Application a direct/cohesive zone method for the evaluation of scarf adhesive joints (original) (raw)
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A Review Article on Analytical, Experimental and Comparative Study of Adhesive Scarf Joint
Structures built from different components which require some means of joining. Bonding with adhesives has major advantages compared to traditional joining methods like welding, riveting or fasting e.g. reduction of stress concentrations, reduced weight, easy joining for very thin surfaces as well as used for two different materials also. An investigation based on several experimental and finite element analysis studies was carried out to understand the failure mechanisms of scarf adhesive joint under tensile load. Various parameters were investigated such as the bondline thickness, adherend thickness, scarf angle for either same adherend or different adherend and used different adhesive for the investigation. Also the external parameter like temperature considers for some experiments also they combine two different adhesive to get better result. A lot of studies and researches have been done to improve all these characteristics that are reviewed in this paper.
Strength prediction of epoxy adhesively bonded scarf joints of dissimilar adherends
International Journal of Adhesion and Adhesives, 2011
In this study, strength of epoxy adhesively bonded scarf joints of dissimilar adherends, namely SUS304 stainless steel and YH75 aluminum alloy is examined on several scarf angles and various bond thicknesses under uniaxial tensile loading. Scarf angle, y¼451, 601 and 751 are employed. The bond thickness, t between the dissimilar adherends is controlled to be ranged between 0.1 and 1.2 mm. Finite element (FE) analysis is also executed to investigate the stress distributions in the adhesive layer of scarf joints by ANSYS 11 code. As a result, the apparent Young's modulus of adhesive layer in scarf joints is found to be 1.5-5 times higher than those of bulk epoxy adhesive, which has been obtained from tensile tests. For scarf joint strength prediction, the existing failure criteria (i.e. maximum principal stress and Mises equivalent stress) cannot satisfactorily estimate the present experimental results. Though the measured stress multiaxiality of scarf joints proportionally increases as the scarf angle increases, the experimental results do not agree with the theoretical values. From analytical solutions, stress singularity exists most pronouncedly at the steel/adhesive interface corner of joint having 45-751 scarf angle. The failure surface observations confirm that the failure has always initiated at this apex. This is also in agreement with stress-y distribution obtained within FE analysis. Finally, the strength of scarf joints bonded with brittle adhesive can be best predicted by interface corner toughness, Hc parameter.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2019
In this study, curved lap joints were designed, particularly for the cases in which configuration or aerodynamic design was essential. Furthermore, the effect of the surface area on their strength was investigated. Hence, curved joint types were prepared on aluminum plates (A2024-T3) that are commonly used for aviation, and an angled joint type was created by increasing the radius of curvature. The created joint types were then joined by a two-component acrylic structural adhesive (DP410). The joint models were designed in three dimensions, and a finite element analysis was performed. Cohesive zone models (bilinear, exponential, and separation-distance) based on energy principles were used in the finite element analysis to estimate the strength of the adhesively bonded joint. The mechanical properties of the materials used in the joint models were experimentally determined to obtain the numerical solutions, which were validated by further experiments. The obtained results demonstrat...
Experimental and 3D non-linear stress analysis of adhesively bonded curved and scarf lap joints
2020
Adhesive bonding is an excellent alternative to traditional joining techniques such as welding, riveting, and is commonly used in almost every sector of the industry. However, there are many factors that have to be accounted for during joint design to accurately predict strength of the joint. One of these is the design of adhesively bonded joints. The objective of this work is to study the influence of curvature on strength of adhesively bonded curved-lap joints. For that, different radii of curvature were introduced to the end zones of an aluminium sheet to which the adhesive is applied. Then, a scarf lap joint was obtained by increasing the radius of curvature for the same overlap length, and mechanical behaviour of curved and scarf lap joints was studied experimentally. Additionally, in the analyses, the Extended Drucker-Prager material model was used and to verify the finite element model, experiments were carried out. The results show that thickness, overlap length and curvatur...
Design Concepts for Peel-Dominant Adhesive Joints in Aeronautic Applications
Journal of Research Updates in Polymer Science, 2023
The adhesive bonding technique is employed from the aeronautical/aerospace industry to current house products. To comply with the requirements of distinct applications, different joint configurations are available to the designer. While single-lap joints (SLJ) are the most common in application and research, double-lap joints, scarf joints and T-joints find specific applications. T-joints are seldom studied in the literature, but these are used, for instance, in aircraft to bond the stiffener beams to the skin, or in the cars between the B-pillar and the rocker. Due to the high stress concentrations, T-joints often fail under average stresses much lower than the adhesive strengths, giving rise to the necessity for proper design and strength improvement methodologies. This work initially aims to validate the cohesive zone modelling (CZM) technique with experiments, and then use it to numerically evaluate and optimize the performance of T-joints subjected to peel loads. CZM is nowadays regarded as the most powerful strength prediction tool for adhesive joints, and can be a valuable tool to improve T-joints. Different features are addressed for a complete analysis: adhesive type, geometrical parameters, dual-adhesive technique for strength improvement, and composite joints. The evaluated geometrical parameters are the base adherend thickness (a), T-part thickness (t), overlap or bonding length (l) and curvature radius (r). As a result of this work, the model was successfully validated, and clear design guidelines were provided to define the ideal geometric and material (adhesive) conditions for best performance.
Influence of the Cohesive Law Parameters on the Strength Prediction of Adhesively-Bonded Joints
Materials Science Forum, 2012
Adhesive joints are largely employed nowadays as a fast and effective joining process. The respective techniques for strength prediction have also improved over the years. Cohesive Zone Models (CZM's) coupled to Finite Element Method (FEM) analyses surpass the limitations of stress and fracture criteria and allow modelling damage. CZM's require the energy release rates in tension (G n ) and shear (G s ) and respective fracture energies in tension (G n c ) and shear (G s c ). Additionally, the cohesive strengths (t n 0 for tension and t s 0 for shear) must also be defined. In this work, the influence of the CZM parameters of a triangular CZM used to model a thin adhesive layer is studied, to estimate their effect on the predictions. Some conclusions were drawn for the accuracy of the simulation results by variations of each one of these parameters.
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.
Strength Prediction of Adhesively-Bonded Scarf Repairs in Composite Structures under Bending
Materials Science Forum, 2010
This work reports on the experimental and numerical study of the bending behaviour of two-dimensional adhesively-bonded scarf repairs of carbon-epoxy laminates, bonded with the ductile adhesive Araldite 2015 ® . Scarf angles varying from 2 to 45º were tested. The experimental work performed was used to validate a numerical Finite Element analysis using ABAQUS ® and a methodology developed by the authors to predict the strength of bonded assemblies. This methodology consists on replacing the adhesive layer by cohesive elements, including mixed-mode criteria to deal with the mixed-mode behaviour usually observed in structures. Trapezoidal laws in pure modes I and II were used to account for the ductility of the adhesive used. The cohesive laws in pure modes I and II were determined with Double Cantilever Beam and End-Notched Flexure tests, respectively, using an inverse method. Since in the experiments interlaminar and transverse intralaminar failures of the carbon-epoxy components also occurred in some regions, cohesive laws to simulate these failure modes were also obtained experimentally with a similar procedure. A good correlation with the experiments was found on the elastic stiffness, maximum load and failure mode of the repairs, showing that this methodology simulates accurately the mechanical behaviour of bonded assemblies.
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.
Buckling Behaviour of Carbon–Epoxy Adhesively-Bonded Scarf Repairs
Journal of Adhesion Science and Technology, 2009
The present work is dedicated to the experimental and numerical study of the buckling behaviour under pure compression of carbon-epoxy adhesively-bonded scarf repairs, with scarf angles varying from 2 to 45 • . The experimental results were used to validate a numerical methodology using the Finite Element Method and a mixed-mode cohesive damage model implemented in the ABAQUS ® software. The adhesive layer was simulated using cohesive elements with trapezoidal traction-separation laws in pure modes I and II to account for the ductility of the adhesive used. The cohesive laws in pure modes I and II were determined with Double Cantilever Beam and End-Notched Flexure tests, respectively, using an inverse method. Since in the experiments interlaminar and transverse intralaminar failures also occurred, cohesive laws to simulate these failure modes were also obtained experimentally following a similar procedure. Good correlations were found between the numerical predictions and experimental results for the elastic stiffness, maximum load and the corresponding displacement, plateau displacement and failure mode of the repairs. by an accident (e.g., tool impact during maintenance). Since this kind of damage significantly reduces the structures' strength, replacement or repair must be followed. Repair of these structures is more efficient from economical and ecological points of view, since composite materials are difficult to recycle. Repair by adhesive bonding is a valid option due to its numerous advantages over the conventional bolting or riveting methods, e.g., more uniform stress distributions, reduced weight penalty, minimal aerodynamic disturbance, and fluid sealing characteristics. If a full or significant strength recovery is required, or if a repair without aerodynamic perturbation is needed, a scarf repair should be used. The higher efficiency of this repair method, compared with the easy-execution strap repairs, is due to the larger bond areas and the reduction of stress concentrations at the bond edges due to the adherend tapering effect.