Consolidation of Thermoplastic hybrid yarn materials
Final Report Abstract
The objective of the project “Consolidation of Thermoplastic hybrid yarn materials” (ConThP) was to develop a consolidation model for hybrid textiles that describes the local properties of the composite material such as fibre volume content, pressure distribution and pore content. During the impregnation of hybrid textiles based on thermoplastic and carbon fibres, several phenomena take place. The dry fibre bundles are impregnated by the matrix flow. Occur-ring pressure differences can lead to fibre displacement. Above this, remaining pores lead to incomplete impregnation. Part of the applied stress is absorbed by the ply compaction. As part of the project, a material model was developed to describe the impregnation of hybrid textiles. Compared to previous models, the model takes into account air entrapped in the roving and its dissolution in the matrix. In experimental tests, laminates were pressed at different pressures and holding times. A twostage isothermal tooling concept allowed the laminates to cool down quickly. Thus, the impregnation process was frozen. Samples were then taken and the degree of impregnation at roving level was determined by micrographs analysis. Thus, the degree of impregnation was compared with the prediction. The model shows very good agreement for different materials and pressures. Within the project, a tool concept was developed and implemented with which it is possible to visualise the impregnation in different process stages in the X-ray CT. For this purpose, a hightemperature resistant and X-ray transparent tool mould is used. The degree of impregnation can then be analysed in the X-ray CT by rapid cooling. Subsequently, further impregnation takes place in the press and after further cooling, the impregnation progress can be analysed on the same sample. However, the resolution at filament level is very time-consuming and cost-intensive, so only individual measurements were carried out for model validation. Furthermore, this resolution requires very small distances between sample and source. In further studies, this concept should contribute to a deeper understanding of impregnation. In addition to this investigation at coupon level, qualitative validation was carried out at demonstrator level on a stepped plate. The developed model agrees with the experimental investigations in a wide process window. The impregnation model is an important part of a reliable consolidation model. It is shown that the effect of entrapped air should not be neglected as it leads to plateau behaviour. Models available in the literature do not capture this effect so far. By taking the entrapped air into account, the process times and pressures for the consolidation of hybrid textiles can be adjusted and faulty components can be avoided.
Publications
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ConThP: Consolidation of thermoplastic hybrid yarn materials. 5th International Conference and Exhibition on Thermoplastic Composites ITHEC, Bremen, DE, 2020
Vocke R., Werlen V., Rytka C., Schwanemann P., Michaud V., Dransfeld C., Brauner C. & Herrmann A. S.
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A numerical approach to characterize the viscoelastic behaviour of fibre beds and to evaluate the influence of strain deviations on viscoelastic parameter extraction. Composites Part A: Applied Science and Manufacturing, 143, 106315.
Werlen, Vincent; Rytka, Christian & Michaud, Véronique
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Consolidation of hybrid textiles for aerospace applications. In A. P. Vassilopoulos & V. Michaud (Eds.), Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability (pp. 114-121). Lausanne, CH
Werlen V., Vocke R., Rytka C., Schwanemann P., Michaud V. & Dransfeld C.
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Contribution to the development of a setup for the efficient production of high-performance composite parts based on hybrid textiles. 5th Hybrid Materials and Structures 2022 - International Conference on Hybrid Materials, Leoben & online, AT, 2022.
Vocke V.; Werlen V.; Rytka C.; Schwanemann P.; Michaud V.; Dransfeld C.; Brauner C. & Herrmann A. S.
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A model for the consolidation of hybrid textiles considering air entrapment, dissolution and diffusion. Composites Part A: Applied Science and Manufacturing, 166, 107413.
Werlen, Vincent; Vocke, Richard; Brauner, Christian; Dransfeld, Clemens; Michaud, Véronique & Rytka, Christian
