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Fusion Bonding/Welding of Polymer Composites

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Composites".

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 23211

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Special Issue Editors

Prof. Dr. Patricia Krawczak

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Guest Editor

IMT Nord Europe, Institut Mines Télécom, University of Lille, Centre for Materials and Processes, F-59653 Villeneuve d’Ascq, France
Interests: advanced composites; polymer composites; composites manufacturing and properties; polymer processing and properties; advanced manufacturing; additive manufacturing and 3D printing; structural health monitoring; recycling; bio-based polymers and composites
Special Issues, Collections and Topics in MDPI journals

Dr. André Chateau Akué Asséko

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Centre for Materials and Processes, IMT Lille-Douai, Institut Mines-Télécom, Douai, France
Interests: physics of materials (thermal, optical, mechanical and acoustic); coupling numerical (modeling/simulation) and experimental (validation/identification) aspects for the analysis of the behavior of polymers and composites, their forming and their assembly by different processes (laser or infrared welding, 3D printing/additive manufacturing)

Prof. Dr. Chung-Hae Park

E-Mail Website
Guest Editor

Centre for Materials and Processes, IMT Lille-Douai, Institut Mines-Télécom, Douai, France
Interests: advanced composites; polymer composites; composites manufacturing and properties; advanced manufacturing; numerical simulation and modeling

Special Issue Information

Dear Colleagues,

Most everyday products and industrial structures are made by the assembly of several parts and therefore contain joints. This is the case for example in the aeronautics, railway, or automotive industries where polymer composites become more and more popular as lightweight substitutes of metallic materials. Joining of polymer composites may be achieved by different technologies, as in the case of metals. However, one of the greatest drivers for thermoplastic composites use is the ability to join components via fusion bonding/welding, which is an attractive alternative to conventional methods—mechanical fastening and adhesive bonding—used to join thermoset composite parts.
Although some methods such as resistance welding or induction welding are quite well established, other technologies, including ultrasonic welding, laser welding, infrared welding or conduction welding, are still at a more or less advanced development stage. One of the challenges is to master the interfacial phenomena, structure and quality in the assembly area (welds), which is rather tricky due to the presence of the reinforcement fibers. The same issues are also to tackle for 3D-printed or overmolded parts. Besides, there is a need for reliable predictive process simulation softwares, and also for increased inline monitoring and control of welding process parameters.

This Special Issue welcomes papers (original research articles, state-of-the art reviews, short communications, perspectives, viewpoints, opinions, concept papers or case reports) on the latest advances and development of fusion bonding/welding of thermoplastic composites (i.e., fiber reinforced thermoplastics). Suggested contributions may address materials, processing, modeling/simulation, monitoring/control, performance or application issues, with either experimental or numerical approches.

Prof. Dr. Patricia Krawczak
Dr. André Chateau Akué Asséko
Prof. Dr. Chung-Hae Park
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

welding technology
assembly
joining
fusion bonding
resistance welding
induction welding
ultrasonic welding
laser welding
infrared welding
conduction welding
infrared welding
microwave welding
extrusion welding
additive manufacturing
3D printing
overmolding
inline process control
in situ process monitoring
process modeling and simulation
welds properties
polymer composites
advanced composites
thermoplastic composites

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Published Papers (10 papers)

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Research

15 pages, 5408 KiB

Open AccessCommunication

On the Analyses of Cure Cycle Effects on Peel Strength Characteristics in Carbon High-T_g Epoxy/Plasma-Activated Carbon PEEK Composite Interfaces: A Preliminary Inquiry

by Henri Perrin, Régis Vaudemont and Masoud Bodaghi

Materials 2023, 16(23), 7340; https://doi.org/10.3390/ma16237340 - 25 Nov 2023

Viewed by 1130

Abstract

In this study, a high-T_g aerospace-grade epoxy composite plate was co-curing welded using a unidirectional PEEK thermoplastic carbon fibre tape to develop advanced composite joints. To account for the surface roughness and the weldability of carbon–epoxy/carbon–PEEK composites, plasma treatments were performed. The co-curing was conducted by the following steps: each treated thermoplastic tape was first placed in the mould, and followed by nine layers of dry-woven carbon fabrics. The mould was sealed using a vacuum bag, and a bi-component thermoset (RTM6) impregnated the preform. To understand the role of curing kinetics, post-curing, curing temperature, and dwell time on the quality of joints, five cure cycles were programmed. The strengths of the welded joints were investigated via the interlayer peeling test. Furthermore, cross-sections of welded zones were assessed using scanning electron microscopy in terms of the morphology of the PEEK/epoxy interphase after co-curing. The preliminary results showed that the cure cycle is an important controlling parameter for crack propagation. A noticeable distinction was evident between the samples cured first at 140 °C for 2 h and then at 180 °C for 2 h, and those cured initially at 150 °C for 2 h followed by 180 °C for 2 h. In other words, the samples subjected to the latter curing conditions exhibited consistently reproducible results with minimal errors compared to different samples. The reduced errors confirmed the reproducibility of these samples, indicating that the adhesion between CF/PEEK and CF/RTM6 tends to be more stable in this curing scenario. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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17 pages, 11282 KiB

Open AccessArticle

Effect of Adherend Thickness on Near-Field Ultrasonic Welding of Single-Lap CF/LMPAEK Thermoplastic Composite Joints

by Natalia Sofia Guevara-Sotelo and Irene Fernandez Villegas

Materials 2023, 16(21), 6968; https://doi.org/10.3390/ma16216968 - 30 Oct 2023

Cited by 1 | Viewed by 1254

Abstract

Ultrasonic welding is a fast and promising joining technique for thermoplastic composite parts. Understanding how changing the part thickness affects the process is crucial to its future upscaling and industrialization. This article presents an initial insight into the effect of the adherend’s thickness on the near-field ultrasonic welding of CF/LMPAEK thermoplastic composites. Different thicknesses of the top and bottom adherend were welded and analyzed using the output data of the welding equipment, temperature measurements, and other visual characterization techniques. Increasing the thickness of both the top and the bottom adherends showed to increase the power consumed during welding. An overshoot in the power needed at the onset of the welding process for increased thickness of the top adherend precluded welding beyond a threshold thickness of 4.72 mm. In the case of the thicker top adherends, there was also melting of the energy director and early fiber squeeze-out within the top adherend as a result of increased bulk heating. Increased bulk heating was hypothesized to be caused by increased hammering, as indicated by the amplitude readings for thicker adherends. Welding with a higher force, which is known to reduce hammering, corroborated this hypothesis as fiber squeeze-out within the top adherend was not observed. It is believed that hammering contributes to heating by causing an oscillatory impact excitation that is close to the natural frequencies of the system, which would result in amplification of the cyclic strain and subsequent increase in the viscoelastic heating in the adherend. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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15 pages, 4305 KiB

Open AccessArticle

Investigating the Effect of Interface Temperature on Molecular Interdiffusion during Laser Transmission Welding of 3D-Printed Composite Parts

by Anh-Duc Le, André Chateau Akué Asséko, Benoît Cosson and Patricia Krawczak

Materials 2023, 16(18), 6121; https://doi.org/10.3390/ma16186121 - 7 Sep 2023

Cited by 2 | Viewed by 1542

Abstract

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

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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11 pages, 6875 KiB

Open AccessArticle

On the Hot-Plate Welding of Reactively Compatibilized Acrylic-Based Composites/Polyamide (PA)-12

by Henri Perrin, Masoud Bodaghi, Vincent Berthé, Sébastien Klein and Régis Vaudemont

Materials 2023, 16(2), 691; https://doi.org/10.3390/ma16020691 - 10 Jan 2023

Cited by 3 | Viewed by 1710

Abstract

Joining of dissimilar thermoplastics and their composites is a challenge for thermal welding techniques due to different melting points. Reactive welding with an auxiliary functional material can offer the clear opportunities to develop joining processes due to robustness to joining dissimilar thermoplastic polymers and their composites. The current study employed reactive compatibilization to offer the possibility of joining an acrylic-based glass fiber composite to polyamide (PA)-12 by applying a hot-tool welding technique. For this purpose, composite plates are fabricated by a typical vacuum infusion and thin layer thermoplastic films are formed by a thermostamping of PA12 granules. Subsequently, the reactive welding of the interposed PA12 sheet and Elium^®-GMA-Glass composite is conducted by hot-plate welding. A glycidyl methacrylate (GMA) as a compatibilizing agent is copolymerized with methyl methacrylate Elium^® resin. During the hot-tool welding process of dissimilar thermoplastic material, GMA can react with the polyamide end groups. The heat distribution at the Elium^® GMA/PA-12 interface is responsible for obtaining a strong joint. This study focuses on the functionality of the compatibilizer on the welding of acrylic-based composites with polyamide (PA)-12 while varying the assembly temperature. The flatwise tensile test proved the effectiveness of GMA on the interface bounding. The excellent bounding incompatible polymers Elium^® resin (PMMA) and PA12 was achieved at 200 °C. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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25 pages, 6749 KiB

Open AccessEditor’s ChoiceArticle

Assembling of Carbon Fibre/PEEK Composites: Comparison of Ultrasonic, Induction, and Transmission Laser Welding

by Adrian Korycki, Christian Garnier, Margot Bonmatin, Elisabeth Laurent and France Chabert

Materials 2022, 15(18), 6365; https://doi.org/10.3390/ma15186365 - 13 Sep 2022

Cited by 14 | Viewed by 3388

Abstract

In the present work, an ultrasonic, an induction, and a through transmission laser welding were compared to join carbon fibre reinforced polyetheretherketone (CF/PEEK) composites. The advantages and drawbacks of each process are discussed, as well as the material properties required to fit each process. CF/PEEK plates were consolidated at 395 °C with an unidirectional sequence and cross-stacking ply orientation. In some configurations, a polyetherimide (PEI) layer or substrate was used. The thermal, mechanical, and optical properties of the materials were measured to highlight the specific properties required for each process. The drying conditions were defined as 150 °C during at least 8 h for PEI and 24 h for CF/PEEK to avoid defects due to water. The optical transmission factor of PEI is above 40% which makes it suitable for through transmission laser welding. The thermal conductivity of CF/PEEK is at most 55 W·(m·K)⁻¹, which allows it to weld by induction without a metallic susceptor. Ultrasonic welding is the most versatile process as it does not necessitate any specific properties. Then, the mechanical resistance of the welds was measured by single lap shear. For CF/PEEK on CF/PEEK, the maximum lap shear strength (LSS) of 28.6 MPa was reached for a joint obtained by ultrasonic welding, while an induction one brought 17.6 MPa. The maximum LSS of 15.2 MPa was obtained for PEI on CF/PEEK assemblies by laser welding. Finally, interfacial resistances were correlated to the fracture modes through observations of the fractured surfaces. CF/PEEK on CF/PEEK joints resulted in mixed cohesive/adhesive failure at the interface and within the inner layers of both substrates. This study presents a guideline to select the suitable welding process when assembling composites for the aerospace industry. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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12 pages, 1961 KiB

Open AccessArticle

Facile Surface Depolymerization Promotes the Welding of Hard Epoxy Vitrimer

by Le An and Wenzhe Zhao

Materials 2022, 15(13), 4488; https://doi.org/10.3390/ma15134488 - 25 Jun 2022

Cited by 5 | Viewed by 2172

Abstract

Welding via bond exchange reactions has provided advances in obtaining high-quality joining performance. However, the reported welding method requires a relatively high press force, and challenges are still encountered in welding hard vitrimer. In this work, a facile surface depolymerization strategy was introduced to weld high-performance epoxy vitrimer. The vitrimers were firstly dissolved into ethylene glycol for depolymerization based on the solvent-assisted bond exchange reactions. Then, the depolymerized vitrimers were welded under heat and press force. The effect of the depolymerizing time, welding pressure, welding temperature and welding time on the welding strength were further investigated. It was found that there were optimal values for the depolymerizing time, welding pressure, and welding temperature, respectively, for the welding strength, while the welding strength increased with increasing welding time. Through facile surface degradation, the welding pressure was highly reduced, while the welding strength was increased. With surface depolymerization, the welding strength was 1.55-times higher, but the magnitude of press force was 1/1000-times than that with no surface depolymerization. It is elucidative that surface depolymerization can be used to weld hard vitrimer composites alongside reducing the press force effectively. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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14 pages, 5176 KiB

Open AccessArticle

The Mechanical Characterization of Welded Hybrid Joints Based on a Fast-Curing Epoxy Composite with an Integrated Phenoxy Coupling Layer

by Lucian Zweifel, Klaus Ritter and Christian Brauner

Materials 2022, 15(3), 1264; https://doi.org/10.3390/ma15031264 - 8 Feb 2022

Cited by 3 | Viewed by 2615

Abstract

The joining of composites mostly relies on traditional joining technologies, such as film or paste adhesives, or mechanical fasteners. This study focuses on the appealing approach of using standard thermoplastic welding processes to join thermosets. To achieve this, a thermoplastic coupling layer is created by curing with a thermoset composite part. This leads to a functional surface that can be utilized with thermoplastic welding methods. The thermoplastic coupling layer is integrated as a thin film, compatible with the thermoset resin in the sense that it can partially diffuse in a controlled way into the thermoset resin during the curing cycle. Recent studies showed the high affinity for the interphase formation of poly hydroxy ether (phenoxy) film as coupling layer, in combination with a fast-curing epoxy system that cures within 1 min at 140 °C. In this study, an investigation based on resistance and ultrasonic welding techniques with different testing conditions of single-lap shear samples (at room temperature, 60 °C, and 80 °C) was performed. The results showed strong mechanical strengths of 28.9 MPa (±0.7%) for resistance welding and 24.5 MPa (±0.1%) for ultrasonic welding, with only a minor reduction in mechanical properties up to the glass transition temperature of phenoxy (90 °C). The combination of a fast-curing composite material with an ultra-fast ultrasonic joining technology clearly demonstrates the high potential of this joining technique for industrial applications, such as automotive, sporting goods, or wind energy. The innovation allowing structural joining performance presents key advantages versus traditional methods: the thermoplastic film positioning in the mold can be automated and localized, joint formation requires only a fraction of a second, and the joining operation does not require surface preparation/cleaning or structure deterioration (drilling). Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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11 pages, 2707 KiB

Open AccessEditor’s ChoiceArticle

Radiative Thermal Effects in Large Scale Additive Manufacturing of Polymers: Numerical and Experimental Investigations

by Benoît Cosson, André Chateau Akué Asséko, Lukas Pelzer and Christian Hopmann

Materials 2022, 15(3), 1052; https://doi.org/10.3390/ma15031052 - 29 Jan 2022

Cited by 2 | Viewed by 1824

Abstract

The present paper addresses experimental and numerical investigations of a Large Scale Additive Manufacturing (LSAM) process using polymers. By producing large components without geometrical constraints quickly and economically, LSAM processes have the capability to revolutionize many industries. Accurate prediction and control of the thermal history is key for a successful manufacturing process and for achieving high quality and good mechanical properties of the manufactured part. During the LSAM process, the heat emitted by the nozzle leads to an increase in the temperature of the previously deposited layer, which prepares the surface for better adhesion of the new layer. It is therefore necessary to take into account this part of heat source in the transient heat transfer equation to correctly and completely describe the process and predict the temperature field of the manufactured part. The present study contributes to experimental investigations and numerical analysis during the LSAM process. During the process, two types of measurements are performed: firstly, the heat emitted by the nozzle is measured via a radiative heat sensor; secondly, the temperature field is measured using an infrared camera while varying the process speed. At the same time, a numerical simulation model is developed in order to validate the experimental results. The temperature fields of the manufactured parts computed by numerical simulations are in very good agreement with the temperature fields measured by infrared thermograph with the contribution of the nozzle’s heat exchange. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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17 pages, 24786 KiB

Open AccessArticle

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

by Bram C. P. Jongbloed, Julie J. E. Teuwen, Rinze Benedictus and Irene Fernandez Villegas

Materials 2021, 14(21), 6620; https://doi.org/10.3390/ma14216620 - 3 Nov 2021

Cited by 17 | Viewed by 2925

Abstract

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. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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19 pages, 34750 KiB

Open AccessArticle

Experimental and Numerical Development on Multi-Material Joining Technology for Sandwich-Structured Composite Materials

by Lucian Zweifel, Igor Zhilyaev, Christian Brauner, Martin Rheme, Gregor Eckhard, Valentin Bersier, Slobodan Glavaški and Ricardo Pfeiffer

Materials 2021, 14(20), 6005; https://doi.org/10.3390/ma14206005 - 12 Oct 2021

Cited by 1 | Viewed by 2185

Abstract

Creating connection points for sandwich-structured composites without losing technical performance is key to realising optimal lightweight structures. The patented LiteWWeight^® technology presents cost-effective connections on sandwich panels in a fraction of a few seconds without predrilling. Ultrasonic equipment is used to insert a thermoplastic fastener into the substrate material and partially melt it into the porous internal structure. This creates a highly interlocked connection (connection strength is above 500 N) suitable for semi-structural applications. This study focused on the simulation and experimental validation of this process, mainly on the interaction between the pin and the substrate material during the joining process. The dynamic thermo-mechanical model showed reasonable agreement with experimental methods such as process data, high-speed camera monitoring or computed tomography and allowed the prediction of the connection quality by evaluation of the degree of interlock. The connection strength prediction by the developed model was validated within several various process setups, resulting in a prediction accuracy between 94–99% depending on the setup. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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