Search Results (30)

Laser technology is widely regarded as a highly effective method for welding thermoplastic polymers due to its precision, cleanliness, and versatility. This study investigates the effects of laser power and scanning speed on the through-thickness hardness of polypropylene plates, analyzing the heat-affected zone (HAZ) and hardness variations along the depth of the weld bead. Using the Trumpf Trudisk 6602 laser source, multiple polypropylene passes were made with different power levels (200 W and 300 W) and scanning speeds (5, 10, 20, 30, 40, and 50 mm/s). The results indicate a direct correlation between laser power and scanning speed in the final width and depth of the weld bead. Furthermore, results indicate that higher scanning speeds and lower power promote a more uniform distribution of hardness across the thickness. This study contributes to understanding laser-assisted welding processes in polymeric materials, providing information on the influence of different laser parameters on weld quality and resulting material properties. Full article

The conventional near-infrared laser transmission welding (LTW) process for joining dissimilar transparent polymers is limited by the need to incorporate optical absorbents, which compromises joint performance and raises biocompatibility concerns. To address these issues, this study proposed a surface modification technique using femtosecond laser ablation prior to the welding process. Experiments involved 520 nm femtosecond laser ablation of transparent polymers, followed by LTW of dissimilar transparent polymers using an 808 nm laser, with subsequent characterization and mechanical property evaluations. A maximum joint strength of 13.65 MPa was achieved. A comprehensive investigation was conducted into the physical and chemical mechanisms through which laser ablation improved the welding performance of dissimilar transparent polymers. The results demonstrated that laser ablation generated microstructures that serve as substitutes for optical absorbents while also facilitating the formation of numerous oxygen-containing functional groups. These enhancements improve miscibility and bonding performance between dissimilar polymers, enabling absorbent-free welding between ablated polycarbonate (PC) and polystyrene (PS). This work confirms both the feasibility and potential application of this process for direct LTW of dissimilar transparent polymers. Full article

The rise of Industry 4.0 has introduced challenges and new production models like additive manufacturing (AM), enabling the creation of complex objects previously unattainable. However, many polymers remain underutilized due to the need for improved mechanical properties and reduced process-induced anisotropy. ME-based part construction involves successive filament deposition, akin to welding. Upon exiting the nozzle, the polymer solidifies within seconds, limiting the time and temperature available for diffusion and efficient bonding with the adjacent filament. Therefore, optimizing this welding process is essential. The primary objective of this review was to report on the equipment utilized to enhance the bonding between filaments deposited during manufacturing. While higher temperatures improve welding, most equipment cannot endure prolonged high-heat operations, limiting the use of engineering-grade polymers. Modifying polymer matrices by incorporating low-molar-mass molecules can boost welding and mechanical strength. Significant gains in mechanical properties have come from matrix modifications and new in situ welding devices. Reported devices use light (laser, UV IR), electric current, radio frequency and heat collection from the nozzle. The simplest device is a heat collector, while a double laser beam system has achieved the highest mechanical properties without matrix modification. There was an improvement in properties ranging from 20% to 200%. Full article

In the industry sector, it is very common to have different types of dissimilar materials on the same construction rather than products made from a single type of material. Traditional methods (welding, mechanical fastening, and adhesive bonding) and hybrid techniques (friction stir welding, weld bonding, and laser welding) are used in the assembly or joining of these materials. However, while joining similar types of materials is relatively easy, the process becomes more challenging when joining dissimilar materials due to the structure and properties of the materials involved. In recent years, additive manufacturing and 3D printing have revolutionized the manufacturing landscape and have provided great opportunities for the production of polymer-based multi-materials. However, developments in the joining of multi-material parts are limited, and their limits are not yet clear. This study focuses on the joining of 3D-printed products made from PLA-based multiple materials (PLA and PLA Wood) using friction stir welding. Single-material and multi-material parts (with 100% infill ratio and three different combinations of 50% PLA/50% PLA Wood) were welded at a feed rate of 20 mm/min and three different tool rotational speeds (1750, 2000, and 2250 rpm). Tensile and bending tests were conducted on the welded samples, and temperature measurements were taken. The fractured surfaces of the samples were examined to perform a damage analysis. It is determined that the weld strength of multi-materials changes depending on the combination of the material (material design). For multi-materials, a welding efficiency of 74.3% was achieved for tensile strength and 142.68% for bending load. Full article

High-density polyethylene (HDPE) has emerged as a promising alternative to fiber-reinforced plastic (FRP) for small vessel manufacturing due to its durability, chemical resistance, lightweight properties, and recyclability. However, while thermoplastic polymers like HDPE have been extensively used in gas and water pipelines, their application in large, complex marine structures remains underexplored, particularly in terms of joining methods. Existing techniques, such as ultrasonic welding, laser welding, and friction stir welding, are unsuitable for large-scale HDPE components, where extrusion welding is more viable. This study focuses on evaluating the impact of key process parameters, such as the preheating temperature, hot air movement speed, and nozzle distance, on the welding performance of HDPE. By analyzing the influence of these variables on heat distribution during the extrusion welding process, we aim to conduct basic research to derive optimal conditions for achieving strong and reliable joints. The results highlight the critical importance of a uniform temperature distribution in preventing defects such as excessive melting or thermal degradation, which could compromise weld integrity. This research provides valuable insights into improving HDPE joining techniques, contributing to its broader adoption in the marine and manufacturing industries. Full article

Traditional resistance spot welding (RSW) has been unsuccessful in forming quality composite joints between steel– or aluminum–polymer-based composites. This has led to the development of spot welding variants such as friction stir spot welding (FFSW), ultrasonic spot welding (USW), and laser spot welding (LSW). The paper reviewed the differences in the bonding mechanisms, spot weld characteristics, and challenges involved in using these spot welding variants. Variants of RSW use series electrode arrangement, co-axial electrodes, metallic inserts, interlayers, or external energy to produce composite joints. FFSW and USW use nanoparticles, interlayers, or energy directors to create composite spot welds. Mechanical interlocking is the common composite joint mechanism for all variants. Each spot welding variant has different sets of weld parameters and distinct spot weld morphologies. FFSW is the most expensive variant but is commonly used for composite spot weld joints. USW has a shorter welding cycle compared to RSW and FFSW but can only be used for small components. LSW is faster than the other variants, but limited work was found on its use in composite spot weld joining. The use of interlayers in FFSW and USW to form composite joints is a potential research area recommended in this review. Full article

Recent research focuses on replacing metal current collectors with metallized polymer foils. However, this introduces significant challenges during cell production, as manufacturing steps must be adapted. Currently, copper is used as the current collector on the anode side and aluminum on the cathode side. These current collectors are then joined within the cell with an arrester tab. This step, known as contacting, is carried out industrially in pouch cells using ultrasonic welding or laser beam welding. However, since the polymer foil is electrically insulating, the current contacting procedures cannot be directly transferred to the metal–polymer current collectors. In this work, ultrasonic welding, laser beam welding, and a mechanical contacting method are considered, and the challenges arising from the material properties are highlighted. The properties of the joints are discussed as a function of the number of foils and the coating thickness of the metallization. It is demonstrated that successful contacting by ultrasonic welding and mechanical clamping is possible, as both mechanical strength and electrical conductivity are ensured by the joint. Laser beam welding was unsuccessful. Additionally, the electrical resistance is one to two orders of magnitude higher than that of pure aluminum and copper foils, which necessitates further optimization. Furthermore, ultrasonic welding is limited to welding 16 foils or fewer. This does not match industrial requirements. Consequently, novel approaches for contacting metal–polymer current collectors are required. Full article

Polyether ether ketone (PEEK) is frequently employed in biomedical engineering due to its biocompatibility. Traditionally, PEEK manufacturing methods involve injection molding, compression molding, additive manufacturing, or incremental sheet forming. Few studies have focused on rotational friction welding (RFW) with PEEK plastics. Based on years of RFW practical experience, the mechanical properties of the weldment are related to the burn-off length. However, few studies have focused on this issue. Therefore, the main objective of this study is to assess the effects of burn-off length on the mechanical properties of the welded parts using PEEK polymer rods. The welding pressure can be determined by the rotational speed according to the proposed prediction equation. The burn-off length of 1.6 mm seems to be an optimal burn-off length for RFW. For the rotational speed of 1000 rpm, the average bending strength of the welded parts was increased from 108 MPa to 160 Mpa, when the burn-off length was increased from 1 mm to 1.6 mm and the cycle time of RFW was reduced from 80 s to 76 s. A saving in the cycle time of RFW of about 5% can be obtained. The bending strength of the welded part using laser welding is lower than that using RFW, because only the peripheral material of the PEEK cylinder was melted by the laser. Full article

Polyetheretherketone (PEEK) is a promising biomaterial due to its excellent mechanical properties. Most PPEK manufacturing methods include additive manufacturing, injection molding, grinding, pulse laser drilling, or incremental sheet forming. Rotary friction welding (RFW) is a promising bonding technique in many industries. However, very few studies have focused on the RFW of PEEK. Conventionally, the number of revolutions is fixed during the welding process. Remarkably, the rotary friction welding of PEEK polymer rods using an innovative variable rotational speed is investigated in this study. The average bending strength of the welded part using a three-stage transformation rotational speed was enhanced by about 140% compared with a rotational speed of 1000 rpm. The advantage of computer numerical controlled RFW of PEEK using variable rotational speed is a reduced cycle time of RFW. A reduction in cycle time of about 6% can be obtained using the proposed RFW with a three-stage transformation rotational speed. The innovative approach provides low environmental pollution and high energy efficiency and complies with sustainable development goals. Full article

The present study investigated the influence of temperature on molecular interdiffusion at the interface during the laser transmission welding of 3D-printed continuous carbon-fiber-reinforced thermoplastic composites. In order to accurately measure the temperature at the weld interface, a series of thermocouples were embedded in the laser-absorbent composite part. Two different molecular interdiffusion models were implemented to calculate the degree of healing and to predict the effects of temperature on the welding process. The degree of healing and the weld line width were computed and compared with microscopy observations. The discrepancy between the two proposed numerical models was less than $6\%$. Both models showed good agreement with the experimental data, with an average error of $13.28\%$ and $7.26\%$, respectively. The results revealed a significant correlation between the thermal history and molecular interdiffusion at the interface. Furthermore, the relationship between the welding parameters (laser beam scanning speed) and weld line width was established. The findings of this study provide a comprehensive understanding of the underlying mechanisms involved in the laser welding of 3D-printed composites and offer insights to optimize the welding process for enhanced weld quality and superior mechanical properties in the final product. Full article

Among the various welding techniques used to bond thermoplastic composites, induction welding stands out as a fast, clean, and contact-free process that shortens the welding time and prevents the weight increase of mechanical fastening, such as rivets and bolts. In this study, we manufactured polyetheretherketone (PEEK)-resin-based thermoplastic carbon fiber (CF) composite materials at different automated fiber placement laser powers (3569, 4576, and 5034 W) and investigated their bonding and mechanical characteristics after induction welding. The quality of the composite was evaluating using various techniques, including optical microscopy, C-scanning, and mechanical strength measurements, and a thermal imaging camera was used to monitor the surface temperature of the specimen during its processing. The results revealed that the preparation conditions of the polymer/carbon fiber composites, such as the laser power and surface temperature, significantly affect the quality and performance of the induction-welding-bonded composites. A lower laser power during preparation resulted in weaker bonding between components of the composite and yielded samples with a lower shear stress. Full article

The search for lightweight structures increases the demand for non-metallic materials, such as polymers, composites, and hybrid structures. This work presents the dissimilar joining through direct laser joining between polymethylmethacrylate (PMMA) and S235 galvanised steel using a pulsed Nd:YAG laser. The main goal is to determine the influence of processing parameters on joint strength and quality. In addition, the impact of surface conditions on the joint quality was also analysed. Overall, the optimum ranges of process parameters were found, and some are worth highlighting, such as the laser beam diameter and pulse duration, which significantly influenced the joint strength. Failure of the welded samples occurred in PMMA component, demonstrating good joint efficiency. Additionally, a maximum increase of 5.1% of the tensile shear strength was achieved thanks to the mechanical pre-treatment. It is possible to conclude that the joining between PMMA and the S235 galvanised steel can be performed by optimising the process parameters. Additionally, it can be enhanced through surface pre-treatments by exploring the mechanical interlock between both materials. Full article

Sandwich panels are promising composite materials, although the possibilities for their thermal joining are limited due to the degradation of the polymer core at elevated temperatures. The purpose of this study is to improve the quality of the butt joints in metal–polymer sandwich composites performed by laser welding. A pulsed Nd:YAG Rofin StarWeld Performance laser was used to perform the two-sided welding of the metal–polymer three-layer composite material. On each of the two sides of the material, a welded joint was made with partial penetration of the covering steel sheets, which was considered a prerequisite for preventing the degradation of the core polymer layer. The energy density of the laser irradiation was redistributed by increasing the diameter of the laser spot. The structure of the welded joints was examined using a polarized optical microscope and a scanning electron microscope. It was determined that the laser treatment resulted in a partial penetration weld on each of the two covering metal sheets of the material, reaching a depth of more than 50% of the sheet’s thickness without damaging the polymer. The welding area consisted of two zones, one being the weld metal and the other the heat-affected zone. As a result of relatively rapid heating and cooling cycles, fine-dispersed structures were formed in the heat-affected and remelted zones. The performed tensile tests showed that the strength of the welded area was about 80% of that of the base material. Full article

Quality and reliability are of the utmost importance for manufacturing in the optical and medical industries. Absorber-free laser transmission welding enables the precise joining of identical polymers without additives or adhesives and is well-suited to meet the demands of the aforementioned industries. To attain sufficient absorption of laser energy without absorbent additives, thulium fiber lasers, which emit in the polymers’ intrinsic absorption spectrum, are used. Focusing the laser beam with a high numerical aperture provides significant intensity gradients inside the workpiece and enables selective fusing of the internal joining zone without affecting the surface of the device. Because seam size and position are crucial, the high-quality requirements demand internal weld seam monitoring. In this work, we propose a novel method to determine weld seam location and size using optical coherence tomography. Changes in optical material properties because of melting and re-solidification during welding allow for weld seam differentiation from the injection-molded base material. Automatic processing of the optical coherence tomography data enables the identification and measurement of the weld seam geometry. The results from our technique are consistent with microscopic images of microtome sections and demonstrate that weld seam localization in polyamide 6 is possible with an accuracy better than a tenth of a millimeter. Full article

In the production of metal-polymer multilayer composite parts, e.g., for automotive applications, the possibilities of thermal joining are limited due to the instability of the polymer core at elevated temperatures. Accordingly, such materials require a special approach to their welding. The three-layered metal-polymer-metal samples were made of DPK 30/50+ZE dual-phase steel as cover sheets that were electrolytic galvanized, and a polypropylene-polyethylene foil as core material, with thicknesses of 0.48/0.3/0.48 mm. The samples were welded on both sides using a 1.06 µm Nd:YAG ROFIN StarWeld Manual Performance laser. Significant improvements of the welding conditions are achieved by machining the edges of materials to be welded. The parameters of laser welding were chosen in such a way that the polymer structure remained almost unchanged. The weld thickness was about 40% of the thickness of each steel layer. It was established that within the selected laser processing parameters the melting occurred uniformly, while the polymer layer practically did not change its structure. Therefore, it can be stated that two-sided joint welding of metal-polymer-metal composite sandwich panels, without significant degradation of the polymer core layer, is feasible. Full article