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End date: 2022 × Start date: 2020 × Subject: Konferenzschrift × WGL Institute: IPF ×

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Now showing 1 - 5 of 5
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    Heterogeneous freezing on pyroelectric poly(vinylidene fluoride-co-trifluoroethylene) thin films
    (Chichester [u.a.] : Wiley, 2020) Apelt, Sabine; Höhne, Susanne; Uhlmann, Petra; Bergmann, Ute
    Active deicing of technical surfaces, such as for wind turbines and heat exchangers, currently requires the usage of heat or chemicals. Passive coating strategies that postpone the freezing of covering water would be beneficial in order to save costs and energy. One hypothesis is that pyroelectric active materials can achieve this because of the surface charges generated on these materials when they are subject to a temperature change. High-quality poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) thin films with a high crystallinity, prefererd edge-on orientation, low surface roughness, and comprised of the β-analogous ferroelectric phase were deposited by spin-coating. Freezing experiments with a cooling rate of 1 K min−1 were made on P(VDF-TrFE) coatings in order to separate the effect of different parameters such as the poling direction, film thickness, used solvent, deposition process, underlying substrate, and annealing temperature on the achievable supercooling. The topography and the underlying substrate significantly changed the distribution of freezing temperatures of water droplets in contact with these thin films. In contrast, no significant effect of the thickness, morphology, or pyroelectric effect of the as-prepared domain-state on the freezing temperatures was found.
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    Process Monitoring of a Vibration Dampening CFRP Drill Tube in BTA deep hole drilling using Fibre-Bragg-Grating Sensors
    (Amsterdam [u.a.] : Elsevier, 2022) Summa, Jannik; Michel, Sebastian; Kurkowski, Moritz; Biermann, Dirk; Stommel, Markus; Herrmann, Hans-Georg
    The large tool length in BTA deep hole drilling often leads to strong torsional vibrations of the tool system, leading to a reduced bore hole quality failures. When substituting steel drill tubes with tubes from composite material, the laminate structure dampens these vibrations. Secondly, the integration of sensors allow to monitor process vibrations. This contribution introduces a new sensor platform to measure process vibrations, feed force and drilling torque using Fibre-Bragg Grating Sensors. The presented experimental results focus on characteristic frequency spectra with natural torsional and compression frequencies of the CFRP drill tube, which show variations due to changed feed.
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    Beamline-implemented stretching devices for in situ X-ray scattering experiments
    (Bristol : IOP Publ., 2022) Euchler, E.; Sambale, A.K.; Schneider, K.; Uhlig, K.; Boldt, R.; Stommel, M.; Stribeck, A.; Schwartzkopf, M.; Rothkirch, A.; Roth, S.V.
    Two recently developed experimental devices for investigating soft matter deformation are presented. Both devices exploit the capabilities of a modern synchrotron beamline to enable advanced and highly precise materials-science experiments in which X-ray scattering is registered. The devices can be operated both in monotonic as well as cyclic mode and are implemented into a beamline at DESY, Hamburg (Germany). Hence, relevant experimental parameters, such as displacement, force and temperature, are recorded synchronously with the individual X-ray scattering patterns. In addition, spatial variation of materials deformation can be monitored and recorded with optical microscopy. This unique sample environment enables in situ X-ray experiments in transmission, i.e. small- or wide-angle X-ray scattering (SAXS or WAXS), and in grazing-incidence geometry, i.e. grazing-incidence (GI-) SAXS or WAXS. One device with stepper motors is designed for studies of slow, (quasi-) static deformation and the other one with pneumatic actuators can be used for fast, impact deformation. Both devices are available to external beamline users, too.
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    Chemical Bonded PA66-PTFE-Oil Composites as Novel Tribologically Effective Materials: Part 2
    (London [u.a.] : Institute of Physics, 2021) Nguyen, Thanh-Duong; Kamga, Lionel Simo; Gedan-Smolka, Michaela; Sauer, Bernd; Emrich, Stefan; Kopnarski, Michael; Voit, Brigitte; Karjust, Krist; Otto, Tauno; Kübarsepp, Jakob; Hussainova, Irina
    Polytetrafluoroethylene (PTFE) exhibits excellent non-stick properties and a very low coefficient of friction under tribological stress, but it is incompatible with almost all other polymers. In the first part of this study we presented the generation of the novel tribological material based on unsaturated oil, radiation-modified PTFE (MP1100) and Polyamide 66 (PA66). To get a better understanding of the chemical properties and chemical composition of the compounds, the PA66-MP1100-oil-cb (chemical bonded) compounds were examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In this part, the mechanical properties of the compounds are compared with plain PA66 and PA66-MP1100-cb. The tribological investigation was carried out using the Block-on-Ring tribometer. It was found that the mechanical properties of PA66-MP1100-oil-cb with 20 wt.% MP1100-oil-cb only show slight differences compared to PA66, but the tribological properties of the compounds have been significantly improved through chemical coupling between the three components. Finally, the amount of the compound that was deposited on the surface of the steel disc counterpart was analyzed after the tribological testing.
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    Basic material and technology investigations for material bonded hybrids by continuous hybrid profile fabrication
    (London [u.a.] : Institute of Physics, 2021) Schubert, K.; Gedan-Smolka, M.; Marschner, A.; Rietzschel, T.; Uhlig, K.; Löpitz, D.; Wagner, D.; Knobloch, M.; Karjust, Krist; Otto, Tauno; Kübarsepp, Jakob; Hussainova, Irina
    The development of multi-material hybrids by injection molding has been studied very intensively at the IPF in the past. For that, a material bonding between the different substrates was achieved by using a newly developed two-step curing powder coating material as latent reactive adhesive. The aim of the project “Hybrid Pultrusion” was to perform a novel approach for the fabrication of material bonded metal-plastic joints (profiles) in a modified pultrusion process. Therefore, powder pre-coated steel coil is combined with a glass-fiber reinforced epoxy resin matrix. For initial basic studies, the impregnated fiber material has been applied on the pre-coated steel sheets using the Resin Transfer Molding process (RTM-process). It was proved via lap shear tests, that this procedure resulted in very high adhesive strengths up to 35 MPa resulting from the formation of a covalent matrix-steel bonding as well. In addition, the failure mechanism was subsequently studied. Furthermore, by adapting the successful material combination to the pultrusion process it was demonstrated that material bonded hybrids can be achieved even under these continuous processing conditions.