TY - BOOK

T1 - On the Potential of Epoxy Binder Rovings in Automated Dry Fiber Filament Winding

AU - Neunkirchen, Stefan

N1 - no embargo

PY - 2024

Y1 - 2024

N2 - Filament winding has been a well-established process in the manufacturing of composite parts for decades. In recent years it has gained increased attention due to the demand for gas transport and storage systems, especially hydrogen. Apart from automation and monitoring, which are essential for every modern-day manufacturing process, new design methods as well as process modifications and variations are now the focus of research. One such process variation is dry (fiber) filament winding, where, unlike the established wet and prepreg winding processes, unimpregnated fibers are used. The usage of dry, untwisted fiber bundles, so-called rovings, comes with certain challenges but also opportunities. On the one hand, the process speed can be increased, and the potential for automation rises. Whereas, on the other hand, an additional subsequent process step is required to impregnate the reinforcing structure. This can lead to increasing production time and cost. The main challenge of the winding process itself is the different behavior and properties of the roving. Especially, the tendency of the roving to slip off the mandrel needs to be investigated. One possible solution to overcome this problem is the usage of binder. These polymeric materials can be activated, commonly by temperature, and then become tacky. This can (locally) increase the adherence of the roving to the surface on which it should be wound. In this thesis, the dry fiber filament winding process with binder rovings is studied. The process and its characteristics are presented and compared to established processes, namely wet and prepreg winding. Based on these findings, experiments were conducted to examine specific challenges. Building a dry winding system based on robotic winding machinery, showed some new aspects in the practical implementation, especially in handling tasks. With appropriate adaptions and adjustments, the process proved to be suitable for the winding of geometrically complex shapes such as a cone. Experiments on the friction behavior of (activated) binder rovings on an aluminum mandrel showed an increase in available friction and hence design possibilities. Several parameters were tested, which proved to be comparable to values stated in literature for the non-binder rovings and generated new knowledge for the binder rovings. As an important process parameter, the monitoring of the roving¿s profile via a laser light sectioning sensor is presented. Experiments with binder and reference material have been executed in various settings. Based on an earlier developed algorithm, the so-gained data was evaluated and interpreted. It could be shown that the light sectioning method is a suitable technique for inline monitoring. In dry fiber winding a preform is produced which then needs to be infiltrated with resin to produce the final part. The quality of a resin injection or infusion process is strongly dependent on the flow of the liquid through the porous media. While permeability has been discussed extensively in literature, the capillary flow in bindered rovings has not been examined yet. Capillary rise experiments show that the velocity increase of the straightened binder rovings is larger than the obstruction by binder particles. When activating the binder, the flow velocity decreases due to absorption by the rovings and blocking of the flow channels. Depending on the desired part specifications, dry fiber winding can be a viable option. Further consideration of the cost and the resulting part quality needs yet to be done.

AB - Filament winding has been a well-established process in the manufacturing of composite parts for decades. In recent years it has gained increased attention due to the demand for gas transport and storage systems, especially hydrogen. Apart from automation and monitoring, which are essential for every modern-day manufacturing process, new design methods as well as process modifications and variations are now the focus of research. One such process variation is dry (fiber) filament winding, where, unlike the established wet and prepreg winding processes, unimpregnated fibers are used. The usage of dry, untwisted fiber bundles, so-called rovings, comes with certain challenges but also opportunities. On the one hand, the process speed can be increased, and the potential for automation rises. Whereas, on the other hand, an additional subsequent process step is required to impregnate the reinforcing structure. This can lead to increasing production time and cost. The main challenge of the winding process itself is the different behavior and properties of the roving. Especially, the tendency of the roving to slip off the mandrel needs to be investigated. One possible solution to overcome this problem is the usage of binder. These polymeric materials can be activated, commonly by temperature, and then become tacky. This can (locally) increase the adherence of the roving to the surface on which it should be wound. In this thesis, the dry fiber filament winding process with binder rovings is studied. The process and its characteristics are presented and compared to established processes, namely wet and prepreg winding. Based on these findings, experiments were conducted to examine specific challenges. Building a dry winding system based on robotic winding machinery, showed some new aspects in the practical implementation, especially in handling tasks. With appropriate adaptions and adjustments, the process proved to be suitable for the winding of geometrically complex shapes such as a cone. Experiments on the friction behavior of (activated) binder rovings on an aluminum mandrel showed an increase in available friction and hence design possibilities. Several parameters were tested, which proved to be comparable to values stated in literature for the non-binder rovings and generated new knowledge for the binder rovings. As an important process parameter, the monitoring of the roving¿s profile via a laser light sectioning sensor is presented. Experiments with binder and reference material have been executed in various settings. Based on an earlier developed algorithm, the so-gained data was evaluated and interpreted. It could be shown that the light sectioning method is a suitable technique for inline monitoring. In dry fiber winding a preform is produced which then needs to be infiltrated with resin to produce the final part. The quality of a resin injection or infusion process is strongly dependent on the flow of the liquid through the porous media. While permeability has been discussed extensively in literature, the capillary flow in bindered rovings has not been examined yet. Capillary rise experiments show that the velocity increase of the straightened binder rovings is larger than the obstruction by binder particles. When activating the binder, the flow velocity decreases due to absorption by the rovings and blocking of the flow channels. Depending on the desired part specifications, dry fiber winding can be a viable option. Further consideration of the cost and the resulting part quality needs yet to be done.

KW - Binder Roving

KW - Dry Fiber Filament Winding

KW - Robotic Winding

KW - Inline Monitoring

KW - Capillary rise

KW - Binder activation

KW - Binder Roving

KW - Trockenwickeln

KW - roboterunterstütztes Faserwickeln

KW - Prozessüberwachung

KW - kapillare Steigung

KW - Binderaktivierung

U2 - 10.34901/mul.pub.2024.227

DO - 10.34901/mul.pub.2024.227

M3 - Doctoral Thesis

ER -