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Adhesively bonded joints are formed in different configurations. T- adhesively bonded joint is one of these configurations and has an important position in industrial applications. The purpose of this study was to numerically study the stress distributions, strength, damage evolution of different T-joints with or without adhesive filling at the curvature of the L-shaped adherends under tensile load via 3D nonlinear finite element method. Here, type-I T-joint is the first model without adhesive filling at the curvature of the L-shaped adherends and type-II T-joint is the second model with adhesive filling at the curvature of the L-shaped adherends. In this study, FM73 and 3M 2214 adhesives and AA2024-T3 aluminum alloy adherends have been used to create two different T-joints numerically. Numerical analysis results have shown that the presence of filler adhesive has a direct influence on joint strength. It has also been observed that ABCD interface is the most critical region in terms of damage occurrence, while is AB and BC lines on the ABCD interface are the most critical lines. In addition, it was observed upon comparing the stress distributions of lines AB and BC that the shear and normal stress values decreased in lines AB and BC of the type-II T-joints. Therefore, it can be put forth that the strength of Type-II T-joints is greater in comparison with the strength of type-I T-joints and the use of a type-II T-joints is more suitable for loads which are close to the fracture load of the T-joints. [ABSTRACT FROM AUTHOR]

Adhesively bonded structures are widely used in many industries such as aerospace, aeronautics, automotive and nautical fields. It is very important to determine accurate and reproducible mechanical properties of an adhesive layer in the adhesively bonded joints via experimental methods. In accordance with the design objectives, a widely used experimental method in the determination of the shear stress-shear strain curve for adhesives is the Thick Adherent Shear Test (TAST). The purpose of this method is to determine the adhesive properties from single lap joints subjected to shear load. In this study, the mechanical properties of adhesives from the joints prepared by using three different structural adhesives (SBT 9244, FM 73 and DP460) are measured via TAST method. Firstly, some experiments were conducted on the samples that were prepared by using FM 73 film adhesive. The obtained data were compared with the literature and system accuracy was controlled. At a later stage of the study, the shear stress-shear strain curves of SBT 9244 and DP 460 structural adhesives were determined. In conclusion, the TAST method is a very affective method of producing repeatable and accurate data in determining mechanical properties of structural adhesives. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an approach to predict the three-dimensional effects (anti-clastic, free edge and bending–twisting coupling effects) and to assess the effects of the fiber orientation angle of the laminates on the stress distributions and the failure prediction in the Single Lap Composite Joints (SLJs) subjected to a bending moment via a 3-D non-linear finite element method. In the analysis, the composite adherends (AS4/3501-6) with five different fiber orientation angles ([90/±45/0]2s, [0/90]4s, [45/−45]4s, [0]16 and [90]16) were assumed to behave as linearly elastic materials while the adhesive layer (FM 73) was assumed to be nonlinear. Also, the nonlinear geometric deformations of the SLJs were also taken into account. Consequently, it is seen that the state of stress in the vicinity of the free edge of the joint is fully three dimensional which has not been taken into account in any classical theory so far and the normal and shear stress distributions are extremely sensitive to this three-dimensional effects. From this aspect, the three-dimensional finite element analysis is a necessity for understanding explicitly the stress and failure states. Also, for both the adherends and the adhesive layer, the ply stacking sequence has a significant effect on the stress distribution and the failure. [Copyright &y& Elsevier]

Abstract: In this study, the normal (σx , σy , σz ) and shear stress (τxy , τyz , τzx ) distributions occurring in a bi-adhesively bonded T-joint with was investigated via a non-linear three dimensional finite element analysis. For this purpose, first of all, using 2024-T3 aluminum alloy as the adherend and the support, a two-part paste (DP 460) and a film type (SBT 9244) as adhesive, two different types of T-joint samples (single-adhesively bonded T-joint and bi-adhesively bonded T-joint) were produced for experimental studies. After experimental studies on the three different T-joint types were conducted, stress analyses in the T-joints were performed with a three-dimensional finite element analysis by considering the geometrical non-linearity and the material non-linearities of the adhesive (DP460 and SBT9244) and adherend (AA2024-T3). Finally, for a given adherend, the lower the stiffness of the adhesive used in the overlap, the lower the stress concentration, leading to potentially higher joint strength. The use of relatively low stiffness adhesives at the ends of the overlap in a bi-adhesive can decrease the stress concentration and, therefore, potentially lead to higher joint strength. [Copyright &y& Elsevier]

Abstract: In the present study, it is aimed to compare mechanical behaviors of T-joint types with embedded and non-embedded supports subjected to bending moment. For this purpose, after experimental studies on the two different T-joint types were conducted, stress analyses in the T-joints were performed with a three-dimensional finite element method by considering the geometrical non-linearity and the material non-linearities of the adhesive (DP460) and adherend (AA2024-T3). Finally, stress analyses and experimental results show that the variation of the geometry of the bonding zone, e.g., embedding the supports, would change the stress distributions and strength of the joint. Additionally, it is seen that T-joints with embedded supports carry 30% more load than T-joints with non-embedded supports although their bending stiffnesses decrease. [Copyright &y& Elsevier]

A 3-D nonlinear finite element code was established to assess the effects of the fiber orientation angle of the laminates on the stress distributions and the failure prediction in single lap joints (SLJs) subjected to uniaxial tensile loading. Eight different configurations were considered and the unidirectional prepregs were laid up in quasi-isotropic ([90/±45/0]2s and [90/±30/90]2s), cross-ply ([0/90]4s and [30/60]4s), angle-ply ([45/ - 45]4s and [55/ - 55]4s), and unidirectional ([0]16 and [90]16). The composite adherends (AS4/3501-6) were assumed to behave as linearly elastic materials while the adhesive layer (FM 73) was assumed to be nonlinear. The nonlinear geometric deformations of the SLJs were also taken into account. The first step in the analysis, a complete 3-D stress analysis, is carried out with a special importance for the evaluation of out-of-plane stresses. Then, the failure index distributions are calculated by using the Tsai-Wu failure criterion for composite adherends and the extended Drucker-Prager failure criterion for the adhesive layer. Consequently, it is seen that the state of stress in the vicinity of the free edge of the joint is fully 3-D which has not been taken into account in any classical theory so far and the normal and shear stress distributions are extremely sensitive to these 3-D effects (anti-clastic, free edge, and bending-twisting coupling effects). Hence, in real applications of adhesively bonded composite joints, the out-of-plane stresses and 3-D effects cannot be neglected and a 3-D finite element method is essential to evaluate explicitly the stress and failure states. Also, for both the adherends and the adhesive layer, the ply stacking sequence has a significant effect on the stress distribution and the failure. [ABSTRACT FROM AUTHOR]

It is important to be able to predict the mechanical response of adhesively bonded joints. To succeed in this, the accurate simulation of the behavior of adhesively bonded joints is an essential requirement because of the strain rate, temperature, and hydrostatic sensitivity of adhesive properties, which should be taken into consideration when developing a material model [1-111, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]. On the other hand, the load capabilities of adhesively bonded joints are affected by both applied pressure and temperature during cure. For this reason, in this study, the tensile load capabilities of single lap joints (SLJs) bonded with a flexible adhesive that possesses pressure-sensitive properties were experimentally investigated with respect to the applied pressure during the curing operation, and the experimental results were compared with finite element analysis (FEA) results. Finally, in addition to other parameters, such as the dependence on strain rate and the lack of yield criteria of adhesives, it was seen that the residual thermal stresses that occurred as a result of the applied pressure during the curing process at elevated temperature need to be taken into consideration to accurately simulate the mechanical behavior of adhesively bonded joints. [ABSTRACT FROM AUTHOR]

In this work, elasto-plastic stress analysis of a Single Lap Joint (SLJ) subjected to bending moment was investigated using 2D non-linear Finite Element Analysis (FEA). The SLJs, consisting of hardened steel as the adherend bonded by two adhesives, one stiff and one flexible, with very different mechanical behaviors were analyzed. In order to determine the effect of geometrical parameters on the performance of the SLJs, four different adherend thicknesses and overlap lengths for each adhesive were used. For verification of the analysis, the FEA results were compared with experimental results. It was observed that there was a significant effect of adherend thickness on the strength of the joint with both adhesives. However, the load carried by the SLJ with the flexible adhesive increased with increasing overlap length. [ABSTRACT FROM AUTHOR]

Experimental and numerical analyzes of single lap joints formed by combining AA2024-T3 aluminum alloys with two-component liquid structural adhesive DP410 were carried out in the present study. Tension and four-point bending experiments of single lap joints were performed in the experimental analysis section of this study in addition to 2-D Digital Image Correlation (DIC) analyses performed via the processing of the images obtained during these experiments. Whereas, three dimensional nonlinear finite element analyses of tensile and four point bending of single lap joints were performed for the numerical analysis section of the study by taking into consideration the load and boundary conditions applied during experimental analyses. Normal and shear strain distributions obtained via DIC and finite element method were compared by taking into consideration the middle line of the adhesive layer in the case of tensile and four-point bending loads of single lap joints. As a result of this comparison, it was found that there was a sufficient level of compatibility (not very close agreement) in strain distributions between finite element analyzes and DIC technique. As a result, it can be said that three-dimensional DIC analysis will yield more harmony and more accurate results when it is taken into account that three-dimensional finite element analysis and 2D DIC analysis were performed in the study. [ABSTRACT FROM AUTHOR]

The most important point to be taken into consideration in the use of bonding joints is the reliability of the joints created with the adhesive. Therefore, many analytical, experimental and numerical studies have been done to determine the mechanical properties of adhesives and to ensure the reliable use of adhesively bonding joints. This study presents the first stage of the two-stage study, which aims to determine the mechanical properties of the DP410 structural adhesive in the first stage and the mechanical behavior of the adhesively bonded single lap joints formed using the same adhesive in the second stage. In the study, mechanical properties of the DP410 structural adhesive were investigated experimentally via two dimensional Digital Image Correlation (DIC) technique. Bulk (tensile, Iosipescu and Arcan) and joint form (TAST) specimens were produced from structural bicomponent liquid adhesive (DP410) and subjected to uniaxial tensile and shear loads in the study. Mechanical properties of the DP410 bulk specimens were determined by two different measurement methods (DIC and video extensometer). It was observed upon comparing the results obtained that the DIC technique yielded reproducible results in the determination of the mechanical properties of adhesives and this method of optical measurement could be an alternative to other strain measurement methods. Shear mechanical properties of the DP410 adhesive were obtained via two different strain measurement methods, (DIC and contact extensometer) in the TAST specimens. When the results obtained from TAST specimens were examined, it was observed that the results obtained from DIC method were compatible with contact extensometer and it could be an alternative to contact extensometer. In addition, since local strain distributions can be obtained in the DIC method, it has been observed that this method allows to performe damage analysis of the specimens in bulk and joint form and to obtain the strain values at the desired positions. In this study, the accuracy of the results obtained from the 2D DIC analysis can be increased by using the software which allows to perform the 3D DIC analysis via high resolution cameras and by preparing the sample with the right methods. [ABSTRACT FROM AUTHOR]

In this work, elasto-plastic stress analysis of single lap joints with and without protrusion in adhesive bondline subjected to tension and bending was carried out using 2D non-linear finite element analysis and confirmed experimentally. AA 2024-T3 aluminum adherends were bonded with SBT 9244 film adhesive. The protrusion was obtained by extending the adhesive film by 2 mm from the overlap length at both overlap ends. Three different adher-end thicknesses and overlap lengths for each loading and bondline type were used. The joints with and without protrusion, for comparison, were loaded with the same load for each adherend thickness and overlap length. Finally, it was observed that the protrusion reduces the strength in the joint under tension, while the protrusion increases the strength in the joint under bending. [ABSTRACT FROM AUTHOR]

Abstract: The stresses and deformations in the shrink-fitted hub–shaft joint for various fit forms have been analysed using finite element method. First, the results of finite element method (FEM) were compared with the results of Lame’s equations along central radial line of one shrink fit type for accuracy of model and it was proved by these results. Then, the most appropriate fit type was investigated. It was observed that the most effective parameter to determine appropriate fit type is to be stepped or not for shaft and the geometries of hub of which edges were wasted have been found as more appropriate to reduce the stresses and deformations. Finally, it was also observed that the each point of the shaft or the hub at the moment of the first meeting to its partner during fit can enter the plastic region, and this situation must be taken into consideration as design parameter. [Copyright &y& Elsevier]

The use of adhesive bonding as fastener presents very high usage potential, especially for different environments. However, the designers do not have enough data yet to address the changes in the mechanical properties of adhesives in the course of time. In this study, the ageing of film-type adhesives, Structural Bonding Tapes (SBT) 9244 and 9245, which are different in thickness and possess pressure-sensitive and visco-elastic properties, was investigated. First, the bulk adhesive specimens were prepared and exposed to two different environmental conditions until saturated. In the same time, single lap joints with two different adhesive layer thicknesses, consisting of AA2024-T3 as the adherend, were exposed to the same environmental conditions for exposure times of 90 days. The immersion environments were 100% relative humidity (RH) and 3.5% NaCl solution. At the end of exposure time, the failure surfaces were examined by Scanning Electron Microscopy (SEM) after the strength of joints was determined with the lap shear test. Both SBT adhesives absorb more water from 100% RH than from 3.5% NaCl solution and, therefore, they deteriorate rapidly in 100% RH. In addition, as the thickness of adhesive layer increases, the loss in the strength increased. [ABSTRACT FROM AUTHOR]

Abstract: In this study, mechanical properties of adhesively bonded single-lap joint (SLJ) geometry with different configurations of lower and upper adherends under tensile loading were investigated experimentally and numerically. The adherends were AA2024-T3 aluminum and carbon/epoxy composite with 16 laminates while, the adhesive was a two-part liquid, structural adhesive DP 460. In experimental studies, four different types of single-lap joints were produced and used namely; composite–composite (Type-I) with lower and upper adherends of the same thicknesses and four different stacking sequences, composite–aluminum (Type-II) with lower and upper adherends of the same thicknesses and four different stacking sequences, composite–aluminum (Type-III) with lower adherend (composite) of the same thickness but upper adherend of three different thicknesses, aluminum–aluminum (Type-IV) with lower adherend of the same thickness but upper adherend of three different thicknesses, composite–composite (Type-V) with [0]16 stacking sequences and three different overlap length, aluminum–aluminum (Type-VI) with three different overlap length. In the numerical analysis, the composite adherends were assumed to behave as linearly elastic materials while the adhesive layer and aluminum adherend were assumed to be nonlinear. The results obtained from experimental and numerical analyses showed that composite adherends with different fiber orientation sequence, different adherend thicknesses and overlap length affected the failure load of the joint and stress distributions in the SLJ. [Copyright &y& Elsevier]

In the single-lap joint (SLJ) geometry, peel stresses occur at the overlap ends due to load eccentricity and the presence of shear-free adhesive termination surfaces. These peel stresses, along with the transverse tensile stresses which occur along the overlap longitudinal axes, and adhesive shear stresses, ultimately cause joint failure. Obviously, reductions in these stresses should result in higher joint strength and increased load capacity. In the present study, the mechanical behavior of the SLJ geometry of various widths having spew fillets, which was subjected to tensile loading, were investigated experimentally and numerically. For this purpose, firstly, four different types of SLJ samples (without spew fillet, with spew fillet at joint edges, with spew fillet at joint ends, and with spew fillet at all edges) were produced for experimental studies by using two-part paste adhesive. Then, stress analyses in the SLJ were performed with a three-dimensional non-linear finite element method by considering the geometrical non-linearity and non-linear material behaviors of both adhesive (DP460) and adherend (AA2024-T3). It was concluded that the spew fillet in the SLJ geometry with variable widths decreases stress concentrations and increases the load carrying capacity of the joint. [ABSTRACT FROM PUBLISHER]

Abstract: The mechanical behaviors of an adhesively bonded single lap joint with a spew fillet under bending moment, where the widths of the upper-adherend and lower-adherend are not the same, were studied experimentally and numerically. Using AA2024-T3 aluminum alloy as adherend and DP460 as paste adhesive, four different types of single-lap joint samples (without spew fillet, with spew fillet at joint edges, with spew fillet at joint ends and with spew fillet at all edges) were produced for experimental studies. Stress analyses in the single-lap joint were performed with a three dimensional non-linear finite element method by considering the geometrical non-linearity and non-linear material behaviors of both adhesives (DP460) and adherend (AA2024-T3). The single lap joint with the spew fillet with different widths had a significant effect on the stress distribution. Additionally, the spew fillet increased the load carrying capacity of the joint and decreased the stress concentration of the joint. [Copyright &y& Elsevier]