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 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 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 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.

Features of the Heating Process in Ultrasonic Welding of Polycarbonate Products under Independent Pressure

2020 ◽  
pp. 54-62
Author(s):  
S.S. Volkov ◽  
A.L. Remizov ◽  
A.S. Pankratov
Keyword(s):  
Welded Joints ◽  
Welded Joint ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Heating Process ◽  
Mechanism Of Formation ◽  
High Quality ◽  
Acoustic Contact ◽  
Welding Pressure

This paper presents a mechanism of formation of a hard-to-weld polycarbonate joint by ultrasonic welding. The method utilizes internal and external friction occurring in the welded joint area on abutting surfaces due to shear vibrations of the end of the upper part relative to the lower part. A layer of the heated welded material is formed, localized by thickness, in which predominant absorption of the ultrasonic vibrations occurs, which allows one to obtain high-quality and durable welded joints without significant deformation due to the concentration of thermal energy in the welding zone. The effect of independent welding pressure on the strength of the welded joint of polycarbonate is considered. A new method of ultrasonic welding under the conditions of independent pressure is proposed. The method consists of dividing the static welding pressure into two components: the pressure of the acoustic contact in the zone of contact of the waveguide with the product, and the welding pressure that compresses the welded products, with the latter component being lower than the former. In order to obtain high-quality welded joints made of polycarbonate and to prevent displacement of the welded edges during the welding process relative to each other, a special preparation of the welded edges is developed, which allows one part to be moved vertically relative to the other during the welding process. It is established that the quality of welding depends on the speed of movement and the angle of cutting the edges.

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.

scholarly journals Advances in Ultrasonic Welding of Thermoplastic Composites: A Review

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1284 ◽  
Author(s):  
Somen K. Bhudolia ◽  
Goram Gohel ◽  
Kah Fai Leong ◽  
Aminul Islam
Keyword(s):  
Composite Structures ◽  
Dissimilar Materials ◽  
Processing Parameters ◽  
Ultrasonic Welding ◽  
Thermoplastic Composite ◽  
Thermoplastic Composites ◽  
Pressure Amplitude ◽  
Advantages And Disadvantages ◽  
Cost Efficient ◽  
Weld Time

The ultrasonic welding (UW) technique is an ultra-fast joining process, and it is used to join thermoplastic composite structures, and provides an excellent bonding strength. It is more cost-efficient as opposed to the conventional adhesive, mechanical and other joining methods. This review paper presents the detailed progress made by the scientific and research community to date in the direction of the UW of thermoplastic composites. The focus of this paper is to review the recent development of the ultrasonic welding technique for thermoplastic composites to thermoplastic composites, and to dissimilar materials. Different ultrasonic welding modes and their processing parameters, namely, weld time, weld pressure, amplitude, type of energy directors (EDs) affecting the welding quality and the advantages and disadvantages of UW over other bonding techniques, are summarized. The current state of the ultrasonic welding of thermoplastic composites and their future perspectives are also deliberated.

scholarly journals The dangers of single-lap shear testing in understanding polymer composite welded joints

2021 ◽  
Vol 379 (2203) ◽  
pp. 20200296 ◽  
Author(s):  
Irene Fernandez Villegas ◽  
Calvin Rans
Keyword(s):  
Polymer Composite ◽  
Welded Joints ◽  
Failure Modes ◽  
Local Heating ◽  
Welding Process ◽  
Joint Mechanics ◽  
Process Testing ◽  
Lap Shear ◽  
Design Values ◽  
Welding Processes

Single-lap shear (SLS) joints are straightforward to manufacture. This makes them especially attractive for testing polymer composite welded joints. Owing to local heating, which is characteristic of composite welding processes, the production of more geometrically intricate joints (such as double-lap or scarfed joints) or bigger joints (such as end-notched flexure or double cantilever beam) typically entails significant complexity in the design of the welding process. Testing of SLS joints is also uncomplicated and, even though, owing to mixed-mode loading and uneven stress distribution, it does not provide design values, it is widely acknowledged as a valuable tool for comparison. Even so, comparing different aspects of composite welded joints through their corresponding SLS strength values alone can be deceptive. This paper shows that comparison of different welding processes, adherend materials, process parameters or different types of joining techniques through SLS testing is only meaningful when strength values are combined with knowledge on other aspects of the joints such as joint mesostructure, failure modes and joint mechanics. This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’.

Investigation of ultrasonically welded thermoplastic composite joints using netlike energy directors

2021 ◽  
pp. 1-23
Author(s):  
Kaifeng Wang ◽  
Xue Wang ◽  
Miran Yi ◽  
Yang Li ◽  
Jingjing Li
Keyword(s):  
Welding Process ◽  
Cyclic Strain ◽  
Fracture Morphology ◽  
Ultrasonic Welding ◽  
Thermoplastic Composite ◽  
Shear Load ◽  
Cross Sectional ◽  
Pull Out ◽  
Joint Fracture ◽  
Joint Quality

Abstract This paper proposes a netlike energy director (ED) made of carbon fiber-reinforced thermoplastic (CFRP) composites to improve the ultrasonic welding energy efficiency. To explore the benefits of using netlike EDs, the joint qualities with flat EDs and without EDs are included for references. Also, the influence of the netlike ED geometry (i.e., hexagonal nets with different side lengths and thicknesses) on weld attributes and joint quality are investigated in terms of joint cross-sectional microstructure, fracture morphology, and maximum shear load. It is found that for both the netlike and flat EDs, the welding process can be accelerated compared to the one without EDs, which is caused by the concentration of welding energy into the expected welding region and the avoidance of welding edges introduced by surface curvature. Meanwhile, compared with flat EDs, the maximum shear loads of the joints with netlike EDs are improved, introduced by the decrease of the contact area and consequent higher cyclic strain, resulting in more melted materials during the ultrasonic welding process. However, with the increasing of the netlike ED thickness, more porosities are generated in the welding layer leading to reduced bonded region and decrease of the maximum shear load. From the joint fracture morphology analysis, it is found that the netlike EDs introduces carbon fibers in the welding layer, and the fracture modes include fiber-matrix debonding and fiber pull-out in addition to polymer fracture, confirming the feasibility of improving joint quality by introducing CFRP netlike EDs.

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