Methodology for the determination of short-term dynamic properties of textile high-performance materials

• Applicant: Professor Dr.-Ing. Chokri Cherif
• Subject Area: Lightweight Construction, Textile Technology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 532623057

The overall objective of the project is to determine and physically describe the strain rate-dependent material properties of high-performance materials (glass (GF), carbon fibres (CF), aramid fibres (AF) and polyethylene (PE) fibres) and textile structures in a wide strain rate range that has so far remained largely unexplored, using a uniform testing methodology that generates comparable results. For these materials, the specific characteristics of the respective fibre, e.g. stiffness, strength, non-linearity, energy absorption and high elongation, are to be taken into account. The strain rate range from 1 s-1 (for softer materials, such as PE) or from 25 s-1 (for highly rigid materials, such as GF and CF with very low elongations at break) to at least 1000 s-1 is to be considered. On the one hand, there are no established testing methods and machines for the whole of this range and, on the other hand, a large number of physically determined strain rate-dependent material properties occur for many material classes. In order to achieve the overall objective, two scientific issues are to be investigated technically and physically/mathematically: (i) On the one hand, the uniform testing methodology with which the addressed fibre-like and fibre-based structures can be reliably and reproducibly characterised over the entire targeted strain rate range is to be developed. For this purpose, the results of a previous project are used, in which a rotation-based test rig was developed and used for testing, with which strain rates of high-performance materials up to approx. 285 s-1 could be applied. (ii) On the other hand, the focus is on the determination of strain-rate-dependent material properties (elongation at break, strength, stiffness and fracture energy as well as pull-out forces in pull-out tests) and the analysis and scientific explanation of the derived material properties. The material properties determined here are each to be derived analytically as material-specific strain-rate and specimen-length-dependent laws and then linked via the hierarchical structures from the yarn to the textile surface. Based on this, specific textile weaving reinforcement structures for composite applications (e.g. for impact scenarios) with particularly good short-term dynamic property profiles can be derived. With the help of the results of further analytical tests, the strain rate-dependent material laws determined in this way also represent important input parameters for future molecular dynamic simulations of textile high-performance materials or composite materials based on them under short-term dynamic loads.

• DFG Programme: Research Grants