Investigation of residual stresses in polypropylene using hot plate welding
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RESEARCH PAPER
Investigation of residual stresses in polypropylene using hot plate welding Andrea Wübbeke 1 & Volker Schöppner 1 & Bastian Geißler 2 & Michael Schmidt 2 & Arnaud Magnier 3 & Tao Wu 3 & Thomas Niendorf 3 & Fabian Jakob 4 & Hans-Peter Heim 4 Received: 16 April 2019 / Accepted: 14 June 2020 / Published online: 5 August 2020 # The Author(s) 2020
Abstract During the cooling process of the molten material, residual stresses appear because the reduced volume of the cooled material cannot fully fill the space formerly occupied by the molten material. The morphology in and around the weld is formed by different factors depending on the material and process parameters. Different morphological structures relate to different mechanical properties. The process parameters and the welding results including morphology and residual stress are linked together. In this article, residual stresses and the mechanical properties of a hot-plate-welded polypropylene specimen with 0.1 wt.-% content of carbon black are investigated in relation to the morphology. Different measurement positions and joining displacements of parts to be joined result in different residual stress states and morphological structures. The higher the joining displacement, the higher the residual stress. Investigations of the morphology show a relation between the size of the alpha spherulites and the joining displacement. Diffractions patterns of wide-angle X-ray scattering (WAXS) are not able to resolve the beta phase of the specimen. Keywords Hot plate welding . Morphology . Residual stress
1 Introduction Polypropylene (PP) is widely used in polymer industry, and welding of PP is an important process. Due to the welding process, residual stresses and different morphological structures appear based on different process parameters. For
welding of polymers, no research has been published which investigated the residual stresses, the mechanical properties of the weld and the morphology of the material at the same time. In this study, the influences of the process parameters on the mechanical properties of PP with carbon black content of 0.1 wt% are investigated. Mechanical properties are
Recommended for publication by Commission XVI - Polymer Joining and Adhesive Technology * Andrea Wübbeke [email protected]
Thomas Niendorf [email protected] Fabian Jakob [email protected]
Volker Schöppner [email protected]
Hans-Peter Heim [email protected]
Bastian Geißler [email protected] Michael Schmidt [email protected] Arnaud Magnier [email protected] Tao Wu [email protected]
1
Kunststofftechnik Paderborn, Paderborn University, Paderborn, Germany
2
Bayerisches Laserzentrum, Erlangen, Germany
3
Kassel University, Kassel, Germany
4
Institut für Werkstofftechnik—Kunststofftechnik, Kassel University, Kassel, Germany
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characterized by tensile test. Furthermore residual stresses in the weld are measured by the hole drilling method. Finally, the morphological structures of the different specimens are characterized by ana
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