Influence of the geometry of coaxial adhesive joints on the transmitted load under tensile and compression loads

More and more accurate models have been developed for describing the mechanical behavior of an adhesive in an assembly which allow to numerically optimize the design of bonded assemblies. This paper deals with stress analysis in coaxial bonded joints. The objective was to analyze the effect of various geometries of the different parts of the assembly in order to optimize the maximal transmitted load of such joints. In the case of tensile loads, the stress distributions were analyzed using axisymmetric theory of elasticity. A pressure-dependent elastic limit of the adhesive was used, in order to accurately represent the difference between tensile-shear and compression-shear loads in the mechanical response of the adhesive. In adhesively bonded joints, stress concentrations can contribute to the initiation and propagation of cracks in the adhesive. Therefore, designing adhesively bonded assemblies which strongly limit stress concentrations can significantly increase the load transmitted by the assembly. Moreover, cylindrical joints are associated with high substrate strength in the radial direction, meaning that peel and cleavage forces have different effects compared to single lap joints. A comparison between the mechanical behavior of these two joints is proposed, starting from 2D simulations in the case of tensile and compressive loads. Furthermore, the influence of the angle of conical geometries of the bonded area, which can easily be used for such assemblies, is analyzed with respect to the stress distributions. It is shown that several geometries allow a large reduction of stress concentrations and thus lead to stronger assemblies. Moreover the influences of several geometries which strongly limit stress concentrations are presented.