Experimental analysis and numerical modeling of the influence of adhesive threads on the material and damage behavior of FRP laminates under quasi-static and cyclic mechanical loading

• Applicant: Professor Dr.-Ing. Maik Gude
• Subject Area: Lightweight Construction, Textile Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555932565

The use of continuous fiber-reinforced plastic composites (FRP) in series applications requires the provision of textile products that not only meet application-specific requirements, but also processing requirements. For this purpose, delivery in the form of rolls has become established. For production and processing, the textile fiber products, e.g. non-crimp fabrics, in roll form are provided with bonding yarns that ensure adequate handling properties. The bonding yarns, which remain in the composite after manufacturing, consist of temperature-resistant thermoplastic material. They thus represent initial flaws in the composite component, which characterize the initiation and progression of the component damage. It has not yet been scientifically clarified how these bonding yarns influence the local stress state and the load-bearing capacity of the FRP and to what extent the formation of inter fiber failures in the composite is influenced by the geometry and arrangement of the bonding yarns, so that efficient material use is currently difficult. The aim of the project is to gain a deeper understanding of the influence of the adhesive bonding yarns on the material behavior with the help of experimental and numerical methods. As an example, glass fiber reinforced epoxy resin composites (GF-EP) with unidirectional and bidirectional reinforcement and different adhesive bonding yarn arrangements are to be characterized with regard to damage behavior. Quasi-static tensile and tensile-tensile fatigue loading tests are planned, which will provide comprehensive insights into the influence of the adhesive bonding yarns on the material behavior. Accompanying finite element simulations will be used to determine the critical fracture energies of the GF-EP base material and the adhesive bonding yarn separately by means of micromechanical modeling, which takes into account the adhesive bonding yarn and the actual crack propagation. With the help of subsequent mesoscopic modelling of the inter fiber failure, transfer functions are to be determined depending on the impurity properties, which enable the microstructural findings to be used in homogenized laminate layers. In the proposed project, comprehensive experimental and numerical investigations on the influence of impurities and especially adhesive bonding yarns on the damage behavior of uni- and bidirectionally reinforced FRP will be carried out for the first time. The multi-scale approach promises in-depth findings on the damage behavior of FRP with impurities under plane loading, which will serve as an important basis for the design and dimensioning of textile-reinforced composite components in engineering practice.

• DFG Programme: Research Grants