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Welding and Joining of Materials for Advanced Aerospace Applications

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (20 August 2022) | Viewed by 36493

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Special Issue Editors

Dr. Damjan Klobcar

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Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia
Interests: additive manufacturing; characterization of weld joints; ultrasonic welding; laser welding; friction stir welding; friction welding; resistance spot welding; arc welding technologies; adhesive bonding
Special Issues, Collections and Topics in MDPI journals

Dr. Uroš Trdan

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Guest Editor

Faculty of Mechanical Engineering, University of Ljubljana, Ljubljana, Slovenia
Interests: dissimilar joints; high-intensity laser interaction with matter; corrosion phenomena; material passivation ability; microstructural evaluation; mechanical testing; fatigue; acoustic emission monitoring; welding

Special Issue Information

Dear Colleagues,

Predictions of air traffic reveal that by the year 2050 the number of air passengers will have more than doubled. In order to make air traffic sustainable, fuel consumption and CO₂ emissions must be significantly reduced. Lightweight aerospace structures represent a promising way to achieve that. They are usually made of metallic and non-metallic materials, with good strength-to-weight ratio. The commonly used materials are high-strength aluminum and titanium alloys, stainless steels, high-strength steels, high-temperature nickel and cobalt superalloys, and various types of fiber-reinforced composites. These aerospace structures are often joined by welding, mechanical joining, adhesive bonding, or hybrid joining technologies, since similar and dissimilar metals and non-metals must be joined together to obtained the required structural component. However, the selection of proper materials and joining technologies with respect to cost efficiency, joint reliability, the weight of the structure, and joint strength efficiency (especially with high-cycle fatigue) is just one of the unique sets of challenges. To achieve the cleaner and sustainable production of such structures, an optimal use of energy, resources, and critical raw materials must be considered together with proper disassembly methods for optimal repair, replacement, and re-use of in-service components in high-tech applications. Often, joining can only be achieved using sophisticated modern welding and joining technologies, which must be thoroughly investigated and optimized for each specific component.

This Special Issue will cover new findings in the field of welding, mechanical joining, adhesive bonding, and hybrid joining of similar and dissimilar aerospace materials, additively manufactured parts, and hybrid manufactured parts. It will reveal new, crucial findings in the field of welding and joining technologies, weld microstructure, heat-affected zones, static and dynamic joint strength efficiency, in-service life predictions, and the disassembly of structures with respect to repair and reuse purposes. Manuscripts describing new experimental and theoretical studies on these fields are highly welcome in this Issue.

Dr. Damjan Klobcar
Dr. Uroš Trdan
Guest Editors

Manuscript Submission Information

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Keywords

friction welding
friction stir welding
laser welding
hybrid laser-arc welding
mechanical fastening
diffusion bonding
adhesive bonding
brazing
aerospace materials
dissimilar joints
composite-to-metal joining
microstructure
mechanical properties
fatigue properties
corrosion resistance
corrosion fatigue resistance
disassembly
repair
re-use

Published Papers (12 papers)

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12 pages, 2675 KiB

Open AccessArticle

Influence of Friction Riveting Parameters on the Dissimilar Joint Formation and Strength

by Damjan Klobčar, Franci Pušavec, Drago Bračun, Ivica Garašić, Zoran Kožuh, Aleksandar Vencl and Uroš Trdan

Materials 2022, 15(19), 6812; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15196812 - 30 Sep 2022

Cited by 3 | Viewed by 1179

Abstract

Friction riveting represents a promising technology for joining similar and/or dissimilar materials of light-weight components. However, the main drawback of the technology is that it is primarily used only with special machines for friction welding that have a force control. In this study we used accessible CNC machines with a position control. A set of friction riveting experiments was performed to establish the relationship between the processing parameters, the rivet formation and its mechanical strength. During the manufacturing process, the axial force and torque were constantly measured. The fabricated joints were examined using an X-ray imaging technique, microstructural analyses, and mechanical tests. The samples were subjected to the pull-out test to analyse the joints’ strength and determine the failure mode type. In addition, a correlation between the friction riveting processing parameters, the rivet penetration depth, the rivet shape and the joint strength was established. The results depict that a higher axial force in the first production phase at the higher feeding rate increases the penetration depth, while in the second phase at lower feeding rate, an anchoring shape of a rivet forms. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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28 pages, 9220 KiB

Open AccessArticle

Joining of Dissimilar Al and Mg Metal Alloys by Friction Stir Welding

by Ramandeep Singh Sidhu, Raman Kumar, Ranvijay Kumar, Pankaj Goel, Sehijpal Singh, Danil Yurievich Pimenov, Khaled Giasin and Krzysztof Adamczuk

Materials 2022, 15(17), 5901; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15175901 - 26 Aug 2022

Cited by 11 | Viewed by 1775

Abstract

In engineering applications, such as automobile, marine, aerospace, and railway, lightweight alloys of aluminum (Al) and magnesium (Mg) ensure design fitness for fuel economy, better efficiency, and overall cost reduction. Friction stir welding (FSW) for joining dissimilar materials has been considered better than the conventional fusion welding process because of metallurgical concerns. In this study, dissimilar joints were made between the AA6061 (A), AZ31B (B), and AZ91D (C) combinations based on the varying advancing side (AS) and retreating side (RS). The dissimilar joints prepared by the FSW process were further characterized by tensile testing, impact testing, corrosion testing, fracture, and statistical and cost analysis. The results revealed a maximum tensile strength of 192.39 MPa in AZ91 and AZ31B, maximum yield strength of 134.38 MPa in a combination of AA6061 and AZ91, maximum hardness of 114 Hv in AA6061 and AZ31B, and lowest corrosion rate of 7.03 mV/A in AA6061 and AZ31B. The results of the properties were supported by photomicrographic fracture analysis by scanning electron microscopy (SEM) observations. Further, the performance of dissimilar joints was statistically analyzed and prioritized for preference by similarity to the ideal solution (TOPSIS) method. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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10 pages, 4244 KiB

Open AccessArticle

by Gui-Lin Yue, Tai-Cheng Chen, Ren-Kae Shiue and Leu-Wen Tsay

Materials 2021, 14(20), 5949; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14205949 - 10 Oct 2021

Cited by 3 | Viewed by 1552

Abstract

Dissimilar brazing of Ti–15Mo–5Zr–3Al (Ti-1553) to commercially pure titanium (CP-Ti) using Ti–15Cu–15Ni foil was performed in this work. The microstructures in different sites of the brazed joint showed distinct morphologies, which resulted from the distributions of Mo, Cu, and Ni. In the brazed zone adhered to the Ti-1553 substrate, the partitioning of Mo from the Ti-1553 into the molten braze caused the formation of stabilized β-Ti without Ti₂Cu/Ti₂Ni precipitates. In the CP-Ti side, the brazed joint displayed a predominantly lamellar structure, composed of the elongated primary α-Ti and β-transformed eutectoid. The decrease in the Mo concentration in the brazed zone caused the eutectoid transformation of β-Ti to Ti₂Cu + α-Ti in that zone. The diffusion of Cu and Ni from the molten braze into the CP-Ti accounted for the precipitation of Ti₂Cu/Ti₂Ni in the transformed zone therein. The variation in the shear strength of the joints was related to the amount and distribution of brittle Ti₂Ni compounds. Prolonging the brazing time, the wider transformed zone, consisting of coarse elongated CP-Ti interspersed with sparse Ti₂Ni precipitates, was responsible for the improved shear strength of the joint. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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19 pages, 3422 KiB

Open AccessArticle

Linear Friction Welding of an AZ91 Magnesium Alloy and the Effect of Ca Additions on the Weld Characteristics

by Luis Angel Villegas-Armenta, Priti Wanjara, Javad Gholipour, Isao Nakatsugawa, Yasumasa Chino and Mihriban Pekguleryuz

Materials 2021, 14(11), 3130; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14113130 - 07 Jun 2021

Cited by 4 | Viewed by 2620

Abstract

Solid-state welding offers distinct advantages for joining reactive materials, such as magnesium (Mg) and its alloys. This study investigates the effect of linear friction welding (LFW) on the microstructure and mechanical properties of cast AZ91 (Mg–9Al–1Zn) and AZ91–2Ca alloys, which (to the best knowledge of the authors) has not been reported in the literature. Using the same set of LFW process parameters, similar alloy joints—namely, AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca—were manufactured and found to exhibit integral bonding at the interface without defects, such as porosity, inclusions, and/or cracking. Microstructural examination of the AZ91/AZ91 joint revealed dissolution of the Al-rich second phase in the weld zone, while the Mn containing phases remained and were refined. In the AZ91–2Ca/AZ91–2Ca joint, the weld zone retained Ca- and Mn-rich phases, which were also refined due to the LFW process. In both joint types, extensive recrystallization occurred during LFW, as evidenced by the refinement of the grains from ~1000 µm in the base materials to roughly 2–6 µm in the weld zone. These microstructural changes in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints increased the hardness in the weld zone by 32%. The use of digital image correlation for strain mapping along the sample gage length during tensile testing revealed that the local strains were about 50% lower in the weld zone relative to the AZ91 and AZ91–2Ca base materials. This points to the higher strength of the weld zone in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints due to the fine grain size, second phase refinement, and strong basal texture. Final fracture during tensile loading of both joints occurred in the base materials. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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15 pages, 9637 KiB

Open AccessArticle

Powder Interlayer Bonding of Nickel-Based Superalloys with Dissimilar Chemistries

by Olivia Stanners, James Russell, Sean John, Helen M. Davies and Silvia Marchisio

Materials 2021, 14(8), 2029; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14082029 - 17 Apr 2021

Cited by 5 | Viewed by 2081

Abstract

Novel joining methods are crucial for the aerospace industry to repair components damaged in the high stress, high cycle environment of the jet turbine engine. Powder interlayer bonding (PIB) is a novel joining technique that is being explored for use in the aerospace industry. PIB involves the use of a powder interlayer between two faying surfaces alongside a localised temperature gradient and compressive force to produce one joined workpiece. The use of a localised temperature gradient not only reduces the heat affected zone (HAZ) but also reduces the energy requirements for the process as only a small area of the component needs to be elevated in temperature. Nickel-based superalloys are commonly used in the gas turbine engine due to their superior mechanical properties that are maintained even under the most elevated temperatures experienced in the jet turbine engine. It is therefore essential these alloys can be easily repaired. Conventional joining methods such as friction welding have proved difficult for new generation nickel-based superalloys; therefore, there is much interest in PIB as an alternative repair technology. This study shows the potential of PIB to join dissimilar nickel-based superalloys: bonds with very little porosity were observed after only a short processing time. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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13 pages, 15887 KiB

Open AccessArticle

Influence of Welding Speed on Fracture Toughness of Friction Stir Welded AA2024-T351 Joints

by Miodrag Milčić, Dragan Milčić, Tomaž Vuherer, Ljubica Radović, Igor Radisavljević and Aleksija Đurić

Materials 2021, 14(6), 1561; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14061561 - 22 Mar 2021

Cited by 8 | Viewed by 2449

Abstract

In order to ensure a quality welded joint, and thus safe operation and high reliability of the welded part or structure achieved by friction stir welding, it is necessary to select the optimal welding parameters. The parameters of friction stir welding significantly affect the structure of the welded joint, and thus the mechanical properties of the welded joint. Investigation of the influence of friction stir welding parameters was performed on 6-mm thick plates of aluminum alloy AA2024 T351. The quality of the welded joint is predominantly influenced by the tool rotation speed n and the welding speed v. In this research, constant tool rotation speed was adopted n = 750 rpm, and the welding speed was varied (v = 73, 116 and 150 mm/min). By the visual method and radiographic examination, imperfections of the face and roots of the welded specimens were not found. This paper presents the performed experimental tests of the macro and microstructure of welded joints, followed by tests of micro hardness and fracture behavior of Friction Stir Welded AA2024-T351 joints. It can be concluded that the welding speed of v = 116 mm/min is favorable with regard to the fracture behavior of the analysed FSW-joint. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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14 pages, 20883 KiB

Open AccessArticle

Comparative Insight into the Interfacial Phase Evolutions during Solution Treatment of Dissimilar Friction Stir Welded AA2198-AA7475 and AA2198-AA6013 Aluminum Sheets

by Mohammad Reza Jandaghi, Hesam Pouraliakbar, Abdollah Saboori, Sun Ig Hong and Matteo Pavese

Materials 2021, 14(5), 1290; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14051290 - 08 Mar 2021

Cited by 22 | Viewed by 1704

Abstract

In the current research, dissimilar friction stir welded (FSW) sheets of AA2198-AA7475 and AA2198-AA6013 were solution treated at 460–580 °C for 1 h. Annealing at 580 °C led to complete degradation of both dissimilar weldments from the AA2198 side. According to the microstructure inspection, solution treatment triggered abnormal grain growth within the stir zone (SZ), and applying higher treatment temperatures enhanced the fraction of transformed grains. SEM analysis revealed that the pre-melting of grain boundaries (GBs) over 540 °C encouraged the diffusion of solute atoms to the GBs. The massive diffusion of Cu to the GBs led to the formation of Cu-rich eutectic phases in AA7475 and AA2198 and dense Cu-rich particles in AA6013. In the meantime, the diffusion of Mg and Zn to the GBs of AA7475 and Fe and Si to the GBs of AA6013 eventuated in the formation of coarse particles at the GBs which, in return, attenuated the bonding adhesion of the grains at SZ. The formation of remarkable Cu-rich phases in the pre-melted regions and significant contraction of the eutectic phase while cooling as well as the formation of particles at GBs resulted in intergranular failure of the joints from the AA2198 side of the SZ. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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9 pages, 3143 KiB

Open AccessArticle

Analysis of the Microstructure and Mechanical Properties of TiB_w/Ti-6Al-4V Ti Matrix Composite Joint Fabricated Using TiCuNiZr Amorphous Brazing Filler Metal

by Hao Tian, Jianchao He, Jinbao Hou and Yanlong Lv

Materials 2021, 14(4), 875; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14040875 - 12 Feb 2021

Cited by 7 | Viewed by 1512

Abstract

TiB crystal whiskers (TiB_w) can be synthesized in situ in Ti alloy matrix through powder metallurgy for the preparation of a new type of ceramic fiber-reinforced Ti matrix composite (TMC) TiB_w/Ti-6Al-4V. In the TiB_w/Ti-6Al-4V TMC, the reinforced phase/matrix interface is clean and has superior comprehensive mechanical properties, but its machinability is degraded. Hence, the bonding of reliable materials is important. To further optimize the TiB_w/Ti-6Al-4V brazing technology and determine the relationship between the microstructure and tensile property of the brazed joint, results demonstrate that the elements of brazing filler metal are under sufficient and uniform diffusion, the microstructure is the typical Widmanstätten structure, and fine granular compounds in β phase are observed. The average tensile strength of the brazing specimen is 998 MPa under room temperature, which is 97.3% of that of the base metal. During the high-temperature (400 °C) tensile process, a fracture occurred at the base metal of the highest tensile test specimen with strength reaching 689 MPa, and the tensile fracture involved a combination of intergranular and transgranular modes at both room temperature and 400 °C. The fracture surface has dimples, secondary cracks are generated by the fracture of TiB whiskers, and large holes form when whole TiB whiskers are removed. The proposed algorithm provides evidence for promoting the application of TiB_w/Ti-6Al-4V TMCs in practical production. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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18 pages, 5554 KiB

Open AccessArticle

Joining of Hypereutectic Al-50Si Alloys Using Lead-Free Brazing Filler Glass in Air

by Zhenjiang Wang, Zeng Gao, Xianli Ba, Junlong Chu, Peng He and Jitai Niu

Materials 2020, 13(24), 5658; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13245658 - 11 Dec 2020

Viewed by 1381

Abstract

Hypereutectic Al-Si alloys are attractive materials in the fields of electronic packaging and aerospace. A Bi₂O₃-ZnO-B₂O₃ system lead-free brazing filler glass was employed to braze hypereutectic Al-50Si alloys in air. The hypereutectic Al-50Si alloys were pre-oxidized and the low-temperature glass powder was flake-shaped in the brazing process. The effects of brazing temperature and time on joints microstructure evolution, resulting mechanical strength, and air tightness were systematically investigated. The results indicated that the maximum shear strength of the joint was 34.49 MPa and leakage rate was 1.0 × 10⁻¹⁰ Pa m³/s at a temperature of 495 °C for 30 min. Crystalline phases, including Bi₂₄B₂O₃₉ and Bi₂O₃, were generated in the glass joint. The formation of a diffusion transition layer with a thickness of 3 μm, including elements of Al, Si, Zn, Bi, Na, and B, was the key to form an effective joint. The elements of Al, Si, and Bi had a short diffusion distance while the elements of Zn, Na, and B diffused in a long way under brazing condition. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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11 pages, 12322 KiB

Open AccessArticle

Influence of Metallic Oxide Nanoparticles on the Mechanical Properties of an A-TIG Welded 304L Austenitic Stainless Steel

by Sebastian Balos, Miroslav Dramicanin, Petar Janjatovic, Nenad Kulundzic, Ivan Zabunov, Branka Pilic and Damjan Klobčar

Materials 2020, 13(20), 4513; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13204513 - 12 Oct 2020

Cited by 3 | Viewed by 1787

Abstract

Austenitic stainless steels represent a significant aerospace material, being used for various castings, structural components, landing gear components, afterburners, exhaust components, engine parts, and fuel tanks. The most common joining process is tungsten inert gas (TIG) welding, which possesses many advantages such as suitability to weld a wide range of ferrous and non-ferrous metals and alloys, providing high quality welds with good mechanical properties. Its major disadvantage is low productivity due to low penetration and welding speed. This can be overcome by introducing an activating flux before welding. The activating flux reverses the material flow of the weld pool, significantly increasing penetration. Therefore, shielding gas consumption is reduced and welding without a consumable is enabled. However, the consumable in conventional TIG also enables the conditioning of the mechanical properties of welds. In this study, Si and Ti metallic oxide nanoparticles were used to increase the weld penetration depth, while bend testing, tensile, and impact toughness were determined to evaluate the mechanical properties of welds. Furthermore, optical emission spectroscopy, light, and scanning electron microscope were used to determine the chemical compositions and microstructures of the welds. Chemical compositions and weld mechanical properties were similar in all specimens. The highest tensile and impact properties were obtained with the specimen welded with the flux containing 20% TiO₂ and 80% SiO₂ nanoparticles. Although lower than those of the base metal, they were well within the nominal base metal mechanical properties. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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21 pages, 11440 KiB

Open AccessArticle

Influence of Rivet Diameter and Pitch on the Fatigue Performance of Riveted Lap Joints Based on Stress Distribution Analysis

by Jintong Liu, Anan Zhao, Zhenzheng Ke, Zhendong Zhu and Yunbo Bi

Materials 2020, 13(16), 3625; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13163625 - 16 Aug 2020

Cited by 14 | Viewed by 3603

Abstract

Interference-fit riveting is one of the most widely used mechanical joining ways in aircraft assembly. The fatigue performance of riveted joints has a significant impact on the service life and reliability of aircraft. In this paper, the fatigue performance of the riveted lap joints with various rivet diameters and pitches are studied based on stress distribution analysis under tensile load. First, a theoretical model of the riveted lap joint under tensile load is developed by using the spring-mass model. The rivet-load stress, bypass stress, and interference stress around the riveted hole are analyzed. Then, the finite element (FE) model of riveted lap joints are established. The influence of rivet diameter and pitch on stress distribution around the riveted hole are discussed. Finally, the fatigue tests are conducted with riveted lap joint specimens to verify the theoretical model and FE results, and a good agreement is observed. Based on the simulation and experimental results, a good combination of structural parameters of the riveted lap joint is found which can optimize the stress distribution around the riveted hole and improve the fatigue life of the riveted lap joint. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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Review

Jump to: Research

43 pages, 8119 KiB

Open AccessEditor’s ChoiceReview

Review on Adhesives and Surface Treatments for Structural Applications: Recent Developments on Sustainability and Implementation for Metal and Composite Substrates

by Ana C. Marques, Alexandra Mocanu, Nataša Z. Tomić, Sebastian Balos, Elisabeth Stammen, Asa Lundevall, Shoshan T. Abrahami, Roman Günther, John M. M. de Kok and Sofia Teixeira de Freitas

Materials 2020, 13(24), 5590; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13245590 - 08 Dec 2020

Cited by 63 | Viewed by 12217

Abstract

Using adhesives for connection technology has many benefits. It is cost-efficient, fast, and allows homogeneous stress distribution between the bonded surfaces. This paper gives an overview on the current state of knowledge regarding the technologically important area of adhesive materials, as well as on emergent related technologies. It is expected to fill some of the technological gaps between the existing literature and industrial reality, by focusing at opportunities and challenges in the adhesives sector, on sustainable and eco-friendly chemistries that enable bio-derived adhesives, recycling and debonding, as well as giving a brief overview on the surface treatment approaches involved in the adhesive application process, with major focus on metal and polymer matrix composites. Finally, some thoughts on the connection between research and development (R&D) efforts, industry standards and regulatory aspects are given. It contributes to bridge the gap between industry and research institutes/academy. Examples from the aeronautics industry are often used since many technological advances in this industry are innovation precursors for other industries. This paper is mainly addressed to chemists, materials scientists, materials engineers, and decision-makers. Full article

(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)

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