Laser Transmission Welding Of Polymers Research Articles

Numerical study of thermo-mechanical responses in laser transmission welding of polymers using a 3-D thermo-elasto-viscoplastic FE model

Numerical study of thermo-mechanical responses in laser transmission welding of polymers using a 3-D thermo-elasto-viscoplastic FE model

Laser beam positioning in quasi-simultaneous laser transmission welding of polymers

Laser beam positioning in quasi-simultaneous laser transmission welding of polymers

Laser transmission welding of polymers – A review on welding parameters, quality attributes, process monitoring, and applications

• A comprehensive review on several aspects of the laser transmission welding process is presented. • Laser transmission welding parameters and their effects on the performance of the welds are discussed. • Laser transmission weld quality attributes used to assess the quality of the welded joints are reviewed. • Process monitoring techniques for the laser transmission welding process are discussed. • Several applications of laser transmission welding in different industrial sectors have been identified. Laser transmission welding (LTW) is nowadays a well-received polymer joining process. New applications are emerging more and more due to the unique advantages of LTW over conventional joining processes. This paper provides a comprehensive review on various aspects of LTW techniques through a detailed survey of several scholarly publications, industrial studies, scientific reports, etc. This review focuses primarily on five major aspects of LTW, which are (a) welding parameters and their effects, (b) weld quality attributes, (c) process monitoring techniques, (d) material combinations, and (e) industrial applications. After an introduction to the process, the welding parameters, and how they influence the LTW process are described first. This is followed by a description of the quality attributes of LTW, including weld strength, weld pool dimensions, part gap-bridging ability, meltdown, and weld morphology. Several process monitoring techniques applied to LTW are then discussed for pre-, post-, and real-time monitoring of the process. Subsequently, material combinations that are successfully welded using LTW are described, including welding of polymer to polymer, metal, ceramic, glass, wood, etc. Finally, several applications of LTW in different industrial sectors are identified, and the results of the review are concluded.

State-of-art review of laser irradiation strategies applied to laser transmission welding of polymers

Laser transmission welding (LTW) offers superior weld quality and mechanical performance over conventional polymer welding processes. The ever-increasing applications in a wide range of industrial products prove its competitive process advantages and cost-efficiency. The process capability and performance depend on material properties, process parameters, and laser irradiation and application strategies. A wide range of laser irradiation and application strategies have been developed and implemented in laser transmission welding. They vary in laser scanning methods, cycle time, process flexibility, etc. and their specific selection varies depending on the welding profile, work materials, part size, variety and volume of production, etc. A comprehensive survey of these approaches is carried out to evaluate their operating concepts, key features, process specifications, and implementations. Focusing on these objectives, this paper presents a state-of-the-art review of laser irradiation and application strategies applied to laser transmission welding of polymers.

Laser transmission welding of polymers – A review on process fundamentals, material attributes, weldability, and welding techniques

Laser technology often offers solutions where existing technologies have struggled or require improvements. Over the last two decades, laser transmission welding (LTW) has become a viable fabrication method for industries that engaged in polymer welding. This paper presents a comprehensive review on several aspects of LTW process. In specific, this review focuses on four major aspects of the LTW: (a) process fundamentals, including operating principles and process requirements; (b) compositions and pre-welding conditions of polymers and their effects; (c) laser weldability of polymers, considering compatibility and non-compatibility issues; and (d) welding techniques and application strategies, including technological variants and the transformation of application strategies from absorber-based to absorber-free laser welding of polymers. The conclusion of the review and the prospects for further research work are eventually addressed.

Laser transmission welding of polymers – Irradiation strategies for strongly scattering materials

In laser transmission welding of thermoplastics the optical properties of the transparent part have great influence on the weld seam quality. Especially scattering, for example at crystalline structures or additives, can significantly affect the intensity distribution of the radiation in the joining zone. Since scattering is a strongly wavelength dependent process the right choice of the laser wavelength can enable laser transmission welding even for challenging materials. It is shown that the necessary optical material properties needed to assess the weldability of scattering materials can be directly obtained from NIR-spectroscopy.

Matching of laser intensity distribution for laser transmission welding of thermoplastics

Laser transmission welding of polymers is becoming more and more important in industrial applications. In contrast to other polymer welding processes, for example hot plate welding or vibration welding, the exact definition of the major process tool, the laser beam, is challenging. The comparison of investigation results with each other can be very difficult, because of, for example, the different intensity distribution and the specimen geometries. In this study, a method to match the laser power profiles of two different laser systems was developed. Shear-test results confirm that statistically equal weld strengths can be achieved when laser power profiles and test geometries are matched.

Absorbing TiOx thin film enabling laser welding of polyurethane membranes and polyamide fibers

We report on the optical properties of thin titanium suboxide (TiOx) films for applications in laser transmission welding of polymers. Non-absorbing fibers were coated with TiOx coatings by reactive magnetron sputtering. Plasma process parameters influencing the chemical composition and morphology of the deposited thin films were investigated in order to optimize their absorption properties. Optical absorption spectroscopy showed that the oxygen content of the TiOx coatings is the main parameter influencing the optical absorbance. Overtreatment (high power plasma input) of the fiber surface leads to high surface roughness and loss of mechanical stability of the fiber. The study shows that thin substoichiometric TiOx films enable the welding of very thin polyurethane membranes and polyamide fibers with improved adhesion properties.

Prediction of molten area in laser transmission welding of thermoplastic polymers

The prediction of the molten area is of great significance for laser transmission welding (LTW) of polymers. The purpose of the present study is to develop a mathematical model for LTW of polymers. The cross-sectional molten area of weld can be calculated through this model. The mathematical model was developed and deduced on the basis of the physical heat calculation formula. Subsequently, the model was validated by laser irradiating polyamide-66 (PA66) plaque containing 30 wt-% carbon fibre (CF), as well as LTW of PA66 containing 30 wt-% glass fibre with PA66 containing 30 wt-% CF. A viewpoint that the melt area of the upper layer to the bottom layer ratio (SU/SL) depends on the allocation proportion of the line energy between the interface during LTW of thermoplastic polymers was proposed. The model can well predict the molten area and help optimise process parameters during LTW of polymers.

Molten Depth Modeling of Laser Transmission Welding Based on Temperature Distribution of Moving Point Heat Source

Laser transmission welding (LTW) is a new and efficient technology. During LTW of polymers, the size and morphology of the weld have great influence on the welding quality. In order to better evaluate the welding quality and optimize process parameters, many researches on the morphology and mathematical analytical model of the molten pool have been conducted. This study attempts to build an analytical model for calculating the depth of the molten pool (molten depth), based on the temperature field distribution theory of the moving point heat source acting on the semi-infinite body. The influence of the welding power and welding speed on the molten depth is studied emphatically. The mathematical analytical model is solved through MATLAB mathematical software. Subsequently, the test experiment about LTW of PA66 is conducted to validate the model. During the test experiment, the upper layer contains 30 wt. % glass fibers (GF) and the bottom layer contains 30 wt. % carbon fiber (CF). The result shows that the mathematical analytical model can well predict the trend of the molten depth. However, the error exists indeed. The detailed analysis about the error is also made in this article.

폴리카보네이트와의 레이저 투과 용접성 개선을 위한 폴리프로필렌 개질

동종 혹은 이종의 고분자를 레이저로 접착시키는 방법은 레이저 접착이 가지는 장점들로 인해 많은 산업분야에서 광범위하게 사용되고 있다. 산업적으로 많이 사용되는 폴리프로필렌(PP)과 폴리카보네이트(PC)가 레이저 투과용접이 가능하다면 자동차 헤드램프에 큰 이점을 갖고 적용할 수 있을 것이다. 하지만, 폴리프로필렌과 폴리카보네이트는 상용성이 낮아 레이저 접착을 시켜도 강도가 낮은 문제점이 있다. 본 연구에서는 반응압출을 통해 폴리프로필렌을 글리시딜메타크릴레이트(GMA)로 개질하고, 폴리카보네이트와의 상용성, 기계적 물성 및 레이저 투과 용접을 통해 접착성을 조사하였다. Laser transmission welding of polymers is now used in a very wide range of industries due to its advantages. If the joining between polypropylene (PP) and polycarbonate (PC) occurs by laser transmission welding, the automotive headlight will get a large profit. However, PP/PC have poor miscibility. In the laser transmission welding results, the adhesion strength between PP and PC was very weak. In this study, PP was modified by grafting of glycidyl methacrylate (GMA). The adhesion strength of PC and PP-g-GMA as a reactive compatibilizer was observed. The adhesion strength was investigated by compatibility with PC, mechanical properties and laser transmission welding.

Influence of titanium dioxide pigments on the optical properties of polycarbonate and polypropylene for diode laser wavelengths

ABSTRACTIn laser transmission welding of polymers, additives and colorants could influence the welding result. In this work, polypropylene and polycarbonate probes colored with titanium dioxide (TiO2) pigments of various concentrations are investigated. The probes are produced using an extrusion process to obtain a homogeneous distribution of colorants. The TiO2 pigments change the optical properties of the polymers considerably. The measured reflectance increases with increasing pigment load while the transmittance decreases. From the measured data of transmittance, reflectance, and collimated transmittance, the scattering, the absorption coefficient, and the anisotropy factors are calculated. It is shown that the scattering coefficient at 1530 nm (laser) wavelength is smaller than for 968 nm, while the absorption coefficient is negligible for both wavelengths. Scattering coefficient and anisotropy factor are used to simulate the propagation of the laser radiation in the polymers. The influence of the scattering process on the beam propagation is represented by the change of the power density distribution. It is shown that the maximum intensity of the distribution is reduced more than the transmittance with increasing pigment concentration. The effect is higher for 968 than for 1530 nm wavelength making the larger wavelength more favorable for transmission welding. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40073.

Irradiation Strategy for Laser Transmission Welding of Thermoplastics Using High Brilliance Laser Source

This article describes the correlation between crystallinity degree and spatial seam homogeneity for laser transmission welding of polymers applying TWIST method, which is based on a superposition of slow regular feed and fast periodic circular or elliptical beam motion. Laser welding experiments and measurements of optical polymer properties (transmittance, reflectance and collimated transmittance) are reported for thermoplastic polypropylene PP and Polyamide PA66 as well as for thermoplastic elastomer PEBAX. The shape of the seam is visualized by measuring the heat affected zone (HAZ). Compared to the circular the elliptical motion leads to a homogeneous HAZ, which is advantageous for the welding process in many cases. Besides TWIST parameters, scattering of the laser radiation influences the welding result considerably. This is shown for high-crystallinity PA66, which needs more laser power to achieve similar weld seams than PP or PEBAX. The correspondence between homogeneous HAZ and good welding results is investigated by measuring the strength of welded T-shape samples with respect to the laser power. The elliptic TWIST motion leads to a broader processing window, if the ratio of the beam diameter and the major TWIST radius is smaller than a certain value (<1/2). For PEBAX, a local maximum of strength-vs.-power curve is obtained for all TWIST® radii. For welding PP, the maximum is observed only for big radii.

Description of transmitted energy during laser transmission welding of polymers

It is important to describe the laser energy distribution in polymers properly when modeling heat transfer during laser transmission welding of thermoplastics. This paper presents an analytical model that describes the energy transmission in laser transmission welding of light scattering polymers. The model considers that the transmitted laser beam in a scattering polymer can be represented by scattered and unscattered components. The distribution of the scattered energy from any point in the incident beam is Gaussian. The transmitted power from the discretized input beam is summed to create a normalized power flux distribution model. The model was validated using the measured laser energy distributions after transmission through parts made of polypropylene, as well as unreinforced and glass fiber reinforced polyamide 6.

Effect of carbon black on temperature field and weld profile during laser transmission welding of polymers: A FEM study

The influence of the carbon black on temperature distribution and weld profile, during laser transmission welding of polymers, is investigated in the present research work. A transient numerical model, based on conduction mode heat transfer, is developed to analyze the process. The heat input to the model is considered to be the volumetric Gaussian heat source. The computation of temperature field during welding is carried out for polycarbonates having different proportion of carbon black in polymer matrix. The temperature dependent material properties of polycarbonate are taken into account for modeling. The finite element code ANSYS ® is employed to obtain the numerical results. The numerically computed results of weld pool dimensions are compared with the experimental results. The comparison shows a fair agreement between them, which gives confidence to use the developed model for intended investigation with acceptable accuracy. The results obtained have revealed that the carbon black has considerable influence on the temperature field distribution and the formation of the weld pool geometry.

Fibre laser welding for packaging of disposable polymeric microfluidic-biochips

An essential step in the development of microfluidic-biochips is represented by the assembly process. Among the thermal bonding processes used for the assembly of such devices the laser transmission welding of polymers offers several advantages, especially when it comes about local deposition of energy and minimum thermal distortion in the joining components. The research presented in this paper proposes a new approach for the laser transmission welding developed for the packaging of disposable polymeric microfluidic-biochips. The new approach based on the use of a fibre laser and a tailored method for the laser energy deposition was tested on the sealing of polymeric biochips made from plexiglas and polypropylene with a covering foil. This method combines the characteristics of the polymer contour welding and quasi-simultaneous welding and allows the achievement of contamination-free, high quality weld seams as narrow as 100 μm with a high dynamic making it suitable for the high volume production also.