Owing to twisting of filament fiber bundle, the structure and consequently various parameters and properties of a fiber bundle are changed. The aim of the work is to verify the effect of multifilament yarn twist (or twist coefficient) on selected mechanical properties such as multifilament tenacity, breaking elongation, and coefficient of fiber stress utilization in the yarn. Furthermore, the influence of twist on structural parameters such as the angle of peripheral fibers, the packing density, and the substance cross-sectional area of fiber bundle is observed. Two multifilament yarns with different filament cross-section shape and material were used for the experiment. Experimentally obtained data was compared with the known model dependencies derived decades ago based on the helical model. It can be stated that multifilament yarn retraction can be predicted based on the angle of peripheral fibers using the Braschler’s model. The coefficient of fiber stress utilization in the multifilament yarn determined experimentally corresponds with a theoretical curve, constructed according to Gégauff and Neckář, in the area of Koechlin’s twist coefficient α > 54 ktex1/2 m−1. Results as well as possible causes of deviations of experimental data from the theoretical one are discussed in this work.
We report on a particular direction of currently conducted extended research on novel textiles with integrated thin metallic filaments made of an intermetallic shape memory NiTi alloy exhibiting functional behaviour such as superelastic deformation up to 10% and a thermally induced shape memory effect. Within this research direction we focus on development of single and multi-layered warp-knitted fabrics that are directionally reinforced with superelastic NiTi filaments. First, we describe the expected properties of such novel structures and their potential applications. Second, we present the functional thermomechanical behaviour of applied superelastic NiTi filaments. Third, we address questions related to the design and fabrication of warp-knitted fabrics with integrated NiTi filaments. Then, we describe experimental methods applied on novel functional textiles in order to evaluate their functional properties. Finally, we present and discuss results of experiments carried out on these novel functional textiles.
The development of novel biomass carriers is an option for increasing the efficiency of processes at wastewater treatment plants (WWTPs). Biomass carriers support the adhesion of specific bacteria and the subsequent biofilm formation. As part of this work, a new type of microfibrous biomass carrier with a unique sandwich structure was developed. Technologically, the structure of the biomass carrier is based on warp knitted spacer fabric created on a double-needle bar machine. Commercially available microfiber materials were used to achieve a large specific surface area (SSA) and internal porosity of the carrier to ensure high microorganism capture. A yarn combination was chosen to reach a final carrier density slightly lower than water to float in an aqueous environment. As the first, was developed and described a three-dimensional warp knitted microfiber biomass carrier. Next, were evaluated the properties of this carrier for post nitrification on WWTPs and compared with commercially available biomass carriers. Testing biofilm (using respirometry, real-time polymerase chain reaction, and next-generation sequencing) growing on the developed carrier in a post-nitrification laboratory reactor showed excellent adhesion, stability, and abundance of microorganisms. A high rate (more than 95%) of ammonia nitrogen removal was achieved in post-nitrification, and molecular genetics methods confirmed the high concentration of nitrifying bacteria in the biofilm. The developed three-dimensional microfiber biomass carriers have proven their functionality and can be considered an advance in biofilm processes.
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