Dr.-Ing.

Janssen, Henning

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  • 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
    Data Collection and Analysis for the Creation of a Digital Shadow During the Production of Thermoplastic Composite Layers in Unbonded Flexible Pipes
    ( 2018)
    Schäkel, Martin
    ;
    McNab, John
    ;
    Dodds, Neville
    ;
    Peters, Tido
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    Unbonded flexible pipes present a mature technology for the efficient recovery and transport of hydrocarbons offshore. The substitution of metallic reinforcement layers in the multilayered structure by thermoplastic fiber-reinforced polymer (FRP) presents a solution for self-weight issues of especially long pipes, as FRP materials display high specific strength and modulus while being resistant to external pressure and corrosion. The production of these layers is automated by the laser assisted tape winding process without the need of additional curing steps. During the manufacturing process, several data like process temperature and consolidation pressure are continuously monitored by non-contact sensors to ensure process stability without interfering in the consolidation process. To gain additional information about the temperature distribution within the multi-layered laminate, contact temperature sensors were introduced in the tape winding process. By this method the temperature of subjacent tapes can be assessed during the continued winding process. Additionally, this paper features a new approach of utilizing winding path data for relating the time-dependent sensor data to the exact position on the produced part. The visualization of path-dependent sensor data opens up possibilities of linking quality monitoring results to manufacturing insufficiencies and potential part defects.
  • Publication
    Manufacturing of miniaturized thermoplastic FRP components using a novel reaction injection pultrusion process
    ( 2017)
    Brack, Alexander
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    Fiber-reinforced polymers (FRP) are used for many applications because of their lightweight, high strength and variability. Besides large structural parts, there is a demand for miniaturized components, mostly used for medical applications. Main reason is the excellent compatibility with advanced imaging methods such as Magnetic resonance imaging (MRI). However, only the use of thermosetting polymers is currently feasible for the pultrusion of miniaturized FRP-components, which have major drawbacks such as their non-formability after curing. Therefore, thermoplastic polymers are required for many applications. However, the processing of thermoplastic polymers by pultrusion is more demanding due to their high melt viscosity. This becomes even more challenging the smaller the dimensions. Fraunhofer IPT has developed a miniaturized reactive pultrusion process to manufacture profiles with diameters of 1 mm and below using thermoplastic matrix materials. In this process, monomers with a very low viscosity are used for improved fiber impregnation, which then polymerize directly in the tool form. Using this method, a reliable and cost-efficient manufacturing of miniaturized profiles with excellent properties can be achieved. In this paper, the developed process is described and compared with alternative methods. Experimental test results are presented to show the feasibility of the developed process and the potential for industrial applications.
  • Publication
    Efficient production of tailored structural thermoplastic composite parts by combining tape placement and 3d printing
    ( 2017)
    Janssen, Henning
    ;
    Peters, Tido
    ;
    Brecher, Christian
    Thermoplastic composites, such as organosheets and unidirectional tapes, have become more and more popular in recent years. In certain high volume applications, they are often combined with non-reinforced plastics in overmolding processes. However, for product development or customized parts, more flexible process chains for the production of continuous fiber-reinforced thermoplastic parts are required. The automated placement of continuous fiber-reinforced thermoplastic tapes is an additive manufacturing technology which can be used to produce load-optimized tailored blanks. These blanks can be formed and joined with 3d printed structures to complex, function integrated, customized hybrid thermoplastic structures without the need of expensive molds.
  • Publication
    System improvement for laser-based tape placement to directly manufacture metal / thermoplastic composite parts
    ( 2017)
    Peters, Tido
    ;
    Kukla, Christian
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    The possibility to manufacture economic efficiently structural functionalized parts using high-volume suited processes is crucial to implement lightweight strategies and fulfil the economic and ecologic needs for responsible use of energy and resources. One key strategy to overcome current obstacles of long cycle times and high material costs is to combine metal and thermoplastic composites within one part. Thus, the advantage of having the right material in the right place to fulfil all requirements to the part is used. However, applied solutions to manufacture these kind of multi-material structures still lack in terms of flexibility, productivity, quality and ideal material utilization. One solution for overcoming these current obstacles is the application of the selective diode laser-based tape placement process to locally reinforce metallic parts aiming to generate an optimum weight, reinforcement and cost profile within the part. Key requirement to establish in-situ a sufficient joint between a textured metallic surface and the applied thermoplastic composite tape is the generation of a sufficient heat distribution in both joining partners. Achieving these required conditions becomes even more challenging as both joining partners have completely different thermo-physical and optical properties. Especially, the latter leads to difficulties when using conventional diode laser-based tape placement systems to consolidate tape locally on metal parts, as a local heat input into the metallic component cannot be sufficiently achieved by the diode laser system of these placement units. The present work deals with initial trials to locally reinforce textured metal surfaces using conventional diode laser-based tape placement. Based on these findings the work derives the concept for a novel laser-based tape placement system which considers the use of Philips VCSEL (Vertical cavity surface emitting laser) technology.
  • Publication
    Laminate aus duroplastischen Prepregs mit aktivierbarer Adhäsion
    ( 2016)
    Werner, Daniel
    ;
    Janssen, Henning
    ;
    Brecher, Christian
    Neben der Reduktion des manuellen Fertigungsaufwands ist die Senkung der Materialkosten ein wesentlicher Aspekt zur wirtschaftlichen Herstellung faserverstärkter Kunststoffbauteile. Beide Ziele werden durch die Entwicklung neuartiger Matrixsysteme und durch die Entwicklung hierfür anwendbarer automatisierter Verarbeitungsprozesse fokussiert. Die neuartigen Matrixsysteme kombinieren die Vorteile konventioneller duroplastischer und thermoplastischer Matrixsysteme (kostengünstige Harze, einfache Imprägnierung durch niedrige Viskosität bzw. trocken und adhäsionsfrei bei Raumtemperatur, niedrige Taktzeiten, Lagerung bei Raumtemperatur). Die Verarbeitung im automatisierten Tapelegeprozess ermöglicht die Herstellung belastungsoptimierter Strukturbauteile, bei denen Faseranordnung und -orientierung an die erwartete Belastungssituation des Bauteils anpasst sind. Die hieraus resultierenden Möglichkeiten zur Verarbeitung werden am Fraunhofer IPT hergeleitet und untersucht.
  • Publication
    In Serie lokal verstärken
    ( 2016)
    Brecher, Christian
    ;
    Janssen, Henning
    ;
    Buschhoff, Clemens
    ;
    Peters, Tido
  • Publication
    Development of an artifact-free aneurysm clip
    ( 2016)
    Brack, Alexander
    ;
    Senger, Sebastian
    ;
    Fischer, Gerrit
    ;
    Janssen, Henning
    ;
    Oertel, Joachim
    ;
    Brecher, Christian
    For the treatment of intracranial aneurysms with aneurysm clips, usually a follow-up inspection in MRI is required. To avoid any artifacts, which can make a proper diagnosis difficult, a new approach for the manufacturing of an aneurysm clip entirely made from fiber-reinforced plastics has been developed. In this paper the concept for the design of the clip, the development of a new manufacturing technology for the fiber-reinforced components as well as first results from the examination of the components in phantom MRI testing is shown.