Speed Up Development of Fiber-Reinforced Plastic

The draping process of textiles is carried out during production by experienced specialists. Since standards and objective criteria are lacking, we create a draping catalogue for the »OptiDrape« project. Picture: 45° diagonal tensile test of a dense fiberglass fabric fixed in a frame, performed at ITA, with its simulation.

Optimizing the Draping Process for FRP Components Made From High Performance Textiles

AIF Project »OptiDrape«

Fiber-reinforced plastics are the basis for many applications in state-of-the-art lightweight design, and they offer numerous advantages. One major obstacle for smaller companies, however, is the requisite know-how concerning the ideal fiber and textile arrangement. In collaboration with the Institut für Textiltechnik (ITA) and the Assoc. Institute for Management Cybernetics (IfU) in Aachen, the Fraunhofer Institute for Industrial Mathematics ITWM has now developed a mathematical simulation method for optimizing the drapability (deformability) of textiles.

The potential of components made from fiber reinforced polymers (FRP) is highly dependent on the type of reinforcing textiles used and their drapability (ductility). The draping quality is evaluated on the basis of defects and wrinkles in the textile after preforming. Preforming refers to the process for producing a dry reinforcement structure. The potential of the anisotropic material is enormous for lightweight construction and can be specifically exploited only if the textile fibers are present locally in the required orientation. The draping process takes place during the production of complex geometries by experienced specialists. From a technical and economic point of view, the process lacks standards and objective criteria and requires optimization.

Critical Shear Angle
© Institut für Textiltechnik (ITA) and Fraunhofer ITWM
Left: Determining the critical shear angle of a woven fabric. Test performed at ITA. Right: Simulation of the same test with an incipient crease using TexMath.
Von dem Experiment wurden REM-Aufnahmen erstellt und ausgewertet.
© Institut für Textiltechnik ITA
Von dem Experiment wurden REM-Aufnahmen erstellt und ausgewertet.
Pulling a fabric onto a sample, in the initial and final state; simulated with TexMath.
© Fraunhofer ITWM
Pulling a fabric onto a sample, in the initial and final state; simulated with TexMath.

Improve Quality and Shorten Times

The aim of the »OptiDrape« project is to improve the quality of the preforms for FRP components and to shorten the development time. We classify the different mats and weaves in terms of draping properties according to the type of bond as well as by the roving material and cross-sections. A roving is a bundle, strand, or multi-filament yarn made from parallel filaments. Also, a textilespecific shear angle is given. This indicates the point at which the textile starts to wrinkle.

Mit unserem Simulationstool können wir Materialien in unterschiedlichen Situationen simulieren. Hier wird eine Leinwand mit verschiedenen Materialeigenschaften analysiert.
© Fraunhofer ITWM
Mit unserem Simulationstool können wir Materialien wie diese Leinwand in unterschiedlichen Situationen simulieren.
Durch Variation des Abstandes zwischen den Roving-Mittellinien können wir die Biegesteifigkeit der Leinwand analysieren.
© Fraunhofer ITWM
Durch Variation des Abstandes zwischen den Roving-Mittellinien können wir die Biegesteifigkeit der Leinwand analysieren.

We selected a total of 16 carbon and glass fiber textiles with different cross sections and bond types as well as various offsets. ITA conducted a number of experiments and determined the effective tensile, shearing, and bending properties and shear angles. In parallel, we also used our FEM software to simulate and validate these properties. In contrast to experimentation, simulation at the roving level enables a virtual material design with precision detail. Among other things, the roving cross sections as well as the materials and distances of the bonds can be more efficiently varied; and, the experiment catalog was significantly expanded.

 

Model for a Wide Range of Uses

The project used comprehensive mathematical analysis to develop a predictive model that calculates the critical shear angle. It relies on previously defined roving materials and dimensions, the type of bond, as well as experimentally determined contact point data. Additional model parameters include the offset of the bond as well as the distances. The resulting model not only allows companies to set up a very broad catalog, but also to continuously vary all of the design parameters for any application and requirement in the interests of optimizing the design.