Development of a hybrid yarn and pultrusion structure for efficient production of thermoplastic Profiles

The Institute für Textiltechnik of RWTH Aachen University has developed a hybrid yarn for the efficient production of Profiles by thermoplastic pultrusion process. Fully impregnated and consolidated thermoplastic composites were developed under limited pressure.  

The economic potential for the use of thermoplastic composites is mostly based on the shorter processing times. Recyclability of these composites is an advantage, too. Unfortunately, it is often the case that these thermoplastic matrices do not result in a fully consolidated component. This leads to unacceptable mechanical properties and halts the wide spread use of thermoplastic composites. To address this, hybrid yarn based on carbon fibre and polyamide 6 was produced for the development of a continuous production of thermoplastic FRP-profiles. The production process aimed to consolidate thermoplastic reinforced profiles by production speed of 1-5 m/min.

This work was sub-divided into the production steps and analysis of the various intermediate products. The development of hybrid yarns, which address the challenges of thermoplastic pultrusion, was the main focus of this project. For this purpose, different thermoplastic yarns were spun on a melt spinning plant. These thermoplastic fibres were mixed together with the carbon fibre. The hybrid yarn produced were tested by flat unidirectional composites, produced under limited pressure, in preliminary tests. Analyses methods like microscopy, shrinkage tests and tensile strength tests accompanied the entire process chain. The manufacturing of pultruded composites will validate the results by thermoplastic profile production.

The result of this work is a fully consolidated thermoplastic fibre composite component under limited pressure, which can be produced by designing the melt spinning process. This material meets the expected requirements for fully consolidated thick-walled profiles produced in the thermoplastic pultrusion process. The upscaling of the thermoplastic yarn production by melt spinning and the intermingling with carbon fibre bay commingling to the industrial scale also was successful. Subsequently, consolidation tests will be carried out on the pilot plant pultrusion line for thermoplastic FRP components at the ITA.

Dominik Granich, Jeanette Ortega, Thomas Gries

Contact

Dominik Granich

Reinforcement fiber division / yarn structures and composites
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 (0) 241 80-22092
Mail: dominik.granich@ita.rwth-aachen.de

Development of an induction-based braidtrusion process for the production of thermoplastic profiles

An efficient production of braided profiles based on a thermoplastic matrix has been developed by IFF GmbG, Ismaning, and the Institute für Textiltechnik of RWTH Aachen University (ITA). The innovative braidtrusion process linked with the induction based heating offers many economic opportunities for mass FRP-profile production.

Fibre Reinforced Plastics (FRP) with thermoplastic matrix offer new opportunities for fast and efficient processing technology since thermoplastics have no cross-linking time. The continuous pultrusion process of such thermoplastics also offers the possibility of producing time efficient fibre-reinforced profiles. The main challenge of processing such composites is the high viscosity of the thermoplastic matrix, especially in the time and pressure limited continues pultrusion process. The aim of this research project named InduPull is the development of a pultrusion process for braided thermoplastic hollow profiles (pipes) based on commercial hybrid yarn (carbon fibre and polyamide 6 – PA6).
The approach was to combine the braiding process for tube production with a pultrusion line. This pultrusion line includes heating system, forming tool, cooling unit and a belt haul-off machine. The investigation was carried out on plural stages. The braided fibre architecture, the textile processing of braiding, the introduction of induction energy and the pultrusion tool have been developed. Finally, various test series were successfully carried out.
ITA developed the braiding process and the design addressing the challenges of thermoplastic pultrusion by inductive heating. Because of a limited forming tool diameter the braided fiber structure was developed, that a sufficient consolidation was possible. In addition, an efficient introduction of the induction heat through a high number of crossing points, which can be formed in the braid, was taken into account.
The IFF GmbH, Ismaning, Germany developed an induction-based consolidation system. The combination of all the developments and the integration in one line allows the production of thermoplastic profiles. In the preliminary process test, fully consolidated pipes with an outer diameter of 25 mm with a speed of 0.1-0.2 m/min could be achieved. Barriers in the process speed have been detected and solutions of these deficits have been discussed. In further test series, process speed above 1 m/min is aimed. The “proof of concept” of the new developed technology was successfully shown. In Further investigations the upscale to a pilot pultrusion line will be developed.

Dominik Granich, Victor Reimer, Thomas Gries

Contact

Dominik Granich

Reinforcement fiber division / yarn structures and composites
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 (0) 241 80-22092
Mail: dominik.granich@ita.rwth-aachen.de

Flexible autoclave: Development of a flexible and modulary expandable textile-based autoclave for the production of composites

Prepreg technologies are well suited for high quality performance parts, but the acquisition and operating costs of autoclave technology are a decisive obstacle to the spread of this technology among small and medium sized companies. The deficits with current autoclaves are the high investment and production costs as well as the construction of solid steel and inflexibility, which makes the autoclaves location bond and limits the mobility.

The goal of the project “Autoclaveflexible” is to develop an appealing variant of an autoclave for small and medium-sized companies. This will be cost-effective, low space requirement and easily transportable for possible sharing concepts. Therefore, a flexible and modular expandable textile-based autoclave will be developed. Figure 1 shows the general design as well as the benefits of this project. The textile mantle basically consists of the following components: carbon fibres, epoxy resin and an elastomere and is produced with the winding technology. The requirement for all components is to keep the autoclave gas tight up to 10 bar and to maintain a temperature of at least 200 °C. The transport of the autoclave should be possible with as little effort as possible. This can be made possible by the lightweight construction, modular design and foldability of the textile mantle. The flexible autoclave consists of at least 3 modules, which are, a start module, an expandable module and an end module. The autoclave can have up to 15 expandable modules. This corresponds to a total length of 25 m. The general design is shown in Figure 2.

The project will enable small and medium-sized companies to enter the autoclave technology market. This will enable high-quality products to be purchased more cost-effectively on the market.

The project is carried out in cooperation between IDVA GmbH, Germany and the Institute of Textile Technology (ITA) of RWTH Aachen University. The Project was launched in July 2017. The findings from the project will be used to further develop the flexible autoclave into a series-ready product.

The “Autoclaveflexible” project is promoted by the Federal Ministry of Economics and Technology via the ZIM as part of a programme to promote innovation and competitiveness among SMEs.

The authors would like to acknowledge the contributions from our industrial partner Momentive Performance Materials Inc. for their extensive support during this research project.

Contact

Waldemar Biche

Researcher
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 (0)241 8024711
Mail: waldemar.biche@ita.rwth-aachen.de

Hans-Christian Früh

Researcher
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 (0)241 8023272
Mail: hans-christian.frueh@ita.rwth-aachen.de

 Jonas Velten

Managing Director
IDVA GmbH
Phone: +49 761 2144453-0
Mail: jonas.velten@idva.de

New Labcoater for small scale coating experiments

Within the IGF-project FreshonFresh, novel coating materials for reinforcement textiles for curing in concrete are identified and analyzed. For this purpose, a new labcoater enabling the controlled coating of small scale textile samples has been obtained.

While textile reinforced concrete (TRC) offers many advantages over traditional steel reinforced concrete, like greater freedom in design and higher strength, current coating materials for reinforcement textiles limit the potential of TRC. Current coating materials are either stiff and offer a high bond strength with the concrete matrix, limiting freedom in design but providing a strong composite, or they are flexible but offer low bond strength, allowing for greater freedom in design but providing a lower strength composite.

The project FreshonFresh aims to provide reinforcement textiles with high freedom in design and high bond strength by adapting a material type commonly used in automotive and aerospace industries: prepregs. These prepregs are flexible until curing, which only happens after the textile is placed in the concrete matrix. Within the project, suitable prepreg materials will be identified, characterized and applied in a concrete prototype.

Prepreg materials for curing in concrete need to cure in very different environmental conditions than in traditional prepreg manufacturing. Traditional prepregs are cured with the application of moderately high temperatures > 100 °C for short amounts of time. The application of such temperatures on concrete specimens is not advisable because of high energy requirements and because the concrete hardening process is impeded at temperatures >80 °C. Therefore, the project aims to identify prepreg materials which either cure at lower temperatures of through other curing mechanisms. Most promising for the application in TRC are materials which cure either with the water present in the concrete or through the alkaline environment provided by the concrete matrix.

To allow for a rapid testing of various different coating materials, a labcoater (as depicted in the image) has been obtained. The labcoater allows for the controlled and repeatable coating of small scale textile samples (roughly DIN A3 sized). Additionally, coating experiments only require very small amounts of coating material.

We would like to thank the AiF for funding the research project from BMWi research funds within the framework of the program for the promotion of joint industrial research and development (IGF).

New Labcoater enabling the rapid production of small scale coating samples (Model provided by COATEMA Coating Machinery GmbH)

Contact

Martin Scheurer

Researcher
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 (0)241 80 23471
Mail: martin.scheurer@ita.rwth-aachen.de