adhesively bonded structural components. The cohesive zone model (CZM) approach has been used in numerical models to assess degradation by fatigue under pure mode conditions. However, in real life, components are subjected to multiaxial loads, the aim of this paper is to perform a numerical estimation of the fatigue behavior of an epoxy-based adhesive subjected to mixed mode loading conditions. To achieve this, the mixed mode was split into the corresponding components of mode I and mode II. For each mode, the adhesive's cohesive properties were degraded by fatigue, according to a relation previously published for pure mode I and which has also been validated for pure mode II. Fatigue tests were performed on DCB specimens to calibrate the degradation model which, along with a triangular shaped CZM, was included in an Abaqus user material subroutine (UMAT) to perform a simulation of the fatigue behavior. Results showed that such approach can be applied to estimate the fatigue life of adhesive joints under mixed mode loading conditions.