Effects of Partial Bonding and Adhesive Thickness on the Load-Carrying Capacity of Tension Specimens Bonded with Epoxy Adhesive Investigated by Microindentation, Tensile Testing, and FEM Simulation

Abstract

The use of epoxy adhesives in metal structures for adhesive reasons is a continuously growing market, because of the increasing demand of lightweight constructions, which renders in certain cases conventional mechanical bonding unpractical. Furthermore, epoxy adhesives possess enhanced mechanical, chemical, and physical properties, i.e., increased shear and compression strength and resistance in solvents, whereas maintaining these properties at higher temperatures than traditional mechanical bonding methods. Next generation aircraft engines and pipelines are common application areas of these adhesives. In order, however, to ensure the safe use of epoxy adhesives in such structures, computational analyses must be conducted to simulate eventual failure mechanisms. These simulations require the exact determination of the epoxy adhesion strength properties with respect to several parameters. A systematic investigation of these properties will be presented, on the basis of tensile tests of standard aluminium tension specimens bonded together with epoxy adhesives, whereas their failure mechanisms will be simulated by a FEM-supported model to evaluate the extracted characteristics. The specimens were cemented by means of a developed experimental device under constant temperature and humidity conditions. The deformation as well as the developed stress distribution of the specimens during the tensile experiments were simulated by means of a FEM-supported software package, considering the stress-strain curves of the adhesive, determined by a FEM-based evaluation of microindentation results.