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

Frick, Thomas; Schkutow, Andreas

doi:10.1016/j.procir.2018.08.118

Cited by 14 publications

(8 citation statements)

References 6 publications

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“…The analyzed specimen has the dimensions of 10 × 20 × 1 mm and is of a dark, almost black color, a characteristic favorable to the absorption of light in these wavelengths. With reference to the work performed by Frick, [ 22 ] after performing the test for characterization of transmittance, the Beer–Lambert's law was used to calculate the absorbance of the material at a wavelength of 1064 nm.…”

Section: Methodsmentioning

confidence: 99%

Study of the optical, thermal, morphological and mechanical characteristics of a laser weldable fiber reinforced polymer

et al. 2022

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In recent years, varied industrial users such as the automotive and electronic manufacturers, have greatly expanded the application of technical polymers, exploring the lower weight, improved moldability of complex parts and good mechanical performance that these materials can provide, especially when reinforced with fibers. Among these materials, polybutylene terephthalate reinforced with 30% glass fiber, designated as PBT GF30, is highly interesting, since it combines excellent mechanical properties with watertightness, allowing PBT GF30 to be used in the encapsulation of sensitive electronic elements. However, to maintain access, PBT GF30 products always require the use of joints, which are often created using laser welding. This work presents a detailed characterization of the thermal, optical, mechanical, and morphological characteristics of PBT‐GF30 suitable for laser welding, supported by a numerical analysis. This process allowed to determine the influence of thermal energy on the behavior of the material and thus fully understand the mechanical response of the material after laser welding. Testing of the PBT GF30 in the as received state confirmed a fusion temperature of 225°C and large energy absorption for wavelengths around 1000 nm. Exposure to large temperatures leads to increased fiber exposure and matrix degradation, with a deleterious effect on the mechanical properties. When treated at the highest temperature under consideration, the material exhibited a reduction of 66% in its ultimate tensile stress, 67% in the yield at failure, 45% in the Young's modulus and 44% in the stress intensity factor. Hardness was less affected by the temperature increase. From the numerical model for the tensile and the compact tension tests, it was possible to find a good degree of convergence. This material was generally found suitable for laser welding processes and the determined useful to support the modeling the behavior of laser welded joints.

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Section: Methodsmentioning

confidence: 99%

Study of the optical, thermal, morphological and mechanical characteristics of a laser weldable fiber reinforced polymer

et al. 2022

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“…The radiation is attenuated due to absorption in the upper polymer, which is also taken into account in the calculation of the heat input in the lower polymer. As the laser radiation at k = 1070 nm is not scattered significantly in unreinforced polyamide [19], scattering is neglected in the calculation. Due to the very high feed rate and the low thermal conductivity of plastics, temperature gradients in feed direction are negligible small.…”

Section: Process Modelmentioning

confidence: 99%

Measurement of core temperature through semi-transparent polyamide 6 using scanner-integrated pyrometer in laser welding

Schmailzl

Käsbauer

Martan

et al. 2020

International Journal of Heat and Mass Transfer

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Predicting the core temperature during welding is an ambitious aim in many research works. In this work, a 3D-scanner with integrated pyrometer is characterized and used to measure the temperature during quasi-simultaneous laser transmission welding of polyamide 6. However, due to welding in an overlap configuration, the heat radiation emitted from the joining zone of a laser transmission weld has to pass through the upper polymer, which is itself a semi-transparent emitter. Therefore, the spectral filtering of the heat radiation in the upper polymer is taken into account by calibrating the pyrometer for the measurement task. Thermal process simulations are performed to compare the temperature field with the measured temperature signal. The absorption coefficients of the polymers are measured, in order to get precise results from the computation. The temperature signals during welding are in good agreement with the computed mean temperature inside the detection spot, located in the joining area. This is also true for varying laser power, laser beam diameter and the carbon black content in the lower polymer. Both, the computed mean temperature and the temperature signal are representing the core temperature. In order to evaluate the spatial sensitivity of the measurement system, the emitted heat radiation from both polymers is calculated on basis of the computed temperature field. Hereby it is found, that more than 90 percent of the detected heat radiation comes from the joining area, which is a crucial information for contact-free temperature measurement tasks on semi-transparent polymers.

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“…This can result in slightly increased weld seam widths and an increased demand in laser power for moderately scattering materials. For strongly scattering materials however, the beam profile of the laser beam can be considerably impaired and, in the worst case, the laser radiation is isotropically scattered out of the joining zone, which makes the welding process impossible or severely limits the weldable material thickness [7]. Since scattering processes are strongly wavelength dependent, the application of longer laser wavelengths can enable welding of materials that cannot be welded using conventional laser sources [6,7].…”

Section: Authorsmentioning

confidence: 99%

2.0 μm Laser Transmission Welding

Fuhrberg¹,

Ahrens²,

Schkutow³

et al. 2020

PhotonicsViews

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2.0 μm fiber lasers provide a high beam quality and a high‐power output, which makes them ideal for welding and cutting a wide variety of commercially used plastics, as well as marking plastics, metals or even food. At 2.0 μm wavelength the intrinsic absorption of most thermoplastics is high enough to weld or cut without applying any absorbent additives or coatings. Compared to commonly used near‐infrared systems, welding with 2.0 μm lasers can improve heat distribution and gap bridging and enable transmission welding for challenging materials.

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

Cited by 14 publications

References 6 publications

Study of the optical, thermal, morphological and mechanical characteristics of a laser weldable fiber reinforced polymer

Study of the optical, thermal, morphological and mechanical characteristics of a laser weldable fiber reinforced polymer

Measurement of core temperature through semi-transparent polyamide 6 using scanner-integrated pyrometer in laser welding

2.0 μm Laser Transmission Welding

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