The assessment of modified block samples for the investigation of impact strength of adhesive joints

Abstract The described research relates to the methodology of block bonded joints, dealing with one of its aspects. The authors made an experimental comparison of samples for the research into impact strength of adhesive joints which differ in the shape and the height of the upper element. The experimental testing was carried out with an impact dropping tool, designed to examine adhesive joints. The maximum energy of the pendulum used in the research was 15 J. The elements of the samples were made of steel S235 or aluminum alloy 2017A. In order to bond the samples, the authors used Epidian 57 epoxide resin with Z1 hardener or the Loctite EA 9450 adhesive. The authors examined samples with upper element rectangular, 3 mm high or disc ones - 3, 5 and 7 mm high. The surface area of the adhesive joints in the tested samples equalled 125 mm2 or 250 mm2. In the research, the authors focused on the determination of specifying the optimum height of the application of the load and the height of the sample which has a circular cross-section, at which the plastic deformation will not affect the stress distribution in the joint.The analysis shows that the impact strength of the tested joints depends on the shape of the tested joint (adhesive joint). With the same surface, connections to the upper disk-shaped element are twice as strong as those made according to the ISO 9653 standard.The impact strength of the modified block sample with upper disk-shaped element significantly depends upon the distance from the edge of the impactor to the surface of the adhesive joint. The conducted studies and analyses show that these could be the following values: 5 mm and 2.8 mm.