JEC COMPOSITES MAGAZINE - Issue #52 - October 2009 - 40

FEATURE Three-dimensional tailored fibre placement The Tailored Fibre Placement (TFP) method is used to produce near-net-shaped preforms. With the classic TFP method, preforms are stitched in 2D and then draped to create a near-net-shaped form. The three-dimensional TFP process is being investigated at the RWTH Aachen University (Germany). JULIAN EICHHOFF, SCIENTIFIC RESEARCHER & THOMAS GRIES, PROFESSOR, INSTITUT FÜR TEXTILTECHNIK (ITA), RWTH AACHEN UNIVERSITY he Tailored Fibre Placement (TFP) method is a technical stitching process used to produce near-net-shaped preforms. Rovings are placed on a basic textile and are fixed by stitching threads. The principle of the process is shown in Figure 1. The stitching head is stationary while the basic fabric can be moved in the x and y direction to create the pattern. With the TFP method, load-capable preforms can be produced, placing the reinforcement fibres on the main load paths. Complex geometries and special reinforcements for inserts, cut-outs and load injection points can be created. T form. During the draping process, the reinforcement fibres are deflected from the designed (optimal) placement position and undulate, thus reducing the mechanical properties of the FRP part. The Institut für Textiltechnik (ITA) at the RWTH Aachen University (Germany) is currently investigating the threedimensional TFP process as part of the 3D-Sticken (3Dstitching) project. In this process, the preforms are directly stitched in 3D to eliminate the draping process, thus preventing any undulation in the reinforcement fibres. A stitching machine from ZSK Stickmaschinen GmbH (Krefeld, Germany) is used. The stitching process on the machine has been modified to enable the three-dimensional placement of carbon fibres. Details cannot be published yet due to a pending patent. However, we would like to share our future vision of the TFP process, depicted in Figure 2. A robot bearing a TFP stitching head using a one-sided sewing technology is used to guide the head over a three-dimensional basic fabric. The stitching head can be moved freely by the robot to achieve complex geometries. A foam or rigid foil can be used to form the supporting structure for the TFP preform. The current one-sided stitching or sewing technologies are not compatible with tailored fibre placement. The TFP process requires a zigzag stitch to fix the roving onto the basic fabric (see Figure 1), which cannot be provided by present one-sided sewing techniques. Additional research and development beyond the 3D-Sticken project will be necessary to materialize this concept. Two different example parts were designed for this project. The parts will be manufactured using both the “classic” TFP method (2D stitching + draping) and the direct 3D stitching process developed by the Institut für Textiltechnik. The advantages of the direct 3D method can be evaluated by comparing the differently produced parts. ITA wants to illustrate the advantages of a direct 3D method Fig. 1: Principle of the conventional (2D) TFP Process (Source: ITA). With the classic TFP method, preforms are stitched in 2D, and then draped to create the near-net-shaped, three-dimensional jec composites magazine / No52 October 2009

http://www.jeccomposites.com

JEC COMPOSITES MAGAZINE - Issue #52 - October 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #52 - October 2009