Ultrasonic Plastic Welding Research Articles

Ultrasonic welding of continuous carbon fiber reinforced PEEK with embossed energy directors

Ultrasonic plastic welding (UPW) is an efficient and environmentally friendly method for joining carbon fiber reinforced thermoplastic (CFRTP). A crucial aspect of UPW is the design of the energy director (ED). In this study, ultrasonic embossing technology was used to process flat EDs to obtain a new type of ED, named embossed ED. The effect of embossed EDs on the joint formation in ultrasonic welding of continuous carbon fiber reinforced PEEK was investigated in terms of tensile shear properties, macro and micro-morphologies, and fracture morphology. The results show that the use of embossed EDs makes a more homogeneous temperature distribution at the welding interface which significantly reduces defects in the joint. The use of embossed EDs increases the failure load of welded joints by about 50 % (up to 39.6 MPa) and reduces the variation of the joint quality compared with the use of flat EDs. In the optimal condition, the joints made with embossed EDs experiences interlaminar failure of the base material.

Ultrasonic welding of CF/PA6 composite to 6061Al alloy utilizing an interfacial coating as energy director

This study investigates ultrasonic plastic welding to join the carbon fiber-reinforced thermoplastics and 6061Al alloy in a lap-type joint configuration. An interfacial polymer coating through a fluidized bed on aluminum alloy was considered an energy director, as it was essential for concentrating heat at the interface during welding. The significant ultrasonic process setting (weld pressure: 0.5 MPa, weld time: 600 ms, hold time: 1000 ms) was statistically realized for a maximum lap shear strength of the joint that showed the interlaminar shear (first-layer ply) failure of the composite, while the welding interface morphology revealed interdiffusion of thermoplastics with the load-bearing carbon fibers attached to the composite-coating resin mixtures, whereas the coating interface offered a strong adhesion of polymer on the aluminum surface asperities through mechanical interlocking. An efficient multi-material joint was obtained within 1.6 s in comparison to the adhesive bonding technology that required at least 20 min. Additionally, the interfacial coating serves as an insulator, avoiding galvanic corrosion in joints as well as fretting damage. The encouraging findings of this research provide deeper insight into joining thermoplastic composites to metals by ultrasonic plastic welding without the use of a separate energy director, which simplifies the process of industrialization.

Numerical calculation and analysis of temperature field in ultrasonic welding of polypropylene dialyzer

Ultrasonic plastic welding is widely used in the bonding process of medical device accessories. In this paper, a thermo-force indirect coupling finite element analysis model was established in the ultrasonic plastic welding process between the blood cap and the shell of polypropylene (PP) dialyzer. The temperature field distribution between the blood cap and the shell was simulated and analyzed by using finite element analysis software, and the influence of welding process parameters on the temperature field was studied. The results show that: by changing the ultrasonic amplitude parameters, welding time parameters, initial pressure, etc., the longer the ultrasonic welding time, the temperature of the welding area will increase. In order to ensure the quality of the dialyzer, it should be controlled within 0.8-1 seconds. The increase of ultrasonic amplitude will make the welding temperature continue to rise, and in order to avoid poor welding, the amplitude should not exceed 120 ?m. The initial pressure has little effect on the temperature field.

Effect of ultrasonic embossing and welding time on the joint performance of ultrasonically welded short carbon fiber reinforced PEEK

Ultrasonic plastic welding (UPW) is a highly efficient and environmental friendly method that has gained gradually increased attention in joining carbon fiber reinforced thermoplastic (CFRTP). A crucial aspect in UPW of CFRTP is the design of the energy director (ED). This paper employs ultrasonic embossing, a cost-effective way to manufacture ED on the surface of CFRTP sheets. The effect of ultrasonic embossing time and welding time on the joint performance is investigated in terms of microstructure, tensile-shear property, and fracture surface morphology. The results show that the structured surface made by ultrasonic embossing can be used as ED to concentrate welding energy. This process reduces the randomness and dispersion of weld distribution, improves the failure load of welded joints by 30 % compared with the joints made without using ED. The ultrasonic embossing time has a limited influence on the joint failure load. Sound welded joints can be obtained when welding with one structured surface and welding time of 1.5 s.

Enhancing the ultrasonic plastic welding strength of Al/CFRTP joint via coated metal surface and structured composite surface

Ultrasonic plastic welding (UPW) is a promising technology for joining metal to carbon fiber reinforced thermoplastic composite (CFRTP) but shows poor joint strength in the existing studies. This work conducts UPW of AA6061 aluminum alloy to carbon fiber reinforced PA66 (CF/PA66) by employing a polymer coating as an interlayer. Simple metal surface grinding and silane coupling agent (SCA) treatment are used to strengthen the bonding of the metal/coating interface. Structured CF/PA66 surface fabricated by ultrasonic embossing acts as energy directors to improve the bonding strength of the coating/plastic interface. The results show that relatively high tensile-shear strength (about 31.0 MPa) can be obtained. Micro-mechanical interlocking and chemical bonding (Al-O-C and Al-O-Si bonds) are considered as the bonding mechanism of the metal/coating interface.

Optimizing the Control Level Factors of an Ultrasonic Plastic Welding Machine Affecting the Durability of the Knots of Trawl Nets Using the Taguchi Experimental Method

Ultrasonic welding is a high-frequency method of welding that uses mechanical energy to generate heat. This is a clean welding method and very suitable for plastic welding. In this study, using the Taguchi experimental method, the control factors of an ultrasonic plastic welding machine were optimized to affect the durability of knots of trawl nets made from polyamide (PA) and polypropylene (PP) filaments as an alternative to the traditional mesh knitting method. After optimization, the PA knots had an amplitude of 32 µm (34%), a welding pressure of 2.5 kg/cm2 (41%), a hold time of 0.35 s (24%), and a speed of 5.5 mm/s (1%). The knots made of PP filament had relatively stable strength after optimization, with an amplitude of 36 µm (25%), a welding pressure of 2.0 kg/cm2 (22%), a hold time of 0.25 s (16%), and a speed of 6.0 mm/s (37%). Finally, validation experiments were conducted to verify the results obtained in this study.

CORRIGENDUM to Interconnecting embroidered hybrid conductive yarns by ultrasonic plastic welding for e-textiles

CORRIGENDUM to Interconnecting embroidered hybrid conductive yarns by ultrasonic plastic welding for e-textiles

Технологические особенности ультразвуковой сварки разнородных пластмасс

The paper considers technological features of heterogeneous plastics ultrasonic welding, which specificity is manifested in the volumetric interaction nature. Results of studying the mechanism of a welded joint formation showed that micro-volumes mixing, polymer molecules mutual diffusion in the contacting surfaces and emergence of the new chemical bonds with the block copolymers formation were the simultaneous processes. Their common feature was that all these processes proceeded in the temperature range corresponding to the polymer viscous-flow state. It was experimentally confirmed that one of the criteria for weldability of the heterogeneous plastics was their compatibility in terms of acoustic properties being estimated by the melt density and viscosity. Technological methods were proposed making it possible to compensate for differences in the welded materials acoustic properties, and thereby obtain the high-quality welded joints. Four stages of the welded joints formation mechanism were determined during ultrasonic welding of the heterogeneous plastics. It was established that physical and mechanical properties of the heterogeneous plastics were playing a decisive role in the mechanism of heat generation during the ultrasonic welding. An ultrasonic welding unit for welding the heterogeneous plastics in vacuum was developed.

Measurement of vibration transmitted through welded object and welding strength in ultrasonic welding

Ultrasonic welding of plastics has been used in a wide range of industries and improving welding quality and production speed are still important issues. This paper introduces a method to evaluate the welding condition during welding. In this method, vibrations propagated during welding were acquired using a piezoelectric element. By fast fourier transform analysis, tracking analysis, and calculation of the data, the total harmonic distortion with the welding time was obtained. The welding condition can be determined by comparing the welding strength against the welding time obtained from the 180° peeling test. As a result, it was found that the propagated vibration has characteristics that indicate the completion of welding, making it possible to efficiently evaluate the quality of the weld.

Submerged ultrasonic plastic welding: A computational and experimental investigation

Thermoplastics hold utmost importance in the day-to-day life of modern-day society, being widely employed in water transport and storage vessels commonly made from thermoplastics such as PVC, i.e., polyvinyl chloride, and PP, i.e., polypropylene. This urge for a joining technique is applicable even with water in the vessel or the submerged case. The present investigation explores ultrasonic welding as an option to weld thermoplastics in water-submerged conditions. We have performed FEM simulations and experimental validation to prove the viability of the proposed ultrasonic welding process used in welding PVC and PP in water-submerged conditions. The discussed results demonstrate a decrease in melting and degradation of adherend material at the weld interface while welding PVC and PP in water-submerged conditions and attaining 65.78% and 107% of weld strength, unlike their open-air counterparts, respectively.

Design Optimization of Two Diagonal Slotted Block Horn for Ultrasonic Plastic Welding

One of the inescapable techniques which are widely used in different engineering fields and manufacturing industry is ultrasonic plastic welding. It is recommended to make the design of the main components of ultrasonic technique to have high precision and good accuracy. Ultrasonic horn remains the main components, as this part is always working contact to the working area. Therefore, design and optimization of this tool become more essential due to large number of application. In this research a horn type block contain two slots was successfully designed and its dimensions were precisely optimized utilising from the principles of ANSYS finite element software package, theoretical calculation and mathematical analysis expression in order to conduct the requirements application of plastic welding. The three dimensional model analysis of the block horn was carried out to identified from many criteria such as allow the horn to vibrate in purely longitudinal manner relative to the frequency excitation of generator, normally 20 kHz, obtained acceptable tuning mode and avoidance from participating with other non tuned flexural and torsional modes, insure high sufficient displacement amplitude at working area and low stress concentration shift close to the area of zero deformation, getting high surface uniformity at block horn tip and ensure the horn having acceptable gain. High amplification of block horn with configuration of two slots was calculated using modal and harmonic analyses of simulation models, while optimization of designed horn was done through performing response surface methodology (RSM) matrix obtained from MINITAB software and further connected with genetic algorithm (GA) by aid using of MATLAB software code. The results inferred that good estimation and prediction of vibration amplitude for the exciting slotted block horn can help to ensure sufficient amount of energy delivered to the working area for any application referred to plastic welding.

Analysis on electric impedance-controlled active ultrasonic horn in radial vibration

As a key component of high-powered ultrasonic vibration systems, ultrasonic horns play an important role in various practical application scenarios. Recent advances in longitudinal ultrasonic horns have enabled them to magnify the Langevin transducer's mechanical vibration and efficiently transmit the mechanical vibration to the mechanical load. However, limited research has been devoted to active radial ultrasonic horns in radial vibration. Here we propose an electric impedance-controlled active radial ultrasonic horn (ARUH) capable of tuning both resonance frequency and displacement magnification in radial vibration. The resulting device consists of a radially polarized piezoelectric ring connected with adjustable electric impedance and two metal rings with variable sections. The underlying mechanism is that the change of the converted mechanical impedance of the piezoelectric material by the external electric impedance connected to the piezoelectric material modulates the resonance frequency and displacement magnification of the ARUH. It can be found that the resonant frequency shifts to higher frequencies as the resistance increases and the resonant frequency shifts to lower frequencies as the inductance and capacitance increase, while the displacement magnification has the opposite trend to the resonance frequency. For example, the resonance frequency of the constant-section radial horn is 41130.2 Hz. When the inductance increases from −0.007 to 0.007H, the resonance frequency shifts from 41171.3 to 34606.2 Hz and the displacement magnification moves from 1.189 to 3.5. The experiments are conducted to verify the effectiveness of the resulting device, which is in good agreement with the simulated results and theoretical predictions. Our design with functionality and flexibility opens up possibilities for the design of ARUHs and may find important application prospects in diverse fields such as cold-drawn steel tubes and ultrasonic plastic welding.

Use of Rotary Ultrasonic Plastic Welding as a Continuous Interconnection Technology for Large-Area e-Textiles

For textile-based electronic systems with multiple contacts distributed over a large area, it is very complex to create reliable electrical and mechanical interconnections. In this work, we report for the first time on the use of rotating ultrasonic polymer welding for the continuous integration and interconnection of highly conductive ribbons with textile-integrated conductive tracks. For this purpose, the conductive ribbons are prelaminated on the bottom side with a thermoplastic film, which serves as an adhesion agent to the textile carrier, and another thermoplastic film is laminated on the top side, which serves as an electrical insulation layer. Experimental tests are used to investigate the optimum welding process parameters for each material combination. The interconnects are initially electrically measured and then tested by thermal cycling, moisture aging, buckling and washing tests, followed by electrical and optical analyses. The interconnects obtained are very low ohmic across the materials tested, with resulting contact resistances between 1 and 5 mOhm. Material-dependent results were observed in the reliability tests, with climatic and mechanical tests performing better than the wash tests for all materials. In addition, the development of a heated functional prototype demonstrates a first industrial application.

A cold spray-based novel manufacturing route for flexible electronics

In this research, we propose a cold spray-based novel manufacturing route that enables the custom production of flexible electronics (FE) at high spatial resolution without a need of high-temperature post-sintering process. The proposed manufacturing route sequentially comprises: (1) cold spray metallization; (2) femtosecond laser machining; and (3) ultrasonic plastic welding. First, the flexible polymer (i.e., PET) surface is metallized by cold spray direct writing of Tin (Sn) particles under vacuum-and mask-free conditions. The as-metallized polymer film is then precisely cut into arbitrarily designed high-resolution electrodes (i.e., 500 μm linewidth) by femtosecond laser machining. Lastly, the laser-cut electrodes are joined onto a base polymer substrate via ultrasonic plastic welding to constitute mechanically resilient and conformal FE. In this way, the proposed route enables exploiting the unique features of cold spray deposits in FE (e.g., strong adhesion, high conductivity, minimal thermal input). The resultant printings show excellent electrical conductivity (1.08 × 106 S·m−1), flexibility (60 % elongation), and adhesion strength without significantly compromising intrinsic polymer and functional coating properties. Moreover, a serpentine-shaped flexible microheater (10 × 10 mm2) is also fabricated to demonstrate the viability of the introduced platform in flexible microelectronics. This work potentially provides a promising route toward the rapid, scalable, and cost-effective production of high-resolution and high-performance FE in a mechanically resilient and conformal manner.

Study on the SPCC and CFRTP Hybrid Joint Performance Produced with Additional Nylon-6 Interlayer by Ultrasonic Plastic Welding

Due to the high degree of dissimilarity in physicochemical properties between metal and carbon fiber, it presents a tremendous challenge to join them directly. In this paper, cold rolled steel (SPCC) and carbon fiber reinforced thermoplastic (CFRTP) chopped sheet hybrid joints were produced with the addition of Nylon 6 (PA6) thermoplastic film as an intermediate layer by the ultrasonic plastic welding method. The effect of ultrasonic welding energy and preheating temperature on the hybrid joint microstructure and mechanical behavior was well investigated. The suitable joining parameters could obtain a strong joint by adding the PA6 film as an intermediate layer between the SPCC and bare carbon fibers. Microstructural analysis revealed that the interface joining condition between the PA6 film and the SPCC component is the primary reason for the joint strength. The crevices generated at the interface were eliminated when the preheating temperature arrived at 200 °C, and the joint strength thus significantly increased. The lap shear test results under quasi-static loading showed that the welding energy and preheating temperature synergistically affect the joint performances. At 240 °C, the joint strength value reached the maximum. Through the analysis of the microstructure morphology, mechanical performance, and the failure mechanism of the joint, the optimized joining process window for ultrasonic plastic welding of SPCC-CFRTP by adding an intermediate layer, was obtained.

Interconnecting embroidered hybrid conductive yarns by ultrasonic plastic welding for e-textiles

This article presents a novel approach for the electrical interconnection of embroidered conductive yarns with each other at defined cross-points using ultrasonic spot welding. The electrically conductive yarns are made of silver-coated copper microwires plied with polyester filament fibers into a hybrid embroidery yarn. In this study we evaluated the influence of different material properties (number of microwires of conductive yarn, fabric substrate, and adhesive film), the embroidery designs of contact pads, and the main parameters of the welding process (energy, force, amplitude, and tools) on the welded interconnection. The results were evaluated by the process yield and the contact resistance of the welded contacts. The electrical contacts were then tested for long-term reliability (elevated temperature and humidity, temperature shock change, bending, washing and drying) and analyzed. In addition, the contacts were examined with scanning electron microscopy (SEM) and micro-computed tomography and in the form of cross-sections with optical and SEM techniques to discuss interconnection and failure mechanisms. The results show that ultrasonic spot welding can enable the production of highly reliable interconnections of textile-integrated conductive yarns with contact resistances of a few milliohms that are resistant to mechanical, environmental, and washing conditions, leading to potential new manufacturing processes of e-textiles.

An analytical approach to design horns and boosters of ultrasonic welding machines

This paper presents a new design approach for two main components of an ultrasonic plastic welding machine, booster and horn, based on an analytical model. The design procedure is developed due to the lack of a comprehensive and precise analytical model for rapid design and analysis of these components. The previous analytical models use the one-dimensional wave equation that causes significant errors in designing components with large lateral dimensions. Three-dimensional vibrations are considered for developing an analytical model using the apparent elasticity method. In this way, longitudinal frequency equations are coupled with radial frequency equations by mechanical coupling coefficients. Also, the damping of materials is taken into account. The model can be adapted to calculate the resonant length of the components or calculate the resonant frequency. To verify the model, the results are compared to a numerical simulation. The difference between analytical and numerical resonance frequency is less than 0.02%. Moreover, an experimental modal analysis is performed, which shows 0.9% error with analytical results.Article highlightsA new design approach for boosters and horns has been developed based on an analytical model.Three-dimensional vibrations are considered in the model using the apparent elasticity method.The accuracy of calculating resonant frequencies is more than one-dimensional design method.

Numerical Study of Contact Behavior and Temperature Characterization in Ultrasonic Welding of CF/PA66.

Ultrasonic plastic welding (UPW) is a promising method for joining carbon fiber reinforced thermoplastic (CFRTP). The interface temperature determines weld quality to a large extent. This paper numerically analyzes the contact behavior and temperature characterization during welding using harmonic balance method (HBM). The simulation and experimental results show that amplitude and welding time are important factors determining the interface temperature. Increasing amplitude and welding time can significantly increase the interface temperature. Plunging speed and trigger force have little effect on the interface temperature. For nonlinear contact and heat generation, the results show that there is a certain separation between workpieces and the heat source is mainly friction heat generation in the early stage of welding. With the progress of welding, there is no separation between the workpieces and viscoelastic heat generation begins to dominate.

Numerical simulation of ultrasonic welding for CFRP using energy director

For ultrasonic welding of carbon fiber-reinforced plastics (CFRPs), a sharp shaped resin called the energy director (ED), is usually inserted between them. In this study, finite element analyses for ultrasonic welding of CFRPs were performed using a two-dimensional model. The effects of the shape of the ED on the temperature increase, deformation history, and dissipated energy behaviors are discussed. Flat and triangular ED shapes are considered. From the results, it is easier for a triangular ED to increase the temperature than for a flat ED, and hence, the consumed energy and time are less for a triangular ED than for a flat ED. However, in the triangular ED, the temperature is distributed significantly, that is, there is a very high temperature at some point and a very low temperature at other points. Thus, unexpected chemical reactions, such as oxidation, may occur. This study concludes that a triangular ED is not always better than a flat ED. In any case, it was found that an abrupt temperature increase was caused by a synergistic effect. That is, the increase in temperature causes the viscoelastic and frictional dissipated energy to be remarkable, and the increase in the dissipated energy increases the temperature.

Experimental investigation on ultrasonic vibration-assisted manufacturing of fiber-reinforced thermoplastics

ABSTRACT The ultrasonic energy-assisted manufacturing of fiber-reinforced thermoplastics is gaining importance in recent years because of its quicker heat generation with less energy requirement than other heating methods. However, a semi-finished raw material such as prepreg or preform with prior processing method is predominantly used. This study investigates the manufacturing of fiber-reinforced thermoplastics from dry and solid raw materials using the ultrasonic plastic welding process. Layers of dry thermoplastics and woven roving synthetic fibers are stacked successively and consolidated with high-frequency ultrasonic vibrations. Influential process settings were experimentally realized for different material stacking sequences to obtain a uniform fusion bonding in thermoplastics. The cross-sectional morphology reveals a strong interfacial attraction between fibers and matrix for the higher contact pressure of the ultrasonic horn along with a longer hold duration that promoted an effective resin impregnation through wetting and intermolecular diffusion in thermoplastics, thereby reducing the void contents and increasing the fiber volume in composites. Furthermore, the tensile, flexural, and interlaminar strength of composites are determined and compared with those obtained using the compression molding process. The thermogravimetric and differential scanning calorimetry data provided thermally stable composites. An efficacious composite with substantial properties was manufactured in a cycle time of 10 s.