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End date: 2024 × Start date: 2020 × Subject: Forming ×

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    Pattern transfer of sub-micrometre-scaled structures into solid copper by laser embossing
    (Amsterdam [u.a.] : Elsevier, 2014) Ehrhardt, M.; Lorenz, P.; Lotnyk, A.; Romanus, H.; Thelander, E.; Zimmer, K.
    Laser embossing allows the micron and submicron patterning of metal substrates that is of great interest in a wide range of applications. This replication process enables low-cost patterning of metallic materials by non-thermal, high-speed forming which is driven by laser-induced shock waves. In this study the surface topography characteristics as well as the material structure at laser embossing of sub-micrometre gratings into solid copper is presented. The topography of the laser-embossed copper pattern is analysed with atomic force microscopy (AFM) in comparison to the master surface. The height of the embossed structures and the replicated pattern fidelity increases up to a laser fluence of F ∼ 10 J/cm2. For higher laser fluences the height of the embossed structures saturates at 75% of the master pattern height and the shape is adequate to the master. Structural modifications in the copper mono crystals after the laser embossing process were investigated with transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). Almost no modifications were detected. The residual stress after laser embossing of 32 MPa (F = 30 J/cm2) has only a limited influence on the surface pattern formation.
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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.