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System for forming textile semi-finished products for fibre-reinforced plastic components

System for forming textile semi-finished products for fibre-reinforced plastic components

The manufacture of fibre-reinforced plastic components (FRP) is cost-intensive due to the high proportion of manual work in prototype and small series sector. The component quality can vary considerably and depends on the experience and competence of the employees.

In order to reduce the risk of undesired component failures, FRP components are often reinforced with additional material layers. The added material increases the component weight, the manufacturing costs and the resulting component costs.

In the case of FRP components, reinforced fibres absorb the applied forces. In the draping process, the laminar reinforced textile is formed into a desired component geometry. Thus, the process has a decisive influence upon the quality of the fibre orientation. Due to the high degree of automation, stamp forming, adapted from metal processing, has become established for draping complex textile preforms. Industrially, hydraulic presses are used for this purpose. The use of these machines is almost exclusively profitable in large series production due to the high investment and operational costs.

DrapeCube© ITA of RWTH Aachen University

To hold the reinforcing semi-finished products in the required geometry, thermoplastic adhesive powder is applied between the individual textile layers. The powder is melted by the application of heat before forming and holds the preform in the desired geometry after cooling. Industrially, continuous furnaces are used for melting. However, due to high operating costs, the systems are only economical for large material throughputs in continuous operation.

With the aim to provide cost-effective heating and forming of reinforced textiles for small production quantities, the Institute of Textile Technology is developing a forming station, the so-called DrapeCube. To heat the textiles, hot air is injected into the tool cavity from a pneumatic pressure pipe. It is heated up to 200°C by an electric coil. Thus, the heat is applied to the textile in a controlled manner over a short period of time. This approach enables the adhesive material to be melted and cooled before, during or after shaping. Pneumatic cylinders are used to generate the contact pressure. With a component projection area of 100 mm x 200 mm, contact pressure of up to 100 kPa can be achieved.

In summary, the DrapeCube offers a cost-effective system for heating and forming reinforced textiles for prototypes and small series. Currently, ITA uses the DrapeCube for research purposes.

DrapeCube© ITA of RWTH Aachen University

 

Boris Manin, Dr. Sven Schöfer, Julian Fendrich & Michael Winter

Contact

Boris Manin

Portrait NewsLIGHT
Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 241 80 22089
Mail: boris.manin@ita.rwth-aachen.de

 

Ultra-sonic consolidated bio-based hybrid tapes for structural parts in lightweight applications

Ultra-sonic consolidated bio-based hybrid tapes for structural parts in lightweight applications

In the present project, a process chain for the economical production of completely bio-based tapes (quasi-endless) was developed. The process chain for the production of tapes was developed and implemented together with three industrial partners, and a laboratory-scale tape production facility was put into operation at the Institut für Textiltechnik of RWTH Aachen University (ITA). The resulting 100% bio-based thermoplastic tapes can be processed on tape laying machines or tape weaving machines like conventional tapes made of glass or carbon fibers. Due to the untwisted, parallel alignment of the flax fibers, the properties of the fibers can be fully exploited and a high-quality application for example in the automotive sector or blades for wind turbines is possible.

The project partner Sofila textured the PA11 fibers and processed them into staple fibers. In cooperation with the ITA, Safilin has processed the flax and PA11 fibers into a hybrid sliver. This hybrid sliver is drawn and consolidated into a tape using ultrasonic welding. The ultrasonic module was developed and built by the project partner EM-Systeme specifically for the requirements of the present hybrid sliver. The energy of the mechanical vibration of the sonotrode is converted into internal friction and interfacial friction, which leads to the heating and melting of the thermoplastic PA11 fibers. The drawn and parallel flax fibers are impregnated with the melted thermoplastic. This procedure offers the advantage of a very efficient, local energy input.

The produced tape was processed into UD-layers, which were consolidated in a heat press to composites. These composites were cut to test specimen for mechanical characterization. Very good results in tensile and bending properties were obtained. Tensile strength is up to 233 MPa and Young’s modulus is up to 13 GPa. Bending strength is up to 280 MPa and flexural modulus is up to 30 GPa. In comparison to the commercially available flax/PP tapes and the cited experiments at Chemnitz University of Technology, the NFC produced in the Sonic Bio-Tapes project has on average both significantly better bending strength and bending stiffness. Furthermore, demonstrators were made from woven tapes at the ITA Augsburg. The whole process chain and the demonstrator is presented in the figure below.

For the upscaling of the pilot plant and for the implementation of the new technology in industrial practice, ITA and the project partners are looking for composites manufacturers or end users. Possible applications could be, for example, automotive, wind, sports and leisure, as well as design and furniture. If you are interested and want to get involved in an innovative future technology, please contact us.

DrapeCube© ITA of RWTH Aachen University

 

Acknowledgement

The ITA would like to thank the Federal Ministry of Economics and Energy – BMWi for funding the research project as part of the „Zentrales Innovationsprogramm Mittelstand – ZIM“. We also want to thank our project partners Sofila, Safilin and EM-Systeme for the good collaboration.

Matthias Reuter, Thomas Köhler, Alexander Janßen, Thomas Gries

Contact

Matthias Reuter

Portrait AZL NewsLIGHT
Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 241 80-23420
Mail: matthias.reuter@ita.rwth-aachen.de

 

Development of TowPregs from glass, basalt, carbon and aramid fibers for hybrid 3D-wound building structures – HyPreg –

Development of TowPregs from glass, basalt, carbon and aramid fibers for hybrid 3D-wound building structures – HyPreg –

Mission Statement

For the production of fiber composite components, winding processes are widely used cost effective methods with suitability for high volume production. Wet winding is established on the market for rotationally symmetrical components such as pipes and tanks. Up to four carbon fiber or glass fiber rovings are usually drawn from a creel, impregnated with epoxy resin in an immersion bath and then wound onto a core.

Another modern application of wet winding is the robot-assisted 3D winding of filament structures. In this process, reinforcement rovings are also impregnated in an impregnation bath and then individually placed by a robot on a carrier frame, whereby the rovings partially support each other at their crossing points. In this way, complex three-dimensional structures can be created freely in space. The main areas of application are in the building industry, especially as façade elements or for free-standing structures.

DrapeCube

© ITA of RWTH Aachen University | 3D-wound roofing element of FibR GmbH

A disadvantage of the state of the art is the impregnation process and the limited selection of suitable fibre-matrix combinations for the special requirements in construction and engineering. For dip impregnation directly before placement, the resin system must have a low viscosity in the uncrosslinked state in order to successfully impregnate the roving. However, the amount of matrix application varies considerably with the speed of the web guidance, which fluctuates greatly, especially in complex depositing processes. This results in rovings of varying degrees of coating or drop formation on the rovings after deposition. In addition, the process must not be interrupted for any length of time due to the limited pot life of the resin. The fibre and matrix combinations available on the market are only suitable to a limited extent for the special requirements of construction and engineering.

DrapeCube© ITA of RWTH Aachen University

 

Approach

The aim of the project is the development of so-called TowPregs made of carbon, glass, Ba-salt and aramid fibres, which are uniformly impregnated with a resin system and can be selectively cured during the winding process directly after deposition. TowPregs are rovings which are impregnated with a resin system and wound on spools before use. The resin is viscous after the impregnation process and cannot drip off. Thus the impregnation process is decoupled from the depositing process and can be carried out continuously and controlled, which increases the quality of the impregnation. In addition, there is more freedom in the depositing process, as material changes and service life are simplified. Due to the completely new development of the resin system, it can be precisely adapted to the desired fiber properties and the innovative curing process during fiber placement.

The specifications for the resin system result from the permissible coefficients of friction (tack, tack), mechanical requirements, curing conditions and storage conditions for the 3D winding process. A new impregnation unit is being developed at ITA. In addition, the nozzle will be designed in such a way that only a single tool component at the outlet of the nozzle needs to be replaced when changing the material. With the customizable nozzle outlets it is also possible to produce TowPregs with different cross sections. In cooperation with the partner F.A. Kümpers, a scaling up to industrial scale will follow.

FibR GmbH will convert its production in such a way that TowPregs with different fiber types can be processed and will extend the winding robot by an energy source for local curing of TowPregs. Furthermore, a depositing process will be developed, in which the TowPregs are guided freely in the room and cured. The goal is to be able to guide and deposit freeforms away from the shortest connection between two holding elements. The process control is especially designed in such a way that crossing points can be cured in a targeted manner

DrapeCube© ITA of RWTH Aachen University

 

Acknowledgement

We would like to thank the Federal Ministry for Economic Affairs and Energy for funding of the research project as part of the Central Innovation Programme for SMEs

Contact

Max Schmidt

Portrait AZL NewsLIGHT
Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 241 80 24749
Mail: max.schmidt@ita.rwth-aachen.de

 

FLOTANT – Development of thermoplastic based mooring cable of deep water wind
farms

FLOTANT – Development of thermoplastic based mooring cable of deep water wind
farms

The Institut für Textiltechnik of RWTH Aachen University participates with a team of 17 partners to develop the conceptual and basic engineering of a hybrid concrete-plastic floating structure designed for Deep Water Wind Farms.

FLOTANT includes performance tests of the mooring and anchoring systems and the dynamic cable to improve cost-efficiency, flexibility and robustness. The FLOTANT project aims at the concept deployment in water depths from 100 m to 600 m, optimizing the Levelized Cost of Energy (LCOE) of the floating solution (85 – 95 €/MWh by 2030).

A holistic approach will be taken and realistic designs will be tested in relevant environments. ITA will be part of two main developments through the FLOTANT project. The partners TFI Marine and Future Fibres lead together with ITA the design of a new concept of a mooring system based on the use of high-performance polymer/carbon fibre mooring cables. The development of a flexible power cable is also supported by ITA. Challenges, besides the sensor integration, are especially the integration of anti-bite and antifouling properties to protect the ecological system of the oceans. ITA supports the partner AIMPLAS in the development and implementation of this innovative power cable and the mooring systems.

DrapeCube© ITA of RWTH Aachen University

For mooring cable design, ITA developed a new process for the pultrusion of thermoplastic profile components based on pre-impregnated reinforcing fibres (TP-Profiles). This innovative process allows the continuous production of unidirectional reinforced rods based on carbon fibre (CF) and polyamide (PA6). With sea water as an aggressive environmental medium and the simultaneously very high mechanical requirements on the profiles, several challenges are in focus. In the first stage of process development ITA reached a 14-hour circle of continuous production. A completely impregnated and consolidated TP-Profile could be produced over the entire period. In the next step, these profiles are tested for mechanical properties and the cable design for the high loads of mooring offshore platforms will be developed. The introduction of a protective part for wildlife and flora of the oceans will be developed in the second half of2020. FLOTANT focuses on the protection of the ecological system of the oceans as a central aspect of any development.

An upscale of the lab scale pultrusion process to industrial scale will be carried out until the end of 2021.

Contact

Dominik Granich

Portrait AZL NewsLIGHT
Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 241 80 220 92
Mail: dominik.granich@ita.rwth-aachen.de

 

Modelling and Simulation of reinforcement textiles to predict the draping behavior

A novel approach to model and simulate the behavior of reinforcement textiles is introduced at the Institut für Textiltechnik of RWTH Aachen University. The method is utilized to predict the draping properties of textiles.

The demand for lightweight materials is rising due to a growing awareness for environmental issues and legal obligations. Fiber reinforced polymers (FRPs) are among the most desirable lightweight materials, due to the high mechanical property-to-weight-ratio in comparison to other materials like aluminum. The widespread use of FRP is currently prevented by the high costs which emerge within the process chain of FRP. About 50% of total part the cost is originated within the preforming. During preforming the textiles are stacked, jointed and formed into near-net shape. Usually the trial-and-error is used during the design of the forming process. Within the trial-and-error, a textile which fits the mechanical requirements is produced, stacked and formed. The previously mentioned steps are repeated, if the processing results in errors like gaps or wrinkles in the textiles.

The goal of the research presented in this article is to reduce the trial-and-error method through the application of a virtual textile design, which is utilized to predict the draping behavior of the textile in advance of the textile production.

To achieve the goal, a novel meso-scale textile model is developed. Inputs for the textile are roving material properties like axial stiffness or friction behavior. With the model, a virtual shear frame test is conducted. The results of the test are used to evaluate the draping behavior of the textiles. Further, the modelling method can be utilized to virtually investigate material properties (e.g. shear, tensile) of different textile patterns or gaps sizes from woven and non-crimp fabrics. This digital twin can be used to preliminarily design the textile without an expensive textile production including trial-and-error, which could result in wasting expensive materials. Additionally, material properties of rovings, e.g. friction values or tensile stiffness, can be changed to investigate the influence on the textile properties.

AZL Partner ITA of RWTH Aachen University© ITA of RWTH Aachen University

Contact

Stefan Hessler

Portrait AZL NeswLIGHT

Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 241 80 23449
Mail: stefan.hesseler@ita.rwth-aachen.de