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  • 1
    Electronic Resource
    Electronic Resource
    A boundary element simulation of compression mold filling (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 413-420 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents the development of the boundary element equations for the compression molding process of isothermal Newtonian fluids. It shows the numerical implementation of the boundary element equations and presents a simple method of carrying out the domain integral present in the governing equations. The results and accuracy of a boundary element simulation are discussed, and the numerical results compared to experimental values.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280703
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Predicting shrinkage and warpage of fiber-reinforced composite parts (1994)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 15 (1994), S. 270-277 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: One major problem that arises in the design of plastic parts, especially those that are fiber reinforced, is the change of shape and dimension as a result of shrinkage and warpage. These material inhomogeneities are caused by flowinduced fiber orientation, curing, poor thermal mold lay-out, and other processing conditions. This paper presents a simulation that predicts shirnkage and warpage of 3-D compression molded fiber reinforced composite parts. The simulation represents the structure with the 3-noded shell elements used in mold filling simulations. The calculated results indicate that fiber orientation strongly affect the final properties, which vary with different chage locations, have a significant effect on warpage. Unsymmetric curing, caused by uneven mold temperatures, could lead to a thermal moment that could possibly help reduce warpage.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750150405
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    Paper (German National Licenses)
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  • 3
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    Fiber-Reinforced Composite Sandwich Structures by Co-Curing with Additive Manufactured Epoxy Lattices (2019)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2019-05-16
    Description: In this paper, a new process of joining additive manufactured (AM) lattice structures and carbon fiber-reinforced plastics (CFRPs) to manufacture hybrid lattice sandwich structures without secondary bonding is investigated. Multiple variations of lattice structures are designed and 3D printed using Digital Light Synthesis (DLS) and a two-stage (B-stage) epoxy resin system. The resulting lattice structures are only partially cured and subsequently thermally co-cured with pre-impregnated carbon fiber reinforcement. The mechanical properties of the additive manufactured lattice structures are characterized by compressive tests. Furthermore, the mechanical properties of hybrid lattice sandwich structures are assessed by flexural beam testing. From compressive testing of the additive manufactured lattice structures, high specific strength can be ascertained. The mechanical behavior shows these lattice structures to be suitable for use as sandwich core materials. Flexural beam testing of hybrid lattice sandwich structures shows high strength and stiffness. Furthermore, the strength of the co-cured bond interface is high enough to surpass the strength of the lattice core.
    Electronic ISSN: 2504-477X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Molecular Diversity Preservation International
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  • 4
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    Validating a Failure Surface Developed for ABS Fused Filament Fabrication Parts through Complex Loading Experiments (2019)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2019-05-10
    Description: Fused Filament Fabrication (FFF) is arguably the most widely available additive manufacturing technology at the moment. Offering the possibility of producing complex geometries in a compressed product development cycle and in a plethora of materials, it has gradually started to become attractive to multiple industrial segments, slowly being implemented in diverse applications. However, the high anisotropy of parts developed through this technique renders failure prediction difficult. The proper performance of the part, or even the safety of the final user, cannot be guaranteed under demanding mechanical requirements. This problem can be tackled through the development of a failure envelope that allows engineers to predict failure by using the knowledge of the stress state of the part. Previous research by the authors developed a failure envelope for acrylonitrile butadiene styrene (ABS) based, Fused Filament Fabrication (FFF) parts by use of a criterion that incorporates stress interactions. This work validates the first quadrant of the envelope by performing uniaxial tensile tests with coupons produced with a variety of raster angles, creating a combined loading stress state in the localized coordinate system. Results show the safe zone encompassed by the failure envelope proved adequate.
    Electronic ISSN: 2504-477X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Molecular Diversity Preservation International
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  • 5
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    Editorial for the Special Issue on Discontinuous Fiber Composites, Volume II (2021)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2021-03-05
    Description: This Special Issue on discontinuous fiber composites and its published papers, like its predecessor, give the polymer engineer and scientist an insight into challenges and research topics in the field of discontinuous fiber-reinforced composites [...]
    Electronic ISSN: 2504-477X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Molecular Diversity Preservation International
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  • 6
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    Direct Fiber Simulation of a Compression Molded Ribbed Structure Made of a Sheet Molding Compound with Randomly Oriented Carbon/Epoxy Prepreg Strands—A Comparison of Predicted Fiber Orientations with Computed Tomography Analyses (2020)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2020-10-31
    Description: Discontinuous fiber composites (DFC) such as carbon fiber sheet molding compounds (CF-SMC) are increasingly used in the automotive industry for manufacturing lightweight parts. Due to the flow conditions during compression molding of complex geometries, a locally varying fiber orientation evolves. Knowing these process-induced fiber orientations is key to a proper part design since the mechanical properties of the final part highly depend on its local microstructure. Local fiber orientations can be measured and analyzed by means of micro-computed tomography (µCT) and digital image processing, or predicted by process simulation. This paper presents a detailed comparison of numerical and experimental analyses of compression molded ribbed hat profile parts made of CF-SMC with 50 mm long randomly oriented strands (ROS) of chopped unidirectional (UD) carbon/epoxy prepreg tape. X-ray µCT scans of three entire CF-SMC parts are analyzed to compare determined orientation tensors with those coming from a direct fiber simulation (DFS) tool featuring a novel strand generation approach, realistically mimicking the initial ROS charge mesostructure. The DFS results show an overall good agreement of predicted local fiber orientations with µCT measurements, and are therefore precious information that can be used in subsequent integrative simulations to determine the part’s mesostructure-related anisotropic behavior under mechanical loads.
    Electronic ISSN: 2504-477X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Molecular Diversity Preservation International
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  • 7
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    Experimental Investigation of In-Plane Shear Behaviour of Thermoplastic Fibre-Reinforced Composites under Thermoforming Process Conditions (2021)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2021-09-15
    Description: In order to meet environmental regulations and achieve resource efficiency in the series production of vehicles, recyclable polymer composites with a high strength-to-weight ratio are increasingly being used as materials for structural components. Particularly with thermoplastic fibre-reinforced polymers or organo-sheets, the advantage lies in the tailored mechanical properties of the final component by adapting the orientation of fibres based on the direction of loads. These components produced by thermoforming organo-sheets also offer a cost benefit and short cycle times. During the thermoforming process, the shear behaviour of the organo-sheet is the most dominant and determines the mechanical properties and quality of the resulting component. However, the current standard for characterising the shear behaviour of organo-sheets does not consider the strain and cooling rates inherent in the thermoforming process. This research investigates the influence of thermoforming process parameters on the shear behaviour of organo-sheets with a new methodology combining DSC and DMA experiments. During the thermoforming process, the transition of the matrix material from a molten state to a solid state is dictated by the crystallisation kinetics and their dependence on heating and cooling rates. Thus, non-isothermal DSC scans, which correspond to a temperature cycle in a thermoforming process, are used in the DSC experiments to establish the relationship between the recrystallisation temperature of the organo-sheet material and the cooling/heating rates in the thermoforming process. In order to achieve thermoforming-process-relevant cooling rates, fast scanning calorimetry (Flash DSC) is used in addition to conventional DSC measurements. DMA experiments carried out with 45° fibre orientation show that the recrystallisation temperature consequently influences the shear storage modulus of the organo-sheet. The results from DSC measurements show a shift of recrystallisation temperatures to lower temperatures as the cooling rate increases. The combined analysis of results from the DSC and DMA experiments supports the findings and shows the influence of the process temperature, cooling rate and strain rate on the recrystallisation temperature and, in turn, the shear behaviour of organo-sheets. Thus, a recommendation for establishing a new standard for characterising the shear behaviour of organo-sheets is made.
    Electronic ISSN: 2504-477X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Molecular Diversity Preservation International
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