Ultrasonic plastic welding of CF/PA6 composites to aluminium: Process and mechanical performance of welded joints

2019 ◽  
Vol 53 (18) ◽  
pp. 2607-2621 ◽  
Author(s):  
Umberto F Dal Conte ◽  
Irene F Villegas ◽  
Julien Tachon
Keyword(s):  
Mechanical Performance ◽  
Lightweight Design ◽  
Welding Process ◽  
Thermoplastic Composites ◽  
Process Time ◽  
Reinforced Plastics ◽  
Lap Shear ◽  
Physical Treatments ◽  
Reinforced Thermoplastics ◽  
Plastic Welding

Due to environmental challenges and need for action with regard to CO2 emission, reducing the weight of vehicles has become one of the most important goals of car manufacturers in Europe. Materials like fibre-reinforced plastics and aluminium are the core of the research for lightweight design. However, efficiently joining these materials together is still a challenge. When thermoplastic composites are used, direct joining (i.e. without adhesives or fasteners) with the metal substrate can be obtained using welding technologies which melt the thermoplastic at the interface. In this study, ultrasonic plastic welding was investigated as a candidate technology for joining aluminium and carbon fibre-reinforced thermoplastics. The goal was to understand the main mechanisms involved in the welding process and how they affect the performance of the joint. Initially, the technique proved to be successful, but moderate strengths were obtained. Therefore, several surface pre-treatments of aluminium were analysed to improve the performance in terms of lap shear strength; mechanical, chemical and physical treatments were also carried out. With laser structuring, strengths comparable to adhesive bonded joints were obtained, but in a much shorter process time. Other treatments led to considerable improvements as well. The encouraging results achieved represent an important step in the development of ultrasonic plastic welding for multi-material joining in the automotive industry.

scholarly journals Multi-Objective Optimization of Resistance Welding Process of GF/PP Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2560
Author(s):  
Guowei Zhang ◽  
Ting Lin ◽  
Ling Luo ◽  
Boming Zhang ◽  
Yuao Qu ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Welding Process ◽  
Welding Current ◽  
Resistance Welding ◽  
Thermoplastic Composites ◽  
Current Time ◽  
Process Factor ◽  
Welding Equipment ◽  
Lap Shear ◽  
Adhesive Connections

Thermoplastic composites (TPCs) are promising materials for aerospace, transportation, shipbuilding, and civil use owing to their lightweight, rapid prototyping, reprocessing, and environmental recycling advantages. The connection assemblies of TPCs components are crucial to their application; compared with traditional mechanical joints and adhesive connections, fusion connections are more promising, particularly resistance welding. This study aims to investigate the effects of process control parameters, including welding current, time, and pressure, for optimization of resistance welding based on glass fiber-reinforced polypropylene (GF/PP) TPCs and a stainless-steel mesh heating element. A self-designed resistance-welding equipment suitable for the resistance welding process of GF/PP TPCs was manufactured. GF/PP laminates are fabricated using a hot press, and their mechanical properties were evaluated. The resistance distribution of the heating elements was assessed to conform with a normal distribution. Tensile shear experiments were designed and conducted using the Taguchi method to evaluate and predict process factor effects on the lap shear strength (LSS) of GF/PP based on signal-to-noise ratio (S/N) and analysis of variance. The results show that current is the main factor affecting resistance welding quality. The optimal process parameters are a current of 12.5 A, pressure of 2.5 MPa, and time of 540 s. The experimental LSS under the optimized parameters is 12.186 MPa, which has a 6.76% error compared with the result predicted based on the S/N.

scholarly journals Static ultrasonic welding of carbon fibre unidirectional thermoplastic materials and the influence of heat generation and heat transfer

2021 ◽  
pp. 002199832097681
Author(s):  
F Köhler ◽  
IF Villegas ◽  
C Dransfeld ◽  
A Herrmann
Keyword(s):  
Cross Sections ◽  
Weld Line ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Thermoplastic Composites ◽  
Squeeze Flow ◽  
Anisotropic Flow ◽  
Lap Shear ◽  
Anisotropic Thermal Conductivity ◽  
Edge Defects

Ultrasonic welding is a promising technology to join fibre-reinforced thermoplastic composites. While current studies are mostly limited to fabric materials the applicability to unidirectional materials, as found in aerospace structures, would offer opportunities for joining primary aircraft structures. However, due to the highly anisotropic flow of a molten unidirectional ply undesired squeeze flow phenomena can occur at the edges of the weld overlap. This paper investigates how the fibre orientation in the plies adjacent to the weld line influences the welding process and the appearance of edge defects. Ultrasonic welding experiments with different layups and energy director configurations were carried out while monitoring temperatures at different locations inside and outside the weld overlap. The joints were characterized by single lap shear tests, analysis of corresponding fracture surfaces and microscopic cross-sections. Results showed that the anisotropic flow and the anisotropic thermal conductivity of the plies adjacent to the weld line have a distinct effect on the appearance and location of edge defects. By using energy directors that cover only part of the weld overlap area a new approach was developed to mitigate edge defects caused by the highly directional properties of the unidirectional plies.

The Effect of Infill Patterns and Annealing on Mechanical Properties of Additively Manufactured Thermoplastic Composites

2017 ◽  
Author(s):  
Sridher Rangisetty ◽  
Larry D. Peel
Keyword(s):  
Best Practices ◽  
Composite Structures ◽  
Fused Deposition Modeling ◽  
Mechanical Performance ◽  
Short Fiber ◽  
Thermoplastic Composite ◽  
Thermoplastic Composites ◽  
Limited Information ◽  
Fused Deposition ◽  
Reinforced Thermoplastics

Recently, carbon fiber-reinforced thermoplastics (CFRTPs) have become popular choices in desktop-based additive manufacturing, but there is limited information on their effective usage. In Fused Deposition Modeling (FDM), a structure is created by layers of extruded beads. The degree of bonding between beads, bead orientation, degree of interlayer bonding, type of infill and the type of material, determines overall mechanical performance. The presence of chopped fibers in thermoplastics increases melt viscosity, changes coefficients of thermal expansion, may have layer adhesion issues, and causes increased wear on nozzles, which makes FDM fabrication of thermoplastic composites somewhat different from neat thermoplastics. In the current work, best practices and the effect of annealing and infill patterns on the mechanical performance of FDM-fabricated composite parts were investigated. Materials included commercially available PLA, CF-PLA, ABS, CF-ABS, PETG, and CF-PETG. Two sets of ASTM D638 tensile and ASTM D790 flexural test specimens with 3 different infill patterns and each material were fabricated, one set annealed, and all tested. Anisotropic behavior was observed as a function of infill pattern. As expected, strength and stiffness were higher when the beads were oriented in the direction of the load, even for neat resins. All fiber-filled tensile results showed an increase in stiffness, but surprisingly, not in strength (likely due to very short fiber lengths). Tests of annealed specimens resulted in clear improvements in tensile strength, tensile stiffness and flexural strength for PLA, CF-PLA, and PETG, CF-PETG but a reduction in flexural stiffness. Also, annealing resulted in mixed improvements for ABS and CF-ABS and is only useful in certain infill patterns. This work also establishes ‘Best Practices’ of FDM-type fabrication of thermoplastic composite structures and documents the minimum critical fiber lengths and fiber fractions of several CF-filled FDM filaments.

Modelling resistance welding of thermoplastic composites with a nanocomposite heating element

2020 ◽  
pp. 002199832095705
Author(s):  
David Brassard ◽  
Martine Dubé ◽  
Jason R Tavares
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Welding Process ◽  
Element Model ◽  
Resistance Welding ◽  
Thermoplastic Composites ◽  
Process Window ◽  
Cohesive Failure ◽  
Electrically Conductive ◽  
Lap Shear

Electrically conductive nanocomposite heating elements are being developed as a complement to traditional carbon fibre or stainless steel heating elements in resistance welding of thermoplastic composites. Here we present the development of a finite element model of the resistance welding process with these new heating elements, from which we establish a process window for high quality welded joints. The finite element model results were validated experimentally and a lap shear strength improvement of 28% is reported relative to previously published results. Fractography analysis of the broken joints revealed a thin-layer cohesive failure mode due to the brittleness of the nanocomposite heating elements.

The Consequence on Structural Adhesive Bonding of Humid Thermoplastic Composites and Possibilities of Prevention

2015 ◽  
Vol 825-826 ◽  
pp. 490-497
Author(s):  
Anselm Tobias Bochtler ◽  
Christian Knappe ◽  
Klaus Dilger
Keyword(s):  
Bonding Strength ◽  
Adhesive Bonding ◽  
Lightweight Design ◽  
Dissimilar Materials ◽  
Negative Influence ◽  
Thermoplastic Composites ◽  
Lap Shear ◽  
Lap Shear Test ◽  
Paint Drying ◽  
Cutting Processes

A modern lightweight design with dissimilar materials such as metals in combination with fiber-reinforced polycaprolactam represents a possible lightweight variant in the automotive body shop. One of the issues arising from the use of polycaprolactam is its hygroscopy. The collected moisture evaporates out during the curing of the adhesive in the paint drying process and causes the adhesive to foam up. This leads to a decrease of the structural bonding strength. Many different factors, such as waterjet cutting processes, transportation and storage in undefined environmental conditions before the gluing process, as well as the flushing bath of the painting pretreatment, can contribute to the component humidity.Based on the common lap-shear test, this essay presents the influence of the substrate humidity on the bonding strength as well as possible pretreatment methods to avoid or decrease the negative influence of the substrate humidity. Using infrared radiation or atmosphere plasma localized at the bonding spot, the substrate begins to dry resulting in a bond with better bonding strength. For the future it is planned to test other options like laser substrate drying, adhesive modifications with regard to viscosity and moisture catcher enrichment.

scholarly journals Joining of Thermoplastic Composites with Metals Using Resistance Element Welding

2020 ◽  
Vol 10 (20) ◽  
pp. 7251 ◽  
Author(s):  
Juliane Troschitz ◽  
Julian Vorderbrüggen ◽  
Robert Kupfer ◽  
Maik Gude ◽  
Gerson Meschut
Keyword(s):  
Welding Process ◽  
Thermoplastic Composites ◽  
Innovative Technology ◽  
Welding Parameters ◽  
Compression Moulding ◽  
Steel Sheets ◽  
Lap Shear ◽  
Before And After ◽  
Resistance Element Welding ◽  
Glass Fibre Reinforced

Joining is a key enabler for a successful application of thermoplastic composites (TPC) in future multi-material systems. To use joining technologies, such as resistance welding for composite-metal joints, auxiliary joining elements (weld inserts) can be integrated into the composite and used as an interface. The authors pursue the approach of embedding metal weld inserts in TPC during compression moulding without fibre damage. The technology is based on the concept of moulding holes by a pin and simultaneously placing the weld insert in the moulded hole. Subsequently, the composite component can be joined with metal structures using conventional spot welding guns. For this purpose, two different types of weld inserts were embedded in glass fibre reinforced polypropylene sheets and then welded to steel sheets. A simulation of the welding process determined suitable welding parameters. The quality of the joints was analysed by microsections before and after the welding process. In addition, the joint strength was evaluated by chisel tests as well as single-lap shear tests for the different weld insert designs. It could be shown that high-quality joints can be achieved by using the innovative technology and that the load-bearing capacity is significantly influenced by the weld inserts head design.

Microstructure and Mechanical Performance of Cold Metal Transfer Spot Joints of AA6061-T6 to Galvanized DP590 Using Edge Plug Welding Mode

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Haiyang Lei ◽  
Yongbing Li ◽  
Blair E. Carlson ◽  
Zhongqin Lin
Keyword(s):  
Mechanical Performance ◽  
Welding Process ◽  
Metal Transfer ◽  
Weld Nugget ◽  
Weld Strength ◽  
Welding Parameters ◽  
Feed Speed ◽  
Cold Metal Transfer ◽  
Lap Shear ◽  
Cold Metal

Dissimilar joining of aluminum to steel poses a challenge for arc welding. In this study, aluminum AA6061-T6 and hot dipped galvanized DP590 steel were joined using the Fronius cold metal transfer (CMT) welding process applying an edge plug welding mode (EPW). The correlation of the welding parameters, weld characteristics, and weld strength was systematically investigated. It was found that the EPW mode created a zinc-rich zone at the weld root along the Al–steel faying interface which transitioned to a continuous and compact intermetallic compounds (IMC) layer in the middle portion of the joint. The fracture propagation in lap-shear specimens was affected by this increase of IMC layer thickness. At a wire feed speed (wfs) of 5.6 m/min, the fracture initiated along the zinc-rich layer at the faying interface and then, upon meeting the compact IMC layer, propagated into the aluminum weld nugget. Propagation followed a path within the weld nugget along the boundary between columnar and equiaxed grains leading to weld nugget pullout upon fracture. For IMC layer peak thicknesses below 10 μm, the strength increased as a function of weld nugget diameter. However, larger heat inputs resulted in IMC layer thicknesses greater than 10 μm and interfacial fracture.

scholarly journals Novel Process Approach for in-situ Insertion of Functional Elements in RTM-Applications

2016 ◽  
Vol 6 (1) ◽  
pp. 15 ◽  
Author(s):  
Mathias Bobbert ◽  
Florian Augethaler ◽  
Zheng Wang ◽  
Thomas Troster ◽  
Gerson Meschut
Keyword(s):  
Mechanical Performance ◽  
Lightweight Design ◽  
Process Approach ◽  
Functional Elements ◽  
Reinforced Plastics ◽  
Rtm Process ◽  
Pull Out ◽  
New Process ◽  
Transfer Moulding

Lightweight design in vehicles leads to an increasing use of fibre-reinforced-plastics (FRP). To ensure the possibility of detachable joints in those constructions specific joining technologies have to be developed. Available technologies are not suitable for mass production or are leading to damage in the FRP. The aim of this paper is to show the possibilities and the general feasibility of a new process approach for the application of functional elements in FRP or hybrid materials during resin transfer moulding (RTM) processes. Therefore the movement of the RTM-tool-punch is utilised to produce an interlock between the splay stud and the fibres of the non-consolidated preform. This enables the application of the elements during the RTM-process. The resin infusion leads to the consolidation of the CFRP and a further fixation of the splay stud. Pull-out-tests as well as torsion tests are showing the mechanical performance of the joints.

New Possibility for the Connection of Metal Sheets and Fiber Reinforced Plastics

2011 ◽  
Vol 690 ◽  
pp. 465-468 ◽  
Author(s):  
Stephan A. Ucsnik ◽  
Georg Kirov
Keyword(s):  
Adhesive Bonding ◽  
Load Transfer ◽  
Reaction Force ◽  
Welding Process ◽  
Cold Metal Transfer ◽  
Reinforced Plastics ◽  
Lap Shear ◽  
Metal Sheets ◽  
Form Closure ◽  
Cold Metal

This research paper presents a new possibility for the connection of metal sheets and fibre reinforced plastics (FRPs) through a cold metal transfer welding process. Small metal projections (pins) are welded onto metal surfaces by introduction of additional filler wire. These provide the possibility for building up a fixation with composites through fibre-friendly form-closure and co-curing. Results of tensile loaded double-lap shear geometries are presented for three types of pin geometries. The hybrid joints will be characterized and compared in terms of maximum reaction force and failure history. Joints with cylindrical and spiky pins inside show a certain load transfer capability, where ultimate bearing load and post failure behaviour have a high dependence on the quality of the co-cured adhesive bonding and the bending characteristics of the pins. Joints with spherical ending pins show twice as high ultimate bearing loads at a much more distinctive joint expansion.

scholarly journals ROBOTIC SEQUENTIAL ULTRASONIC WELDING OF THERMOPLASTIC COMPOSITES: PROCESS DEVELOPMENT AND TESTING

2021 ◽  
Author(s):  
ABHAS CHOUDHARY, ◽  
IRENE FERNANDEZ
Keyword(s):  
Welded Joints ◽  
Industrial Robot ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Thermoplastic Composite ◽  
Thermoplastic Composites ◽  
Robot Arm ◽  
Spot Welds ◽  
Robotic Platform ◽  
Lap Shear

Multi-spot sequential ultrasonic welding is a promising joining technique for fibre-reinforced thermoplastic composites structures (TPC). In existing research on the multi-spot sequential ultrasonic welding process, welds are produced through the use of a static table-top welding machine, at a coupon level. However, in order to apply this joining technology to large structures, the welding process needs to be up-scaled through the use of a robotic platform. At the Smart Advanced Manufacturing (SAM|XL) automation field lab and TU Delft Aerospace Engineering, a robotic sequential ultrasonic welding system has been developed. The system consists of a welding end-effector (EEF) equipped with various sensors that enable online process monitoring and control, which can be mounted on an industrial robot arm to perform sequential multi-spot welds. The goal of this study was to assess the welding performance of the ultrasonic welding EEF, which was mounted on an industrial KUKA KR210 R2700 Extra 10-axis robot arm, by comparing it to the performance of welds produced through the static table-top machine. In this study, single and multi-spot welds were produced on thermoplastic composite coupons, based on welding conditions which were defined in a preliminary study. The robot and EEF deflections observed during the welding process were analysed to assess the deviation of the robotic process from the static one. The feedback obtained from the welding equipment in terms of consumed power and tool displacement in both processes was also compared. The weld quality was assessed though single lap shear testing of the welded joints as well as fractography of the failure surface. The results of this study indicate that the developed robotic welding process is quite robust and is capable of producing high-quality sequential welded joints despite significant system deflections observed during the welding process. Slightly lower welded area and weld strength was obtained which can be attributed to the system deflections. Finally, the results indicate that the use of a stiffer robotic platform as well as a stiffer EEF construction will result in better system rigidity and weld spot positioning accuracy, and through this the welding process shows promise for large-scale industrial applications.

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