Service Life Modelling of Single Lap Joint Subjected to Cyclic Bending Load

Bonded joints used in wing sections and frames of aircraft structures are mostly exposed to cyclic loadings instead of static ones during their services. Bending types of dynamic loadings are mostly encountered. In this study, the fatigue response of a single lap joint (SLJ) exposed to bending loading was studied with the developed advanced finite-element (FE) model. The cohesive zone model describing the behaviour of the adhesive layer used the damage mechanism, where static and fatigue damages were linked to each other; i.e., the total damage was accumulated because of material deterioration and cyclic plastic separation. This enabled us to predict the fatigue characteristics including the finite fatigue life, crack propagation rate using Paris law. The model was implemented via a user-defined UMAT subroutine offered in ABAQUS-Standard. The numerical model was validated by experiments available in the literature. The fatigue performance of an SLJ subjected to bending loading was investigated for different lap joint configurations. A smaller bending load, a thicker adherend or a longer overlap length (OL) led to enhanced fatigue life. For instance, the fatigue life was observed to increase up to 50 times for a 66% increase in OL.