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Die Permeabilität trockener Verstärkungstextilien ist eine wichtige Materialeigenschaft, die zu einem besseren Verständnis des Infiltrationsprozesses in Flüssigimprägnierverfahren beiträgt. Zur Bestimmung der Permeabilität textiler... more
Die Permeabilität trockener Verstärkungstextilien ist eine wichtige Materialeigenschaft, die zu einem besseren Verständnis des Infiltrationsprozesses in Flüssigimprägnierverfahren beiträgt. Zur Bestimmung der Permeabilität textiler poröser Medien sind verschiedene Methoden bekannt, jede mit ihren Vorund Nachteilen. In diesem Aufsatz werden Prüfstände zur Bestimmung der gesättigten und ungesättigten Permeabilität vorgestellt, welche den Prinzipien für eindimensionalen (1D) und radialen (2D) Fluss folgen. Neben den Messergebnissen werden der dazu notwendige Zeitund Materialeinsatz der verschiedenen Methoden zur Bestimmung der Permeabilität in Bauteilebene verglichen. Außerdem wird ein Simulationsansatz zur Bestimmung der Permeabilität vorgestellt, welcher auf der digitalen Abbildung des Materials mit einem Scanner beruht.
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Sheet Molding Compound (SMC) materials offer attractive specific strength and stiffness properties. With an addition of short cycle times, the possibility for complex geometries and a high recycling potential, this material is a promising... more
Sheet Molding Compound (SMC) materials offer attractive specific strength and stiffness properties. With an addition of short cycle times, the possibility for complex geometries and a high recycling potential, this material is a promising solution for the manufacture of lightweight components of numerous industrial sectors. Accurate and reliable simulation can contribute to a fast and competitive development process and effectively reduce the time-to-market. Especially, the accuracy of the simulative filling process is crucial to be able to predict the mechanical properties and hence, pave the way to structural parts. An appropriate characterization of the rheological behavior is therefore, crucial for accurate simulation results. To this purpose bar flow tests are performed and the experimental results are compared to the numerical results. A sensitivity analysis is performed to investigate the influence of each parameter on the simulation outcome. Furthermore, guidelines to improv...
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Large structural parts manufactured by Extrusion Additive Manufacturing (EAM) are limited by strong anisotropy due to insufficient bond formation and reduced molecular entanglement along the layer interface. To understand the correlation... more
Large structural parts manufactured by Extrusion Additive Manufacturing (EAM) are limited by strong anisotropy due to insufficient bond formation and reduced molecular entanglement along the layer interface. To understand the correlation between process and material parameters and to enable digital modeling of EAM, the effect of different substrate temperatures and layer heights on tensile strength was investigated. A simple testing methodology for pelletized carbon fiber-filled polyamide 6 was developed. Tensile tests were performed in a full factorial Design of Experiments (DoE) to determine the tensile properties. For bulk simulation, the nominal strength and modulus were also determined based on contact width obtained by optical microscopy. The results demonstrated high anisotropy, with the maximum transverse tensile strength reaching only 27% of the corresponding longitudinal results and the transverse tensile modulus reaching only 20% of its longitudinal value. The effects of ...
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Composite Mould Based on 3D Printing—COMBO3D COMBO3D aimed to produce a mould for a passenger aircraft flaperon using 3D printing and high-performance polymers. Taking advantage of new design freedom, the mould was designed to be... more
Composite Mould Based on 3D Printing—COMBO3D COMBO3D aimed to produce a mould for a passenger aircraft flaperon using 3D printing and high-performance polymers. Taking advantage of new design freedom, the mould was designed to be functionalised for a faster and more robust production process of the aerospace composite part.
Two-dimensional (2D) materials have aroused remarkable attention since the successful separation of graphene, atomic layers of carbon, has demonstrated novel electronic properties. Boron nitride (BN) is a structural analog of carbon. BN... more
Two-dimensional (2D) materials have aroused remarkable attention since the successful separation of graphene, atomic layers of carbon, has demonstrated novel electronic properties. Boron nitride (BN) is a structural analog of carbon. BN can be exfoliated to form unique 2D crystal structures called boron nitride nanosheets (BNNSs). BNNSs are believed to have potential to find applications in heat-releasing composite materials, since they are electrically insulating, besides being as thermally conductive and mechanically robust as graphene. In this study, a microfluidizer, high pressure fluid processor, was conducted for the first time to exfoliate few layer two dimensional (2D) boron nitride nanosheets (BNNSs) from micro-sized hexagonal boron nitride (h-BN) precursors of large flakes. The mixture of N,N-dimethyl formamide and chloroform was conducted as solvent. Secondary electronscanning electron microscopy (SE-SEM) imaging, bright field-transmission electron microscopy (BFTEM) imag...
Edge race-tracking is a frequently reported issue during resin transfer molding. It is caused by highly permeable channels and areas between the preform edge and cavity, which can significantly change the preform impregnation pattern. To... more
Edge race-tracking is a frequently reported issue during resin transfer molding. It is caused by highly permeable channels and areas between the preform edge and cavity, which can significantly change the preform impregnation pattern. To date, information is scarce on the effect of edge race-tracking in compression resin transfer molding (CRTM). To close this gap, laboratory equipment was developed to study the CRTM preform impregnation via flow visualization experiments. The preform was thereby encapsulated in thin thermoplastic films sealing its impregnation. Film-sealed compression resin transfer molding (FS-CRTM) experiments of preforms with a small geometrical aspect ratio showed fast filling of the injection gap and a subsequent through-thickness preform impregnation. Creating an edge race-tracking channel, an additional lateral in-plane flow from the channel towards the preform center was observed, initiating soon after the injection started and caused by the spatial connecti...
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This paper handles four points. First, a very brief introduction into the microwave technologies background is given. This will help understand the challenges when changing from conventional heating to microwave heating. Second, a view on... more
This paper handles four points. First, a very brief introduction into the microwave technologies background is given. This will help understand the challenges when changing from conventional heating to microwave heating. Second, a view on the current state of development in form of a literature sum-up is presented. For this, the literature will be analyzed in respect to the type of publications, equipment used, and the materials investigated. Third, some practical challenges will be described that were faced in microwave process development by the author and how they were overcome. Last, an outlook with potential applications for microwave processing and further needs of development is given.
Despite the ambitions for increasing numbers of Carbon Fiber Reinforced Plastics (CFRP) parts no reductions in quality aspects can be accepted. Therefore new quality inspection methods have been taken into account. Online Process... more
Despite the ambitions for increasing numbers of Carbon Fiber Reinforced Plastics (CFRP) parts no reductions in quality aspects can be accepted. Therefore new quality inspection methods have been taken into account. Online Process Monitoring (OPM) systems offer the opportunity to monitor process data, compare them with the ideal course of the process and draw conclusions about part quality. In this study, three commercially available OPM systems Dielectrical Analysis (DEA), Direct Current Resistivity (DCR) and Ultrasonic Technology (US) are discussed for use in serial production. DEA measures the change in dielectrical properties of the resin, DCR is based on resistivity changes of the resin during processing and US analyses changes in ultrasonic speed of the matrix material. All systems promise to monitor flow front arrival, in-mold viscosity and curing. Furthermore effects of aged resin and different mixing ratios and detection of toughening thermoplastics are investigated in this ...
Faserverstarkte Kunststoffe finden Anwendung in Luft- und Raumfahrt, Automobil, Maschinenbau und Sport. Das Anwendungspotential ist jedoch noch lange nicht erschopft, auch wegen zu hoher Bauteil- bzw. Herstellungskosten. Um dem... more
Faserverstarkte Kunststoffe finden Anwendung in Luft- und Raumfahrt, Automobil, Maschinenbau und Sport. Das Anwendungspotential ist jedoch noch lange nicht erschopft, auch wegen zu hoher Bauteil- bzw. Herstellungskosten. Um dem existierenden Kostendruck Rechnung zu tragen, gewinnen die Aspekte der Automatisierung und Effizienzsteigerung immer mehr an Bedeutung. Die Ergebnisse des Verbundprojektes FLAME zeigen, dass durch Einsatz von Mikrowellen im Prozess hier deutliche Vorteile erreicht werden.
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In order to enhance lightweight potential and fabrication efficiency of structural parts from carbon fiber-reinforced plastics, the approach of locally tailored component properties has proven effective. For braided hollow profiles,... more
In order to enhance lightweight potential and fabrication efficiency of structural parts from carbon fiber-reinforced plastics, the approach of locally tailored component properties has proven effective. For braided hollow profiles, however, technical possibilities to achieve process integrated adaption of a components’ mechanical properties are limited. Therefore, a novel braiding process approach for cycle-time-neutral adjustment of a triaxial braids filler yarn count is examined and its advantages for component design are illustrated. The main objective of this study is to evaluate the approaches applicability with regard to process stability and disturbance of product quality. Two consecutive test series are carried out to identify the most influential process variables and to link the variation of these variables with multiple criteria of process quality. A clear dependency between quality and braid angle, braid yarn tension as well as the number of filler yarns the approach is...