Fraunhofer Institute for Casting, Composite and Processing Technology IGCV
Fraunhofer Institute for Casting, Composite and Processing Technology IGCV

CO2-SaVer – Sustainable Lightweight Construction Using Recycled Carbon Fiber Nonwoven

Resource Efficiency and CO2 Savings Through the Use of Recycled Carbon Fiber Nonwovens in the Production of Sandwich Structures

 

Carbon fibers (CF) are considered the »black gold« of lightweight construction due to their high specific strength and stiffness combined with low density. However, rising demand is leading to significant amounts of composite waste that must be effectively recycled. Currently, the production of new carbon fibers is energy-intensive and generates high CO2 emissions. By using recycled CF (rCF)—for example, obtained through the primary industrial recycling processes of pyrolysis or solvolysis—significant amounts of CO2 equivalents can be saved in the production of carbon fiber-reinforced plastic (CFRP) components, and the demand for new CF can be reduced. Furthermore, CFRP component manufacturing generates up to 40 mass-% of carbon fiber scrap, of which less than 1% is actually reused.

 

Aim of the project »CO2-SaVer«

...is therefore to develop and establish a process for manufacturing components with 100% rCF reinforcement. In particular, nonwoven fabrics based on rCF offer great potential for closing the CF cycle in a resource- and cost-efficient manner, which is why they are the focus of the project. In addition, the »3D Lofter« technology for applying localized reinforcements to nonwoven surfaces will be further developed, and research will be conducted into the lofting process for manufacturing high-strength sandwich components in a single process step.

Innovative Recycled Carbon Fiber Nonwovens

As part of the »CO2-SaVer« project, innovative rCF nonwovens are being produced that are locally reinforced using the additive »3D lofter process«. In this process, fiber mass is applied in a targeted manner and can be adapted to potential stress paths within the nonwoven. The precise placement of the reinforcing fibers improves mechanical properties and optimizes the potential for lightweight construction. Another key aspect of the project is the creation of a sandwich-like structure through the so-called lofting effect. This effect is achieved in the low-pressure RTM process by opening the mold during the process. As »compressed« stress concentrations are released following the previous interlacing of the fibers, the fibers straighten out within the nonwoven structure and form voids in the component (»spring-back effect«). The result is an increase in volume combined with a decrease in density. The core structures produced in this way are characterized by high flexural and compressive stiffness. Another distinctive feature of the project is the use of bio-based resin systems, whose fire-retardant properties are ensured by newly developed additive blends.

CO2-Saver: gestackter Halbzeugstapel
© Fraunhofer IGCV
Schematic diagram of the thermoplastic lofting process; a finished stack of semi-finished products for the pressing process (rCF-PA6 dry nonwoven) (left), a pressed CFRP panel (center), and a lofted, cured structure after the material has once again exceeded its melting temperature (right).

Research Focus: Optimizing Nonwoven Fabric Processing

As a research institute specializing in production technology, Fraunhofer IGCV focuses on optimizing nonwoven fabric processing. This includes the further development of both the low-pressure RTM and WCM processes with a view to establishing an efficient lofting process based on duromer matrix systems. In addition, the integration of cover layers onto lofted core structures presents research challenges that Fraunhofer IGCV aims to address. The panels and components produced are also mechanically characterized at Fraunhofer IGCV, with the lofted components in particular requiring new testing methods. In addition to static tests, dynamic and long-term tests are also conducted on the new materials to ensure their performance.

CO2-Saver: Prüfverfahren der rCF-Sandwichstrukturen, Teil 1
© Fraunhofer IGCV
Testing of Lofted rCF Sandwich Structures and Various Failure Modes
CO2-Saver: Prüfung von rCF-Sandwichstrukturen, Teil 3
© Fraunhofer IGCV
CO2-Saver: Prüfverfahren der rCF-Sandwichstrukturen, Teil 1
© Fraunhofer IGCV

Project Demonstrator: Representing Complex Geometries Using the Lofting Method

CO2-Saver: Lofting-Sandwichstruktur
© Fraunhofer IGCV
Lofted sandwich structure with complex conical geometry

One advantage of working with nonwoven fabrics is their generally good drapability, which corresponds to the resulting structures; this is why even complex geometries can be reproduced using the lofting process. For this reason, the project aims to develop an industry-standard demonstrator with various contours.

The demonstration project specifically focuses on a side panel for a battery-powered truck. Research on fire protection, electromagnetic shielding, and vibration behavior is being conducted and evaluated using this panel.

The practical benefits and project results are also transferable to other industrial sectors.

CO2-SaVer: Demonstratorbauteil für das Projekt
© EDAG Group
Design of the demonstrator component for the »CO2-SaVer« project – side panel for a battery-powered truck made of Lofting sandwich panels

More information about our research on composite recycling:

 

© A3 | Christian Strohmayr

Wet-laid technology

This pilot plant is used to manufacture innovative and novel nonwoven fabrics. It is designed to be highly flexible and can process natural, chemical, and technical fibers (such as recycled carbon fibers).

Innovative wet-laid technology
 

© eaumstocker - stock.adobe.com

Recycling of
Composites

Through numerous research projects, we are working to ensure a more sustainable approach to this group of materials throughout the entire recycling chain.  

Recycling von Composites