Development of fundamental process technology for the production of Multiaxial Warp Knitted (Stitch-Bonded) Fabric with three dimensional Geometry

• Applicant: Professor Dr.-Ing. Chokri Cherif
• Subject Area: Lightweight Construction, Textile Technology
• Term: from 2010 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 160013724

• Final Report Year: 2016

Final Report Abstract

The focal point of this research work was to achieve a universal process chain for manufacturing of 3D-Near net shape warp knitted preforms (open-grid and closed) with complex geometries. The development of a geometrical model has enabled the calculation of the required yarn course based on the final surface geometry and thereby closing the loop from design to production. The development of this technological process chain has resulted in a better understanding of the processing behavior for the materials used, the calculation methods and the process technology. The development and integration of NC-Warp yarn delivery and doffing systems as well as the realization of a modified working cycle has ensured that a fundamental large scale technological possibility based on Multiaxial Warp Knitting now exists for the production of textile preforms in near-component contours. The validation of the textile process chain was demonstrated by production of sample patterns. A target/actual comparison show a good concurrence between the computed and measured warp yarn lengths. Furthermore, it can be experimentally concluded through the sample production that the numerically controlled doffing system in combination with variable warp yarn delivery system offers better accuracy and flexibility than a mechanical controlled doffing system. The maximum additional warp yarn length factor that can be delivered for achieving a reproducible production of near net shape preforms using the mechanical doffing system was 1.3. In case of numerical controlled doffing system, the delivered length factor was improved to 1.5. Also, the following insights about the production process could be gained, • the influence of doffing force transfer on the warp yarns as a result of the fabric formation between the doffing system and knitting unit;• the relevance on the fabric cut-off from the transport chain and their influence on the doffing force as well as on the fabric take-up;• the influence of different doffing control mechanism (NC and mechanical) on the accuracy of the system. With this innovation, a viable solution for energy efficient production of textile preforms with warp yarn reserves can be realized. This also offers a greater flexibility to adapt the textile reinforcements in accordance to the applied loads that makes the lightweight composite structures suited for complex demands and large-scale manufacturing as well as an efficient utilization of the fiber properties, thereby fulfilling an essential requirement of semi-finished products for high performance composites. Also the textile branch benefits from extended possibilities in the development of new, quality products that promise an improved market position, while offering an aid in successfully meeting current economic challenges. Along with potential application possibilities in mineral composite materials, matrices made of plastic using these preforms also open up possibilities for integral constructions in the fields of vehicle and aerospace construction and engineering as well as general mechanical engineering. Furthermore, these developed methods are modular and can also be transferred to other textile technologies such as Leno weaving or multilayer knitting.

Publications

• DE 10 2007 038 931 B4. Fadenlagen-Nähwirkstoffe. 13.08.2007 /23.09.2010
  Engler, Th.; Waldmann, M.; Cherif, Ch.; Trips, K.
  
• 3-D Stitch-Bonded Fabrics. In: Proceedings. 12th World Textile Conference AUTEX 2012, Zadar (Croatia), June 13-15, 2012, pp. 495-500
  Sankaran, V.; Bardl, G.; Cherif, Ch.
  
• A novel processing solution for the production of spatial three-dimensional stitch-bonded fabrics. Textile Research Journal, 82(2012)15, 1531-1544
  Sankaran, V.; Younes, A.; Engler, T.; Cherif, Ch.
  
• Entwicklung von multiaxialen Gelegestrukturen mit dreidimensionaler Geometrie aus Hochleistungsfaserstoffen. In: CD-Rom. 51. Chemiefasertagung Dornbirn, Dornbirn (Austria), 19.-21. September 2012
  Sankaran, V.; Cherif, Ch.
  
• New machine concept for producing 3-D stitch-bonded fabrics. Fibres and Textiles in Eastern Europe, 21(2013)1, pp. 92-96
  Sankaran, V.; Cherif, Ch.
  
• Recent advances in the development of multiaxial warp knitting machines for the fabrication of spatial textile preforms and online textile coating. In: tts8.3- 1350-vignaesh-sankaran.pdf. Techtextil Symposium, Frankfurt, 11.-13. Juni 2013
  Sankaran, V.; Cherif, Ch.
  
• Biomimetic multifunctional textile reinforcements for large scale production of composite structures. In: CD-Rom und Kurzreferateband. 8. Aachen-Dresden International Textile Conference, Dresden, 27.-28. November 2014, pp. 78-80
  Cherif, Ch.; Ruder, T.; Sankaran, V.; Rittner, S.
  
• Potential and challenges of multimaterial design for composites based on merging textile, metal and plastic technologies. In: Proceedings. 15th AUTEX World Textile Conference 2015, Bucharest (Romania), June 10-12, 2015
  Cherif, Ch.
  
• Development of multiaxial warp knitting technology for production of three-dimensional near net shape shell preforms. Textile Research Journal, Volume: 87 issue: 10, page(s): 1226-1241, June 2017
  Sankaran, V.; Rittner, S.; Hahn, L.; Cherif, Ch.