Tests to determine the influence of stress on the strength of metal-polymer adhesive joints

It is promising to expand the scope of applications of metal-polymer adhesive joints in order to create composite materials, honeycomb and layered structures that combine high strength and low weight. For an adequate design of metal-polymer joints using modern engineering analysis systems, it is necessary to have information about the ultimate mechanical properties of adhesive joints under stress conditions that can be realized in the designed structural elements during operations. The article describes the features of using the methods for conducting and processing the results of a set of mechanical tests for tension of modified Arkan samples and transverse compression of glued cylindrical BNS-samples. At the edges of the samples, it was proposed to form an additional volume of adhesive extending beyond the contact surface to reduce the concentration of dangerous stresses. It was proposed to test multilayer samples for a three-point bending with a simultaneous video recording of the sample deformation process to take into account the characteristics of the damage of layered metal-polymer compounds. The initial moment of damage of the adhesive joint is determined by the occurrence of a relative shift of previously applied reference lines. The criterion was proposed for evaluation of the damage of adhesive joints, based on the consideration of the limit state of a selected microvolume containing the boundary of the connection of materials. Analytical formulas were given for calculating the effective values of the modulus of elasticity and Poisson's ratio of the selected microvolume. The features of the proposed methods were considered using examples of testing metal-polymer adhesive joints of aluminum alloy surfaces using epoxy resins. Based on the results of the tests, diagrams of the ultimate deformation energy density were constructed, which can be used for the design assessment of the resource of the adhesive strength of metal-polymer adhesive joints.