Yarn Bending Rigidity Research Articles

Research on the Knittability of Metallic Yarns in the Warp-knitted Mesh of a Deployable Antenna

Abstract Metallic yarns are difficult to be knitted. To resolve the problem, the paper used the knitted yarn strength utilization factor to quantitatively characterize knittability, which was the ratio of yarn strength after being knitted to that of the original yarns. Furthermore, the relationship between the yarns' basic mechanical properties and the knitted yarn strength utilization factor was investigated by testing the yarns' basic mechanical properties. The results showed that it was feasible to quantitatively characterize the yarns' knittability using the knitted yarn strength utilization factor. And also the breaking strength of yarn was not correlated with the knittability. The elongation at break of the yarn was positively correlated with knittability. The bending stiffness of the yarn was negatively correlated with the knittability. Finally, a multiple linear regression model of the knittability and the mechanical properties of the yarn was developed. The model showed that there was a significant linear relationship between knittability and the elongation of yarns at break and the bending rigidity of yarns, with the bending stiffness of yarns being more significant.

Development and experimental validation of a mathematical model of shear rigidity of woven fabric structures

Shear is one of the most important mechanical behaviours which differentiates a woven fabric from papers and polymeric sheets. In this work a generalised mathematical model of shear rigidity of woven fabric applicable to all types of weaves has been proposed. The model demonstrates the shear rigidity of woven fabric as a function of yarn bending rigidity, fabric structural parameters and crossover firmness factor. Experimental shear rigidity results are compared with the theoretically predicted ones and a very good agreement is reached. The proposed mathematical model can able predict the shear rigidity of any woven fabric structure and thus foretells the usefulness of the fabric for a particular use.

Bending rigidity of yarns using beam method on a two-support configuration

This paper reports a simple, quick and reasonably accurate approach for measuring the bending rigidity of yarns. The beam method has been adapted and applied using a bending frame that has a fixed support and a simple support. The yarns are left to bend under the effect of their own weight. The accuracy and the precision of that bending frame are assessed over the time using an isotropic material and then compared against the ring-loop method and the KES-FB-2 pure bending tester. The findings show that the precision of this bending frame is acceptable. However, this bending frame gives at least 1.6 times greater values of bending rigidity than the KES-FB-2 pure bending tester, though the relationship between these two methods is linear and significant. Moreover, the spun yarns appear to have high levels of variability of the bending rigidity. This study is important as it overcomes the challenges faced while using other methods to measure the bending rigidity of yarn. It also provides a comprehensive account of the variation in this property. Further, it gives an indication of the highly non-uniform structure of spun yarns and the impact of yarn defects on the bending properties of yarns.

The method of determination of yarn bending rigidity and friction factor during interaction of fibers

This paper addresses a method of textile yarn bending rigidity determination and gives substantiation thereof. This method is characterized by the closest conformity of the yarn actual bending pattern in fabric. This is achieved by placing the yarn under load between two supports in the form of two taught fibers. The yarn curvature is not determined experimentally but computed thus reducing any computation errors. The tensile load is determined by the deflection angle of the support with the yarn. The supports with the yarn are printed on a 3D printer to reach the maximum accuracy in the determination of their masses’ center. The computation accuracy of the yarn rigidity during bending is also achieved by filling the yarn curve space with epoxy resin and a subsequent analysis of the deflection with the microscope. This results in the creation of a mathematical model that contains the bending moment, yarn curvature and tensile load. The findings of the determination method of the yarn bending rigidity are used to establish the factor of friction of the tested fibers against each other. The dependence of the friction factor on the yarn curve point coordinates will be determined for a certain type of carbon fiber.

Theoretical and experimental analysis of bending rigidity of plain and twill woven fabrics

The study of bending behavior of woven fabrics is an important issue in textile scientific researches and its industrial applications. Different behavior of fabrics such as drape, comfort, and handling can be understood by this study. Bending rigidity of fabric depends on several factors such as weave geometry, bending rigidity of yarn, and yarn density. In this study, estimation of bending rigidity of woven fabric with different twill and plain structures, have been carried out using energy method. Generally, the woven fabric structure is divided into three different section lengths i.e. rigid, semi-rigid, and flexible sections. Thereafter, bi-component and tri-component models for predicting bending behavior of plain and twill woven fabric have been presented. Then, bending properties of fabric based on Shirley apparatus as well as weight per area as a physical property were measured. Good agreement between measured and predicted values, validated our theoretical models for obtaining bending rigidity, except considerable differences observed between experimental and predicted values using bi-component model of plain fabric. Therefore, using assumptions in calculation of the ratio of rigid section length to flexible section length (R1), the modified model of plain fabric has been proposed.

Verification of the effect of yarn torsional rigidity on fabric bending rigidity in any direction

The effect of yarn torsional rigidity was verified on the Cooper model for fabric bending rigidity in any direction. We made five cotton fabrics with different weft densities and prepared three commercial fabrics as experimental samples. The torsional rigidity of yarn from the bobbin and that of yarn directly extracted from fabric were measured with a yarn torsional tester. The bending rigidity of yarn from the bobbin was measured using the same pure bending tester as used in fabric bending testing. The bending rigidity of thin fabric was calculated using torsional rigidities of yarns extracted from the fabric and showed better agreement with the experimental values than that calculated using the torsional rigidity of yarn from the bobbin. Indeed, measurements showed that the torsional rigidity of yarn from the bobbin was appreciably higher than the torsional rigidity of yarn from the fabric. This is due to the crimp in the yarn. The fabric bending rigidity can be predicted using the Cooper model with torsional rigidities of yarns extracted from the fabric.

Theoretical study on the bending rigidity of filament yarns with an elliptical cross-section using energy method. II. Numerical evaluation

This is the second part of a series of work investigating on the bending rigidity of filament yarn with an elliptical cross-section. In the present paper, the quantitative error analysis of the earlier simplification of a circular cylindrical of yarn geometry under deformation is evaluated, and the effects of filament properties on yarn bending rigidity are also evaluated. It is highly useful in preciously predicting yarn bending property from filament behaviors for virtual processing of textile materials. So the explicit formula derived in the Part I of this series for the elliptical cylindrical of yarn geometry is used to compute the quantitative error of the earlier model. The four characters, including the eccentricity of elliptical cross-section of yarn, the ratio of bending to torsional rigidity of filament, the helix angle of filament on yarn surface and the number of filaments inside the yarn, are adopted to quantify the bending rigidity relationship between the filaments and yarn. Based on the analytical method, the earlier method in which the circle shape takes place of the elliptical shape of yarn cross-section for simplification is evaluated. The simulation results show that the relative error of the circle assumption is not higher than 10 % when the eccentricity of yarn cross-section is lower than 0.8. However if the eccentricity is higher than 0.8 and the helix angle is larger than 30 degrees, it is suggested to conduct the deformation analysis based on the elliptical cross-section of yarn.

Measurement of yarn bending and torsion rigidities of naturally curved yarns Part 1: Monofilament yarn in helical shape

A new method to determine yarn bending and torsional rigidities was proposed in this paper. Measuring methods of yarn bending and yarn torsion were reviewed. The proposed method is a combination of theoretical modeling, instrumentation and statistical analysis. One major feature of this method is that bending and torsional rigidities of a naturally curved yarn, like those yarns in knitted fabrics, can be measured. With the aid of modeling, a recently developed Crimped Yarn Length Measurement Instrument (CLI) is able to measure both bending and torsional rigidities at the same time. The CLI generates a large amount of data points for the force and extension relationship during the decrimping of the curved yarn, multiple regression analysis was applied to determine bending and torsional rigidities. In this way, the experimental errors can be minimized and hence more representative results can be obtained. Experimental results from the new proposed method were compared with those measured by the KES-F bending tester and the KES-YN yarn torsion tester; good agreement was evident in testing results from both methods. The advantages of the proposed method were discussed including the capability of measuring the yarn bending rigidity at higher curvature. This is part 1 of the paper in which crimped nylon monofilament was used for the study. The measurements of bending and torsion moduli of crimped short staple spun yarn unraveled from knitted fabric will be further studied in Part 2.

Bending Rigidity of Yarns

The bending behavior of yarn is affected by mechanical properties, arrangement and interaction between its constituent fibers and yarn geometry. In this study the yarn bending rigidity was obtained from the tensile modulus of its constituent fibers and yarn geometry and structural parameters and it was shown that the dimensionless yarn bending rigidity decreased as the ratio of tensile modulus to the shear modulus of the constituent fibers increased. Furthermore, the yarn bending rigidity decreased as the surface helix angle of the yarn increased. When compared with previous research, there was good agreement between the findings of Owen, Zurek, and Platt’s and the results of this study.

Influence of Fiber Morphology and Yarn Spinning Process on the 3D Loop Shape of Weft Knitted Fabrics in Terms of Roughness and Thickness

The literature reports the parameters as well as their influence at different levels on the geometric properties of single-jersey fabrics: the main role of stitch length, the medium importance of fabric tightness, the minor influence of yarn physical properties, and the non-influence of the knitting process. This study reveals that even if yarn physical properties and the knitting process have a very small influence on fabric geometric characteristics relative to stitch length and fabric tightness, the effects must not be neglected on fabric roughness and thickness, i.e., the 3D loop shape. Even a very small difference in loop shape can change fabric tactility and quality, and therefore fabric sales. This paper shows experimentally the influence on roughness and thickness of fiber fineness and the yarn spinning process for three different cover factors, i.e., indirectly on the three-dimensional loop shape. In fact, both fiber fineness and the yarn spinning process influence yarn properties and more precisely, bending rigidity. Moreover, the influence of fabric tensile stress during knitting on 3D loop shape properties is discussed. After full relaxation, the loop shape depends on yarn characteristics, stitch length, and tensile stress walewise due to the knitting process. In fact, yarn bending rigidity and the interyarn friction coefficient are very important for loop shape: when bending rigidity decreases and the frictional coefficient increases, tensile stress in the knitting process is more influential.

Influence of the shape of fiber cross section on fabric surface characteristics

Fiber cross sections for use in textiles and composites are becoming more and more complex. Shape impacts fiber or filaments properties and therefore the yarn and fabric characteristics. This paper presents the influence of the fiber cross section on the fabric surface characteristics. The material used was polyester staple fibers, of four different shapes: round, scalloped oval, cruciform and hexachannel. All fibers had the same cut length with different fineness. Yarns obtained from these fibers had nominally the same yarn count, torsion value and structure. Plain jersey fabrics were knitted from each of the yarns under identical conditions and then relaxed prior to testing. Friction behavior was evaluated and a roughness-friction criterion developed. An indirect measurement of the real area of contact was obtained in order to provide roughness and friction properties. The influence of fiber cross section on yarn bending rigidity and on the state of the knitted fabric surface was characterized.

Study of Fundamental Factors Affecting Fabric Surface Protrusion Part II: The Effect of Yarn Bending Rigidity on the Fabric Surface Protrusion

This paper reports the results of an investigation on the effects of yarn bending rigidity on fabric surface protrusion. The bending rigidity is regarded as the multiple of the elastic modulus E, and the moment of inertia of the cross-section of the yarn (EI). The study was based on an analytical model adopted from the elastic theory. The experimental results are found to be in reasonable agreement with the theoretical values.

The Bending Properties of Multi‐ply Worsted Yarns

Presents a mathematical treatment of the large‐scale bending behaviour of multi‐ply yarn. Based on the assumptions that: each individual fibre in the yarn has the form of a doubly‐wound helix; each fibre is an inextensible slender rod; and interaction between fibres is ignored. The yarn‐bending rigidity is calculated as an average rigidity of an assembly of coaxial helices. There is good agreement between the predicted and measured values of yarn bending rigidity for a wool worsted knitting yarn. Also predicts the position, curvature and twist components as well as the strain energy of the deformed fibre.

Effect of Fiber Length, Fineness, and Twist on the Bending Behavior of Polyester and Viscose Staple Rotor Spun Yams

The effects of fiber length, fineness, and twist of polyester and viscose staple rotor spun yams have been examined for their bending behavior using a bending hysteresis tester. For the polyester staple rotor spun yarns, use of shorter and coarser fibers leads to a higher magnitude of bending hysteresis, yarn bending rigidity, and bending re covery ; the percent reduction in bending hysteresis and yarn bending rigidity is greater for coarser, shorter fibers with increasing twist. For the viscose staple rotor spun yarns, use of longer staple fibers leads to increased bending hysteresis and yarn bending rigidity; the percent reduction in bending hysteresis and yarn bending rigidity is greater for longer fibers with increasing twist. An increase in twist leads to a drop in the bending hysteresis and yam bending rigidity, regardless of the length or fineness. Wrapper fibers do contribute to the bending behavior of rotor spun yams.

Effects of Yarn Twist on the Mechanical Properties of Plied Yarn Fabrics

Twisting effect is an important factor determining the mechanical properties and structure of fabrics. An investigation was made of the relation between yarn and fabrics properties in terms of their tensile and bending properties when the resultant count of the plied yarn was varied.1) A high correlation was found between yarn and fabric properties such as tensile, bending, and physical properties (thickness, and weight).2) Surface roughness increases with increasing resultant count of piled yarn. Superficial crepe effect was obtained in coarse yarn fabrics when the constituent single yarns differed greatly in count.3) The bending rigidity of gray and finished fabrics of coarse yarns were greater than those of fine yarn fabrics. The constant (R) indicating the degree of correlation between yarn and fabric in their bending rigidities is expressed as: R=Xf; /N•Xy; where, Xf; : bending rigidity of fabrics, Xy; : bending rigidity of yarns, and bending rigidity of fabrics, N: number of yarns per unit width of fabric.The value of R for cotton/cotton plied yarn fabrics is larger than those for cotton/polyester multi-filament plied yarn fabrics irrespective of the resultant yarn count.

The Contribution of the Fibre-diameter Distribution to the Bending Rigidity of Yarns

The Contribution of the Fibre-diameter Distribution to the Bending Rigidity of Yarns

1—THE INITIAL LOAD–EXTENSION BEHAVIOUR OF PLAIN-WOVEN FABRICS

An analysis of the initial load–extension behaviour of plain-woven fabrics is presented, Castigliano's theorem being used as the principal method of attack. Yarn compression and extension are taken into account in addition to yarn bending rigidity. The theory is compared with some experimental data.

39—AN ENERGY ANALYSIS OF WOVEN-FABRIC MECHANICS BY MEANS OF OPTIMAL-CONTROL THEORY PART I: TENSILE PROPERTIES

The general energy analysis of fabric mechanics by means of optimal control presented in a previous publication is applied to the woven-fabric structure for deformations whereby the yarns remain in the same plane. The three-dimensional equations of the general theory are reduced to two-dimensional form, the boundary conditions are evaluated for the plain-weave fabric in biaxial tension, and an important mechanism of woven-fabric extension, which was not included in the general analysis, namely, the possibility of yarn extension, is introduced into the theory. The fabric load–extension curves and yarn-decrimping curves for the plain-weave construction are computed for a realistic range of input parameters: the yarn extension rigidity, weave crimp, degree of set, lateral yarn compression, and ratio of the curvilinear length of yarn in the warp direction to that in the weft direction of the fabric. The computed results are discussed in terms of the following dimensionless parameters: the applied tension per thread and the interaction force on the crossing thread (divided by the yarn bending rigidity), the relative fabric extension (the fabric extension divided by the yarn crimp), the initial relative fabric tensile rigidity, the Poisson's ratio of the fabric, and the initial tensile rigidity of the crimped yarn unravelled from the fabric. The tensile properties of plain-weave fabrics in both the grey state and the finished state are illustrated by reference to the computed results, which are also employed to explain the behaviour of yarns during the extension of woven fabrics.

40—AN ENERGY ANALYSIS OF WOVEN-FABRIC MECHANICS BY MEANS OF OPTIMAL-CONTROL THEORY PART II: PURE-BENDING PROPERTIES

The energy analysis of woven-fabric mechanics developed in Part I of this series is extended by considering the pure-bending behaviour of the plain-weave structure as a generalization of the tensile deformation. The boundary conditions for the plain-weave fabric in bending are evaluated, and the ratio of fabric bending rigidity per thread to yarn bending rigidity is computed for a range of fabric structures of different values of weave crimp and degree of set by introducing inequality constraints on the curvature or control variable, a concept borrowed from optimal-control theory. The theoretical results for fabric bending rigidity are compared with experimental work reported by previous workers, and the theoretical shape of the yarn axis in a bent fabric is computed for different fabric curvatures. A comparison of the theoretical results computed by means of optimal-control theory for plain-weave, plain-knitted, and 1 × 1 rib-knitted structures is presented in terms of the following parameters expressed ...

平編地の引張特性と糸の曲げ剛さ

平編地の引張特性と糸の曲げ剛さ