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Tapecrete - Carbon Fiber Tapes for Concrete Reinforcement

Tapecrete – Carbon Fiber Tapes for Concrete Reinforcement

Textile reinforced concrete (TRC) enables new design and construction possibilities for the construction industry, since the high performance textiles used as reinforcement do not rust and therefore only need minimal concrete cover. TRC has been investigated since the late 1990s and is currently entering the market. Established reinforcement textiles consist of biaxial grids made from carbon or alkaline resistant glass, which are resistant to the highly alkaline concrete matrix. For optimal bond properties with the concrete, reinforcement textiles are coated with polymers such as epoxy resin.

Another popular type of textile reinforcement for concrete are fiber reinforced plastic rebars. These rebars are made from carbon, glass or basalt fibers via pultrusion and also utilize a polymer matrix to transfer loads from the concrete matrix into the fibers. Rebars boast comparatively high diameters, ranging from 8 to more than 30 mm.

Within a pilot project at the Institut für Textiltechnik of RWTH Aachen University, an alternative type of textile reinforcement for concrete is being researched: carbon fiber tapes. Tapes are produced via spreading a roving, either through mechanical spreading utilizing rods or through pneumatic spreading using a V-shaped nozzle. These tapes can be integrated into the concrete without polymeric coating, since all carbon filaments are in direct contact with the concrete matrix. Therefore, the loads can be transferred from the concrete matrix directly into the carbon filaments. Initial results show an increase in bending strength by 125 % when comparing carbon fiber tapes with uncoated, unspread carbon rovings. However, particular attention needs to be paid to the integration of the tapes into the concrete matrix. If the tapes are spread too much and cover a large part of the concrete filled area, the concrete forms two separate layers above and below the tape. These layers separate easily under bending loads, leading to significantly lower performance.

Research into this new type of reinforcement, which lends itself particularly well to the reinforcement of 3D-printed concrete, is currently ongoing.

© ITA of RWTH Aachen University | CT-Scan of tape embedded in concrete

 

Contact

Martin Scheurer

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

TFPInsert - An automated process for manufacturing functionalized reinforcement textiles used in

hybrid composites

TFPInsert – An automated process for manufacturing functionalized reinforcement textiles used in hybrid composites

The Institut für Textiltechnik (ITA) at RWTH Aachen University and project partner Hollmann GmbH in Cologne have developed a highly automated preforming process to produce and functionalize preforms for composites in a single-step process. In the framework of the “TFPInsert” project, the Tailored Fiber Placement (TFP) process is used for this purpose. The TFP process enables the production of near-net-shape and load-path oriented preforms for structural components and thus has a very high lightweight construction potential. Additionally, TFP allows the integration of functional elements, such as inserts, within the preform. Currently inserts are bonded to the consolidated component using adhesives or holes have to be drilled for insert integration. Adhesives are limited by the bonding surface and thus the bonding strength. On the other hand, drill wear and thus high tool wear is a problem.

The main development of the “TFPInsert” project is the so-called insert applicator, which can be used for the TFP process and is installed on a TFP embroidery machine at the project partner Hollmann GmbH (see Figure 1 and 2). The goal using the insert applicator is to simplify and automatize the insert integration as well as increasing the mechanical performance of the metal-composite hybrid components. The insert applicator can complete the deposition, precise positioning and fixation of the insert in approximately 10 seconds. Additionally, the stitching of inserts onto the preform and the integration between preform layers can improve out-of-plane strength by 20 to 40 %.

© ITA of RWTH Aachen University  Figure 1

© ITA of RWTH Aachen University Figure 2

To demonstrate the advantages of automated insert integration, the structural part of a bicycle brake was chosen as the demonstrator component. The preform is shown in Figure 1. A total of 6 inserts are integrated into the preform so that the steel friction surfaces can be detached from the cured component The preform is manufactured without fiber waste and the stitched layers of the compact preform prevent the preform layers from glipping. This significantly simplifies handling and insertion of the preform into the mold for the vacuum resin infusion process. The project results enable Hollmann GmbH to offer a process for fixing inserts in preforms for structural components and to produce functionalized preforms at the same time.

The project “TFPInsert” is funded by the Federal Ministry of Economic Affairs and Energy (BMWi) within the framework of the Central Innovation Programme for SMEs (ZIM) and was completed in spring 2021.

Contact

Max Schwab

Portrait AZL NewsLIGHT neu
Researcher “Composite Production”
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49 (0) 241 80 – 23473
Mail: Max.Schwab@ita.rwth-aachen.de

Lars Hollmann

CEO
Hollmann GmbH
Phone: +49 (0)  221 422 – 9393
Mail: info@hollmann.ag

 

Real time detection of carbon fiber twist using a convolutional neural network

Real time detection of carbon fiber twist using a convolutional neural network

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. One method to produce FRPs is using unidirectional tapes in automated tape laying processes. Tapes are produced by fiber spreading, where carbon fiber heavy tows are widened and homogenized. The spreading process can be disturbed by fiber twists which are induced during the fiber production or winding of the fibers. If these twists remain within the tape, they cause defects within the laminate which subsequently lead to a reduction of up to 32% of the part strength. Cutting out the twisted fiber parts during production is costly, due to machine down time and manual interference. Thus, an automated twist removal system is needed.

At the Institut für Textiltechnik of RWTH Aachen University, a novel automated twist removal system is developed with partners from Gebr. Klöcker GmbH within a ZIM research project (ZF4558968PK9). To achieve this goal, a twist detection system and a twist removal system are developed. The twist detection is performed by utilizing a camera system, a convolutional neural network (CNN) and a so called ”TwistRunner”-module to detect the twist in real time. After the detection of twist and its direction of rotation, a bobbin rotation module is activated and rotates the whole bobbin to remove the twist online. This online real time removal system prevents defects induced from twists as well as machine down time during production.

The research project of AiF Projekt GmbH, Berlin/Germany, is funded by Ministry of Economics and Energy (Bundesministerium für Wirtschaft und Energie) within the framework of the Central Innovation Program for SMEs (ZIM) based on a resolution of the German Government (Bundestag).

© ITA of RWTH Aachen University | Twistrunner

 

Contact

Stefan Hesseler

Portrait AZL NeswLIGHT
Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone:+49 (0) 241 80 23449
Mail: stefan.hesseler@ita.rwth-aachen.de

Philipp Quenzel

Portrait AZL NeswLIGHT
Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone:+49 (0) 241 80 23444
Mail: philipp.quenzel@ita.rwth-aachen.de

Analysis of energetic and process-related improvement potential of impregnation and drying processes

in FRP production

Analysis of energetic and process-related improvement potential of impregnation and drying processes in FRP production

In terms of ecological responsibility and economic interests, reducing energy consumption and greenhouse gas emissions has become a central challenge of our time. For this purpose moving masses must be reduced, particularly in the area of ​​mobility. Due to their excellent structural mechanical properties combined with low density, fiber composites are superior to metallic materials in numerous industrial applications, e. g. in the field of automotive and aviation. Among other things, high production costs still prevent a widespread use of fiber composite materials.

In the manufacture of FRP such as tapes, pregregs and organo sheets, the impregnation and drying process is of particular importance, as it has a major influence on the quality of the products, the production costs and the consumption of resources. In the sense of an economical, process-technologically favorable and ecological production of FRP, it is necessary to optimize the impregnation and drying process in terms of energy and process technology.

For this purpose, a model has been developed at the Institut für Textiltechnik (ITA) of RWTH Aachen University to analyze and optimize existing impregnation and drying processes in terms of energy and process technology. It offers the possibility of quantifying the minimum amounts of energy required for the impregnation and drying of FRP. In comparison with the actual energy consumption, the energetic savings potential of the analyzed processes can be determined. In addition, the model enables the determination of the thermal losses of impregnation and drying processes, on the basis of which improvements can be derived. Furthermore, the model offers the possibility of determining overall energy efficiency and realizable production speeds. These parameters can be used to determine the efficiency and potential of the processes and to compare them with one another.

© ITA of RWTH Aachen University 

Contact

Andreas Bündgens

Portrait AZL NewsLIGHT
Research Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Phone: +49/(0) 241 80-23260
Mail: andreas.buendgens@ita.rwth-aachen.de

Leonhard Wagner

Portrait AZL NewsLIGHT
Student Assistant
Institut für Textiltechnik (ITA) of RWTH Aachen University
Mail: leonhard.wagner@rwth-aachen.de