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

WiBreak – Measurement of the Mechanical Properties of Reinforcing Fibers by the Single-Fiber Tensile Test

Standardization of the single fiber tensile test for the most common reinforcement fibers such as carbon fibers, recycled carbon fibers, and glass fibers

 

Testing the mechanical properties of reinforcing fibers such as carbon and glass fibers is becoming increasingly important as lightweight construction techniques are being used in more and more sections to save resources. A fast and reliable testing method is essential for quality testing of these fibers. This is relevant not only for newly manufactured fibers but also for recycled fibers. This is because the fast and reliable determination of mechanical characteristics also enables the qualification of recycled reinforcing fibers and the processes used to obtain them, thus forming the basis for all innovations in this field.

© Textechno

FAVIMAT+ from Textechno is designed for the mechanical testing of reinforcing fibers in the form of individual fibers; it can be used, for example, to test carbon, glass, basalt, or ceramic fibers and their recycled variants.

The single fiber tensile test

© Fraunhofer IGCV
Carbon fiber clamped in the FAVIMAT+ clamps

To quickly and easily determine the mechanical properties of individual fibers, it is advisable to clamp the fibers directly into suitable clamps and test them, rather than having to laboriously glue them onto individual paper frames in accordance with ISO 11566. An example of a testing device developed for this purpose is the FAVIMAT+ from Textechno. This can also be used for single fiber pull-out tests (further information can be found under WiPull). Identification of parameters influencing single fiber pull-out measurements Thanks to many years of Research and development work with reinforcing fibers, the project partners have acquired important expertise in their characterization, which is to be compiled in the standard to be created. Nevertheless, it is necessary to investigate possible, often fiber-specific influencing parameters such as handling during sample preparation, conditioning of glass fibers, system compliance, or the influence of test speed, and to identify further parameters. Conducting interlaboratory tests The fibers will then be tested in initial comparative laboratory tests using different testing machines between the partners, and possible deviations in the tests will be investigated and minimized. Subsequently, interlaboratory tests will be conducted with the optimized test conditions in order to generate reliable values for the repeatability and reproducibility of the method for a standard. Development of a necessary DIN SPEC Many companies already test single fiber strength using similar techniques without being able to rely on a current standardized test method for single fibers. The aim of the project is therefore to create a DIN SPEC to ensure the comparability of measurements between different laboratories.

Other projects dealing with the characterization of individual fibers and recycled carbon fibers include: WiPull, Carina and Izi-Direct