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CT scan (voxel-resolution 4.8 μm) of hybrid joints: (a) three-dimensional view of GFRP with marked fiber orientations and (b) top view and detail view of CFRP edge with labeled fiber orientation.
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The development of a new joining technology, which is used to manufacture high strength hybrid constructions with thermoplastic composites (FRP) and metals, is introduced. Similar to natural regulation effects at trees, fibers around the FRP joint become aligned along the lines of force and will not be destroyed by the joining process. This is achi...
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Carbon fiber reinforced plastics (CFRP) has been applied as structural components not only in aeronautics and astronautics but also in the automobile industry. Among those CFRP materials, randomly oriented carbon fiber reinforced thermoplastics, in particular, chopped carbon fiber tape reinforced thermoplastics (CTT), have been one of the research...
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Citations
... As a result of fiber displacement during the joining process, there is a higher fiber density of 78% on the metallic sleeve, while the fiber distribution away from the joint is sparse, reaching only 35%. This fiber centering in the joint can positively impact joint load-bearing capacity [81]. Reproduced with permission from [81]. ...
... This fiber centering in the joint can positively impact joint load-bearing capacity [81]. Reproduced with permission from [81]. 2014, Open Access by Hindawi. ...
... (a) Process principle; (b) schematic presentation of realigned fibers in the joined specimen; (c) comparison of the maximum shear tensile force with load-adjusted formed and predrilled FRP bore holes; (d) inhomogeneous fiber content in the joining area. Reproduced with permission from[81]. 2014, Open Access by Hindawi. ...
The extensive use of carbon fiber-reinforced composites and aluminum alloys represents the highest level of automotive body-in-white lightweighting. The effective and secure joining of these heterogeneous materials remains a prominent and actively researched topic within the scientific community. Among various joining techniques, clinching has emerged as a particularly cost-effective solution, experiencing significant advancements. However, the application of clinching is severely limited by the properties of the joining materials. In this work, various clinching processes for the joining of composites and aluminum alloys reported in recent research are described in detail according to three broad categories based on the principle of technological improvement. By scrutinizing current clinching technologies, a forward-looking perspective is presented for the future evolution of clinching technology in terms of composite–aluminum joints, encompassing aspects of tool design, process analysis, and the enhancement of joint quality. This work provides an overview of current research on clinching of CFRP and aluminum and serves as a reference for the further development of clinching processes.
... Rakesh and Kumar analyzed the thrust forces developed with the four types of drilling tools for the drilling of glass fiber reinforced polymers and determine that the hollow drill bit are suitable for the minimum delamination [19]. Tsao et al. performed drilling experiment for the CFRP by using core saw drill and proposed a new delamination factor and concluded that delamination is highly sensitive with feed rate [20].Holger Seidlitz et al. [21] produce hole like feature without drilling in thermoplastic resin composite for manufacturing of composite to metal joint. From the above literature review, it can be easily depicted that most of the researchers optimized the process or geometric parameters of the drilling to control the delamination. ...
In aerospace and aeronautics industries, composite laminates’ products are often rejected or scrapped due to defects produced during the machining or drilling processes, which incurs high cost of quality. It is essential to eliminate such defects, but it is very challenging and incurs huge cost of rework. These defects are either delamination at entry or exit of the laminate or damage in the surface finish of the holes. In this research, carbon fiber reinforce polymer (CFRP) is used as the composite laminate and three techniques are used, which modify the composite laminate before drilling. These modifications are i) pre-cure cut of the fabric, ii) through thickness reinforcement by stitching of fabric layers and iii) hybrid layers in the laminate of thick and thin layers. The aim of these modified layers of fabric is to reduce exit side delamination or push out delamination. Three controllable parameters; feed rate, spindle speed and point angle of drill bit are considered for the drilling experiments. Combination of control parameters for drilling experiments are determined using Taguchi orthogonal array L9. Optimal controllable parameter combination for the drilling of each modified composite laminate is determined by using entropy objective weighting method, desirability function analysis and Taguchi analysis. Then a comparative study is conducted by basis of ease of manufacturing and amount of delamination reduction. The result of the research shows that by keeping the feedrate 0.15 rev/min, spindle speed 1500 rpm, point angle of drill 130° and applying the strategy of hybrid layers of carbon fabric, the minimum delamination and surface roughness are achieved.
Graphical Abstract
... Shear strengths calculated from the maximum shear loads and the joint area for different clinching technologies. The references where the data was extracted from are given after each technology [13,15,27,28,30,[40][41][42][43]. The two columns in the right marked with thicker contour stand for the joint developed in this work (MECI) and the adhesive joint used as a reference (RS). ...
... С 80-х годов 20 века распространение получили комбинированные соединения с установкой стальных игл (z-pin), закрепленных в металлической детали. Они внедряются в пакет препрега полимерных композиционных материалов и подвергаются совместной полимеризации, совмещая положительные свойства описанных выше типов соединений, не нарушают волокна основы композита, и как следствие, не снижают его прочностные характеристики [7,8,13]. Для облегчения веса авторами [14,15] описана конструкция стыка с использованием композитных игл, однако несмотря на заявленные преимущества, при отрыве и сдвиге стыки более подвержены расслаиванию. ...
A method for improving the reliability of agricultural trailers by replacing steel sides with composite sandwich structures is considered, which makes it possible to reduce their weight with a general improvement in performance. The fastening of such boards to the metal frame of the platform is carried out using steel supports. Carrying out loading and unloading operations can be carried out by overturning the side board around the lower hinged supports, with the opening of the latches on the two upper supports. A comparative analysis of the existing methods of joining "steel-composite" (adhesive, with the help of mechanical fasteners, combined, glue-pin) made it possible to identify their shortcomings when using a multilayer composite structure characterized by insufficient strength of the inner layers adjacent to the support. The design of the lower hinged support, devoid of the described shortcomings, has been developed. The connection is carried out using two steel lugs containing profiles with spearshaped fasteners, which are introduced into the skin prepregs at the stage of composite manufacturing. The lugs are tightened with bolts, which allows you to create a reliable connection between the steel hinged supports and the side plate, which consists of a multilayer composite. A method for calculating the lower support has been developed, as a result of which the most loaded fasteners have been identified, and an expression has been obtained to determine the maximum acting force. Recommendations are proposed for calculating the strength of the most loaded fastener according to the allowable shear stresses of its cylindrical part.
... For this reason, a large number of different joining systems have been developed that are specially tailored to the properties of TPCs [3][4][5]. Thus, the warm formability of TPCs is advantageously exploited in many joining processes, such as the moulding of pins into TPCs [6][7][8][9], flow drill joining [10,11], thermoclinching [12][13][14], embedding of inserts [15][16][17][18], moulding of contour joints [19], and hotclinching [20]. All these processes are based on warm forming the joining zone. ...
... Therefore, they have in common a local change of the material structure. For many processes, modified fibre paths [7,15,18] as well as varying fibre volume contents (FVCs) and matrix-rich zones [11,[21][22][23] are described as a result of the joining processes. The locally varying material structural properties in joining zones influence the load bearing behaviour and must, therefore, be taken into account when predicting the deformation and damage behaviour [15]. ...
... The matrix-rich zones previously located on the counterpunch surface (9) are also pressed upwards (10). The fibres are partially shifted and bent when pressed back into the laminate plane, which is reflected in the cross-section by a reorientation of the fibres in the direction of the counterpunch feed (11). The pressure of the counterpunch ultimately also results in the complete filling of the insert's undercut. ...
Thermoplastic composites (TPCs) are predestined for use in lightweight structures, especially for high-volume applications. In many cases, joining is a key factor for the successful application of TPCs in multi-material systems. Many joining processes for this material group are based on warm forming the joining zone. This results in a change of the local material structure characterised by modified fibre paths, as well as varying fibre contents, which significantly influences the load-bearing behaviour. During the forming process, many different phenomena occur simultaneously at different scales. In this paper, the deformation modes and flow mechanisms of TPCs during forming described in the literature are first analysed. Based on this, three different joining processes are investigated: embedding of inserts, moulding of contour joints, and hotclinching. In order to identify the phenomena occurring in each process and to describe the characteristic resulting material structure in the joining zones, micrographs as well as computed tomography (CT) analyses are performed for both individual process stages and final joining zones.
... Analysis of the defects revealed that the size distribution of the studied worn-out parts is uneven, and obeys the logarithmic law of the distribution of random variables, and that the semi-axles lose less than 5% of their mass during wear; the value of the complex recovery coefficient ranges from 0.87 to 0.98, which indicates the inexpediency of recycling worn parts of this name. At the same time, manufacturers of refurbished auto parts are united in associations: MERA (Association of Manufacturers of Engines and Equipment), ANRAP (National Association of Manufacturers of Automotive Parts), CLEPA (European Association of Automobile Suppliers), APRA (Association of Manufacturers of Automotive Parts), FIRM (European Organization for Engine Repair), and CPRA (Repair Committee of the Chinese Association of Automobile Manufacturers) [4][5][6][7][8][9][10][11][12][13]. ...
The article is devoted to the substantiation of technological foundations for the restoration of extremely worn-out, metal-consuming, and resource-consuming parts, in a method consisting of applying a compensating metal wear with subsequent plastic deformation. Currently, there are no technologies for their restoration in a repair facility that guarantee the resilience of the factory product. The proposed technological process of repair consists of butt welding onto the end of the spline semi-axle shank, compensating for the wear of the metal, the volume of which takes into account the losses resulting from the wear of the slots, as well as allowances for their machining. In the example of forging the axle shaft of a truck’s driving axle, the regularities of the plastic flow of metal during part deformation in the stamp are revealed. In the process of hot volumetric upsetting of long cylindrical parts with a variable diameter, it is important to know the possible directions of metal movements, as well as the energy-power characteristics of the process at various stages of forging. The evaluation criteria of the level of perfection of the technology were indicators of resource conservation and efficiency of the recovery route. The technological direction of the conducted research was analyzed, step by step, from the standpoint of saving repair materials and energy resources. The results of theoretical studies are crucial in the design of die tooling, for the manufacture of blanks, when restoring the rear axle shafts of trucks with pressure. Production tests carried out on the models, obtained as a result of mathematical processing of experimental data, confirmed the reliability of the experimental information. The introduction of the proposed set of repair equipment for the restoration of semi-axles will allow the formation of additional production in the region for the recycling of worn-out metal-intensive steel parts of agricultural machinery.
... Plastification is used to improve formability of TPC in many joining processes, such as in [13]. A rotating tapered pin induced heat by friction. ...
Recent 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.
... Accordingly, FDJ joints contain, in contrast to established technologies, a process-related reinforcement in the critical areas next to the joint [7]. Further investigations and findings on the FDJ joining concept are described in [8][9][10]. ...
By regarding the needs and requirements in modern multi-material joining, the Flow Drill Joining Concept (FDJ) was developed at the Chemnitz University of Technology. The technology allows an efficient and material-adapted joining of thin metal sheets with continuous fibre-reinforced thermoplastics, as required in modern lightweight engineering. For a better understanding of their fatigue behaviour, single-lap FDJ joints were examined in quasi-static and dynamic tests regarding shear loads, cross tension and superimposed shear/cross tension loads. By way of example, joints between micro-alloyed steel with high yield strength for cold forming and a continuous glass/carbon fibre-reinforced polyamide 6 were investigated. The fatigue curves show inclinations between k = 8.01 (shear loads) and k = 5.17 (cross tension loads), depending on the applied load angle. The results of the fatigue testings represent a basis for the enhancement of a failure criterion for FRP/metal joints in highly stressed multi-material designs.
... This allows the realignment of the endless fibre reinforcement when the sleeve is formed without fibre breaking. Subsequently, a closing head is manufactured by a forming tool, creating an undercut [15]. ...
... The phenomena occurring during the forming of the heated TPC as well, as the joint formation and performance for the three technologies, are compared in the following. [8], (b) Friction assisted Clinching [9], (c) Thermoclinching [16], (d) hole [6]/hole free [11,12] clinching, (e) Flow Drill Joining [15], (f) Two-Step Clinching [13], (g) Hotclinching [17], (h) Preheated Clinching [14], (i) Insert Clinching. ...
... In comparison to Thermoclinching, the process cycle including heating of the TPC is significantly faster ( Table 4). The maximum shear load of 2.2 kN is in the same range as [15] (Table 3e). In contrast to Lambiase et al. [11], less fibre failure can be observed in the joining zone. ...
Clinching continuous fibre reinforced thermoplastic composites and metals is challenging due to the low ductility of the composite material. Therefore, a number of novel clinching technologies has been developed specifically for these material combinations. A systematic overview of these advanced clinching methods is given in the present paper. With a focus on process design, three selected clinching methods suitable for different joining tasks are described in detail. The clinching processes including equipment and tools, observed process phenomena and the resultant material structure are compared. Process phenomena during joining are explained in general and compared using computed tomography and micrograph images for each process. In addition the load bearing behaviour and the corresponding failure mechanisms are investigated by means of single-lap shear tests. Finally, the new joining technologies are discussed regarding application relevant criteria.
... Adhesive bonding has limited durability in wet and corrosive environments [89][90][91][92]. Recently developed advanced welding techniques such as friction-spot welding, laser welding, or ultrasonic welding techniques were considered to be better alternatives for mechanical or adhesive joining [93,94], but these techniques have limitations, such as the thickness of the bonding partners, joining size, and processing temperature. Thus, the above-mentioned joining techniques limit the complete utilization of MMD using FRPs and metals. ...
The European Parliament and Council has defined a mandatory specific emission target of 95 g CO2/km by 2020 for passenger cars. Vehicle weight is a significant factor contributing to fuel consumption. Reducing the weight of the vehicle can be one promising option for decreasing CO2 emissions, which becomes a top priority for the automotive industry. In this research, two approaches were used to address the need. One involved developing structural parts using fibre reinforced plastics (FRP), and the other involved designing and developing FRP–metal hybrid laminates, which were constructed by reinforcing FRP locally to the metal surface. Existing joining techniques such as riveting, bolting, adhesive joining, ultrasonic welding, and flow drill joining techniques require additional processing steps to perform the joining, which could considerably increase processing time, cost, and energy expenditure. The present work describes a method to join FRP and metals using the adhesion strength of the investigated polymers. The developed FRP–metal hybrid laminates combine the advantages of metal and FRP together. Steel hot-stamping is known to yield very high strength. Fibre reinforced plastic–metal hybrid laminates were developed using hot stamped steels to transfer their superior mechanical properties to the final structure. To utilize the complete lightweight potential of thermoset and thermoplastic polymers, FRPs and FRP–metal hybrid laminates were developed using both the polymers. Along with this increased demand for FRP structures, there is growing interest in a repair technique in the automotive industry. The second objective of this thesis consists of designing and developing a new repair technique, which regains the strength and stiffness properties of the damaged part. The existing scarf repair technique is not suitable for thin laminates, which have limited access to the damaged area. Perforation damages were introduced into the FRP structures using a low-velocity impact load. A modified injection repair technique is used to repair these damaged FRP structures. Non-destructive techniques were utilized to understand the damage and the effectiveness of the repair.
