Short-term dynamic stress-strain behavior of textile high-performance materials

• Applicant: Professor Dr.-Ing. Chokri Cherif
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Lightweight Construction, Textile Technology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269480495

In the context of an expansion of applications of fiber-based materials and technical textiles in heavy duty fields, the question of mechanical properties of fiber materials under fast-acting strains is gradually gaining center stage. Such strains are common in ballistic protection textiles, but also occur in composite materials with fiber reinforcements (fiber-reinforced plastic composites, textile concrete) exposed to impact strains. The existing tensile strength characteristics for pure high-performance fiber materials, particularly fiberglass (GF), carbon fiber (CF), and aramid (AR) filament yarns, refer largely to the behavior under static and quasistatic load, as no reliable test benches and methods designed to meet the special requirements of such samples under high strain velocities are available for tests under short-term dynamic strain. The aim of the project is the development of a testing method for expansion rate-dependent filament yarn strengths and stiffnesses of impregnated and non-impregnated high-performance filament yarns in the fiber longitudinal direction, especially GF, CF, and AR filament yarns, in a reliable and reproducible manner. A testing methodology conceived at ITM, using an existing drop test rig, is developed further with the requirements of textile high-performance filament yarns and the correspondingly higher testing speeds and expansion rates of up to 100 s-1 in mind. Building on the findings, a special test station for the analysis of the further expansion rate range to 1000 s-1 is developed, based on a rotary drive and customized to these special requirements and including the further development and integration of force and distance measurement technology.Additionally, the groundwork is to be laid for an analytical description of the expansion rate-dependent mechanical material properties of the high-performance filament yarns under tensile strain, based on a Weibull strength distribution. Additionally, the expansion rate-dependent material parameters tensile strength, stiffness and energy absorption capability are determined systematically and described by analytical constitutive equations. These regularities are a substantial basis for the modeling of the local and global mechanical behavior of textile high-performance materials at short-term dynamic impact strains, particularly for the failure case essential in component design, in order to create the decisive prerequisites for well-founded, impact-oriented developments, modelings and simulations of highly resilient high-performance fiber materials and structures and the consequent application possibilities.

• DFG Programme: Research Grants