Evaluation of fatigue strength of adhesively bonded single and single step double lap joints based on stress singularity parameters

Abstract Most adhesively bonded joints have stress singularity points at the corners of the adhesive/adherend interface. Recently, stress singularity parameters, i.e. the intensity of stress singularity, K , and the order of stress singularity, λ , have been used to evaluate the strength of adhesively bonded joints. However, in many cases, stress singularity fields of adhesive joints cannot be formulated strictly by using constant values of K and λ . To apply these parameters to evaluate the strength of an adhesive joint, it is necessary to determine a key stress component and characteristic range for calculating the apparent singularity parameters K app and λ app . In this study, the endurance limits of adhesively bonded single lap, cracked single lap and single step double lap joints are evaluated using the stress singularity parameters. The results indicate that fatigue failure criterion for these joints can be obtained by using the apparent singularity parameters K app and λ app which are calculated by the least square method for the maximum principal stress distributions in the range from 0.05 to 0.5 mm from the singularity point.