3D numerical investigation of tensile loaded lap bonded joint of aircraft structure

Adhesive bonding is becoming one of the most popular joining techniques in automotive and aircraft industry. The adhesively bonded joints need to be designed to minimize tensile stress. The most widely used method of an adhesive joint strength test is the lap-shear test. Single lap joints create bending loads in the adherends and tensile stress in the adhesive. The mechanism of shear deformation of the adhesive and adherend layers and separation occurring at the adherend/adhesive interface are discussed in this paper. Uniaxial tensile test of a lap bonded joint and numerical simulations were carried out. 3D numerical model of single lap bonded joint consists of three components described as separate solids. Glue contact is defined between the joined layers. This approach allows to determine and compare stress distribution along the adhesive and the adherend bondline. Experimental data are used to establish the engineering stress-strain curves for the aluminium adherends and the epoxy adhesive. Two step loadings are applied. The results of laboratory tests compare favourably with VG and Reissner closed-form solutions and numerical simulations. Non-linear analyses of a 0,03 mm thick adhesive layer show that the shear stresses along the adhesive bondline exceed stresses along the adherend line by 1% to 50%.