Research and modeling of the bond behavior of profiled carbon yarns and development of methods for the defined control of the bond between yarn and concrete

• Applicants: Professor Dr.-Ing. Chokri Cherif; Professor Dr.-Ing. Manfred Curbach
• Subject Area: Construction Material Sciences, Chemistry, Building Physics ; Structural Engineering, Building Informatics and Construction Operation ; Lightweight Construction, Textile Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549871995

The use of textile reinforcements in concrete structures has established itself as a technically and economically interesting alternative to conventional steel reinforcements and is increasingly used in construction practice. However, the performance of textile-reinforced concrete can only be fully exploited if high forces can be transmitted non-destructively in the interface between the composite partners endless fiber-based textile reinforcement and concrete matrix. The further development of fiber reinforcements in the recent past has led to yarns with high fineness, tensile strength and stiffness. This increased the stress in the interface and consequently the bond and anchorage lengths of a yarn in the concrete partially significantly, which is disadvantageous for the material consumption and crack pattern. Additionally, due to a large number of fiber materials, impregnation agents and manufacturing processes, it is still not possible to fully understand or predict the bond mechanisms, nor can all aspects of it be modeled or controlled. The thesis of the proposed research project is that the defined profiling of continuous fiber-based yarns reduces the required anchorage lengths, the concrete matrix is more evenly stressed due to a more compact cross-sectional shape and all filaments in a yarn participate more evenly in the load transfer due to its better impregnation. The aim is the numerical-experimental investigation of the effect of yarn profiling in concrete to create a profound understanding, so that a defined modification and control of the bond properties of continuous fiber-based reinforcement structures for concrete constructions is possible through yarn profiling in a reproducible manner. Therefore, the interactions between yarn and profile properties, profiling process, surrounding concrete and their combined influence on the bond mechanisms and furthermore on the failure and cracking behavior must be analyzed, material laws must be derived.In the project, parameterizable yarn profile basic topologies will be developed and realized as a simulation model and for production. For this purpose, a modular test rig for yarn profiling with high geometric variability is being developed. Systematic material investigations are carried out on unloaded consolidated yarns (filament orientation and damage, shape stability, impregnation grade and quality) and on loaded composite samples made of carbon yarns and concrete with focus on bond stress-slip relationship, crack formation process and failure mechanisms. Supported by numerical simulations, principles for targeted bond control and findings about possible reducing effects on the yarn tensile strength through yarn profiling are derived. An analytical description of the bond behavior of profiled yarns in concrete summarizes the knowledge gained.

• DFG Programme: Research Grants