Browsing by Author "Kärger, Luise"

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    Composite forming simulation for non-crimp fabrics based on generalized continuum approaches – AMECOMP : Abschlussbericht / Final project report (DFG 431354059 / ANR-19-CE06-0031)
    (Hannover : Technische Informationsbibliothek, 2024-05) Schäfer, Bastian; Kärger, Luise; Naouar, Naim; Zheng, Ruochen; Schäfer, Bastian; Kärger, Luise; Naouar, Naim; Zheng, Ruochen; Boisse, Philippe; Colmars, Julien; Platzer, Auriane
    Continuously carbon fiber reinforced composites are increasingly used for structural applications in various fields of engineering due to their excellent weight-specific mechanical properties. Non-crimp-fabrics (NCF) provide the highest lightweight potential as reinforcement for the composite due to their straight fibers, compared to woven fabrics with undulated fibers. NCFs are made of one (UD-NCF), two (Biax-NCF) or more directions of fibers linked together with a polymer stitching in specific patterns. The deformation behavior of NCFs is challenging due to the interaction between the fibers and the stitching, which also results in a higher susceptibility to forming effects such as roving slippage, fiber waviness and gapping compared to woven fabrics. The aim of the AMECOMP project was to improve the understanding of the forming behavior of NCFs and to develop suitable simulation models to broaden the range of potential applications. Mesoscopic models that accurately describe the architecture of the NCF were developed for virtual material characterization and detailed analysis of forming defects in critical areas. Macroscopic models that describe the relevant deformation mechanisms of NCF in a homogenized way were developed for efficient analysis of large components and multi-layer stacks.
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    On the Resin Transfer Molding (RTM) Infiltration of Fiber-Reinforced Composites Made by Tailored Fiber Placement
    (Basel : MDPI, 2022) Bittrich, Lars; Seuffert, Julian; Dietrich, Sarah; Uhlig, Kai; de Vargas Lisboa, Tales; Kärger, Luise; Spickenheuer, Axel
    Tailored fiber placement (TFP) is a preform manufacturing process in which rovings made of fibrous material are stitched onto a base material, increasing the freedom for the placement of fibers. Due to the particular kinematics of the process, the infiltration of TFP preforms with resin transfer molding (RTM) is sensitive to multiple processes and material parameters, such as injection pressure, resin viscosity, and fiber architecture. An experimental study is conducted to investigate the influence of TFP manufacturing parameters on the infiltration process. A transparent RTM tool that enables visual tracking of the resin flow front was developed and constructed. Microsection evaluations were produced to observe the thickness of each part of the composite and evaluate the fiber volume content of that part. Qualitative results have shown that the infiltration process in TFP structures is strongly influenced by a top and bottom flow layer. The stitching points and the yarn also create channels for the resin to flow. Furthermore, the stitching creates some eye-like regions, which are resin-rich zones and are normally not taken into account during the infusion of TFP parts.