Laser Joining Research Articles

Effect of laser heat input on the interface morphology during laser joining of CFRTP and 6061 aluminum alloy

Laser joining technology with the advantages of high efficiency and good processing flexibility has the good application prospects in the connection of the Carbon Fibre Reinforced Thermoplastics Plastics (CFRTP) and aluminum alloy. Laser joining of CFRTP and 6061 aluminum alloy is investigated with various laser processing parameters. The microstructure characteristics and energy dispersive spectroscopy (EDS) results are analyzed. Besides, the fracture morphologies of the laser connection joints are studied. The results indicate that there is a partial unconnected area between the resin and the 6061 aluminum alloy due to the existence of the air bubbles, while most of the interface area is tightly connected where the mechanical anchoring effect exists.

Development of Laser Cutting and Joining Processing

Development of Laser Cutting and Joining Processing

Research Status and Development on Laser Joining of Metal to Plastic

Research Status and Development on Laser Joining of Metal to Plastic

Laser assisted joining of St12 to polycarbonate: Experimental study and numerical simulation

In this study dissimilar joining of St12 to Polycarbonate is accomplished by a Nd: YAG pulsed laser and examined by finite element (FE) model and analysed by statistical method. Several experiments are carried out to materialize a direct joint between St12 to Polycarbonate. To investigate thermal phenomena of the laser joining process a FE model is developed by Abaqus software. To approximate heat source distribution, a Cylindrical-Involution-Normal model is programmed in FORTRAN language. To find out the sensitivity of the FE model to the elements size, a number adjustment tests are used and the FE model is validated by experimental data. Effects of laser power (190−230 W) and laser scanning speed (3.6–7.6 mm/s) on average bond width (AW), delta bond width (DW), and maximum of temperature profile (MT) have been investigated via response surface methodology. Results reveal that power of laser is the determinant variable of average bond width and maximum temperature profile, however, scanning speed of laser is the most effective variable on delta bond width. An appropriate process window required to achieve a sound dissimilar joint (without any decomposition of the polymer) is finally suggested.

Influence of defocus distance on laser joining of CFRP to titanium alloy

Laser joining of carbon fiber reinforced polyether ether ketone (CFRP-PEEK) to titanium alloy (TC4) was performed. The influence of defocus distance, also described as irradiance diameter of laser beam on interfacial joining was investigated. The appearance of welded joint and the microstructure at joint interface was observed. The fracture load was thereafter obtained. In addition, temperature field simulation at the joint interface during laser joining process was carried out to clarify the joining mechanism. The results indicated that good appearances were obtained with low defocused distance. The interfacial observation showed that mechanical bonding was generated at the joint interface since the melted resin was embedded in the rough surface of the TC4. Besides, a new phase formed at the interface between CFRP-PEEK and TC4, which was identified as CTi0.42V1.58. The content of the phase increased as the defocus distance increased. Shear force decreased when the defocus distance increased from −4 mm (irradiance diameter 0.84 mm) to 0 mm (irradiance diameter 0.6 mm), and then increased when the defocus distance increased from 0 mm to +8 mm (irradiance diameter 1.06 mm). This phenomenon was explained by simulation result of temperature field that the width of the range of melting temperature of the resin increased as the laser beam diameter increased. The simulation results were consistent with the changes of the width of resin adhesion in actual joint.

Investigation the effect of pulsed laser parameters on the temperature distribution and joint interface properties in dissimilar laser joining of austenitic stainless steel 304 and Acrylonitrile Butadiene Styrene

Direct laser joining of metal to plastic materials is one of the cost effective methods of joining. The demand for laser welding of stainless steels and thermoplastics is going on increase because of having many applications such as automotive, aerospace and aviation industries. This paper presents the experimental investigation of direct laser joining of stainless steel 304 and Acrylonitrile Butadiene Styrene (ABS). The effects of pulsed laser parameters including laser welding speed, focal length, frequency and power on the themperature field and tensile shear load was investigated. The results showed that excessive increase of the joint interface temperature mainly induced by high laser power density results in exiting of the more volume of the molten ABS from the stainless steel melt pool. Also, increasing the laser power density through decreasing the focal length or increasing the laser power led to an increase in the surface temperature, higher beam penetration and high volume of molten ABS. Decreasing the focal length from 5 to 2 mm significantly rose the temperature from 150 to 300 °C. By increasing the laser pulse frequency, the number of bobbles at the ABS interface surface remarkably increased where the temperature increased from 120 to 180 °C. The X-ray spectroscopy results showed the existence of the polymer elements on the metal surface at the joint interface zone. The tensile shear load clearly increased from 280 to 460 N with augmentation of laser average power from 180 W to 215 W. Applying higher levels of laser power has clearly decreased the tensile shear load due to creating bigger bobbles and more cavities at the adhesive zone.

Hybrid laser technique for joining of polymer and titanium alloy

Weight reduction of parts is of great importance in automotive and aerospace industries. Laser direct joining of dissimilar materials had been investigated previously to obtain lightweight characteristics and keep the local excellent plasticity and mechanical property. In the present work, the authors adopt the hybrid laser joining method to bond Ti6Al4V and polyamide (PA66). Laser texturing pretreatment is performed on the Ti6Al4V surface prior to the laser joining process. Oblique microgrooves with the depth ranging from 100 to 550 μm are designed and fabricated on Ti6Al4V surfaces to improve the bonding strength between Ti6Al4V and polyamide. Single lap shear tests are carried out after the laser joining process. The highest breaking force of laser joined Ti6Al4V-PA66 joints reaches around 942 N, which is high up to more than 90% of base PA66 breaking force (1043 N) and about 4.9 times of the joints with a smooth Ti6Al4V surface (194 N). The great enhancement of breaking force of the joints is attributed to the strong mechanical bonding quality between PA66 and surface-textured Ti6Al4V. The employed hybrid laser joining method shows great potential in manufacturing industries.

On the stability, microstructure, and mechanical property of powder metallurgy Al–SiC nanocomposites during similar and dissimilar laser welding

Aluminum matrix nanocomposites consolidated by powder metallurgy (P/M) have significant potential for practical applications in the aerospace and automotive industries considering their admirable strength to weight ratio and good corrosion resistance. Due to dimensional restrictions in traditional P/M manufacturing routes, similar and dissimilar joining would be essential to design complex structures, however, the stability of Al-matrix nanocomposites during joining process is a crucial issue. In this research, the stability of an Al-6 vol% (50 nm, ex-situ) SiC-2 vol% (15 nm, in situ) Al2O3 hybrid P/M nanocomposite was evaluated during laser joining in comparison to similar and dissimilar joints with commercially pure aluminum (AA1050 alloy). The processing parameters were optimized with a constant focus spot size of 200 μm, laser power of 4 kW, and travel speed of 8 m/min to achieve full-penetration joints. According to the experimental results, the similar P/M nanocomposite exhibited unstable behavior during laser welding due to the formation of porosity associated with clustering and void expansion near SiC nanoparticles. Hence, the fusion zone in both joint designs consisting of similar and dissimilar containing nanocomposite material became heterogeneous due to the presence of clusters and shrinkage micro-voids. The mechanical properties of weldments deteriorated considerably, with large fluctuations in the hardness profiles as well as low joining efficiency (<30%) and brittle fracture. Defects present in dissimilar welds were mainly located at the nanocomposite side.

Effect of welding parameters on functionality of dissimilar laser-welded NiTi superelastic (SE) to shape memory effect (SME) wires

Numerous are the applications of NiTi shape memory alloys (SMA) in smart designs and structures. Many researchers and manufacturers investigate laser welding and joining process to integrate the functionalities of NiTi alloys, including superelasticity (SE) and shape memory effect (SME). Accordingly, this integration would provide better flexibility to that class of materials which can be applied in the development of multi-functional systems and components. The present study investigates the laser welding of dissimilar NiTi wires, including both SE and SME wires, using a high-power diode laser (HPDL). The resulting welded joints were investigated using various mechanical and microstructural analysis including optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), and tensile and micro-hardness tests. Various operational parameters, that is, laser power and speed, were investigated to obtain high-quality welded joints, preserve the transformation temperature of the welded zone, and, subsequently, minimize the influence of the welding process on the functionality of the joined materials.

A Laser Joining System for Titanium and Polyethylene Terephthalate Plastic Controlled by Multiple Signal Sources

Laser direct joining of metal and plastic plays a significant role in manufacturing of multiple material structures. To improve the strength of the joint, a controllable laser joining system was developed for polyethylene terephthalate plastic and titanium based on the detected multiple signal sources. The main contribution of this paper lies in sensing 1) the intensity of thermal radiation to control process heat by adjusting the laser power; and 2) the reflection of the helium–neon laser to control the movement of the specimens. The response speeds of thermal radiation intensity when increasing or decreasing the laser powers were measured to guide the adjustment of laser power. The intensities of reflective light before and after the joining process were measured to guide the movement control. Then, the integrated control process was set up. Width, tensile shear strength, and fracture position of the joint produced by the controllable joining system were compared with those produced by the conventional constant power method, which validated the advantage of this newly developed system.

Porosity Elimination in Modified Direct Laser Joining of Ti6Al4V and Thermoplastics Composites

Hybrid lightweight components with strong and reliable bonding qualities are necessary for practical applications including in the automotive and aerospace industries. The direct laser joining method has been used to produce hybrid joints of Ti6Al4V and glass fiber reinforced polyamide (PA66-GF30). Prior to the laser joining process, a surface texturing treatment is carried out on Ti6Al4V to improve joint strength through the formation of interlock structures between Ti6Al4V and PA66-GF30. In order to reduce the generated micro-pores in Ti6Al4V-PA66-GF30 joints, a modified laser joining method has been proposed. Results show that only very few small micro-pores are generated in the joints produced by the modified laser joining method, and the fracture strength of the joints is significantly increased from 13.8 MPa to 41.5 MPa due to the elimination of micro-pores in the joints.

An artificial neural network model for laser transmission welding of biodegradable polyethylene terephthalate/polyethylene vinyl acetate (PET/PEVA) blends

Laser transmission welding is a quick, easy, and viable method to join plastic materials for several industrial domains. The main challenge for manufacturers is still on how to choose the input process parameters to achieve the best joint performance. Joining between PET (polyethylene terephthalate) films does not make an exception, with quality strictly depending on laser joining parameters. The purpose of the present study is to estimate the weldability of a polymeric material couple according to their thermal and optical properties. This paper investigates an experimental study of laser transmission welding of PET 100% and PET-PEVA (polyethylene vinyl acetate) 5%, 10%, and 15% sheets by a diode laser. In the present work, laser power and scan speed were considered as operational parameters, which have a significant influence on the quality of the joint zone. Then, the influence of PEVA aliquots in PET/PEVA blends, which altered the mechanical properties, such as joining behavior, mechanical characterization, and degradation level, was analyzed. In addition, an artificial neural network model is developed to achieve the optimal laser parameters. The obtained results proved the advantage of this model, as a prediction tool, for developing laser welding parameters.

Effect of the Surface Texture on Laser Joining of a Carbon Fiber-Reinforced Thermosetting Plastic and Stainless Steel

A carbon fiber-reinforced thermosetting plastic and stainless steel were joined by the fiber laser. The surface texture effect on the joint was investigated. The abrasive paper scratching is shown to form single directional striae on stainless steel with intermittent ridges. Laser texture processing creates uniformly distributed microdimples and ridges, which forms a rectangular cellular structure. This processing can improve the fluidity of molten polyphenylene sulfite during laser joining. Laser scanning on stainless steel results in the formation of fusion and heat-affected zones. In the heat-affected zone, lathy ferrite is located along the boundary, while in the fusion zone, ferrite forms the skeletal structure and separates austenite into a cellular structure. The surface texture modification can contribute to the adhesive strength between stainless steel and polyphenylene sulfite through on enlarged contact surface area by forming striae, microdimples, and ridges. As compared to the abrasive paper scratching, the stainless steel/plastic joint with laser texture processing exhibits a higher shear strength.

Laser Joining of Carbon-Fiber-Reinforced Polymer and Metal with High-Strength and Corrosion-Resistant Bonds

Abstract The combination of thermoplastic composites and metals is a critical methodology to enable the lightweight structures. Due to the high incompatibility of their physical and chemical properties, the bonding strength is always weak. In addition, the reinforced materials of composites, such as carbon fibers, which are electrically conductive and electrochemically noble, would quickly deteriorate the joint strength through galvanic corrosion. In this study, a novel laser joining process was developed for carbon-fiber-reinforced polymer and aluminum and/or steel. Methods of forming a layer that is more chemically inactive than the metal to be joined with composites, i.e. aluminum oxide on aluminum and stainless steel on steel, through laser surface texturing and cladding processes, are evaluated to improve the corrosion resistance of the joints. Furthermore, the laser-induced surface texture on the metals is created to significantly increase the initial joint strengths due to the effect of mechanical interlock. Finally, the corrosion behavior of the joints is investigated through cyclic corrosion tests and the experimental results indicate that the combination of added noble layers and textured surfaces is very promising for achieving high-strength and corrosion-resistance joints.

Relationship between Temperature and Bonding Strength in a Laser Joining of Metal and Carbon Fiber Reinforced Thermoplastic

Relationship between Temperature and Bonding Strength in a Laser Joining of Metal and Carbon Fiber Reinforced Thermoplastic

Interfacial structure and bonding mechanism of AZ31/carbon-fiber-reinforced plastic composites fabricated by thermal laser joining

Multi-material joining is attracting the attention of the automotive industry given its potential to realize lighter vehicles, and therefore fuel savings and reduced emissions. The aim of the present study was to understand the bonding mechanisms whereby metal and plastic/composites are joined and to improve the multi-material joint strength. In this study, the effect of thermal oxidation of Mg alloy sheets on the strengths of Mg–CFRP (carbon-fiber-reinforced plastic) lap joints prepared using laser-assisted metal and plastic joining technique was investigated. Characterization techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro-computed tomography (MCT), x-ray photoelectron spectroscopy (XPS), and atom probe tomography (APT) were used to study the underlying mechanisms of the thermal oxidation. The formation of bubbles, mechanical interlocking and chemical reactions at the joint interface were found to be the three key factors influencing the strength of joints. Thermal oxidation increased the joint strength significantly through the suppression of bubble formation, CFRP decomposition and the creation of mechanical interlocking effects at the joint interface. Moreover, MgCO3, MgO1+x, and Mg(OH)2 phases were detected by XPS analysis at the joints prepared using thermally oxidized Mg alloy sheets. The presence of the high O/Mg ratio phases was also confirmed by APT analysis. The formation of these phases confirmed the occurrence of chemical reactions between the MgO and CFRP matrix at the nanometer level, which are regarded as contributing to the increase in the joint strength.

Laser Cutting, Positioning, and Joining in One Clamping

AbstractEquipping components which carry media with threaded bushings or fittings, replacing hydroformed components by deep‐drawn half‐shells, and building complex 3D assemblies from individual parts direct from the coil – these are the areas of application for CutFusion from Weil Engineering, the mechanical engineers from Müllheim, South Germany. CutFusion not only saves a great deal of handling time and effort, it also makes the manufacturing workflow much safer.

Effects of oxide layer on adhesion and durability of titanium and transparent polyamide joint by laser joining

A joint of titanium and transparent polyamide with desirable strength was achieved by laser joining. A maximum load capacity of 3400 N was obtained from a lap joining area of 25 × 25 mm2 at a laser power of 350 W and a travel speed of 4 mm/s. The effects of surface oxide layers with different thicknesses and stability were investigated. A joint with a thick oxide layer exhibited lower load capacity due to excessive thermal degradation of polyamide caused by heat buildup inside the thick thermal insulating oxide layer. With UV exposure, more pronounced reduction in joint strength was observed in the joint with the thick oxide layer. Cracking of the oxide layers was responsible for lower strength and expected to be a result of stress from polyamide contraction combining with internal stress of the oxide layer.

Laser Cutting, Positioning, and Joining in One Clamping

AbstractEquipping components which carry media with threaded bushings or fittings, replacing hydroformed components by deep‐drawn half‐shells, and building complex 3D assemblies from individual parts direct from the coil – these are the areas of application for CutFusion from Weil Engineering, the mechanical engineers from Müllheim, South Germany. CutFusion not only saves a great deal of handling time and effort, it also makes the manufacturing workflow much safer.

Shear Strength Optimization of Laser-Joined Polyphenylene Sulfide-Based CFRTP and Stainless Steel

A thermosetting plastic and stainless steel were joined by the fiber laser with and without polyphenylene sulfide (PPS) additive. Its microstructure, interface morphology, and shear strength were investigated. The laser joining is shown to change the microstructure of the stainless steel and result in the heat-affected zone and fusion zone, which contains the lathy ferrite and skeletal ferrite, respectively. Without the PPS interlayer, the additive in the plastic can be overheated and decomposed during laser joining, which is detrimental to the interface bonding. The additive can contribute to the plastic and stainless steel interpenetration, but its amount should be controlled. Insufficient additive quantities cannot fill the gap between stainless steel and plastic, but its higher quantities can cause excessive melting, which would prevent from gaining the joint with optimum shear strength. The appropriate interlayer thickness is 300 μm, which improves the shear strength of the stainless steel and plastic joint to 15.1 MPa.