STRESS-ANALYSIS AND TESTING OF PARALLEL AND TAPERED ADHESIVE BUTT JOINTS

A correlation between numerical results obtained by the finite element (FE) method and experimental data for parallel and tapered butt joint s under tensile load was investigated. Two linear FE simulations were constructed for both joints and the numerical results were used in und erstanding the ultimate strength and failure modes. The data provided the ultimate tensile strength and failure modes for various thicknesse s of polyurethane adhesive bonded between polycarbonate and aluminum a dherends. The numerical and test data results show that a thinner para llel adhesive layer leads to a stronger joint. An optimum adhesive lay er thickness was found for the tapered configuration (0.4-0.5 mm). Thi s thickness was achieved when the stress value and its gradient were d istributed in an optimal ratio. Then the mode of failure was changed f rom interfacial to cohesive. The enhanced sensitivity found for the ta pered joint strength as a function of its thickness leads to the concl usion that in real bonded structures it should be avoided. In addition to other important parameters, i.e. surface treatment and material pr operties which ensure high strength and durable adhesive joints, any e xisting tapered angle of the adhesive layer should be minimized.