Critical Assessment of the Bonded Single Lap Joint Exposed to Cyclic Tensile Loading

Abstract

Single shear or single lap joints are the most prevalent type of adhesive joints used in advanced engineering applications, where they are exposed to fatigue loadings in their services. Although their mechanical performances under static loading have been investigated extensively, the studies related to the fatigue performances were limited. For that purpose, single lap joints’ (SLJs) reaction to fatigue tensile loading was studied by varying the adherend thickness (3 mm to 6 mm) and fatigue load (3250 N to 1500 N). ABAQUS/Standard was used to create its advanced FE model. To represent the progressive damage in the adhesive layer, the fatigue damage model via the Paris Law, which links the rate of the crack expansion to the strain energy release rate (SERR), was integrated into the cohesive zone model with bi-linear traction–separation characteristics. The model was written in a UMAT subroutine. The developed model was validated using experimental data from the literature. The crack initiation cycle (Ni), the failure cycle (Nf), the fatigue load limit, the strain energy release rate, the crack propagation rate, and variation of stress components with their dependency to design parameters were investigated in depth. It was found that the service life of the SLJs with thicker adherends was more responsive to the amount of stress applied. When exposed to lesser loads, the SLJs’ life span changed more noticeably.