Polymer Welding Research Articles

Optimization of polypropylene high-strength injection molding welding and interface structure analysis

Secondary injection molding is an effective method for joining polymer parts, where the weld interface plays a critical role in the overall performance of the part. This study discusses the influence of injection molding parameters on the interface strength of polypropylene and polypropylene (PP-PP) secondary injection molding and analyzes the welding interface structure. The injection molding parameters for PP-PP were optimized using the Taguchi method and the signal-to-noise ratio (S/N). The optimal injection molding parameters were determined to be a mold temperature of 120°C, injection temperature of 350°C, and injection speed of 100 mm/s. The interface tensile strength was measured at 33.42 MPa, corresponding to 98.1% of the tensile strength of the base material. Among these parameters, mold temperature has the greatest influence on the strength of the welding interface. Secondly, polarizing microscopy, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were employed to observe and analyze the crystal structure and fracture failure modes at the interface. The results indicate that elevated injection molding parameters promote the formation of crystal nuclei and spherulite growth at the secondary melt interface, with the spherulite size at the interface significantly affecting the interface strength. This study offers valuable reference for the welding of other polymers and fiber-reinforced materials.

Effect of process temperatures on joining aluminum alloy (AA5052) to polypropylene (PP) by friction lap welding

The joining of aluminum alloy 5052 (AA5052) and polypropylene (PP) by friction lap welding (FLW) was investigated under different process temperature conditions. Welding experiments were conducted at different tool rotational speeds, and the process temperatures were monitored using an infrared camera and thermocouples. The temperature distribution at the cross-section was determined using a validated numerical model. The joint quality was assessed by measuring tensile shear strength and examining the joint morphology. It was found that interfacial temperatures in the range of 156 °C–316 °C were optimal for achieving effective mechanical interlocking, attributed to the appropriate flow of molten PP into the textured aluminum alloy surface. Temperatures below 130 °C resulted in inadequate PP flow, leading to poor joint formation, while temperatures above 316 °C caused over-melting of PP, bubble formation, and approached the PP initial decomposition limit. Raman spectroscopy showed that the process temperatures did not cause significant chemical bonding and that mechanical interlocking was the main contributing joining mechanism. The results showed that dissimilar welding of metals and non-polar polymers can be optimized by the precise monitor and control of the temperature of the process.

Research on ultrasonic-stationary shoulder assisted friction stir lap welding of thermoplastic polymer and aluminum alloy

Friction stir lap welding (FSLW) has advantages on obtaining dissimilar upper polymer and lower aluminum materials joint (polymer/Al joint), and how to heighten the bearing capacity of polymer/Al joint as much as possible is greatly meaningful for the manufacturing industries. In this study, choosing dissimilar polyamide 6 (PA 6) polymer and 6061-T6 aluminum alloy materials as research object, traditional FSLW, stationary shoulder assisted FSLW (SSFSLW) and ultrasonic-stationary shoulder assisted FSLW (U-SSFSLW) processes were compared to understand the mechanism of ultrasonic enhancement on the polymer/Al joint. Firstly, the surface morphologies were studied. Then the analyses of micro/macro-structures, mechanical properties and fracture features were carried out by optical microscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffraction and tensile tests. Results showed that the lap shear failure load of polymer/Al joint by U-SSFSLW reached 1502 N from 814 N by traditional FSLW, because the addition of ultrasonic avoided the bulged-nodule structures on top surface and the cavity defect in stir zone (SZ), broke the Al anchor in upper plate, enlarge the width of SZ in lower plate, and made the deeper micro-pits and larger dents at the interface between SZ bottom and lower plate. The U-SSFSLW process provides an effective way to fabricate the high-strength hybrid joint of dissimilar upper polymer and lower Al materials.

Study on pore behavior of laser welding process between steel and CFRP based on numerical simulation

In order to understand the pore behavior during laser welding of metal and polymer, the laser welding of steel and carbon fiber reinforced plastics (CFRP) was studied. A three-dimensional transient model of multi-physical field couple with heat, flow and force was constructed to simulate the temperature distribution, fluid flow, stress change and solidification under the thermal decomposition of CFRP based on the experiments. The formation, function and evolution mechanism of pores in welded joints were discussed, and the relationship between heat input and pore morphology at the interface was clarified. The results show that the model error is lower than 9 %, and the model is reliable. In laser welding process, bubbles generate, expand and fuse in the center of CFRP molten pool, which changes the local flow velocity and direction, but most of the fluid still flows to the molten pool edge under the action of temperature gradient, and forms pores of stable size with the cooling process. When the heat input is high, the large pores are formed at the interface due to the violent thermal decomposition of CFRP and big stress difference. When the heat input is low, there is still a large stress gradient in the center of the interface, and it is difficult for the insufficiently melted polymer to provide sufficient resistance to deformation, resulting in obvious pore phenomenon in the center of the interface.

Prediction of Ultrasonic Welding Parameters for Polymer Joining

Welding of polymers is a useful assembly process that eliminates the need for adhesives or mechanical fasteners, saving consumable costs. One of the most common polymer welding processes is ultrasonic welding. Effective welding requires that the molten polymer chains at the joint surface diffuse across the joint and become entangled with polymer chains in the parts to be welded. This intermolecular diffusion and chain entanglement are the fundamental characteristics of welding. Using fundamental theories of heat generation and melt flow, optimal weld parameters can be calculated to ensure that diffusion across the weld joint occurs during ultrasonic welding.

A State-of-the-Art Review on Direct Welding of Polymer to Metal for Structural Applications: Part 1 — Promising Processes

Structural lightweighting through the effective use of multiple materials has received increasing attention for fulfilling today’s demands for environmental sustainability in transportation systems. Direct dissimilar material joining methods (versus, e.g., traditional adhesive bonding or mechanical fastening) have become increasingly desirable since they offer process simplicity, production efficiency, and hermetic sealing, among others. In this two-part article, we provide a critical assessment of the state-of-the-art research and promising direct dissimilar material joining techniques reported over the last decades, with a particular emphasis on their potential for structural applications in Part I. As such, recent advances in advanced joint design and modeling methods for enabling optimum joint design for jointability and joint performance are presented along with some detailed examples for demonstrating their potential impacts on industrial applications in Part II. Finally, recommendations on future research and development directions are outlined for supporting the industry’s drive towards multi-material lightweighting.

A review on recent developments in ultrasonic welding of polymers and polymeric composites

A review on recent developments in ultrasonic welding of polymers and polymeric composites

A State-of-the-Art Review on Direct Welding of Polymer to Metal for Structural Applications: Part 2 — Joint Design and Property Characterization

Structural lightweighting through the effective use of multiple materials has received increasing attention for fulfilling today’s demands for environmental sustainability in transportation systems. Direct dissimilar material joining methods (versus, e.g., traditional adhesive bonding or mechanical fastening) have become increasingly desirable since they offer process simplicity, production efficiency, and hermetic sealing, among others. In Part I of this two-part article, we provided a critical assessment of the state-of-the-art research and promising direct dissimilar material joining techniques reported over the last decades, with a particular emphasis on their potential for structural applications. As such, in Part 2, recent advances in advanced joint design and modeling methods for enabling optimum joint design for joint ability and joint performance are presented along with some detailed examples for demonstrating their potential impacts on industrial applications. Finally, recommendations on future research and development directions are outlined for supporting the industry’s drive towards multi-material lightweighting.

Tuning the Mechanical Properties of 3D-printed Objects by the RAFT Process: From Chain-Growth to Step-Growth.

Photoinduced 3D printing based on the reversible addition-fragmentation chain transfer (RAFT) process has emerged as a robust method for creating diverse functional materials. However, achieving precise control over the mechanical properties of these printed objects remains a critical challenge for practical application. Here, we demonstrated a RAFT step-growth polymerization of a bifunctional xanthate and bifunctional vinyl acetate. Additionally, we demonstrated photoinduced 3D printing through RAFT step-growth polymerization with a tetrafunctional xanthate and a bifunctional vinyl acetate. By adjusting the molar ratio of the components in the printing resins, we finely tuned the polymerization mechanism from step-growth to chain-growth. This adjustment resulted in a remarkable range of tunable Young's moduli, ranging from 7.6 MPa to 997.1 MPa. Moreover, post-functionalization and polymer welding of the printed objects with varying mechanical properties opens up a promising way to produce tailor-made materials with specific and tunable properties.

Tuning the Mechanical Properties of 3D‐printed Objects by the RAFT Process: From Chain‐Growth to Step‐Growth

AbstractPhotoinduced 3D printing based on the reversible addition‐fragmentation chain transfer (RAFT) process has emerged as a robust method for creating diverse functional materials. However, achieving precise control over the mechanical properties of these printed objects remains a critical challenge for practical application. Here, we demonstrated a RAFT step‐growth polymerization of a bifunctional xanthate and bifunctional vinyl acetate. Additionally, we demonstrated photoinduced 3D printing through RAFT step‐growth polymerization with a tetrafunctional xanthate and a bifunctional vinyl acetate. By adjusting the molar ratio of the components in the printing resins, we finely tuned the polymerization mechanism from step‐growth to chain‐growth. This adjustment resulted in a remarkable range of tunable Young's moduli, ranging from 7.6 MPa to 997.1 MPa. Moreover, post‐functionalization and polymer welding of the printed objects with varying mechanical properties opens up a promising way to produce tailor‐made materials with specific and tunable properties.

Progress in Friction Stir Welding of Polymer and Aluminum Alloys

Progress in Friction Stir Welding of Polymer and Aluminum Alloys

Steady melting in material extrusion additive manufacturing

PurposeA main cause of defects within material extrusion (MatEx) additive manufacturing is the nonisothermal condition in the hot end, which causes inconsistent extrusion and polymer welding. This paper aims to validate a custom hot end design intended to heat the thermoplastic to form a melt prior to the nozzle and to reduce variability in melt temperature. A full 3D temperature verification methodology for hot ends is also presented.Design/methodology/approachInfrared (IR) thermography of steady-state extrusion for varying volumetric flow rates, hot end temperature setpoints and nozzle orifice diameters provides data for model validation. A finite-element model is used to predict the temperature of the extrudate. Model tuning demonstrates the effects of different model assumptions on the simulated melt temperature.FindingsThe experimental results show that the measured temperature and variance are functions of volumetric flow rate, temperature setpoint and the nozzle orifice diameter. Convection to the surrounding air is a primary heat transfer mechanism. The custom hot end brings the melt to its setpoint temperature prior to entering the nozzle.Originality/valueThis work provides a full set of steady-state IR thermography data for various parameter settings. It also provides insight into the performance of a custom hot end designed to improve the robustness of melting in MatEx. Finally, it proposes a strategy for modeling such systems that incorporates the metal components and the air around the system.

Modeling and optimization of conflicting responses in the laser transmission welding process using RSM, PSO, and TLBO algorithm

Laser transmission welding (LTW) is a widely used polymer welding technology in industries today. The performance of LTW is governed by a number of process parameters, and fine-tuning those parameters is critical for the process to achieve the intended results. Optimization of process parameters for enhancing LTW performance, like weld strength and weld width, is always tricky since they are inherently contradictory. Therefore, in this research, an effort is made to optimize the LTW parameters utilizing the three best-known optimization approaches, and the performance of those optimization approaches in LTW process optimization is compared. First, the response surface method (RSM) is employed to build empirical equations that establish an empirical correlation between process variables and desired performance features. These empirical equations are then employed as objective functions for process optimization utilizing the RSM-based desirability function approach (DFA), particle swarm optimization (PSO), and teaching learning-based optimization (TLBO) algorithms. The performance of the chosen optimization approaches is compared with reference to optimum results, accuracy, convergence rate, and computing time. PSO and TLBO algorithms outperform the DFA approach for single and multi-objective optimizations. TLBO is found to have faster convergence, whereas PSO takes less time for computation.

Моделювання режимів керування технологічним обладнанням при ультразвуковому зварюванні полімерів

Two control modes of technological equipment for ultrasonic welding of polymers are consi-dered: a mode with support of constant time and a mode of support of constant energy during the operation of the ultrasonic generator. The advantages of operation of the oscillating system in the constant energy maintenance mode are shown. A stand for modeling welding processes was developed and manufactured. An example of technological equipment that was manufac-tured based on the results of simulation of welding modes is presented.

Effects of Friction Stir Welding on the Mechanical Behaviors of Extrusion-Based Additive Manufactured Polymer Parts.

The friction stir welding (FSW) of thermoplastic polymers is gradually receiving attention because of its advantages including high efficiency and pollution-free manufacturing. The extrusion-based additive manufacturing (EAM) of polymers has also become one of the main processing methods for thermoplastic parts. In this paper, a hybrid manufacturing method for the FSW process and EAM technology is proposed and explored. The effects of the FSW process using two different welding tools on the mechanical behaviors of 3D printing polymer parts were compared and investigated and the corresponding mechanism was analyzed. The results show that the appropriate welding tool is beneficial for eliminating the anisotropy and decreasing the porosity of 3D-printed parts. Therefore, the improving effects of the FSW process on the mechanical behaviors of the EAM parts are verified. The mechanism was attributed to the high-speed rotation of the welding tool with the appropriate shape, which can promote the flow of polymer melt in the welding region, leading to the formation of dense structures caused by the entanglement of the molecular chains. This study may provide some assistance in modern industrial manufacturing for the processing of large custom components.

Laser intensity and surface distribution identification at weld interface during laser transmission welding of thermoplastic polymers: A combined numerical inverse method and experimental temperature measurement approach

AbstractThe determination of the laser intensity profile necessary to weld two thermoplastic parts is crucial for understanding and optimizing the laser welding process in polymers and composite materials. Traditional methods of measuring the laser beam intensity profile, such as laser beam profiling techniques, can be difficult to implement and expensive. In this paper, we present the development of a technique that combines a numerical inverse method with experimental temperature measurements to determinate the laser intensity distribution at the weld interface. This technique does not require specialized or expensive equipment and accounts for variations in laser beam intensity caused by different components and interfaces. The technique uses thermocouple sensors to measure interface temperatures during welding, and an analytical gaussian model to estimate the laser intensity distribution at the weld interface. The model is then used as input data in a numerical heat transfer model. The technique is validated through experimental investigations on transparent and absorbent Polylactic acid polymers.

Fracture analysis of friction stir spot welded acrylonitrile butadiene styrene sheet in butt configuration

The friction stir spot welding (FSSW) process is a novel technique that overcomes the limitation of resistance spot welding. Recently, FSSW used for welding of polymers which are difficult to be joined by traditional welding processes. The demand for Acrylonitrile Butadiene Styrene (ABS) for industrial applications has increased in recent years. However, to employ this technique the challenge is to get optimal FSSW parameters setting to achieve the best weld strength during the welding of ABS sheets. To achieve this, in the present work, full factorial experimental design layout was employed to investigate the effect of process parameters on weld strength i.e., ultimate tensile strength (UTS) and percentage elongation during FSSW of ABS-ABS sheet in butt configuration. To predict the UTS and percentage elongation, machine learning regression namely, linear, polynomial, support vector machine, and decision tree was used. Further, the study includes the identification of the fracture patterns post tensile test specimens based on the topography of the fracture surface under scanning electron microscopy. It was found that plunge depth is the most significant parameter followed by spindle speed and dwell time. The optimal setting of process parameters i.e., spindle speed of 1000 rpm, plunge depth of 1 mm, and dwell time of 40 s resulted in maximum UTS of 7.849 MPa. The maximum value of percentage elongation obtained was 5 at the parameter setting of spindle speed of 1000 rpm, plunge depth of 0.8 mm, and dwell time of 40 s. Polynomial regression outperformed in the prediction of UTS and percentage elongation with an R-square of 0.99.

Modeling of Output Spectra and Numerical Simulation of Thulium-doped Broadband Fiber Light Sources at 1400-1520nm, 1800-2000nm

Lasers have a great influence in industrial processing and biomedical fields. Thulium-doped fiber lasers have good prospects for communication transmission and polymer welding. In this paper, the research method is as follows: in the pump light at 0. 79um, the values of Thulium-doped fiber, including its core radius, spontaneous radiation rate, cross-sectional absorption area, etc., are preset in advance. Then, by changing the fiber length, pumping power, and doping concentration of the fiber, the curve between the output spectrum of ASE light and the wavelength of ASE light is demonstrated. Finally, the peak power of the Thulium-doped broadband light source fiber is about 1. 6× w at L=3m, N=4× / , Pp=0. 2w. The output spectrum of thulium-doped fiber is mainly concentrated around the 2000nm wavelength band, and examples of thulium-doped fiber lasers for modern medical and industrial fields are presented. The thulium-doped fiber is the main direction of future research and the outlook for the future.

Biomimetic, fire-resistant, ultralight and porous carbon fiber sponges enabling safe and efficient remediation of crude oil spills in harsh environments

Advanced absorbents must meet the requirements of superior hydrophobic/oleophilic behavior, favorable adsorption efficiency, and high photothermal and Joule heating performance to handle frequent crude oil spills. However, current carbon-based absorbents suffer from poor fire resistance, thus severely limiting their application in harsh environments. Herein, inspired by a bird's nest, a polymer “welding” strategy is proposed to design a versatile absorbent in which the polymer serves as a “binder” to interconnect discontinuous fibers together to form a 3D welded structure. The continuous conductive networks endow the absorbent with high photothermal and Joule heating effect, thus achieving all-weather adsorption, and improving the adsorption efficiency of crude oil via the self-heating function. Compared with other absorbents, the absorbent prepared via polymer welding technology exhibited preferable comprehensive performance, such as superhydrophobicity, high fire resistance, and high absorption efficiency. Specially, the noninflammable absorbent can restrain the combustion of crude oil, thereby reducing its combustion in case of fire. The versatile absorbent is expected to provide a promising solution for the safe and efficient cleanup of crude oil spills in harsh environments. Overall, the unique polymer welding strategy can be developed into a universal strategy for other material systems to expand their applications.

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.