Modeling Adhesive Joints by Cohesive Models Using the Direct Method

The industry´s growing interest in adhesive bonds is based on the increased reliability of the strength prediction methods to adhesive structures. This work aims the validation of tensile and shear cohesive laws, estimated by the application of the direct method, in order to predict the failure of bonded joints under mixed-mode loading. In this context, single and double-lap joints were tested with different overlap lengths and adhesives with distinct ductility. The cohesive laws in pure modes enabled obtaining simplified cohesive laws with triangular, trapezoidal and linear-exponential shapes, which were tested for each one of the adhesives. The validation of the referred cohesive law shapes was accomplished by comparing the numerical predictions with the experimental tests. A peel and shear stress analysis in the adhesive was also performed, in order to understand the influence of stresses on the joints’ strength. The use of the direct method allowed obtaining accurate strength predictions, providing the most adequate cohesive law shape for each set of adhesive/joint geometry.