Common Joint Configuration Research Articles

Evaluation of Single-Lap and Block Shear Test Methods in Adhesively Bonded Composite Joints

Adhesive bonding is increasingly being used for composite structures, especially in aerospace and automotive industries. One common joint configuration used to test adhesive strength is the single-lap shear joint, which has been widely studied and shown to produce significant normal (peeling) stresses. When bonding composite structures, the normal stresses are capable of causing delamination before the adhesive bond fails, providing inconclusive engineering data regarding the bonding strength. An alternative test is the block shear joint, which uses a shorter sample geometry and a compressive-shear loading to reduce normal stresses. Analytical models proposed by Goland and Reissner and Hart-Smith are used to compare the edge-bending moment for the two joint configurations. The stress distributions along the bondline are also compared using finite element analysis. Experimental tests are conducted to evaluate these analyses and the failure modes of each configuration are recorded. Block shear samples demonstrate a joint strength over 100% higher than single-lap shear specimen bonded with the same adhesive material. The lower joint strength measured in single-lap shear is found to be potentially misleading due to delamination of the composite adherend.

Single Lap Joints Numerical Modelling and Comparison with Experimental Testing

Adhesive bonding is a joining technique which has been extensively employed in structural design as its ability to join different types of materials allows higher freedom for designers when choosing materials. One of the most common joint configuration used is the single lap joint configuration. In this work a set of experimental procedures were undertaken to characterize a structural adhesive and model the behaviour of a single lap joint manufactured using this adhesive. Two types of surface preparations were used to study its effect in single lap joint strength.

Comparison of different adhesively-bonded joint configurations for mechanical structures

Adhesively-bonded joints are widely used to join structural components. The most common joint configurations are single-lap joints (SLJ), double-lap joints (DLJ), stepped joints and scarf joints. One of the most important parameters that affects the joint strength is the overlap length (LO). The main objectives of this work are to carry out a comparative study involving several joint geometries using various adhesives with different characteristics and to check which type of adhesive is most suitable for a particular joint geometry. For this purpose, SLJ, DLJ, stepped joints and scarf joints were chosen for testing with three adhesives. The experimental results are compared with numerical results obtained using Abaqus® software using an integrated cohesive zone modelling (CZM) module. With this work, it was concluded that the optimal joint configuration depends significantly on the type of adhesive being used, such that less resistant and ductile adhesives are more suitable for joint geometries that exhibit large stress variations, while stronger but more brittle adhesives are recommended for joint geometries with more uniform stresses.

Use of cohesive zone models to design automotive bonded joints

Cohesive-zone models have been widely used for the analysis of interface debonding. In this paper, three of these models are used to study a set of debonding problems. A comparative analysis of the three models is carried out; results are presented and discussed for numerical simulations referring to both single-mode and mixed-mode situations. The results show that the differences between the load-deflection curves obtained for the three models considered, become more evident by increasing the stiffness of the specimen. Considering that the most common joint configuration in automotive industry is the lap-shear joint, the main conclusion of this work is that the joint stiffness will not affect the computational response obtained with the three different models studied here.

Critical Current Density for Inhibiting (Cu,Ni)6Sn5 Formation on the Ni Side of Cu/Solder/Ni Joints

The Cu/solder/Ni structure is a common joint configuration used in microelectronic packages today. In high-temperature operation of this joint structure, an appreciable amount of Cu can readily diffuse across the entire solder to the Ni side, where it might grow into a brittle bilayer structure of (Cu,Ni)6Sn5/(Ni,Cu)3Sn4. The driving force for Cu diffusion is the chemical potential gradient. To counterbalance this chemical-force-induced Cu flux (JchemCu), an attempt to apply a reverse electric current into a Cu/Sn(50 μm)/Ni structure was made in this study. Ten current densities (j = 0 A/cm2 to 2 × 104 A/cm2) were examined at 150°C upon current stressing. The results indicated that, under current stressing of jcrit, and (III) j ≈ jcrit were also examined in this study.

Evaluation of different lap-shear joint geometries for automotive applications

Adhesive bonding is used increasingly by the automotive industry to join structural components of metallic and composite materials. The most common joint configuration is the lap-shear joint, which has been investigated widely and several ideas have been proposed to improve its performance. For example, the introduction of fillets at the overlap ends or tapering of the substrates can reduce the peel stresses at the overlap end. Other approaches include the use of ‘reverse-bent’ substrates and ‘wavy joints’ to reduce peel stresses. This paper compares the stress distribution of the ‘reverse-bent’ and the ‘wavy joint’, with the stresses of the traditional lap-shear joint, using finite element analysis (FEA). A parametric study was carried out showing trends influencing stresses in the adhesive layer. Experimental tests were conducted to evaluate the assumptions used in, and the findings of, the FEA. The joint strength of ‘reverse-bent’ joints was found to be up to 40% higher compared to flat joints using various substrate materials, adhesives and overlap lengths.