Abstract
Double lap adhesive connections made of Sika® PS and Monolith EP2579-1 were studied experimentally in shear tests. The destructive shear tests were conducted under a quasi-static load at 20 °C and 80 °C. The aim was to study the impact of elevated temperature on the load capacity of the joint and make a comparative analysis of the results for two types of adhesives: polyurethane Sika® PS (flexible) and epoxy Monolit EP 2579-1 (rigid). The impact of adhesive layer thickness (t = 1, 2 and 4 mm) on the structural response of the joint was tested in two temperature ranges. A distinct impact of the temperature on the joint deformability was noticed. A visual assessment of the joint failure was performed and the initiation and form of failure was described. At 20 °C, the ultimate loading for epoxy adhesive joint depending on the joint thickness (t) was greater than for the polyurethane joint by, respectively, 282% for t = 1 mm, 88% for t = 2 mm and 279% for t = 4 mm. It was proved that the temperature increases to 80 °C in case of both adhesives reduces the mean destructive force in comparison with the measurements made at 20 °C. For the Sika® PS (PUR two-component polyurethane) adhesive, the greatest load capacity decrease was measured for the joint of thickness t = 2 mm (55%), and in case of the epoxy adhesive for the joint of thickness t = 4 mm (89%). It was found that after reaching the destructive force the flexible joints retain a partial load capacity contrary to the rigid joints.
Highlights
Adhesives are important for industries that shape the everyday life of people
In case of double shear lap joints made with the Sika® PS adhesive at 20 ◦C the mean destructive force, depending on the adhesive layer thickness (t), was: 9.2 kN for t = 1 mm, 11.7 kN for t = 2 mm and 11.3 kN for t = 4 mm, respectively. g
As the temperature increases, the load capacity of the shear double lap joint decreases, and the percent of decrease is greater for the epoxy adhesive than for the flexible adhesive in comparison with 20 ◦C;
Summary
Adhesives are important for industries that shape the everyday life of people. They are widely used, mainly in the automotive and aerospace industries, and find application in medicine, electronics and civil engineering. Liao et al [33] includes an analysis of the adhesive layer thickness and type and scarf angle on the behaviour of a scarf adhesive joint subjected to uniaxial tensile loading, focusing on the failure energy. The author conducted strength testing and numerical analysis of single shear joints with the use of a carbon fibre strip (S512) and three different substrates: brick, concrete and wood. The author proved that polyurethane adhesives used to join glass with wood have a greater fatigue strength than the stresses caused by operational load. The aim of the paper was to study the impact of elevated temperature on the lo capacity of the adhesive joint and make a comparative analysis of the results for two typ of adhesives: polyurethane (flexible) and epoxy (rigid). The paper presents the experimental result for compression test parallel to the grain at 20 ◦C and 80 ◦C
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