Dr.-Ing.

Janssen, Henning

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  • Publication
    Feature based bipolar plate forming
    ( 2024-05-31)
    Meelkop, Dennis
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    By the end of the 1990s, the global peak of energy supply from oil and gas deposits had already been reached. Since then, there has been a clear trend towards the development of new, more sustainable ways of supplying energy. To realize this reduction, a holistic and rapid restructuring of the energy supply towards CO2-free and renewable energy production, storage and processing across all areas of life is necessary. The development and implementation of a functioning hydrogen economy can be crucial with respect to the goal of climate neutrality. The scale-up and commercialization of technologies for the cost-effective production and use of hydrogen carry significant importance. Accordingly, innovative production technologies and process chains must be developed to be able to manufacture fuel cells reliably in high volumes and at optimized costs. In this context, BPPs in the PEM-FC are responsible for about 80 % of the total weight, just over 50 % of the system volume, and up to 40 % of the total cost. Current research approaches in the field of BPP forming focus mainly on the optimization of a pre-selected production technology. Thereby, the possibility of combining different forming technologies to represent a holistic process chain is mostly disregarded. This research gap is to be closed by the developments within the scope of this work. The bipolar plate is not to be regarded as a coherent component, but as a composition of different geometric features.
  • Publication
    Optimierte Prozesse mithilfe lokaler Erwärmung und KI
    ( 2022)
    Janssen, Henning
    ;
    Schmidt, Florian
    ;
    Schmid, Tobias
    Konventionelle Verfahren zur Blechbearbeitung wie das Scherschneiden oder Umformen stoßen bei Hochleistungswerkstoffen häufig an ihre Grenzen. So sind einwandfreie Schneid- und Umformergebnisse bei hochfesten Blechen aus Stahl, Aluminium oder Titan in Transfer- und Folgeverbundwerkzeugen nur schwer zu erreichen. Optimierte Blechbearbeitungsprozesse mit thermischer Unterstützung sowie (Mensch-zentrierten) KI-Applikationen sind eine Möglichkeit, um den steigenden Qualitätsanforderungen gerecht zu werden.
  • Publication
    A fully coupled local and global optical-thermal model for continuous adjacent laser-assisted tape winding process of type-IV pressure vessels
    ( 2021)
    Zaami, Amin
    ;
    Schäkel, Martin
    ;
    Baran, Ismet
    ;
    Bor, Ton C.
    ;
    Janssen, Henning
    ;
    Akkerman, Remko
    A numerical process simulation framework is introduced in this paper to describe and predict the process temperature evolution during the laser-assisted tape winding (LATW) process of a type-IV pressure vessel made of glass-reinforced high-density polyethylene (G/HDPE). A local optical-thermal model is fully coupled with a global thermal model for the simulation of continuous adjacent hoop winding cases. The predicted tape and substrate temperatures are compared with the experimental data to validate the process model's effectiveness. The inline temperature was measured by an infrared thermographic camera during the continuous winding. The continuous process temperature of the substrate is affected significantly due to the previously wound layers including the pressure vessel, and a gradual increase of the temperature of the roller and the air inside the liner. A considerable temperature increase calculated as 80-120°C takes place for the substrate during winding of two consecutive layers of (G/HDPE) prepreg tape at the liner ends. The influence of pressure vessel size on the tape and substrate temperatures is investigated for different liner radii using the validated process model. The peak substrate temperature is found to increase approximately 45°C by reducing the radius of the pressure vessel from 272 mm to 68 mm while maintaining all other process conditions constant.
  • Publication
    Non-uniform crystallinity and temperature distribution during adjacent laser-assisted tape winding process of carbon/PA12 pipes
    ( 2020)
    Amin Hosseini, Seyed Mohammad
    ;
    Schäkel, Martin
    ;
    Baran, Ismet
    ;
    Janssen, Henning
    ;
    Drongelen, Martin van
    ;
    Akkerman, Remko
    The non-uniform temperature and crystallinity distributions present in carbon fiber-reinforced PA12 composite pipes, produced via laser-assisted tape winding (LATW), are investigated in this paper. The width of the laser source is usually larger than the substrate width which causes multiple heating and cooling of some regions of the (neighboring) substrate and hence temperature and crystallinity gradients during the adjacent hoop winding. A kinematic-optical-thermal (KOT) model coupled with a non-isothermal crystallinity model is developed to capture the transient temperature and crystallinity distributions for growing substrate thickness and width. The predicted temperature trends are validated with thermocouple and thermal camera measurements. The substrate temperature varies in the width direction up to 52%. This will lead to extra polymer remelting and possible degradation. The maximum variation of the crystallinity degree across the width is found to be 270% which shows agreement with the trend of the measured crystallinity degree. It is found that a more realistic description of the melting behavior of the matrix is needed to obtain a more accurate prediction of the crystallinity distribution.
  • Publication
    A new global kinematic-optical-thermal process model for laser-assisted tape winding with an application to helical-wound pressure vessel
    ( 2020)
    Amin Hosseini, Seyed Mohammad
    ;
    Schäkel, Martin
    ;
    Baran, Ismet
    ;
    Janssen, Henning
    ;
    Drongelen, Martin van
    ;
    Akkerman, Remko
    A new global kinematic-optical-thermal (KOT) model is proposed to provide a proper understanding and description of the temperature evolution during laser-assisted tape winding and placement (LATW/LATP) on any arbitrary shaped tooling geometry. Triangular facets are utilized in the kinematic model to define a generic tooling together with a user-defined fiber path and time-dependent process settings such as the tape feeding rate. The time-dependent heat flux distribution on the surfaces is calculated by the optical model and subsequently coupled to the thermal model. The numerical implementation of the developed KOT model is first verified for process simulations of the LATP on a flat tooling by comparing the temperature predictions with the available literature data. To validate the KOT model, a total of four pressure vessels are manufactured with in-line temperature measurements. The process temperature predictions are found to agree well with the measured temperature during the helical winding. The influence of the changing tooling curvature and process speed on the process temperature is found to be significant as shown by the experimental and numerical findings.
  • Publication
    Temperature variation during continuous laser-assisted adjacent hoop winding of type-IV pressure vessels: An experimental analysis
    ( 2020)
    Zaami, Amin
    ;
    Schäkel, Martin
    ;
    Baran, Ismet
    ;
    Bor, Ton C.
    ;
    Janssen, Henning
    ;
    Akkerman, Remko
    Laser-assisted tape winding is an automated process to produce tubular or tube-like continuous fiber-reinforced polymer composites by winding a tape around a mandrel or liner. Placing additional layers on a previously heated substrate and variation in material and process parameters causes a variation in the bonding temperature of fiber-reinforced thermoplastic tapes which need to be understood and described well in order to have a reliable manufacturing process. In order to quantify the variation in this critical bonding temperature, a comprehensive temperature analysis of an adjacent hoop winding process of type-IV pressure vessels is performed. A total of five tanks are manufactured in which three glass/HDPE tapes are placed on an HDPE liner. The tape and substrate temperatures, roller force and tape feeding velocity are measured. The coefficient of variation for each round is characterized for the first time. According to the statistical analysis, the coefficient of variation in substrate temperature is found to be approximately 4.88.8% which is larger than the coefficient of variation of the tape temperature which is 2.17.8%. The coefficient of variations of the substrate temperatures in the third round decrease as compared with the coefficient of variations in the second round mainly due to the change in gap/overlap behavior of the deposited tapes. Fourier and thermographic analysis evince that the geometrical disturbances such as unroundness and eccentricity have a direct effect on the temperature variation. In addition to the temperature feedback control, a real-time object detection technique with deep learning algorithms can be used to mitigate the unwanted temperature variation and to have a more reliable thermal history.
  • Publication
    Kostengünstige Produktionstechnologie für nachhaltige Faserverbundhalbzeuge
    ( 2020)
    Janssen, Henning
    ;
    Schulz, Malena
    ;
    Helden, Jonathan von
    ;
    Schwane, Martin
    Faserverstärkte Kunststoffe (FVK) haben sich in den vergangenen Jahrzehnten als ein wichtiger Hochleistungswerkstoff in einer Vielzahl von Branchen etabliert. Trotz der zumeist hohen Bauteilkosten finden sie vielfältige Anwendung, z.B., wenn Kostenvorteile durch Ressourcen­einsparung während ihres Einsatzes entstehen. Hohe Kosten von FVK-Bauteilen lassen sich nicht selten auf ihre teuren Ausgangsmaterialien zurückführen: dazu zählen bspw. Kohlenstofffasern, die unter hohem Energie­aufwand hergestellt werden. Einen nicht unwesentlichen Anteil an den Gesamtkosten stellt zudem die Fertigungs­technik für die Herstellung und Weiterverarbeitung von FVK-Halbzeugen dar. Dabei zählen z.B. teure Verfahren für die Halbzeugherstellung und hohe Verschnittraten bei der Verarbeitung zu den Kostentreibern. Bei der Bauteilauslegung und Materialauswahl spielen neben der Wirtschaftlichkeit verstärkt aber auch Faktoren wie Ressourceneffizienz und Nachhaltigkeit eine wichtige Rolle. Am Fraunhofer-Institut für Produktionstechnologie werden daher kostengünstige Produktionssysteme entwickelt, die zukünftig Schlüsseltechnologien für die Herstellung und Verarbeitung von nachhaltigen FVK-Halbzeugen darstellen können.
  • Publication
    Gesteigerte Zuverlässigkeit für die Herstellung von FVK-Druckbehältern
    ( 2019)
    Schäkel, Martin
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    Druckbehälter aus Faserverbundkunststoff gewinnen für den automobilen Leichtbau zunehmend an Bedeutung. Im Projekt AmbliFibre realisierten Fraunhofer IPT und Partner die Fertigung der komplexen Bauteile austhermoplastischem FVK und stellten mit neuen Simulations- und Qualitätswerkzeugeneine zuverlässige Produktion sicher.
  • Publication
    A Digital Shadow for the Infrared-based Tape Laying Process of Tailored Blanks out of Thermoplastic Unidirectional Tape
    ( 2019)
    Schulz, Malena
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    Due to its benefits in creating load and waste optimized composites, the manufacturing of tailored composites blanks has gained increased attention in industry. The Fraunhofer IPT has developed an infrared (IR)-based, in-situ tape laying process of thermoplastic, unidirectional composite tape proving to be a material and cost efficient technology for producing tailored composite blanks. An important part in the in-situ process is finding optimal process parameters regarding high productivity and quality. Besides the optimization of process parameters, machine design as well as blank design including geometry and ply book involveprocess induced effects. Different fibre angles, amount of layers or insufficient radiation power can result in various defects of the blank, such as residual stresses or non-sufficient consolidation between layers. This study investigates how Digital Shadows (DS)help to characterize the IR-based tape laying process of different blank designs. DS for the tape laying process are created showing relevant parameters localised to its position within the laminate. A temperature sensor is integrated in order to attain data for process characterization. A straightforward design of experiments is conducted demonstrating temperature profiles as well as temperaturedependencies between the amount of layers and the size of the laminate.
  • Publication
    Increased Reliability for the Manufacturing of Composite Pressure Vessels
    ( 2019)
    Schäkel, Martin
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    Pressure vessels made of fiber-reinforced plastics are becoming increasingly important for lightweight automotive design. In the AmbliFibre project, the Fraunhofer IPT and partners realized the manufacture the complex components from thermoplastic FRP and ensured reliable production with new simulation and quality assurance tools.