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Die Rascheltechnologie - Herstellverfahren für anwendungsgerechte 3D-Textilien zur Bewehrung von Betonbauteilen

Stockmann, P. / Maetschke, O. / Wulfhorst, B. / Gries, T.

The Special Research Project SFB 532 'Textile reinforced concret - Basics for the development of a new technology' is an interdisciplinary merger of different departments of the RWTH Aachen. One main task of this scientific project is the concept and manufacturing of grid-like 3D-textiles to reinforce cementious composites. Due to the pressure of costs in the civil engineering branch, the demand for reinforcement textiles that fit optimally to component geometry and load application has been growing. The development of 3-dimensional textiles and the respective textile manufacturing processes enables the production of tailored textiles, in which the stationary threads are located exactly in the zone subject to tensile forces. Here the combination of a lattice like character with a high dimensional stability is a new challenge to the developer. With the help of a Double-Raschel-Machine, spacer fabrics can be produced in which two basic fabrics are joined together by pile threads. Textiles are optimally used in different FRP-applications to absorb tensile forces. Coming from this idea, different textiles are being used in order to reinforce cementious components. In general, textiles can be used to reinforce concret elements, if in their open lattice-like structure the threads are positioned flat and exactly in load direction. These textiles should be resistant to displacement and stable in their dimensions. In addition, they should have a good handling, regardless whether they are flat or 3-dimensional textiles. The use of multi-axial, multi-ply fabrics in FRP-composites has been growing considerably over the last years. The advantages of these textiles, e.g. the good drapeability, and the variability of the number and orientation of the inserted threads, can be used to reinforce cementious components. One task of the development of multi-axial multi-ply fabrics for the reinforcement of concret matrices is the production of a lattice-like grid in order to obtain a fibre volume content of approximately 0.5 to 4 %. Three-dimensional profiled warp-knitted fabrics are a special type of spacer fabrics in which the distance of the basic fabrics can be varied. The reinforcement of cementitous composites with these textiles is a new way to absorb tensile loads. A further development of the circular warp-knitting technology simplifies the production of grid-like tubes with a variety of different binding possibilities. Due to the mesh structure of these textiles, the resistance to slip effects is very small. For that reason the manufacturing of composite elements is very difficult. The manufacturing of planar textiles with a grid-like character to reinforce concrete elements is state-of-the-art in the field of warp-knitting machines with multi-axial weft insertion. The further development of Double-Raschel- and Circular Warp-knitting Machines and the production of 3-dimensional textile with them simplifies the use of 'tailored' textiles for the reinforcement of FRP-and concrete components with a variety of different operative ranges.