Papers by Keyword: Bonded Joints

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Authors: Hugo Biscaia, João Cardoso, Carlos Chastre
Abstract: The bonding between two different materials or between same materials is a quite popular method. Unlike fastener joints, it avoids undesirable stress concentrations and doesn't demand an intrusive application to ensure the good performance of the joint. However, depending on the configuration of the adhesively bonded joint, its performance responds differently and the choice (if possible to make) on the best configuration, i.e. the configuration that originates the highest strength and/or stiffness, may be hard to make. Within this context, several configurations of aluminium-to-aluminium bonded joints unstrengthened and strengthened with fiber reinforced polymers (FRP) were modelled using a commercial finite element code. The linearity and nonlinearity of the FRP composite and the aluminium were considered, respectively, and the adhesively bonded joints were subjected to a regular displacement that intended to simulate a tensioning load. Also, the nonlinearities of the interfaces were considered in the form of nonlinear cohesive adhesive laws. The fracture Modes I and II were defined trough a bond-slip relation with a bi-linear shape and the Mohr-Coulomb failure criterion is used for the coupling of the cohesive adhesive laws of the interface when the debonding process of the bonded joint configuration implies the interaction between both fracture modes, i.e. the joint is under a mixed-mode (Mode I+II) situation. The results are presented and discussed and the configurations of the bonded joints are all compared through bond stress distributions and load-slip responses. The study herein presented is, therefore, a contribution to the analysis of the structural integrity of bonded joints between FRP composites and aluminium substrates, helping also on the choice of the most adequate bonded joint configuration and corresponding reinforcement to be used and applied in practice.
237
Authors: Nabil Chowdhury, Wing Kong Chiu, John Wang
Abstract: A review of some of the various fatigue models introduced over the years for both metallic materials, in particular aluminium alloys followed by fatigue and durability concerns associated with composite materials. The move towards light weight and high stiffness structures that have good fatigue durability and corrosion resistance has led to the rapid move from metal structures to composite structures. With this brings the added concern of certifying new components as the damage mechanisms and failure modes in metals differ significantly than composite materials such as carbon fiber reinforced polymers (CFRP). The certification philosophy for composites must meet the same structural integrity, safety and durability requirements as that of metals. Hence this is where the challenge now lies. Substantial work has been conducted in the reparability of composite structures through bonding using various adherend thicknesses and joint types and has been shown to have higher durability than mechanically fastened repairs for thin adherends however these are currently unacceptable repair methods as they cannot be certified. Repairs are designed on the basis that the repair efficiency can be predicted and should be designed conservatively with respect to the various failure modes and include the surrounding structure.
1597
Authors: Martin Bednarik, David Manas, Martin Ovsik, Miroslav Manas, Michal Stanek, Stepan Sanda, Petr Kratky
Abstract: At the present time bonding has spread into almost all sectors of practice and it would be very difficult to find an industry in which there is no need to use this technology of joining a wide range of materials. In comparison with conventional joining methods (riveting, welding and screwing) provides bonding new combination of options and allows obtaining special shapes and properties which cannot be created by conventional methods of coupling. For the formation of quality bonded joint it is important that the adhesive bonding surface is well wetting. Wettability is characterized by the contact angle of wetting. The liquid must have a lower surface tension than the solid in order to be able to wetting the solid substance. This article describes the effect of beta irradiation on the contact angle of wetting, on the surface energy and on the final strength of bonded joints of HDPE.
79
Authors: Martin Bednarik, David Manas, Miroslav Manas, Michal Stanek, Jan Navratil, Ales Mizera
Abstract: In this study there was found that ionizing beta radiation increased the strength of bonded joints and improved the adhesion properties of polycarbonate (PC). Generally, for the formation of quality bonded joint it is important to wet the adhesive bonding surface well. Wettability is characterized by the contact angle of wetting. The liquid has to have a lower surface tension than the solid in order to be able to wet the solid substance. The measurement results indicated that ionizing beta radiation was a very effective tool for the improvement of adhesive properties and increased the strength of bonded joints of polycarbonate. Bonded surfaces with ionizing beta radiation doses of 0, 33, 66, and 99 kGy were irradiated. The best results were achieved by irradiation at dose of 66 kGy by which the highest surface energy and the highest strength of bonded joints of PC were achieved. The strength of bonded joints after irradiation was increased up to 50 % compared to untreated material. A similar trend was observed even for contact angle of wetting and surface energy.
251
Authors: Pavel Liška, Jiří Šlanhof, Barbora Nečasová, Barbora Kovářová
Abstract: Currently, an increasing emphasis is being placed on the properties of walling systems and efforts are evidently being made to improve the aesthetic look of structures. Vented facade systems with bonded joints are a viable option. Nowadays, the vast majority of such facades utilise mechanical joints. However, facades with bonded joints are more than simply a convenient alternative. The following article, where the potential use of bonded joints in practice is investigated via experimental measurements, deals with this technology in more detail. The presented results are taken from a series of tests which conform to the requirements of relevant technical standards, particularly with regard to the test method. This article deals with the issues connected with testing the most critical element in the whole system – the bonded joint. For this purpose, “Cetris” cement-bonded particleboard was selected for use as cladding material, and a substructure made from aluminium alloy was chosen. Five types of adhesive were selected in order to find the most suitable bonding material. During the testing procedures, the suitability of the selected adhesives for the chosen combination of materials was tested, as was the assumption that the use of the most expensive sealant does not always provide the best results.
50
Authors: Raul D.S.G. Campilho, Arnaldo M.G. Pinto, Mariana D. Banea, Filipe J.P. Chaves, Lucas F.M. da Silva
Abstract: Adhesive-bonding for the unions in multi-component structures is gaining momentum over welding, riveting and fastening. It is vital for the design of bonded structures the availability of accurate damage models, to minimize design costs and time to market. Cohesive Zone Models (CZM’s) have been used for fracture prediction in structures. The eXtended Finite Element Method (XFEM) is a recent improvement of the Finite Element Method (FEM) that relies on traction-separation laws similar to those of CZM’s but it allows the growth of discontinuities within bulk solids along an arbitrary path, by enriching degrees of freedom. This work proposes and validates a damage law to model crack propagation in a thin layer of a structural epoxy adhesive using the XFEM. The fracture toughness in pure mode I (GIc) and tensile cohesive strength (sn0) were defined by Double-Cantilever Beam (DCB) and bulk tensile tests, respectively, which permitted to build the damage law. The XFEM simulations of the DCB tests accurately matched the experimental load-displacement (P-d) curves, which validated the analysis procedure.
513
Authors: Martin Bednarik, David Manas, Miroslav Manas, Michal Stanek, Jan Navratil, Ales Mizera
Abstract: In this study there was found that ionizing beta radiation increased the strength of bonded joints and improved the adhesion properties of polycarbonate (PC). Bonded joints at elevated temperature (60 °C) were tested. Generally, for the formation of quality bonded joint it is important to wet the adhesive bonding surface well. Wettability is characterized by the contact angle of wetting. The liquid has to have a lower surface energy than the solid in order to be able to wet the solid substance. The measurement results indicated that ionizing beta radiation was a very effective tool for improvement of adhesive properties and increased the strength of bonded joints of PC at elevated temperature (60 °C). Bonded surfaces with ionizing beta radiation doses of 0, 33, 66, 99, 132, 165 and 198 kGy were irradiated. The best results were achieved by irradiation at doses of 66 kGy by which the highest surface energy and the highest strength of bonded joints of PC were achieved. The strength of bonded joints after irradiation was increased up to 10 % and surface energy up to 30 % compared to untreated material.
378
Authors: Martin Bednarik, David Manas, Miroslav Manas, Jan Navratil, Ales Mizera, Martin Ovsik
Abstract: Bonding has experienced an enormous expansion in the various applications during the last few years in the field of material joining, due to which it is classified as a new joining technology, although it is, in fact, very old. Compared with the conventional joining methods (riveting, screwing and welding), bonding provides a new material combination possibilities and it allows us to obtain special shapes and properties, which can not be formed by conventional methods. To create a high-quality bonded joint, it is important to wet the bonded surface very well wetted by a wetting liquid. The wettability of the material is characterized by a contact angle of wetting, by which the surface energy is subsequently determined. For a high quality of the joint, the bonded material must have higher surface energy than the witting liquid (adhesive) [1-3]. This paper describes the effect of plasma surface treatment on the surface properties (surface energy, microhardness) of low-density polyethylene (LDPE) and high-density polyethylene (HDPE), and also on the final strength of bonded joints. The measured results indicate, that plasma surface treatment is very effective tool for improvement of surface properties and strength of bonded joints of HDPE and LDPE. The strength of bonded joints after plasma surface treatment was increased up to 350 % compared to untreated material. A similar trend was observed even for surface energy and microhardness of materials.
39
Authors: Raul D.S.G. Campilho, Filipe J.P. Chaves, Arnaldo M.G. Pinto, Mariana D. Banea, Lucas F.M. da Silva
Abstract: 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 (Gn) and shear (Gs) and respective fracture energies in tension (Gnc) and shear (Gsc). Additionally, the cohesive strengths (tn0 for tension and ts0 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.
1000
Authors: Zhe Min Jia, Guo Qing Yuan, David Hui
Abstract: Adhesive bonding is one of the effective ways to reduce the weight of structures. Researchers have done lots of numerical analysis and finite element analysis taking into account of the complex stress state in the bonded area, as well as the stress singularity occurs at the overlap edges with a view to efficiently predict the strength and rigidity of adhesively bonded joints. As they may suffer shock or impact loads in practice which leads to high strain rate in structures, analysis methods for adhesively bonded joints differ from that at quasi-static condition for two reasons: one is the mechanical properties of materials, including adhesives and substrates are different at high strain rates, the other is the additional consideration of elastic wave propagation in solid body. This article summaries several finite element analysis methods for adhesively bonded joints at high strain rate developed by domestic and foreign scholars and corresponding experimental standards for determining required parameters of each analytical method and raised some questions that need for further study.
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