TY - CHAP A1 - Herz, Jonas A1 - Lorenz, Katharina A1 - Muscat, Dirk A1 - Strübbe, Nicole T1 - Polymeric core-shell and mono-material fibers for concrete reinforcement T2 - AIP Conference Proceedings N2 - A reinforcement of concrete structures is needed because of the low tensile strength of concrete. Corrosion of the usually used steel reinforcments cause issues during time. Therfore, alternative reinforcements produced from non-corosive materials - like polymer fibers - become more interesting. A polymer fiber has to reach high mechanical properties and a good bonding ability to concrete. Both properties can be influenced by the selection of polymer and the used production process. Two polymers, polypropylene and aliphatic polyketone are tested within this study. First mono-material fibers of each material are produced and tested, later the materials are combined in a core-shell fiber. All fibers are produced by standard extrusion or coextrusion and a later drawing process. The mechanical properties are determined by tensile tests. The calculation of interfacial shear strength from single fiber pull-out tests allows an evaluation of the bonding ability. Additionally, fiber surface before and after pull-out is examined using reflected light microscopy. Contact angle measurements are done to evaluate possible influences of the surface energy and polarity. Density measurements are used to compare weight potential of the different mono-material and core-shell fibers. The results show good mechanical properties for all fiber materials. The interfacial shear strength is ≈ 2-3 times higher for fibers with polyketone compared to the ones with polypropylene at the fibers surface, which can be explained by higher surface energy and polarity of the polyketone compared to polypropylene and different surface deformation during pull-out. Lower densities are reached by fibers containing polypropylene. KW - polymer fibers KW - concrete reinforcement KW - core-shell fiber KW - coextrusion KW - polypropylene KW - polyketone Y1 - 2024 U6 - https://doi.org/10.1063/5.0204946 VL - 3158 IS - 1 ER - TY - JOUR A1 - Herz, Jonas A1 - Muscat, Dirk A1 - Strübbe, Nicole T1 - The Influence of Fillers on the Reinforcement Capabilities of Polypropylene Based Mono-Material and Core-Shell Fibers in Concrete, a Comparison JF - Polymers N2 - Noncorrosive concrete reinforcement, such as polymer fibers, is needed to overcome the current issues caused by corroded steel reinforcements. Fibers made of polypropylene show a low bonding behavior in concrete. Fillers can help to overcome this issue but often lead to reduced mechanical properties. Core-shell fibers, which split the mechanical properties and the bonding behavior between the core and the shell component, could be a solution. This study investigates mono-material and core-shell fibers produced with calcium carbonate and bentonite fillers and compares their behavior in tensile tests, density measurements, contact angle measurements, topography measurements, single fiber pull-out tests, reflected light microscopy, and thermogravimetric analysis. The fillers caused an increased drawability, resulting in higher mechanical properties. Further, in the core-shell fibers, the calcium carbonate increased the surface roughness, which led to a better anchoring of the fiber in concrete, which was also visible in the deformation during pull-out observed in reflected light microscopy pictures. The thermogravimetric analysis showed a delay in onset of degradation for fibers containing bentonite. KW - fibers KW - extrusion KW - coextrusion KW - polymer drawing KW - polypropylene KW - calcium carbonate KW - bentonite KW - core-shell KW - mono-material KW - concrete Y1 - 2025 U6 - https://doi.org/10.3390/polym17131781 VL - 17 IS - 13 PB - MDPI CY - Basel ER - TY - JOUR A1 - Obermeier, Frederik A1 - Karlinger, Peter A1 - Schemme, Michael A1 - Altstädt, Volker T1 - Thermoplastic Hybrid Composites with Wood Fibers: Bond Strength of Back-Injected Structures JF - Materials N2 - Due to their lightweight potential and good eco-balance, thermoplastic hybrid composites with natural fiber reinforcement have long been used in the automotive industry. A good alternative to natural fibers is wood fibers, which have similar properties but are also a single-material solution using domestic raw materials. However, there has been hardly any research into wood fibers in thermoplastic back-injected hybrid composites. This article compares the bond strength of an injection molded rib from polypropylene (PP) and wood fibers to different non-wovens. The non-wovens consisted of wood fibers (spruce) or alternatively natural fibers (kenaf, hemp), both with a polypropylene matrix. Pull-off and instrumented puncture impact tests show that, given similar parameters, the natural and wood-fiber-hybrid composites exhibit very similar trends in bond strength. Further tests using viscosity measurements, microscopy, and computed tomography confirm the results. Wood-fiber-reinforced thermoplastic hybrid composites can thus compete with the natural fiber composites in terms of their mechanical behavior and therefore present a good alternative in technical semi-structural applications. KW - biocomposites KW - wood fibers KW - polypropylene KW - back-injection molding KW - bond strength Y1 - 2022 UR - https://doi.org/10.3390/ma15072473 VL - 15 IS - 7 SP - 2473 ER -