Effect of the adhesive thickness on butt adhesive joints under torsional loads

Adhesive joints are extensively used in diverse industrial applications, exploiting the improved mechanical performance they offer over classical mechanical joining methods. To effectively design adhesive joints, it is first necessary to determine the mechanical properties of the materials being used (e.g. the adhesives and adherends). In this work, an epoxy based structural adhesive was characterized under tensile and shear loads using butt joints with solid adherends. The tensile tests were performed in a universal tensile machine and the shear tests were carried out in a torsional testing machine that ensures perfect alignment of the specimens and avoids any spurious bending moments, compression and tension loads during the test. The effect of adhesive thickness on the tensile and shear properties of the adhesive was evaluated, showing that under torsional loads there is a significant effect of the adhesive layer thickness on the shear strength and stiffness of the adhesive