Friction Lap Joining Research Articles

Optimization of friction lap joining parameters and exploration connection mechanism of CFRPA6/6061-T6 aluminum alloy hybrid structures

Carbon-fiber-reinforced thermoplastics (CFRTP) and lightweight-metal hybrid structures have been applied in the automotive and aerospace industries. Nonetheless, due to the enormous differences in physical and chemical properties of materials, the stability of the CFRTP and the lightweight-metal hybrid joint interface is challenging to ensure. In current work, the influence of welding parameters (rotational speed, welding speed, and plunge depth) on the stability of friction lap joining (FLJ) hybrid joints between carbon-fiber reinforced polyamide6 (CFRPA6) and 6061-T6 aluminum alloy (6061) was studied. The analysis of variance (ANOVA) showed that the rotational speed was the greatest factor affecting joint strength. By optimizing the welding parameters, a high-strength hybrid joint with a maximum tensile force of 2.5 kN was obtained. To further understand the mechanism of interface connection, experimental methods and density functional theory (DFT) calculations were systemically performed. The results show that the nitrogen and oxygen atoms in CFRPA6 will bond with aluminum on the 6061 surfaces to produce the interfacial Al-N and Al-O covalencies due to the p-orbital hybridization between bonding atoms.

Achieving a Strong Friction‐Lap Joint of Continuous Carbon‐Fiber‐Reinforced Plastic/Aluminum Alloy via a Surface Laser‐Processing Pretreatment

It is difficult to achieve high‐strength joints of metals to carbon‐fiber‐reinforced plastics (CFRPs) with high contents of continuous fibers with the poor fluidity. Herein, a special designed laser‐processing pretreatment is conducted on the surface of 5052Al, and friction‐lap joining (FLJ) is employed to join pretreated 5052Al to the CFRP with 50%–55% fiber content. The maximal tensile shear force and strength reach 4.06 kN and 18.04 MPa, respectively, with an increment of 72% compared to the untreated sample. It is the first time to achieve the high‐strength joint of Al alloys to CFRPs with high contents of continuous fibers via FLJ. The joining area and adhesion work are quantified by theoretical calculations, and the residual stresses are visualized by finite‐element analysis. The laser‐processing pretreatment changes the plain Al alloy surface structure into the rough and porous structure, largely increasing the mechanical interlocking effect of the joint, and also changes the Al alloy surface wetting behavior and increases the adhesion work from 59.66 to 81.17 mN m−1. That largely changes the chemical reaction feature between the CFRP and Al alloy, resulting in their tight bonding. In addition, the residual stresses weaken, which further improve the tight bonding effect.

Femtosecond laser fabricated micro/nano interfacial structures to strengthen CFRPEEK/A6061-T6 FLJ hybrid joints

Metal-thermoplastic hybrid joints have been widely used to lighten weight of advanced flight vehicles in recent years. In the current work, femtosecond laser was used to build double-scale hierarchical structures of microstrip and nanoparticles on A6061-T6 (6061) surface to fabricate stable hybrid joints with carbon fiber reinforced polyetheretherketone (CFRPEEK) by friction lap joining (FLJ). The effects of femtosecond laser modification on bonding strength of CFRPEEK/6061 were uncovered by experimental method and finite element analysis (FEA). The results indicated that the effective mechanical interlocking caused the enhancing bonding strength of CFRPEEK/6061 FLJ joints. Furthermore, by adjusting processing parameters of femtosecond laser modification, 6061 surfaces evolved to be superhydrophobic , resulting in a perfect CFRPEEK/6061 interface without voids and crack, corresponding to the maximal bonding strength of 19.40 MPa. • Femtosecond laser modification was used to build periodic micro/nano structures on 6061 surfaces. • 6061 surfaces were evolved to be hydrophilic and superhydrophobic after modification. • The FLJ joints of superhydrophobic 6061 and CFRPEEK achieved the maximal 19.40 MPa.

Enhancing Interfacial Reliability of Metal–Thermoplastic Hybrid Joints via Adding Carbon Fiber and Adjusting Welding Heat Input

Interfacial structures govern the reliability of metal-thermoplastic hybrid joints used in the aerospace industry. The current work demonstrated by experimental methods and density functional theory (DFT) calculations that introduction of carbon fibers (CFs) enhanced the mechanical properties and weakened the corrosion resistance of polyamide 6 (PA6)/A6061-T6 (6061) joints. The bonding strength of typical PA6/6061 joints was increased by 33.70% with the introduction of CF. However, the differences in intrinsic work functions of the CF and various phases within 6061 led to the formation of serious cracks at CFRPA6/6061 interfaces and heavy corrosion on 6061 surfaces, corresponding to the decreased corrosion resistance of PA6/6061 joints. Herein, we present a potential solution to adjust the welding heat input to enhance metal/thermoplastic interfacial reliability. With a rotation speed of 400 mm/min during friction lap joining (FLJ), the fabricated CFRPA6/6061 joint could achieve a strong interface with high strength (bonding strength = 1.730 kN) and relative corrosion resistance (corrosion rate < 0.1 mm/a). The results provide a reliable explanation for the effect of CF on mechanical properties and corrosion resistance of CFRPA6/6061 joints. Furthermore, the knowledge gained in this work will benefit future research in the optimization of processes to improve the reliability of metal-thermoplastic hybrid structures.

Adhesion enhancement of PEEK/6161-T6 FLJ joints via laser surface modification

The metal-thermoplastic hybrid structure has been widely employed in the aviation and aerospace industry. In this work, we developed a feasible way of laser surface texturing to address the poor adhesion between PEEK and 6061-T6 aluminum alloy. With the laser surface modification on 6061-T6 aluminum alloy, the PEEK/6061-T6 friction lap joining strength was improved significantly. The experimental results showed that the tensile shear strength between PEEK and 6061-T6 with laser textured surfaces achieved the maximum of 48.14 MPa. The enhanced bonding strength was attributed to the mechanical interlocking at the interface between PEEK and 6061-T6 caused by periodic micro-pores and nano-particles. After the progress of laser surface texturing, the double-scale hierarchical structures were produced on the surface of modified 6061-T6 alloy, leading to the formation of superhydrophobic or hydrophobic surfaces. Besides, quantitative fractal analysis of 6061-T6 surfaces was performed to study the relation between the morphology of 6061-T6 surface and the adhesion property of PEEK and 6061-T6. The results indicated that the superhydrophobic surface of 6061-T6 exhibited higher adhesion property with PEEK than the hydrophobic surface. A flawless interface was observed in the joint of PEEK and 6061-T6 with the superhydrophobic surface, compared to the voids observed at the interface of PEEK and 6061-T6 with the hydrophobic surface.

ロボット摩擦攪拌接合・摩擦重ね接合システムの進化 ―ロボットシステムのメリットおよび量産部品への対応と今後の広がり―

ロボット摩擦攪拌接合・摩擦重ね接合システムの進化 ―ロボットシステムのメリットおよび量産部品への対応と今後の広がり―

Achieving strong friction lap joints of carbon-fiber reinforced plastic and metals by modifying metal surface structure via laser-processing pretreatment

Strong dissimilar joints of metals and carbon fiber reinforced plastic (CFRP) are highly demanded for the lightweight design in many fields, which, however, are rather challenging to achieve directly via welding. In this study, 5052 Al alloy and plain carbon steel were first pretreated by a laser-processing method to create rather coarse porous metal surfaces, which were then welded to polyamide 6 based CFRP using friction lap joining. The maximum tensile shear force of the dissimilar joints of CFRP-Al alloy and CFRP-steel achieved 4.9 kN, and 3.9 kN, respectively, and the joint efficiency achieved 78% and 62%, respectively, which were more than three times as those of the CFRP- as-received metal joints. This is the first report on the strengthening of the metal-CFRP friction based joints via the assisting laser treatment technique. The significant improvement of the joint strength could be attributed to a great increase of the mechanical anchors and the chemical bonding area at the metal-CFRP interface.

Research on Friction Lap Joining between Aluminum and Fiber Reinforced Plastics

Research on Friction Lap Joining between Aluminum and Fiber Reinforced Plastics

Effect of silane coupling on the joint characteristics of friction lap joined Al alloy/CFRP

ABSTRACTDissimilar materials joining of an A5052 plate and a carbon fibre reinforced thermoplastic (CFRTP), which consisted of polyamide 6 (PA6) with 20 wt% carbon fibre addition, was performed using friction lap joining (FLJ) with the Al alloy plate as a top and the CFRTP plate as a bottom. The joint characteristics were evaluated to investigate effects of the surface treatment by the silane coupling treatment for A5052 and the joining speed on the joining properties. The joint strength was increased by inducing the silane coupling treatment for the A5052 plate surface. The tensile shear fracture load of the silane coupling treated FLJ joint increased by increasing the joining speed up to 6.67 mm/s and then decreased. The maximum tensile shear fracture load of 5.0 kN was obtained at the joining speed of 6.67 mm/s, and the fracture occurred at the CFRTP base plate with the joint efficiency of 97%. The shear strength of the joint interface of the joint formed at the joining speed of 1.67 mm/s, which fractured at the joining interface by the tensile shear test, was estimated to be about 19 MPa. The covalent bondings between the A5052 plate and the silane coupling layer, and the silane coupling layer and the CFRTP plate were indicated by inducing the silane coupling treatment.

Numerical modelling in friction lap joining of aluminium alloy and carbon-fiber-reinforced-plastic sheets

Multi-material combinations of aluminium alloy and carbon-fiber-reinforced-plastics (CFRP) have gained attention in automotive and aerospace industries to enhance fuel efficiency and strength-to-weight ratio of components. Various limitations of laser beam welding, adhesive bonding and mechanical fasteners make these processes inefficient to join metal and CFRP sheets. Friction lap joining is an alternative choice for the same. Comprehensive studies in friction lap joining of aluminium to CFRP sheets are essential and scare in the literature. The present work reports a combined theoretical and experimental study in joining of AA5052 and CFRP sheets using friction lap joining process. A three-dimensional finite element based heat transfer model is developed to compute the temperature fields and thermal cycles. The computed results are validated extensively with the corresponding experimentally measured results.

Achieving superior mechanical properties in friction lap joints of copper to carbon-fiber-reinforced plastic by tool offsetting

It is a challenge to achieve a sound welded metal/carbon-fiber-reinforced thermoplastic (CFRTP) joint with high strength and few bubbles. In this study, sound lap joints of Cu and CFRTP were obtained by friction lap joining (FLJ) directly at rotation rates of 600–2000rpm, with the welding tool at the joint center and offsetting the tool 7mm away from the center toward the retreating side, respectively. Tool offsetting reduced the non-uniform temperature distribution in the lap joints resulting from the high conductivity of Cu, which not only enhanced the tensile shear force from 0.89–2.25kN to 1.71–3.54kN, with the maximum increasing rate of 135%, but also reduced the bubble area to only 19% of the original level of 2000rpm. It is the first time to report a high-quality Cu/CFRTP joint with a high strength and few bubbles. The large increase of the strength after tool offsetting was attributed to the increase of the joining area, the decrease of bubbles and the decrease of the CFRTP degradation. The details on the generation, quantitative distribution and expulsion of the bubbles in the FLJ joints were discussed.

Direct joining of oxygen-free copper and carbon-fiber-reinforced plastic by friction lap joining

Oxygen-free copper (Cu) was successfully joined to carbon-fiber-reinforced thermoplastic (CFRTP, polyamide 6 with 20wt% carbon fiber addition) by friction lap joining (FLJ) at joining speeds of 200–1600mm/min with a constant rotation rate of 1500rpm and a nominal plunge depth of 0.9mm. It is the first time to report the joining of CFRTP to Cu by FLJ. As the joining speed increased, the tensile shear force (TSF) of joints increased first, and decreased thereafter. The maximum TSF could reach 2.3kN (15mm in width). Hydrogen bonding formed between the amide group of CFRTP and the thin Cu2O layer on the Cu surface, which mainly contributed to the joint bonding. The influence factors of the TSF of the joints at different joining speeds were discussed. The TSF was mainly affected by the joining area, the degradation of the plastic matrix and the number and the size of bubbles. As the joining speed increased, the influence factors varied as follows: the joining area increased first and then decreased; the degradation of the plastic matrix and the number and the size of bubbles decreased. The maximum TSF was the comprehensive result of the relatively large joining area, small degradation of the plastic matrix and small number and sizes of bubbles.

Effect of anodizing on direct joining properties of aluminium alloy and plastic sheets by friction lap joining

We have proposed a novel joining process, friction lap joining (FLJ), to join metallic material sheet directly to polymer sheet and have investigated mechanical and metallurgical properties of these dissimilar joints. The joining mechanism is discussed with an evaluation of the TEM microstructure at the joint interface between A2017 aluminium alloy and two kinds of polymer, ethylene-acrylic acid copolymer (EAA), and high density polyethylene (PE). EAA sheet was easily joined to an as-received aluminium alloy sheet by FLJ, because EAA had a polar functional group, COOH. On the contrary, PE was not able to be joined to an as-received aluminium alloy, because PE had no polar functional group. However, anodizing of aluminium alloy was effective to join these materials by the assistance of the anchor effect.

摩擦重ね接合によるステンレス鋼と炭素繊維強化熱可塑性樹脂との異材接合

The effect of joining speed on the joining strength of the dissimilar materials joint of the SUS304/ carbon fiber reinforced thermoplastic (CFRTP) was investigated. SUS304 plates (150mm×75mm×2.0mm) and CFRTP (consisted of PA6 matrix and 20wt% carbon fiber) plates (150mm×75mm×3.0mm) were joined by friction lap joining (FLJ) using rotational WC-Co tool. Different joining speeds in the range from 1.67mm/s - 16.7mm/s and the tool rotation speed of 8.33 s-1 were selected as processing conditions. Direct joining of SUS304/CFRTP was accomplished at all of joining speeds by FLJ. The tensile shear strength of the joint increased with increasing joining speed up to 3.33mm/s, however, it decreased from the joining speed of 3.33mm/s to 16.7mm/s. The interfacial fracture occurred at all of joining speeds. The fractured surface analysis of SUS304 revealed that teared fragments from the CFRTP base plate were bonded to SUS304. At the lower joining speed, the excessive heat input caused thermal decomposition of PA6 from the matrix of CFRTP resulted bubbles; the joint strength was decreased because of these bubbles. The shortage of the heat input at the higher joining speed caused insufficient wetting of molten PA6 to SUS304, which resulted in the decreased strength of the joint.

Direct joining of plastic to copper by friction lap joining

Direct joining of plastic to copper by friction lap joining

Direct dissimilar joining of aluminium alloys and polyamide 6 by friction lap joining

Direct dissimilar joining of various Al alloy (A1050, A3004, A5052 and A5083) plates and a polyamide 6 plate was performed using friction lap joining (FLJ) with the Al alloy plate as a top and the polyamide 6 plate as a bottom. The effect of Mg content in Al alloys on the joining strength was investigated. TEM analysis made clear that the polyamide 6 and Al alloys were joined via oxide layer consisting of Al2O3 and MgO. The results of XPS analysis indicated that MgO was formed by the heating during FLJ, and the quantity of MgO was increased with increasing Mg content in Al alloys. The tensile shear strengths of A3004, A5052 and A5083 joints were saturated to about 2 kN because of the tensile fracture at the polyamide 6 plate outside the tool-passed zone, which were higher than that of the A1050 joint fractured at the joint interface. The peel strength of the joint was increased with increasing Mg content in Al alloys, and the fracture occurred both at the joint interface and at the polyamide 6 plate on the joint area. The fraction of polyamide 6 plate fracture was also increased with increasing Mg content in Al alloys.

Joining Mechanism of Dissimilar Materials such as Metal and Plastic Sheets by Friction Lap Joining

It is difficult to join dissimilar materials such as metallic material and polymer. We have investigated to join Aluminum alloy and high density polyethylene (PE) and ethylene acrylic acid copolymer (EAA) using Friction Lap Joining (FLJ) and then concluded EAA could be strongly joined with Aluminum alloy. PE could not be joined without anodizing. We have considered that EAA has a polar functional group, COOH. On the contrary, PE cannot be joined to an as-received aluminum alloy, because PE has no polar functional group. So, we have tried to confirm this mechanism with XPS and FTIR to investigate the interface between anodized surface and that of polymer. We find that the possibility of chemical bonding arises between O-H in COOH and O in Al2O3or O in C=O and O in Al2O3 at elevated temperature.

Friction Lap Joining of Thermoplastic Materials to Carbon Steel

Friction Lap Joining of Thermoplastic Materials to Carbon Steel

Effect of Anodizing on Direct joining Property of Aluminum Alloy and Plastic Sheets by Friction Lap Joining

Effect of Anodizing on Direct joining Property of Aluminum Alloy and Plastic Sheets by Friction Lap Joining

Direct joining of carbon-fiber–reinforced plastic to an aluminum alloy using friction lap joining

A carbon-fiber–reinforced thermoplastic (polyamide 6 with 20wt.% carbon fiber addition) and an aluminum alloy (A5052) were joined using friction lap joining. The joint characteristics were evaluated to investigate the effects of A5052 surface treatments and the joining speed on the joint properties. Carbon-fiber–reinforced thermoplastic and A5052 were joined via an interfacial magnesium oxide layer. Surface grinding of the A5052 generated the aluminum hydroxide on the alloy surface and increased the tensile shear strength of the joint. The tensile shear strength increased as the joining speed increased from 100 to 1600mmmin−1, and decreased thereafter.