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.

scholarly journals A Study on Through-the-Thickness Heating in Continuous Ultrasonic Welding of Thermoplastic Composites

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6620
Author(s):  
Bram C. P. Jongbloed ◽  
Julie J. E. Teuwen ◽  
Rinze Benedictus ◽  
Irene Fernandez Villegas
Keyword(s):  
Vibrational Energy ◽  
Continuous Process ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Thermoplastic Composites ◽  
Squeeze Flow ◽  
Transfer Model ◽  
Welding Interface ◽  
Energy Director ◽  
Energy Share

Continuous ultrasonic welding is a promising technique for joining thermoplastic composites structures together. The aim of this study was to gain further insight into what causes higher through-the-thickness heating in continuous ultrasonic welding of thermoplastic composites as compared to the static process. Thermocouples were used to measure temperature evolutions at the welding interface and within the adherends. To understand the mechanisms causing the observed temperature behaviours, the results were compared to temperature measurements from an equivalent static welding process and to the predictions from a simplified heat transfer model. Despite the significantly higher temperatures measured at the welding interface for the continuous process, viscoelastic bulk heat generation and not thermal conduction from the interface was identified as the main cause of higher through-the-thickness heating in the top adherend. Interestingly the top adherend seemed to absorb most of the vibrational energy in the continuous process as opposed to a more balanced energy share between the top and bottom adherend in the static process. Finally, the higher temperatures at the welding interface in continuous ultrasonic welding were attributed to pre-heating of the energy director due to the vibrations being transmitted downstream of the sonotrode, to reduced squeeze-flow of energy director due to the larger adherend size, and to heat flux originating downstream as the welding process continues.

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.

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.

The Effects of Energy Director Shape on Temperature Field during Ultrasonic Welding of Thermoplastic Composites

2007 ◽  
Vol 353-358 ◽  
pp. 2007-2010 ◽  
Author(s):  
Jiu Chun Yan ◽  
Xiao Lin Wang ◽  
Rui Qi Li ◽  
Hui Bin Xu ◽  
Shi Qin Yang
Keyword(s):  
Welding Process ◽  
Element Model ◽  
Ultrasonic Welding ◽  
The Body ◽  
Thermoplastic Composite ◽  
Thermoplastic Composites ◽  
Glass Transformation ◽  
Different Shapes ◽  
Energy Director ◽  
Different Order

The ultrasonic welding process of thermoplastic composite with different shapes of energy director (ED) was simulated using finite element model. The results show that the highest temperature zone locates at the tip for the semicircular and triangular ones, and locates at the middle height for the trapezoid one. But it does not locate at the body of ED for the rectangular one. Energy director with different shapes lead to the temperature rising rate at different order of amplitude. The welding amplitude has same influence on the four shapes of ED. The temperature distributing profiles of semicircular, triangular and trapezoid ED keep constant from the initial welding time to that when the highest temperature on joints arrives the temperature of glass transformation (Tg), but the profile for rectangular ED changes greatly.

scholarly journals Continuous ultrasonic welding of thermoplastic composites: Enhancing the weld uniformity by changing the energy director

2019 ◽  
Vol 54 (15) ◽  
pp. 2023-2035 ◽  
Author(s):  
Bram Jongbloed ◽  
Julie Teuwen ◽  
Genevieve Palardy ◽  
Irene Fernandez Villegas ◽  
Rinze Benedictus
Keyword(s):  
Thin Film ◽  
Heat Generation ◽  
High Speed ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Thermoplastic Composites ◽  
Weld Strength ◽  
Good Contact ◽  
Energy Director ◽  
Welded Seam

Continuous ultrasonic welding is a high-speed joining method for thermoplastic composites. Currently, a thin film energy director is used to focus the heat generation at the interface. However, areas of intact energy director remain in the welded seam, which significantly lowers the weld strength, and result in a non-uniformly welded seam. To improve the weld uniformity of continuous ultrasonically welded joints, we changed to a more compliant energy director. A woven polymer mesh energy director was found to give a significant improvement in weld quality. The mesh was flattened in between the composite adherends during the welding process. This flattening promoted a good contact between the energy director and the adherends, fully wetting the adherend surfaces, resulting in a more uniformly welded seam without areas of intact energy director.

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.

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 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.

scholarly journals Ultrasonic Welding of Novel Carbon/Elium® Thermoplastic Composites with Flat and Integrated Energy Directors: Lap Shear Characterisation and Fractographic Investigation

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1634 ◽  
Author(s):  
Somen K. Bhudolia ◽  
Goram Gohel ◽  
Jayaram Kantipudi ◽  
Kah Fai Leong ◽  
Robert J. Barsotti
Keyword(s):  
Polymer Matrix Composites ◽  
Research Work ◽  
Ultrasonic Welding ◽  
Industrial Applications ◽  
Thermoplastic Composites ◽  
Matrix Composites ◽  
Thermoplastic Resin ◽  
Lap Shear ◽  
Weld Time ◽  
Transfer Moulding

The current research work presents a first attempt to investigate the welding attributes of Elium® thermoplastic resin and the fusion bonding using ultrafast ultrasonic welding technique. The integrated energy director (ED) polymer-matrix composites (PMCs) panel manufacturing was carried out using the Resin Transfer Moulding (RTM) technique and the scheme is deduced to manufacture a bubble-free panel. Integrated ED configurations and flat specimens with Elium® film of different thickness at the interface were investigated for ultrasonic welding optimization. Optimised weld time for integrated ED and flat Elium® panels with film (0.5 mm thick) configuration was found to be 1 s and 5.5 s, respectively. The ED integrated configuration showed the best welding results with a lap shear strength of 18.68 MPa. The morphological assessment has shown significant plastic deformation of Elium® resin and the shear cusps formation, which enhances the welding strength. This research has the potential to open up an excellent and automated way of joining Elium® composite parts in automotive, wind turbines, sports, and many other industrial applications.

scholarly journals Development and Evaluation of the Ultrasonic Welding Process for Copper-Aluminium Dissimilar Welding

2022 ◽  
Vol 6 (1) ◽  
pp. 6
Author(s):  
Rafael Gomes Nunes Silva ◽  
Sylvia De Meester ◽  
Koen Faes ◽  
Wim De Waele
Keyword(s):  
Cross Sections ◽  
Welding Process ◽  
Weld Interface ◽  
Ultrasonic Welding ◽  
Dissimilar Welding ◽  
Dissimilar Metals ◽  
Weld Quality ◽  
Metallographic Examination ◽  
Metallurgical Defects ◽  
The Impact

The demand for joining dissimilar metals has exponentially increased due to the global concerns about climate change, especially for electric vehicles in the automotive industry. Ultrasonic welding (USW) surges as a very promising technique to join dissimilar metals, providing strength and electric conductivity, in addition to avoid metallurgical defects, such as the formation of intermetallic compounds, brittle phases and porosities. However, USW is a very sensitive process, which depends on many parameters. This work evaluates the impact of the process parameters on the quality of ultrasonic spot welds between copper and aluminium plates. The weld quality is assessed based on the tensile strength of the joints and metallographic examination of the weld cross-sections. Furthermore, the welding energy is examined for the different welding conditions. This is done to evaluate the influence of each parameter on the heat input resulting from friction at the weld interface and on the weld quality. From the obtained results, it was possible to optimise parameters to achieve satisfactory weld quality in 1.0 mm thick Al–Cu plate joints in terms of mechanical and metallurgical properties.

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