Papers by Keyword: Hybrid Joint

Abstract: Hybrid joints between aluminium and steel are used sometimes in case of thin sheets for example for a car body. Resistance welding for this joining challenge is not frequently used, but the resistance welded joints basically have good mechanical properties. During resistance spot joining of these hybrid joints, fusion between the two materials cannot occur, but with the right technological parameters an intermetallic compound (IMC) appears in the joint line. The properties of the IMC have significant effect to the joint properties, because the researchers basically investigate this. The original static mechanical tests can show good, comparable results for the joint properties. If we see the dynamic tests basically really difficult to find results in case of spot welding of steels and joining of hybrid aluminium – steel joints. The aim of this paper to show the dynamic properties of these hybrid joints. During our investigation DP600 dual-phase steel was used as the steel part because this grade is frequently used in a car chassis. For the aluminium part, two types of aluminium were applied: non-heat treatable 5754-H22 alloy, and heat-treatable 6082-T6 alloy. The different aluminium alloys have different properties, so different technological parameter combinations were used. To test the resistance of hybrid joints against dynamic loading, instrumented impact tests were performed. This special impact test is considered as an impact-bending test, because the load is perpendicular to the welded point joint. Force – time diagrams of impact tests were shown too in this paper. The intermetallic compound is necessary for joint, but it is very brittle with very big hardness, but in case of dynamic testing this hardness has no significant effect, so these specimens show good result in case of dynamic loading. The two different aluminium – steel joints show different resistance against dynamic loading, and the fracture modes were different too.

Abstract: This work investigates the influence of the sheet edge condition on the fracture behavior of riv-bonded aluminum-magnesium lap joints under monotonic-static and cyclic-dynamic shear-tensile loads. Therefore, sheets of 1.5 mm-thick EN AW-6016-T4 aluminum alloy were joined with sheets of 2.0 mm-thick AZ91 magnesium alloy using two C5.3×6.0-H4 rivets and epoxy-based adhesive. The side edges of the sheets were either shear-cut or milled after cutting. Before testing, the joints were heat-treated at about 180-200 °C for 20 min in order to cure the adhesive and to peak-age the aluminum alloy. The cyclic load maximum was about 40 % of the monotonic load maximum. The cyclic load minimum was 10 % of the cyclic load maximum, i.e., the load ratio was R = 0.1. The edge condition of the sheets did not have any significant influence in monotonic-static testing; however, in cyclic-dynamic testing the number of cycles to fracture was about four-times higher for samples with milled side edges than for samples with shear-cut side edges. Hence, the potential load capacity of riv-bonded aluminum-magnesium joints cannot be exploited under cyclic loading, if the magnesium sheet has edges with poor quality.

Abstract: Composite to metal joints are gradually found in the marine industry for the attachment of lightweight components to metallic structures. The puropose of this study is to invistigate the composite sandwich to steel joint for naval ships. The main emphasis of the study was placed on the mechanical properties of a hybrid joint between a sandwich glass fibre reinforced plastic superstructure and a steel hull. Based on the experiments of a base joint, a new numerical simulation method was used to analyze the performance of the base joint and the optimized joint. The optimized joint was presented due to reducing weight and avoiding eccentric load. The numerical predictions of the base hybrid joint showed a very good correlation with the experiment results, which validated the reliability of the new numerical simulation method. The strength of the optimized hybrid joint was evaluated through static simulation. This phenomenon is similar to the base joint. But there is no additional stress concentration induced by load eccentricity and internal bending. The optimized joint has 11% lower weight than the base joint, and the stress of the optimized joint is only about 4% ~ 67% of the base one. The results of the present work imply that the change of geometry and material is an effective method to improve the performance of the composite sandwich to steel joint.

Abstract: Self-Piercing Riveting (SPR) is receiving more recognition as a possible and effective solution to join body panels and structures. For example self-piercing riveting is still the first choice for the most well-known automotive car industries when considering the intensive use of aluminum alloy. To combine the advantages of the two joints techniques, in the last years hybrid joints combining a classical mechanical fastening (riveting) and a classical adhesive bonding, or a co-cured joint, have attracted great interest.In the present paper the static behavior of single-lap hybrid joints (SPR-bonded) between GFRP and aluminum through experimental tests. In particular, tensile strength, energy absorption and failure modes of studied joints were investigated through tensile tests.

Abstract: Coupling techniques for components of different materials is spreading in mechanical industry; the test case studied in this work deals with the connection of an aluminium alloy component with a carbon fibre composite one. In particular, the first component is made of an aluminium-zinc alloy and exhibits an isotropic behaviour, while the second is made of a carbon fibre reinforced polymer (CFRP) and shows a strongly anisotropic behaviour; both materials are widely used in engineering applications. A titanium bolt connects the parts. This work is focused on the influence of the geometrical parameters which characterize the coupling between the components. In particular, a study has been carried out on the influence of the shank-hole clearance, the bolt head size, the bolt preload and the shape of the bolt head. A numerical model has been built and statically tested; the results have been compared with the experimental ones from literature. Once validated, the same numerical model has been used to evaluate the performance of the joint in presence of a change of the above mentioned characteristic parameters. The required numerical analyses have been performed using Abaqus/Standard® numerical code.

Abstract: In this work, results from a study on bolted joints made of unidirectional, quasi isotropic Carbon Fiber Reinforced Polymer (CFRP) composites, subjected to tensile loads, are reported. CFRP composite materials are widely used in the mechanical industry, such as that of aerospace, where requirements of weight reduction and structural high performances are very compelling. Composite materials generally present a high resistance to fatigue and corrosion; however, the presence of joints produces the major problems and a poor design of joints leads to a drastic reduction of the reliability of structures made of these materials. A hybrid bolted joint involving a metal plate, made of aluminum alloy, and a CFRP composite plate has been considered; the plates are held together by a titanium bolt. Experimental results from literature are compared with those obtained through a numerical analysis developed with Abaqus code. Once the CFRP composite has been analyzed and the numerical model validated through numerical-experimental correlations, other possible configurations have been numerically analyzed in order to ensure the highest strength of the examined hybrid joint. Afterwards the effects of bolt-hole clearance on the stiffness and strength of the same joint have been investigated.

Abstract: There are many instances where the use of weight saving composite materials for an entire structure is either; too complex, too expensive or unfeasible. In these circumstances the use of a hybrid structure can incorporate the benefits of traditional construction materials, for example steel, coupled with the advantages of composite materials in weight critical areas. In the present study, an investigation was undertaken into the fatigue life characterisation of a hybrid joint for marine application. In addition the residual strength of the joint, after a fixed number of fatigue cycles, was assessed under axial compression and bending loads. A progressive damage model was developed to predict the location of major stress concentrations, the path of damage and subsequent loss in stiffness of the joint under axial compression.