Joining of CFRT-steel hybrid parts via hole-forming and subsequent pin caulking

AbstractIn times of increasing global warming, the awareness of the necessity for significant CO2 reduction is growing. Especially in the transport and aerospace sector, lightweight construction has potential to achieve emission reduction goals by reducing the overall vehicle weight. Thereby, adding lightweight fibre-reinforced composites to materials such as steel and aluminium is used to achieve weight savings. Furthermore, continuous-fibre-reinforced thermoplastics (CFRTs) begin to replace more traditional thermoset thermoplastics due to their easier bulk production and uncomplicated storage. Hybrid parts often consist of a CFRT and a higher strength metal component. Here, the joining process poses the main challenge, due to different chemical and physical properties of the components. In the current state of the art, riveted and bolted joints are commonly used, leading to increased weight due to auxiliary elements and requiring precise bolt holes often destroying load-bearing fibres. Joining with cold formed pin structures is an innovative and versatile joining process, which avoids the need for auxiliary elements. These pins are subsequently inserted in warm formed holes in the CFRT component and then caulked to create a form-fitting hybrid joint. To obtain a fundamental understanding of this joining process, hole-forming and pin-caulking, are investigated in this study. First, the hole-forming with IR-radiation is investigated with regard to suitable process parameters and resulting fibre morphology. The formed holes are consequently mechanically characterized. Second, the caulking-process is investigated by iteratively upsetting a pin and subsequently measuring the geometry. Based on these findings two different suitable caulking degrees are defined and samples for mechanical as well as microscopic investigations are manufactured. The created joints are first investigated via micro-sections and reflected light microscopy to identify possible damage in the CFRT component, which can result from the pin caulking process. Second, a mechanical characterisation under shear load as well as pin extraction loads normal to the sample surface is conducted and the normal load tests are compared with the bearing strength of CFRT samples.

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Fretting Wear Behavior and Damage Mechanisms of Inconel X-750 Alloy in Dry Contacts

Advances in Materials Science and Engineering ◽

10.1155/2019/7079819 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15

Author(s):

Ibrohim A. Rustamov ◽

Ozoda Sh. Sabirova ◽

Zixi Wang ◽

Yuming Wang

Keyword(s):

Wear Behavior ◽

Normal Load ◽

Fretting Wear ◽

Partial Slip ◽

Test Duration ◽

Material Transfer ◽

Friction Forces ◽

Frictional Properties ◽

Load Tests ◽

Oxidation Mechanisms

Tribological behavior of the Inconel X-750 alloy disk subjected to fretting against the GCr15 steel ball was investigated in an ambient laboratory air with relative humidity of 55–65%. A high-frequency oscillating Optimol SRV 4 tribometer was employed to execute dry fretting tests in the partial and gross slip regimes under constant 100 N normal load. Tests were carried out for 10, 30, and 90 minutes, and the friction forces vs. displacement amplitudes were monitored during the test duration. Posttest examinations were conducted utilizing advanced tools such as 3D optical surface profiler, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The main objective was to obtain wear scar evolutions, frictional properties, and degradation mechanisms under the different running conditions over time. It was found that fretting wear behaviors of friction pairs were strongly influenced by fretting regimes. Degradation evolutions were greatly influenced by fretting time during partial slip regimes, i.e., evolving from asperity deformation and slight damage to the fatigue crack and material transfer. However, the combination of adhesive, abrasive, delamination, and wear oxidation mechanisms was repeated during the entire gross slip fretting process.

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Computed tomography investigation of the material structure in clinch joints in aluminium fibre-reinforced thermoplastic sheets

Production Engineering ◽

10.1007/s11740-021-01091-x ◽

2021 ◽

Author(s):

Benjamin Gröger ◽

Daniel Köhler ◽

Julian Vorderbrüggen ◽

Juliane Troschitz ◽

Robert Kupfer ◽

...

Keyword(s):

Computed Tomography ◽

Three Dimensional ◽

Material Design ◽

Material Behavior ◽

Thermoplastic Composite ◽

Thermoplastic Composites ◽

Material Structure ◽

Research Activities ◽

Reinforced Thermoplastics ◽

Joining Process

AbstractRecent developments in automotive and aircraft industry towards a multi-material design pose challenges for modern joining technologies due to different mechanical properties and material compositions of various materials such as composites and metals. Therefore, mechanical joining technologies like clinching are in the focus of current research activities. For multi-material joints of metals and thermoplastic composites thermally assisted clinching processes with advanced tool concepts are well developed. The material-specific properties of fibre-reinforced thermoplastics have a significant influence on the joining process and the resulting material structure in the joining zone. For this reason, it is important to investigate these influences in detail and to understand the phenomena occurring during the joining process. Additionally, this provides the basis for a validation of a numerical simulation of such joining processes. In this paper, the material structure in a joint resulting from a thermally assisted clinching process is investigated. The joining partners are an aluminium sheet and a thermoplastic composite (organo sheet). Using computed tomography enables a three-dimensional investigation that allows a detailed analysis of the phenomena in different joining stages and in the material structure of the finished joint. Consequently, this study provides a more detailed understanding of the material behavior of thermoplastic composites during thermally assisted clinching.

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Tapping Mode Near-Field Scanning Optical Microscopy of Molecular Crystals and Thin Films

Microscopy and Microanalysis ◽

10.1017/s1431927600018298 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 994-995

Author(s):

C. Daniel Frisbie ◽

Andrey Kosterin ◽

Helena Stadniychuk

Keyword(s):

Optical Microscopy ◽

Spatial Resolution ◽

Laser Light ◽

Near Field ◽

Sample Surface ◽

Reflected Light ◽

Surface Laser ◽

Scanning Optical Microscopy ◽

Diffraction Effects ◽

Near Field Scanning

The diffraction of visible light limits the spatial resolution in conventional optical microscopy to about 200-300 nm. In near-field scanning optical microscopy (NSOM), resolution is improved by bringing the light source, such as the end of an optical fiber, very close to the sample surface. Laser light coupled into the opposite end of the fiber propagates down the fiber core and is emitted from the aperture of the tip. When the sample is in the near-field(roughly within one tip diameter of the end of the tip), the spatial resolution is essentially equal to the diameter of the aperture at the end of the tip and is not determined by diffraction effects. Two-dimensional imaging is accomplished by raster-scanning the sample underneath the fiber tip and collecting transmitted or reflected light at a photodetector.

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Adhesive Distribution and Global Deformation between Hybrid Joints

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.651-653.1465 ◽

2015 ◽

Vol 651-653 ◽

pp. 1465-1471 ◽

Cited By ~ 3

Author(s):

Dirk Landgrebe ◽

Bernd Mayer ◽

Stephan Niese ◽

Holger Fricke ◽

Ivo Neumann ◽

...

Keyword(s):

Automotive Industry ◽

High Speed ◽

Adhesive Bonding ◽

Measurement Technology ◽

Detailed Knowledge ◽

Small Surface ◽

Mechanical Joining ◽

Hybrid Joint ◽

Hybrid Joints ◽

Joining Process

In multi-material-design, e.g. in the automotive industry, mechanical joining processes like self-pierce riveting are well established, because of their amount of advantages. However, adhesive bonding with one-component structural adhesives is increasingly being used. The combination of the specific advantages of both joining techniques in the form of hybrid joints leads to synergies of quality and reliability, such as high corrosion resistance and better damping properties. A critical issue is the generation of global deformations of the different parts of the mechanical joints. These global deformations of the sheet metal between two or more mechanical connectors (e.g. rivets) are caused by the formation of adhesive bags during the riveting process, before the adhesive curing takes place. This research focuses on the time-dependent formation process of these bags. The aim is to achieve a reduction of global deformations based on detailed knowledge of the adhesive flow during the manufacturing of the joint by means of experiments and simulations. For this purpose experimental techniques and measurement methods for deformations over time are presented for different setups of hybrid joint types of self-piercing rivets in combination with adhesive bonding. The challenge is to track rapid and small surface deformations very accurately in the ongoing mechanical joining process. High-speed optical measurement technology like Point-Tracking and surface scanning are used to track the resulting deformations experimentally. Numerical investigations, which include the interaction of the solid matter influenced in the mechanical joining process and the fluid adhesive, are presented. On the basis a fully coupled fluid-structure interaction simulation of a single hybrid joint, a surrogate model for a multi-point hybrid joint is developed. The comparison of experimental data with simulations allows deriving the pressure distribution and flow velocities inside the adhesive layer. The influence of various parameters can be interpreted based on the physics of the interacting system, ultimately resulting in optimization helpful to the automotive industry.

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Temperature Dependent Modelling of Fibre-Reinforced Thermoplastic Organo-Sheet Material for Forming and Joining Process Simulations

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.883.49 ◽

2021 ◽

Vol 883 ◽

pp. 49-56

Author(s):

Benjamin Gröger ◽

Andreas Hornig ◽

Arne Hoog ◽

Maik Gude

Keyword(s):

Model Calibration ◽

Sheet Material ◽

Tensile Tests ◽

Woven Fabric ◽

Temperature Dependent ◽

Representative Unit Cell ◽

Process Simulations ◽

Element Approach ◽

Reinforced Thermoplastics ◽

Joining Process

Joining and local forming processes for fibre-reinforced thermoplastics (FRTP) like hole-forming or variations of the clinching process require an in-depth understanding of the process induced effects on meso-scale. For numerical modelling with a geometrical description of a woven fabric, adequate material models for a representative unit cell are identified. Model calibration is achieved employing a mesoscopic finite-element-approach using the embedded element method based on tensile tests of the consolidated organo-sheets and a phenomenological evaluation of photomicrographs. The model takes temperature dependent stiffness and fibre tension failure into account.

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Methodology of a glass latern conservation and restoration painted by cold technique

Iskusstvo Evrazii [The Art of Eurasia] ◽

10.25712/astu.2518-7767.2018.04.018 ◽

2018 ◽

Author(s):

Екатерина Никитична Шаркова

Keyword(s):

Paint Layer ◽

Point Of View ◽

Living Room ◽

Chemical Laboratory ◽

Reflected Light ◽

The Subject ◽

Physical And Chemical ◽

Joining Process ◽

Painting Layer ◽

Selection Of

Предметом исследования и реставрации является фонарь матового стекла из коллекции музея-усадьбы Останкино. Он был частью убранства Этрусской гостиной Фонтанного дома графа Д.Н. Шереметева. Состояние сохранности плафона было удручающим, он был разбит на десятки фрагментов, живопись на стекле осыпалась. Для определения плана и материалов консервации и реставрации были проведены физико-химические исследования, устанавливающие технику росписи – необжиговыми красками на основе органической смолы. Далее была разработана методика укрепления, очистки и восполнения красочного слоя. После укрепления и очистки красочного слоя была проведена склейка предварительно подобранных фрагментов. Затем были восполнены утраты: небольшие – доливались по месту клеевым составом, большие – восполнялись путем снятия силиконовых форм и отливки в них восполнений. После восстановления всей формы фонаря были тонированы восполнения и клеевые швы, а также проведен монтаж предварительно очищенной бронзовой оправы. The subject of our research and restoration comes from a collection of the Ostankino Estate. This lantern is a part of decoration of the Etruscan living room of the Fountain House in St. Petersburg belonged to a count Sheremetev. The condition of safety of a lantern was disappointing, it was broken into several large and many medium and very small fragments. It consisted of 100 fragments. Many pieces were lost. On all surface of glass and a painting layer we could observe the strong pollution. The color layer was badly destroyed, the surface of the fragments was very dirty there was a widespread peeling of the paint scales, the painting was constantly crumbling at every touch. From the point of view of conservation and restoration operations it is interesting to know the old manufacturing technology of the lantern, namely technique of painting. Therefore at first we took samples of a paint layer and gave them on the analysis to our physical and chemical laboratory. The research was conducted by the following methods: microscopy in the reflected light, microchemistry, X-ray Fourier microspectroscopy. After that the technique of consolidation, cleaning and filling the gaps of a paint layer was developed. The joining process was initiated with the selection of fragments belonging to each other. Gluing started with the tiny fragments, until you get several large pieces of the lantern, let's call them blocks. Small loss on the already glued small blocks was then filled in place with an adhesive composition. The next stage was making of silicone molds of lost fragments. Large missing fragments were made using Araldite 2020. After reconstruction the whole form of the lantern, was completed tinting all the small losses, chips and adhesive joints by the developed technique. And the last step was the installation of pre-treated bronze frame.

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Development of a new joining technology for hybrid joints of sheet metal and continuous fiber-reinforced thermoplastics

Welding in the World ◽

10.1007/s40194-021-01194-0 ◽

2021 ◽

Author(s):

Dimitri Krassmann ◽

Elmar Moritzer

Keyword(s):

Sheet Metal ◽

Thermoplastic Composite ◽

Thermoplastic Composites ◽

Stress Concentrations ◽

Joining Technology ◽

Hybrid Joints ◽

Process Reliability ◽

Fiber Breaks ◽

Reinforced Thermoplastics ◽

Joining Process

AbstractPunctiform mechanical joining technologies, such as riveting, clinching, or screwing, which are widely used in sheet metal processing, are frequently applied because they have been established for many years. Depending on the process, they offer a variety of advantages such as one-sided accessibility, re-detachability, and no need for pre-punching operations or auxiliary joining elements. In addition, the processes often guarantee a high process reliability and extensive process monitoring. However, with thermoplastic composites, they lead to considerable stress concentrations at the joint due to the fibers. Undesirable fiber and inter-fiber breaks then result. With the development of the novel joining technology of joint stamp riveting, an improvement is achieved in this situation that has been described for hybrid joints on components made of thermoplastic composites and metal sheets. The joining principle is based on the formation of a form lock between the joining partners. The thermoplastic composite is thermomechanically formed by means of a joint stamp without using an auxiliary joining element. Within the scope of a research project, the joining process was characterized with regard to the structure of the joining spot, the geometry of the forming tools, and also the mechanical properties for purposes of analyzing and designing the joining process.

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Modelling of thermally supported clinching of fibre-reinforced thermoplastics: Approaches on mesoscale considering large deformations and fibre failure

10.25518/esaform21.4293 ◽

2021 ◽

Author(s):

Benjamin Gröger ◽

Andreas Hornig ◽

Arne Hoog ◽

Maik Gude

Keyword(s):

Numerical Simulation ◽

Large Deformations ◽

Dissimilar Materials ◽

Single Step ◽

Arbitrary Lagrangian Eulerian ◽

Fibre Failure ◽

Feasibility Robustness ◽

Contact Models ◽

Reinforced Thermoplastics ◽

Joining Process

Thermally supported clinching (Hotclinch) is a novel promising process to join dissimilar materials. Here, metal and fibre-reinforced thermoplastics (FRTP) are used within this single step joining process and without the usage of auxiliary parts like screws or rivets. For this purpose, heat is applied to improve the formability of the reinforced thermoplastic. This enables joining of the materials using conventional clinching-tools. Focus of this work is the modelling on mesoscopic scale for the numerical simulation of this process. The FTRP-model takes the material behaviour both of matrix and the fabric reinforced organo-sheet under process temperatures into account. For describing the experimentally observed phenomena such as large deformations, fibre failure and the interactions between matrix and fibres as well as between fibres themselves, the usage of conventional, purely Lagrangian based FEM methods is limited. Therefore, the combination of contact-models with advanced modelling approaches like Arbitrary-Lagrangian-Eulerian (ALE), Coupled-Eulerian-Lagrangian (CEL) and Smooth-ParticleHydrodynamics (SPH) for the numerical simulation of the clinching process are employed. The different approaches are compared with regard to simulation feasibility, robustness and results accuracy. It is shown, that the CEL approach represents the most promising approach to describe the clinching process.

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Fiber Orientation Mechanism of Continuous Fiber Reinforced Thermoplastics Hybrid Parts Joined with Metallic Pins

Applied Composite Materials ◽

10.1007/s10443-021-09892-0 ◽

2021 ◽

Author(s):

Julian Popp ◽

Tobias Kleffel ◽

David Römisch ◽

Thomas Papke ◽

Marion Merklein ◽

...

Keyword(s):

Fiber Orientation ◽

Laser Scanning ◽

Laser Scanning Microscopy ◽

Confocal Laser ◽

Limiting Factor ◽

Minor Effect ◽

Fiber Reinforced ◽

Continuous Fiber ◽

Hybrid Parts ◽

Reinforced Thermoplastics

AbstractContinuous Fiber Reinforced Thermoplastic (CFRT) hybrid parts offer interesting possibilities for lightweight application, which can exceed the capabilities of mono material metal or CFRT parts. In this case, the joining technology oftentimes is the limiting factor. This study investigates a joining operation with metal pin structures which are additively manufactured via powder bed fusion featuring different diameters and tip geometries, which are inserted into the locally infrared heated CFRT part. The resulting fiber rearrangement is assessed using transmitted light microscopy, confocal laser scanning microscopy as well as micro-computer-tomography. It could be shown that for all assessed pin variants a similar distinct fiber displacement can be seen and that the pin diameter has a significant effect on the resulting fiber orientation with smaller pin diameters being advantageous because of gentle fiber displacement and reduced undulation. The tip geometry has only minor effect on the fiber orientation. Especially in the X/Y plane no systematic influence of the tip geometry on the fiber displacement could be observed. Based on the gained insights a three-stage model of the fiber orientation processes is proposed.

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PROPERTIES OF THE HAND MIXED PMMA BASED CEMENT FOR BIOMEDICAL APPLICATIONS

Contemporary Materials ◽

10.7251/comen2002085z ◽

2020 ◽

Vol 11 (2) ◽

Author(s):

Fatima Živić ◽

Nenad Grujović ◽

Svetlana Pelemiš ◽

Dragan Adamović

Keyword(s):

Mechanical Behavior ◽

Bone Cement ◽

Mechanical Response ◽

Normal Load ◽

Sample Surface ◽

Maximum Load ◽

Material Structure ◽

Hardened Cement ◽

Pmma Bone Cement ◽

Pmma Beads

This paper presents insights into the recent trends in development of PMMA bone cements considering their improvements for applications in clinical practice. Experimental investigation of hand mixed PMMA bone cement was realized, aiming to determine mechanical behavior of the material during nanoindentation. Standard multi-cycle indentation tests were applied, with maximum load of 15 N and immediate load relaxation down to 5 N, with sharp Vickers indenter. Indentation curves were obtained and analyzed as the function of the normal load vs penetration depth, for three different numbers of cycles (100, 200 and 300 cycles) and different indentation positions on the sample surface. Resulting indents were analyses from the aspect of the final material structure and its subsequent mechanical behavior. Agglomeration of PMMA beads was observed in the final hardened cement in some surface zones, thus indicating non-homogenous material structure. Changes in the number of cycles did not show significant influence on the mechanical response of the sample. However, sites with agglomerated PMMA beads showed significantly different indentation curves, thus indicating that hand-mixing of PMMA bone cement can produce non-homogenous final material structure.

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