Grundlagen zur Drapierbeeinflussung beim Thermoformen durch konfektionierte Textilstrukturen
Final Report Abstract
This study has investigated the development of an efficient finite element (FE) model for simulating the deformation of woven fabric preform materials under the influence of stitching patterns. Prior work, material property testing and woven fabric material data taken from the literature has been used to setup and verify a model which is able to consider interactions between stitches and the shearing movement of the weave. By performing a set of calibration and verification simulations, any woven composite preform/prepreg material, either in dry reinforcement/commingled or molten organo sheet form can now be simulated. The innovative modelling approach employed uses a combination of shell and beam elements connected together at common nodal points in order to represent the behaviour of the woven fabric material. To model the presence of stitches, beam (cable) elements are again used together with a material model which considers the key parameters of stitch behaviour. The stitching elements interact with the fabric through special contact definitions and can be placed at any location on the mesh. Initially, physical tensile tests on two dimensional fabric strip specimens with and without centreline stitching were carried out. Force displacement data, centre fibre angle, stitch elongation, and the overall general deformation pattern for both types of specimens were then measured and compared. Once the two dimensional properties have been satisfied, three dimensional verifications in the form of dome forming tests were carried out. This is performed on square sheet specimens, made from a single layer of fabric cut to two different fibre orientations (0/90 and ±45). Specimens in the 0/90 configuration were tested and compared in the presence of several stitch patterns. Once the behaviour of any given material has been verified, simulations can be performed on more complex geometries of up to 0.25 m2 in size within reasonable timeframes on standard level computing resources. Stitch patterns can then be trialled in regions where shear deformation is most prominent and pattern shape and location can be generated and selected based on these results. The present work has certainly demonstrated the feasibility of a macroscale FE model for the efficient prediction of stitch pattern influence during composite sheet forming operations. Future work would focus on establishing a material model database by applying the material characterization techniques developed during the course of this work. In particular, the focus would be on characterizing the forming behaviour of a selection of commercially available organo sheet materials and providing the guidelines for such characterization experiments. In this way manufacturers of such materials could provide their clients with samples of their products along with the material forming data which could be used to perform virtual manufacturing trials to establish whether or not the material is suitable for the given application (component geometry) and to optimize manufacturing parameters. For the development of a more comprehensive material model database, studies to predict the behaviour of different weave reinforcement geometries in the presence of any molten polymer could be performed. The idea here would be to formulate a polymer-independent description of reinforcement deformation behaviour based on viscosity. This would mean that characterization experiments for only the reinforcement at room temperature would be required which are much easier to perform than isothermal elevated temperature tests on organo sheets. This information would then be used together with rheology data of the respective polymer matrix material which is either readily available or easily obtained using polymer rheology testing equipment. Textile composites utilizing high melt temperature polymers such as polyetheretherketone (PEEK), polyetherimide (PEI) and other high performance polymers could then be characterized in a manageable way. A difference in the forming behaviour due to temperature variations in the organo sheet during the forming process is another feature which could be analyzed and predicted. The current model can provide useful manufacturing parameter optimisation information for any composite parts produced this way.
Publications
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Simulating the Deformation of Textile Structures in Polymer Composite Materials. Centre for Advanced Composite Materials, the University of Auckland, New Zealand, 7th December 2009
Duhovic, M., Mitschang, P., Bhattacharyya, D.
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Modelling the influence of stitching on woven fabric composite deformation behaviour. ECCM-14 - 14th European Conference on Composite Materials, Budapest, Hungary, June 7-10, 2010
Duhovic, M., Mitschang, P., Bhattacharyya, D.
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Simulating the deformation of stitched woven structures in polymer composite materials. CACM Foundation for Research Science and Technology (FRST) Visit, Auckland, New Zealand, August 18, 2010
Duhovic, M., Mitschang, P., Bhattacharyya, D.
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Simulating the deformation of stitched woven structures in polymer composite materials. IVW Kolloquium 2010, Kaiserslautern, Germany, November 16-17, 2010
Duhovic, M., Mitschang, P., Bhattacharyya, D.
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Simulation of yarn and stitch interactions during woven fabric draping and composite prepreg stamping. PFAMXIX - 19th International Symposium on Processing and Fabrication of Advanced Materials, Auckland, New Zealand, January 14-17, 2011
Duhovic, M., Mitschang, P., Bhattacharyya, D.
