Warp yarns in their different applications during weaving processes are often required to support loads, either in a static manner (simple tensile) or in a dynamic one (fatigue). For this reason, the investigation into the variations of the mechanical behavior of warp yarns during weaving condition is important. The purpose of this investigation was to simulate the cyclic loading of weaving process on filament warp yarns and report their fatigue behavior. In this study, the general characterization analysis of three types of the most ordinary filament yarns, polyester, polypropylene and nylon, was performed and then their fatigue behavior was simulated as warp yarns under cyclic loading by using the dynamic mechanical analyzer (DMA 2980). For this simulation, by looking at the conditions of the most common weaving looms, two sets of frequencies as loom speed and two sets of strains as loom geometry were chosen. The relevant variations of the yarn elongation, yarn stress, yarn storage modulus, yarn loss modulus and the damping factor of the yarns were measured and studied. Our test results revealed that the polypropylene yarns had the minimum change in their mechanical behavior and the nylon yarns had the minimum amount of characteristics under different loading conditions. It was found that the resistance of nylon to cyclic loads was higher than polyester and polypropylene. Also, polyester was the weakest yarn because of high change range in its mechanical and physical properties. We also demonstrated that only the polyester yarn revealed immediate failure at 2 % strain.

No abstract

No abstract

No abstract

In this work, the sound absorption properties of warp knitted spacer fabrics enhanced with nanofiber were studied. The angle of connecting yarns at two different spacing was considered as knit structure variable. Also, the effect of layering on the sound absorption performance was studied. Besides that, the effect of polyacrylonitrile nanofiber enhancement on sound absorption coefficient of such structures were considered. The polyacrylonitrile nanofibers were manufactured by a single-nozzle electrospinning device using a rotating cylindrical collector. The main variable for the nanofiber enhancement was its deposition amount on the front surface of spacer fabrics. The sound absorption coefficient was measured by using the method of impedance tube. For this purpose, the samples were prepared according to the requirements, and the tests were performed at the frequency range of 500–6000 Hz on single-layer and multi-layer samples. The results showed that increasing the spacing and the angle of connecting yarns will enhance the sound absorption coefficients of samples through increasing their areal mass, thickness and porosity. Moreover, layering will significantly affect the sound absorption performance of samples. Furthermore, nanofiber enhancement increased the absorption of sound at all frequencies.