Yarn Compression Research Articles

Micromechanical modeling and experimental analysis of yarn separation type sewing damage on continuous filament fabrics

Fabrics with weaves of low interlacing density and smooth yarns such as continuous cuprammonium filaments are often susceptible to sewing damage of cracks perpendicular to the sewing line, seriously influencing the aesthetics of the finished garment. To understand how the important factors such as yarn modulus, yarn bending stiffness, sewing needle radius, yarn-on yarn-friction, fabric counts and fabric weaves act on the crack length of such a fabric, a micromechanical model is proposed, and the experimental results are compared with the theoretical prediction. Single yarn pull-out tests and single yarn axial compression tests are performed to estimate yarn-on-yarn friction and yarn bending stiffness, respectively. The model indicates that the sewing crack length is positively proportional to the yarn tensile modulus, yarn bending stiffness and the needle radius and is negatively proportional to the fabric count and the inter-yarn friction. The model predicted crack lengths are within the range of the experimental results in warp direction while the predicted value is substantially larger than the observed crack lengths in weft direction due to the high compressibility of the weft yarn, which decreased yarn tension, bending stiffness and increased yarn cover power. For a given fabric, increasing yarn-on-yarn friction and raising yarn compressibility is an effective way to control the crack lengths.

Structural design of face fabrics and the core as a premise for compression behavior of 3D woven sandwich fabric

In this work, an experimental study on compression properties of two E-glass 3D woven fabrics, known as integrally woven sandwich fabrics, has been presented. Compression properties of 2D face fabrics and the core, as structural parts of integrally woven sandwich fabric, have also been investigated. Compression behavior of the samples (compressibility, compression work, and compressive resilience) was analyzed from the aspect of the weave design of face fabrics and the core structure (shape and density of the pile yarns). Results of the investigation showed that “8” shaped core structure, the greater surface density of the pile yarns, and the less compact structure of face fabrics ensure better compression properties of 3D fabrics. Specific weave design of face fabrics and the structure of the core significantly influence the behavior of 3D fabrics during successive increases, followed by a gradual decrease of pressure. During the loading of 3D woven structures, three regions of curves can clearly be seen compared to two regions which are registered at 2D face fabrics. Concerning 3D woven fabrics, the first region represents compression of the core, the second region is prolonged core compression and the third region refers to the simultaneous compression of pile yarns in the core and face fabrics. The density of pile yarns plays an important role in the region 1. In region 2, both the shape and density of the pile yarns are significant. Influence of the weave of face fabrics on compression behavior of 3D fabric can be noticed to a lesser extent in the region 2 and, especially in the region 3, where highly packed yarns assemblies are created.

Integration of yarn compression in modeling structural geometry of liquid resistant–repellent fabric surfaces and its impact on liquid behavior

Liquid resistant/repellent surfaces are important in many textile applications, especially for the outermost layer. The Cassie–Baxter model is a geometrical model depicting the liquid behavior of a rough surface and predicting the liquid resistance of a surface by calculating the apparent contact angle. The Cassie–Baxter model has been used to develop a geometrical model of woven fabric to define the surface performance of its liquid repellency. However, current geometrical models do not consider yarn flattening, which is observed in actual woven fabrics. A model reflecting the actual geometry of woven fabric should predict liquid wetting more accurately. This study extended the Cassie–Baxter model of woven fabrics to include the yarn flattening factor, e. This theory predicts that the fabric contact angle, θ F, decreases as yarn flattening proceeds by increasing the contact area of a liquid on a fabric surface. Different weave structures also influence the contact angle, θ F. When the yarn contact angle is θ y ≥ 113° and e ≤ 1, the fabric contact angles of the fabrics studied were the highest for plain woven fabric, lower in 2/2 basket, and lowest in 2/1 twill. These predictions are in good agreement with experimental results on manufactured woven fabrics, which varied in their yarn flattening and their different weave structures; they exhibited the same trends as predicted in the models. Yarn compression and its impact on the liquid resistant/repellent surface property were demonstrated by modeling the structural geometry of the lenticular yarn (compressed yarn) in regard to the liquid contact area against the woven fabric surface. As the yarn is compressed, the major axis of a warp or weft yarn, a, increases, while the minor axis, b, decreases. This changes the liquid-fabric contact angle, which is dependent on the liquid surface tension (determining θe and α) and the local surface geometry.

차양막 직물용 코팅사 제조기술에 관한 연구

This paper investigated optimum process conditions of coating yarn for awning fabric. For this purpose, the simulation for processability and yarn quality using SPSS statistics package was carried out, and PP/TPO and PET/PVC coating yarns specimens were made with variation of extruder temperature and feed speed of core yarn on the yarn coating machine for examining simulation result. It was revealed that optimum coating conditions of PP/TPO 1000d coating yarn were extruder temperature , and core yarn feed speed 400~500m/min. Mechanical property and thermal shrinkage of PP/TPO coating yarn made at this conditions were best and core evenness rates of these coating yarns by yarn compression tester were also superior, which was certified by SEM photograph. In addition, these experimental results were coincided with simulation results. It was found that, in PET/PVC coating yarn, yarn physical properties between 1500d and 1200d coated yarns were not shown any difference, and core evenness rates of these coating yarns were superior. It revealed and concluded that these simulated coating conditions are applicable to production field.

Mechanical behaviors of Kevlar 49 fabric subjected to uniaxial, biaxial tension and in-plane large shear deformation

Woven fabrics are used in many applications, including ballistic armors, propulsion engine containment systems and fabric reinforced composites. In order to facilitate the design and improvement of such applications, this paper investigates the stress–strain response in warp and fill directions, the apparent Poisson’s ratio, and the in-plane shear response of Kevlar 49 fabric including the possible effects of specimen size and pre-loading on the mechanical responses of the fabric. Full-field image analysis of the fabric under shear deformation is used to better understand the mechanisms related to in-plane shear. The experimental results show that the fabric exhibits non-linear and orthogonal behavior in tension, and can deform up to 20% before complete failure. It has identical Young’s modulus (pre-peak elastic stiffness) in warp and fill directions, but has different crimp strain, tensile strength and ultimate strain. The apparent Poisson’s ratio is a nonlinear function of strain and dependent upon the levels of pre-loading. It increases with strain quickly at the beginning and decreases gradually until the fabric fails. The shear response is highly nonlinear and has four distinct regions: linear elastic rotation region, dissipative rotation region, yarn compression region and shear locking region, and it is not dependent upon specimen size after normalization.

Deformation analysis of 2/2 twill weave fabrics

Biaxial tensile loading processes in 2/2 twill weave fabrics are studied. The performed calculations are based on the theory of biaxial deformation of woven materials with account of their geometry and mechanical characteristics of the warp and weft threads/yarns. Numerical procedures are proposed, in order to solve the resolving system of equations which allows for yarn compressibility in transversal directions. The effectiveness of numerical algorithms is demonstrated by comparison of predicted results and the experimental data.

Contribution to measurement of real yarn diameter

Measuring yarn diameter, yarn compressibility and their effect on fabric quality is important to both the fabric designer and the textile technologist. Measurement of yarn diameter is used to predict fabric structural parameters such as width and cover factor. In fact, a slight change in yarn diameter can result in a substantial change in the overall cover factor of fabric. Factors affecting yarn diameter are essentially those that affect yarn density or fibre compactness. Sixty-one different yarns (polyester, viscose, acrylic, cotton and wool) were tested to determine their real diameter by an experimental device. The obtained diameter values are close to those calculated by an established theoretical model. The determination of the real and apparent yarn diameter permits to estimate its packing fraction using his intrinsic parameters.

Modelling of mechanical behaviour for woven fabrics under combined loading

This paper presents a modelling approach for mechanical behaviour of textile reinforcements, based on Nottingham’s TexGen textile modelling schema. TexGen allows models to be generated easily for any textile reinforcement, and has automated functions to discretise the model, assign material orientations and properties to elements, and export the model to external analysis software. In this study Abaqus FE software is used, incorporating a transversely isotropic material law with non-linear transverse mechanical properties determined from experimental characterisation of yarn compression. This is validated firstly for discrete load-cases, including compaction and in-plane shear. The approach is then applied to simulate combinations of these loadings to represent important interactions that can occur during fabric forming. For example, compaction combined with shear is modelled to represent the effect of tool normal force on deformation. Combined tension and shear, which can arise due to the use of a blank-holder during forming, can also be analysed. It is hoped that results will assist in understanding of experimental data that is beginning to be generated on combined loadings.

Longitudinal yarn compression textile: An innovative treatment for leg swelling

Longitudinal yarn compression textile: An innovative treatment for leg swelling

Discrete woven structure model: yarn-on-yarn friction

A discrete model of a fabric has been developed from an analogical description, using a mass-spring system of discrete elements. An element of fabric is modeled by a set of grid nodes endowed with a mass and connected with flexional and stretching springs. This model describes the mechanical behavior of a woven structure at a mesoscopic scale. As a novel contribution, the interactions and the friction between yarns are introduced in the present work. An energy analysis of the discrete system of analogical elements is performed, taking into account the compression strain energy of the yarns and the work of the reaction forces exerted between yarns. A suitable discrete variational principle, accounting for the presence of the nonholonomic forces arising from friction, serves as a basis for a numerical implementation. Simulations of uniaxial tractions are performed, that show the effect of the yarn–yarn friction and yarn compressibility on the fabric response. To cite this article: B. Ben Boubaker et al., C. R. Mecanique 335 (2007).

Analysis of a Novel 3D Hybrid Woven/Knitted Fabric Structure

In Part I of this series, a geometric model was developed to predict loop length, yarn consumption, and thickness of a novel 3D hybrid woven/knitted fabric structure. In this part, a mechanical model is generated for estimating the Young's modulus and extension of the 3D hybrid woven/knitted fabric structure. Castigliano's theorem is used to derive the relations. The compression, extension, and bending energies of yarns are considered for the total strain-energy formula of the fabric. The mechanical model is verified for the fabric Young's modulus. There is reasonable agreement between theory and experiment considering the assumptions made and the complexity of the 3D fabric structure. The deviation is less with high performance multifilament fibers in the warp and bias yarns.

Compression of Plain Knitted Fabrics Predicted from Yam Properties and Fabric Geometry

This work proposes a simple theoretical model for plain knitted fabric compression. The work assumes that plain knit compression can be obtained from a combination of piled layer (PL) yarn compression and single layer (SL) yarn compression with a contribution factor depending on the fabric geometry. Experiments involve compression of plain knitted fabrics made from 2/19 and 2/29 tex cotton and 2/43 tex cashmere yams and their compression properties. The relation between compressional energy and cover factor is also investigated. A comparison of the experimental pressure-displacement curves of the fabrics and those calcu lated based on the theoretical model using the experimental compression data of the yarns shows that the model is acceptable for explaining plain knit compression. This model can be considered as a basic step toward improving the knowledge of knitted fabric compression as it relates to yarn compression and fabric geometry.

Mesoscale modelling of interlaced fibre assemblies using energy method

The knowledge of mesoscale behaviour of interlaced fibrous structures is necessary to predict their macroscale behaviour. The aim of this study is to highlight the advantages of energy-based approach to solve fabric mechanics problems with out the necessity of complex 3D finite element analysis. A mechanical model to predict the tensile response of plain-woven fabric unit cell under in-plane uniaxial/biaxial loads is presented here. The model incorporates non-linear properties of constituent yarns, rather than idealised linear behaviour. All possible mechanisms of deformation including elongation, bending and compression of yarns have been considered. A modified geometry of yarn path based on a polynomial has been proposed. The predictions are compared with experimental data reported in literature as well as the finite element analysis. The computational aspects of implementation of the model are also discussed briefly.

A Predictive Model for the Fabric-to-Yarn Bending Stiffness Ratio of a Plain-Woven Set Fabric

A model for woven fabric behavior in bending is formulated based on a representation of fabric deformation as a coordinate transformation. The model is essentially based on previously published assumptions of yarn behavior but provides predictions closer to real fabric properties. It uses the energy approach for mechanical problems of textiles and employs a polynomial approximation of the thread shape. The mathematically subtle contact problem of yarns within a fabric can be turned into a more general consideration of yarn compression, and this can be investigated by independent, practical experimen tation. Comparison with previously published experimental data for a variety of thread types and fabric parameters shows reasonable agreement between predicted and measured bending stiffness of plain woven fabric.

Compression of Woven Reinforcements: A Mathematical Model

A mathematical model for prediction of the compressional behaviour of woven reinforcement is described. The model accounts for the compression of yarns and the change of yarn crimp under pressure applied to a fabric layer. Compression curves of glass rovings are studied experimentally and serve as input for simulation of fabric compression. The model is tested against experimental data for glass reinforcement for the lower and the higher pressure range.

Textile geometry preprocessor for meso-mechanical models of woven composites

A mathematical model of the internal geometry of 2D and 3D woven fabrics is used as a unit-cell geometry preprocessor for meso-mechanical models of composite materials. The model computes a spatial placement of all yarns in a fabric repeat for a given weave structure (a special coding algorithm is employed) and given warp and weft yarns geometrical and mechanical parameters. The source of these data is the manufacturer's documentation for a woven fabric and yarn mechanical behaviour in bending and compression, measured on standard textile-laboratory equipment. The principle of minimum energy of a fibrous assembly leads to the prediction of the yarns crimp, the forces in the warp/weft contacts and the yarn compression within a fabric. The input data for use in meso-mechanical models of composite materials is therefore provided in addition to tools for the 3D representation of the woven structure, for the creation of the unit-cell cross-sections and for the computation of the unit cell porosity.

Solid Modeling Applied to Fibrous Assemblies. Part I: Twisted Yarns

In our earlier work, we developed a model for fibrous assemblies by treating each yarn as a true three-dimensional structure. We then were able to predict various orientation limits by manipulating the model until geometric self-intersection would occur. However, that model treated the yarns as inextensible and incompressible. In this paper, we propose an abstraction to visualize the effects of yarn compressibility and then study the results of applying the new model on a final object that is primarily one-dimensional in nature - a rope-like structure composed of a twisted bundle of individual yarns.

29—THE EFFECT OF FIBRE CRIMP ON FABRIC QUALITY

The relation between fibre crimp and fabric quality is investigated for various fabrics of different grades. It is found that fibres taken from fabrics of good quality have a high crimp level and that fibre crimp plays an important role in yarn extensibility, compressibility, and fabric extensibility and improves fabric quality. Correlation between fibre crimp and primary handle is also surveyed, and it is shown that NUMERI (smoothness) and FUKURAMI (fullness and softness) are strongly correlated with the fibre crimp.

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.

An Energy Analysis of the Mechanics of Weft-knitted Fabrics by Means of Optimal-control Theory: Relaxed-fabric Dimensions and Tensile Properties of the Plain-knitted Structure — Reply

The energy analysis of the plain-knitted structure reported in Part I of this work is further developed by studying the relaxed-fabric dimensions and the fabric tensile properties for extension in the two principal directions of the fabric structure. The relaxed-fabric dimensions are evaluated in terms of the parameters k a, k w and the thickness for fabrics of different tightness of construction and for yarns of different lateral compressibility. The following parameters are also evaluated: inter-yarn distances and inter-yarn forces in the regions of loop-interlocking and length- and width-jamming, the fabric-curling couples, the energies of yarn-bending and lateral yarn compression, and the total energy. Wherever possible, the values of these parameters are compared with experimental results reported in the literature and also with the results of previously reported theoretical models of the plain-knitted structure. The variation of the previously mentioned parameters is studied when a fabric tension is...