Electrically conductive yarns (ECYs) are gaining increasing applications in woven textile materials, especially in woven sensors suitable for incorporation into clothing. In this paper, the effect of ...the yarn count of ECYs woven into fabric on values of electrical resistance is analyzed. We also observe how the direction of action of elongation force, considering the position of the woven ECY, effects the change in the electrical resistance of the electrically conductive fabric. The measurements were performed on nine different samples of fabric in a plain weave, into which were woven ECYs with three different yarn counts and three different directions. Relationship curves between values of elongation forces and elongation to break, as well as relationship curves between values of electrical resistance of fabrics with ECYs and elongation, were experimentally obtained. An analytical mathematical model was also established, and analysis was conducted, which determined the models of function of connection between force and elongation, and between electrical resistance and elongation. The connection between the measurement results and the mathematical model was confirmed. The connection between the mathematical model and the experimental results enables the design of ECY properties in woven materials, especially textile force and elongation sensors.
In recent years, more and more researchers have been focused on electrically conductive textiles that generate heat or transmit electrical signals and energy to embedded electrical components. In ...this paper, the dissipation of heat due to the flow of electric current at given voltages is investigated, and at the same time it is determined how this heat affects the change in the electrical resistance of the electrically conductive yarn in the immediate surroundings. Three fabric samples were woven in a plain weave with three types of different electrically conductive yarns. Three electrically conductive yarns are woven in parallel in the weft direction and separated from each other by one polyester (PES) yarn due to electrical insulaton. Conductive yarns are electrically connected so that the outer yarns are used for heating by the flow of electric current at a certain constant voltage, and the central yarn is used only to measure changes in electrical resistance. When electrothermally conductive fabrics are subjected to certain voltages over time, experimental results have shown that resistance values increase over a short period of time and then gradually decrease, while the temperature gradually increases and stabilizes over time. Based on the analysis of the obtained results of the ratio between the values of applied voltage and temperature to the electrically conductive yarns, the value of thermal dissipation in conductive yarns can be calculated in advance depending on the applied voltage. Furthermore, the obtained results can be further used in applications where conductive yarns are used as heaters for realistic prediction of the obtained heat.
Determination of mechanical properties and predicting the behavior of knitted fabrics during the manufacturing process and finally in the use is an important part of textile science. In this study ...the influence of knitted fabric anisotropy on the values of maximum force, corresponding extension and total work when axial tensile forces act on specimens cut at different angles with respect to the course direction of the knitted fabric were analyzed. A plain double weft knit fabric made of single cotton yarns was studied. For different angles of cutting samples, the curves of the relation between the values of the tensile forces and the extension at break were experimentally obtained. The mathematical models obtained were compared with the experimental results, and the corresponding correlation coefficients were calculated.
This paper deals with the impact of fabric density on fabric thickness change when samples are subjected to uniaxial tensile forces in the weft direction. During stretching, fabric thickness changes ...depending on the value of the tensile force. In an effort to be as precise as possible in measuring fabric dynamic thickness changes and the area on which the tensile force acts, a new measuring apparatus was designed and constructed. This measuring apparatus allows the simultaneous measurement of fabric dynamic thickness, related tensile axial forces and extension. Measurements of the fabric dynamic thickness, breaking force and breaking extension during the stretching process were carried out on five samples of cotton woven fabric with a constant warp density and different weft densities in the same structural plain weave. Based on the experimentally obtained values, the paper presents diagrams of the relationship between dynamic changes in fabric thickness in relation to the tensile force and extension. The research presented in this paper shows that an increase in the tensile force increases fabric thickness for all weft densities. Also, the out-of-plane woven fabric ratio was calculated as a relation between the relative thickness strain and relative axial strain. The characteristic curve shows this ratio.
In this paper, the practical application of uniaxial testing of painting canvas for determining its mechanical properties is presented. Painting canvases have a complex composite structure whose ...mechanical properties are considerably improved in relation with the initial basic material. Painting canvas or coated fabrics are obtained by applying a certain number of coatings to raw fabrics. Experimental testing and determining mechanical properties of painting canvas under tensile force at different angles in relation to the weft direction are discussed in the paper. The fabrics were tested before coating, as well as after one, two and three coatings. The values of tensile force in relation to relative extension of coated textiles were measured, as well as breaking force values, elongation at break, contraction at break, work to rupture. Based on the experimentally obtained values, modulus of elasticity, Poisson’s ratio and the level of anisotropy of the coated textile materials were calculated. The experimental results demonstrate the applicability of theoretical formulae. The number of coated layers on the raw fabric exerts a significant impact on the Poisson’s ratio. The values of breaking force, elongation at break, work to rupture and modulus of elasticity increase with an increase in the number of coated layers, and at the same time coefficient of anisotropy decrease. It has been shown that by increasing the number of coated layers in a coated material, its anisotropic properties decrease, while isotropic properties increase. With an increase in the number of coatings, the differences between experimental and theoretical values of modulus of elasticity decrease.
Influence of Coating on the Poisson's Ratio of Woven Fabrics Penava, Željko; Šimić Penava, Diana; Tkalec, Marijana
Applied Mechanics and Materials,
02/2016, Letnik:
827, Številka:
Applied Methods of the Analysis of Static and Dynamic Loads of Structures and Machines II
Journal Article
Recenzirano
Coated fabrics have complex composite structure whose mechanical properties are considerably improved in relation with the initial basic material. They are obtained by applying a certain number of ...coatings to raw fabrics. In this paper the practical application of uniaxial testing of coated fabrics for determining its breaking properties and Poisson’s ratio is presented. Due to the anisotropy of woven and coated fabrics, Poisson's ratio changes over the fabric sample stretching. Experimental testing were carried out on two samples of plain weave cotton fabrics. The fabrics were tested before coating, and after one, two and three coatings. Samples are stretched with tensile force in the weft and warp direction, and based on different measured values of fabric stretching, warp and weft Poisson's ratio is calculated. The values of tensile force and relative extension of coated fabrics were measured, and breaking force values, elongation at break, contractions at break.
The paper analyses the impact of lateral restraining by trapezoidal steel sheeting on the structural stability of thin-walled C-cross section columns subjected to axial forces. Firstly, mechanical ...properties of the column material (steel) and lateral stiffness of the rotational restraint are determined by testing standard specimens in a laboratory. Based on the obtained data, a stability analysis of unrestrained columns and of columns laterally restrained by trapezoidal steel sheeting has been carried out and critical forces have been determined analytically by using the theory of thin-walled beams, numerically by using the finite element method (FEM), and experimentally by testing the C-cross section columns in a laboratory. The analysis of critical forces and stability shows that the calculation according to the theory of thin-walled beams and the FEM calculation gives results similar to the results of the experimental tests. By comparing the results of the investigation into thin-walled C-cross section columns with and without lateral restraints a significant influence of lateral restraints on the stability of thin-walled C-cross sections subjected to axial forces has been proven: lateral restraint significantly affects final results of the level of the critical force, raising the possibility of optimizing the use of such structures in practice.
This paper analyzes critical forces and stability of steel thin-walled C-cross-section beams without lateral restraints. Mechanical properties of the rods material are determined by testing standard ...specimens in a laboratory. Based on the obtained data, the stability analysis of rods is carried out and critical forces are determined: analytically by using the theory of thin-walled rods, numerically by using the finite element method (FEM), and experimentally by testing the C-cross-section beams. The analysis of critical forces and stability shows that the calculation according to the theory of thin-walled rods does not take the effect of local buckling into account, and that the resulting critical global forces do not correspond to the actual behaviour of the rod. The FEM analysis and experimental test show that the simplifications, which have been introduced into the theory of thin-walled rods with open cross-sections, significantly affect final results of the level of the critical force.
This paper describes an experimental study on the pure shear properties of E-Glass woven fabric by picture frame test. During shear deformation, the fabric yarns experience large angular change ...between warp and weft yarns. The picture frame test is one of the fundamental methods to characterize the in-plane shear behaviour of woven fabrics and can produce a quite uniform shear deformation state in the fabric sheet. Tests are conducted on two different size of EGlass specimens 40x40 mm and 80x80 mm. For a double increase the specimen size, the values of shear force and axial load are also almost double increase at the maximum displacement and shear angle.
Anisotropy is the characteristic which is typical for most materials, especially woven fabrics. Influence of direction of tensile force action on the properties of the fabric is big and frequently ...tested. The woven fabric can be defined as orthogonal elastomer. The values of elastic modulus of woven fabrics for different angles of extension direction were analyzed. Three types of fabric samples of different weaves (plain, twill, sateen) and the same raw material composition were tested under tensile forces in seven directions oriented with 15° increment with respect to the weft direction. Elastic modulus of woven fabrics was determined experimentally in the laboratory. Based on the experimentally obtained values, theoretically calculated elastic modulus for arbitrarily chosen fabric directions was calculated. A good agreement between experimental results and the calculated obtained values of the elastic modulus was shown, so the theoretical equations can be used with high accuracy to calculate the elastic modulus of the fabric in various directions. Therefore, the measurements need to be implemented when the tensile force acting on the fabric only in the warp (90°), weft (0°) and at angle of 45°.
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