Local evaluation of adhesive failure in similar and dissimilar single-lap joints (original) (raw)
Related papers
Failure analysis of dissimilar single-lap joints
Fracture and Structural Integrity, 2016
Single-lap joints made of aluminium and carbon fibre adherends of different thickness are tested to understand better the behaviour of such dissimilar joints. The overlap length and the thickness of the adhesive are kept constant. Local deformation fields are monitored by using the digital image correlation method. Peeling and shearing strains are investigated, emphasizing that peeling is important in the region where failure is initiated, towards an extremity of the overlap region. The use of only carbon fibre adherends is not recommended for a smaller thickness as an additional interface failure is produced and compromises the integrity of the lap joint. However, a dissimilar joint (aluminium-carbon) with smaller thickness adherends succeeds to maintain the stiffness of the assembly, but its strength is diminished. The obtained results are suggesting that a complete monitoring of the failure processes in the overlap region can be fully understood only if local deformation measurem...
Failure analysis of dissimilar single-lap joints.PDF
Single-lap joints made of aluminium and carbon fibre adherends of different thickness are tested to understand better the behaviour of such dissimilar joints. The overlap length and the thickness of the adhesive are kept constant. Local deformation fields are monitored by using the digital image correlation method. Peeling and shearing strains are investigated, emphasizing that peeling is important in the region where failure is initiated, towards an extremity of the overlap region. The use of only carbon fibre adherends is not recommended for a smaller thickness as an additional interface failure is produced and compromises the integrity of the lap joint. However, a dissimilar joint (aluminium-carbon) with smaller thickness adherends succeeds to maintain the stiffness of the assembly, but its strength is diminished. The obtained results are suggesting that a complete monitoring of the failure processes in the overlap region can be fully understood only if local deformation measurements are possible.
Journal of Adhesion Science and Technology, 2016
The paper presents a comparison of the cohesive zone model (CZM) and the continuum damage mechanics approach in predicting the static failure of a single lap joint (SLJ). The effect of mesh size and viscosity were studied to give more understanding on the failure load and computational time. Both the load-displacement response and the backface strain technique were utilised to compare the validity of predictions. Peel and shear stress and damage distributions along with the damage progression are compared to understand the behaviour of the models in predicting the static failure response. In general, both approaches show good accuracy in predicting the failure load; however, the cohesive zone approach requires shorter computation time than the continuum damage approach. The continuum damage approach shows some mesh-dependency particularly for elements with high aspect ratios, whereas the cohesive zone approach is not. The continuum damage approach is less sensitive than the cohesive zone approach to the artificial damping required to achieve convergence. Another interesting finding is using the same ultimate stress level of damage in the continuum damage approach at the peak load is much lower than that in the cohesive approach; but the failure process in this approach is faster.
Procedia Engineering, 2015
Structures built from several components require some means of joining. In this context, bonding with adhesives has several advantages compared to traditional joining methods, e.g. reduction of stress concentrations, reduced weight penalty and easy manufacturing. Adhesives can be strong and brittle (e.g., Araldite ® AV138) or less strong and ductile (e.g., Araldite ® 2015). A new family of polyurethane adhesives combines high strength and ductility (e.g., Sikaforce ® 7888). In this work, the performance of the three above mentioned adhesives was tested in single-lap joints with varying values of overlap length (L O). The experimental work carried out is accompanied by a detailed numerical analysis by Finite Elements, based on Cohesive Zone Models (CZM). This procedure enabled detailing the performance of this predictive technique applied to bonded joints. Moreover, it was possible to evaluate which family of adhesives is more suited for each joint geometry. CZM revealed to be highly accurate, except for largely ductile adhesives, although this could be circumvented with a different cohesive law.
Structures built from several components require some means of joining. In this context, bonding with adhesives has several advantages compared to traditional joining methods, e.g. reduction of stress concentrations, reduced weight penalty and easy manufacturing. Adhesives can be strong and brittle (e.g., Araldite ® AV138) or less strong and ductile (e.g., Araldite ® 2015). A new family of polyurethane adhesives combines high strength and ductility (e.g., Sikaforce ® 7888). In this work, the performance of the three above mentioned adhesives was tested in single-lap joints with varying values of overlap length (L O). The experimental work carried out is accompanied by a detailed numerical analysis by Finite Elements, based on Cohesive Zone Models (CZM). This procedure enabled detailing the performance of this predictive technique applied to bonded joints. Moreover, it was possible to evaluate which family of adhesives is more suited for each joint geometry. CZM revealed to be highly accurate, except for largely ductile adhesives, although this could be circumvented with a different cohesive law.
Frattura ed Integrità Strutturale, 2020
Development in material science imposes to use different materials in production. This causes a problem for joining different materials because traditional joining techniques such as welding could not overcome this problem in industries such as automotive. Hence, adhesive bonding overcomes this problem by its superiorities to join different materials. The joint strength of epoxy-based adhesives is affected by adhesive thickness, adherent's surface quality, and curing conditions. In this study, two different materials (SAE 304 and AL7075) were bonded by epoxy adhesive (3M DP460NS) as single lap joint (SLJ) of Aluminum-Aluminum, Steel-Steel, and Aluminum-Steel. The effects of adhesive thickness (0.05, 0.13, 0.25 mm) and surface roughness (281, 193, 81 nm) to strength were compared. SLJs were tested for 1, 10, 25 and 50 mm/min displacement rates. Adhesive surface structures were imaged by Scanning Electron Microscopy (SEM) to investigate adhesive fractures. Surface roughnesses were examined by using Atomic Force Microscopy (AFM) to compare its influence on failure load. Finite Element Analysis (FEA) was conducted by using Cohesive Zone Model with ANSYS 18.0 software to obtain stress distribution of adhesive. Optimum values according to the present conditions of the thickness (0.13mm) and roughness (<200nm) were determined. Experimental results were demonstrated that while displacement rates rose, failure loads increased as well. FEA analysis was fit to experimental results. It has been observed that along with material type, peel stresses become an important factor for joint strength.
Stress-Strain Analysis of Single-Lap Tensile Loaded Adhesive Joints
2007
Both, experimental investigation and finite element analysis of single-lap adhesive joints subjected to tension have been done to find out an optimal overlap length. As the adherend material aluminum was considered with the two component high-strength engineering adhesive for the bonding of the layers. The thickness of the sheet metal layer was 1,95 mm, while adhesive was 0,15 mm thick. The width of all thin plates was 30 mm, but the overlap length varied as 15, 20, 30, 40 and 60 mm. Real mechanical properties of all materials in the joint have been determined experimentally. Obtained results proved that the overlap length affects directly the joint tensile strength, where an optimum value of overlap length can be defined. Finite element analysis of stress and strain fields could help to determine the moment when the crack initiates at the joint overlap end. In such a manner, complex mechanisms of failure of adhesive joints could be better understood.
Mathematical and Computational Applications, 2011
This paper examines the failures and strengths of joints bonded by a Neoxil CE92 N8 adhesive at different overlap lengths and different taper angles. The study was carried out both as experimental and numerical. In the experimental stage, lap-shear tests on Single-Lap Joints (SLJs) with different taper angles and overlap lengths were conducted. The stress analyses in the SLJs were obtained using a linear Finite Element Analysis (FEA) in numerical stage. It is assumed that adhesive and adherend have both geometrical nonlinearity and linear material behaviour. Scrutinising carefully the surfaces of the SLJs, two different failure types, cohesive failures (CF) and special cohesive failures (SCF) were observed. The obtained numerical results were compared with experimental ones. Results indicate that the increasing of both overlap length and taper angle increase the joint strength and, in particular, the highest strength values in all joint geometries are attained by specimens having a taper angle of 15°.
Single-Lap Joints of Similar and Dissimilar Adherends Bonded with an Acrylic Adhesive
The Journal of Adhesion, 2009
In this study, the tensile strength of single-lap joints (SLJs) between similar and dissimilar adherends bonded with an acrylic adhesive was evaluated experimentally and numerically. The adherend materials included polyethylene (PE), polypropylene (PP), carbon-epoxy (CFRP), and glass-polyester (GFRP) composites.