Yarn Configuration Research Articles

Experiments and progressive damage analyses of three-dimensional full five-directional braided composites under three-point bending

Experimental and numerical studies on the bending properties of three-dimensional full five-directional (3DF5D) braided composites are presented in this article. Three-point bending tests of the braided specimens with different braiding angles were first preformed. Then, the full-scale specimen model was constructed and a strength analysis method based on repeated unit-cell (RUC) model was established to describe the strength characteristics of the 3DF5D braided composites. The differences between yarn configurations in corner, surface and interior RUCs were considered and continuum damage models were introduced into the components such as yarns and matrix of the RUCs in the method. This linked the macroscopic nonlinear response with the damages in the microstructures. Good agreements were achieved in the load-deflection curves and damage morphology between experimental and numerical results. POLYM. COMPOS., 37:2478–2493, 2016. © 2015 Society of Plastics Engineers

Comparative study on appearance and performance of garments made from low-torque ring, conventional ring and open-end spun yarn fabrics using subjective and objective evaluation methods

Low-torque ring yarn spinning is a modified-ring spinning technology with the false-twisting devices attached on the conventional ring spinning machine. The introduction of the false-twisting operation gives low-torque yarn a new fiber and yarn configuration, and thus causes different characteristics of low-torque yarn fabric from that of conventional ring and rotor yarn fabrics. In this paper, a comparative study has been carried out to evaluate the performance of jeans and trousers produced by low-torque yarns to conventional ring and rotor yarns. The results from the objective measurements of fabric performance indicate that the tensile and tear strength of low-torque ring yarn fabrics in the weft direction is similar to or only slightly lower than that of fabrics using conventional ring yarns with a normal twist level as the weft yarns, but they are much higher than that of the fabrics using rotor yarns. Compared to the fabrics produced from conventional ring and rotor yarns, the low-torque ring yarn fabrics exhibit higher compression energy (WC) and lower mean deviation of friction (MMD) and achieve higher values in fabric Numeri and Fukurami. The subjective evaluation of jeans and trousers through wear trials further confirms that low-torque yarn jeans have significant advantages of a better appearance in jean smoothness, less ‘small snake’ patterns, a more prominent slub effect and better overall quality than the conventional ring and rotor yarn jeans. The low-torque yarn trousers also show better luster, smoothness appearance and overall quality than the conventional ring and rotor yarn trousers.

Auxetic Materials and Related Systems

to mechanical metamaterials and related systems with particular emphasis on auxetic systems. Such materials show counter-intuitive, negative behaviours. For example, auxetic materials exhibit negative Poisson’s ratios which mean that these systems get fatter rather than thinner when stretched. Due to the superior properties exhibited by these systems, their study and characterisation has experienced a signifi cant increase, particularly in the last decade, something which may be perceived from the always increasing number of publications and patents in these areas. In fact, this issue is the seventh in a series of special issues published in physica status solidi (b) dedicated to auxetic materials and related systems (see [1–6]).

Ultraviolet Protection by Fabric Engineering

Background. The increasing emission of greenhouse gases has evoked the human being to save the ozone layer and minimize the risk of ultraviolet radiation (UVR). Various fabric structures have been explored to achieve desired ultraviolet protection factor (UPF) in various situations.Objective. In this study, the effect of various filament configurations like twisted, flat, intermingled, and textured in multifilament yarns on fabric in different combinations is assessed in order to engineer a fabric of better ultraviolet protection factor (UPF).Methods. In order to engineer a fabric having optimum UV protection with sufficient comfort level in multifilament woven fabrics, four different yarn configurations, intermingled, textured, twisted, and flat, were used to develop twelve different fabric samples. The most UV absorbing and most demanding fibre polyethylene terephthalate (PET) was considered in different filament configuration.Results. The combinations of intermingled warp with flat, intermingled, and textured weft provided excellent UVR protection comparatively at about 22.5 mg/cm2fabric areal density. The presence of twisted yarn reduced the UV protection due to enhanced openness in fabric structure.Conclusion. The appropriate combination of warp and weft threads of different configuration should be selected judiciously in order to extract maximum UV protection and wear comfort attributes in multifilament woven PET fabrics.

A Numerical Study on the Progressive Failure of 3D Four-Directional Braided Composites

The complexity of the microstructure makes the strength prediction and failure analysis of 3D braided composites difficult. A new unit cell geometrical model, taken as the representative volume element (RVE), is proposed to describe the yarn configuration of 3D braided composites produced by the four-step 1 × 1 method. Then, based on the periodical boundary conditions, a RVE-based micromechanical model by using the nonlinear finite element method has been presented to predict the progressive damage and the strength of 3D braided composites subjected to tensile loading. The numerical model can simulate the effect of damage accumulation on the tensile stress-strain curve by combining the proposed failure criteria and the stiffness degradation model. The longitudinal shear nonlinearity of braiding yarn is considered in the model. To verify the model, two specimens with typical braiding angles were selected to conduct the simulations. The predicted stress-strain curves by the model compared favorably with the experimental data, demonstrating the applicability of the micromechanical finite element model. The effect of the nonlinear shear parameter on the tensile stress-strain curve was discussed in detail. The results indicate that the tensile mechanical behaviors of 3D braided composites are affected by both the yarn shear nonlinearity and the damage accumulation.

Research and Development of the Low Twist Yarn

Using pure cottons as raw materials, a variety of specifications of the low twist yarns were produced through configuration of yarns’ counts, twist of single and ply yarns to ensure strength of yarn weaving. Strength, evenness, hairiness and other properties of the low twist yarns were also investigated. Production process is non-pollution, short, and low cost. The fabric products are fluffy and soft, absorbent, warm and full.

Finite element analysis of 3D braided composites based on three unit-cells models

3D braided composites have a skin-core structure and can be divided into three regions: interior, surface and corner. Each region is built up of identical unit-cells but the yarn configuration in the three regions is different thus must be treated separately. In this paper, three distinct solid structure models of unit-cell located in the interior, surface and corner regions of 3D braided composites are established first. With appropriate boundary conditions, the mechanical responses of 3D braided composites are simulated by using the finite element method. The deformation and stress distribution of the three unit-cell models are presented and the effects of the braiding angle and fiber volume fraction on the elastic constants of 3D braided composites are investigated in detail. Numerical results show that the three unit-cells have distinctive properties and the surface and corner unit cells are stiffer than the interior unit cell. Therefore, the effect of surface and corner regions on the mechanical properties of 3D braided composites must be considered in order to obtain accurate results. The calculated results show good agreement with available experiment data, thus verifies the applicability of the proposed three unit-cells models.

Cross-Sectional Configuration and its Combined Model of Yarns in Woven Fabric

CSCM in fabric is an important content of fabric geometry. Based on research work in the past, cross-sectional configuration of yarn in some real fabrics is observed. Several models can be used to describe it: round, ellipse and so on. Fabric with multiple weave-points below the same float can appear overlapping, staving and abnormal deformed yarns, especially serious in fabric with high density. So it’s unscientific to unify cross-sectional configuration to certain model, although there exist round, ellipse configuration in real fabric, triangle, cuneiform, sector are also observed in compacted fabric with multiple weave points. These models above are just examples only. In this case, it’s no meaningful to analyze the cross-section of mono-yarn. So combined CSCM is proposed to express yarn configuration in compacted fabric with multiple weave points.

Study of three-dimensional spacer fabrics:: Physical and mechanical properties

Spacer is a three-dimensional knitted fabric consisting of two outer textile substrates which are joined together and kept apart by spacer yarns. Spacer fabrics are used for environmental reasons, which can be used in different product groups such as mobile textiles (car seat covers, dashboard cover), industrial textiles (composites), medical textiles (anti-decubitus blankets), sports textiles and foundation garments (bra cups, pads for swimwear). In this study, the characteristics of different spacer fabrics including low-stress mechanical properties, air permeability and thermal conductivity were investigated. Low-stress mechanical properties obtained by the KES-fabric evaluation system revealed that all tensile, bending and compression properties of spacer fabrics are greatly depending on the type of spacer fabric (warp knit or weft knit), the type of spacer yarn used (monofilament or multifilament), the yarn count of the spacer yarn, the stitch density and the spacer yarn configuration. Air permeability and thermal conductivity of spacer fabric are closely related to the fabric density. This experimental work suggests that carefully selecting the spacer fabric according to the envisaged application is of primary importance.

２軸型ディスクフリクション仮撚における糸の経路と張力の解析

The path followed by and the tension generated along a yarn under a false-twist process using an enlarged model unit of a doubly stacked multi-disk spindle are measured and analyzed on the basis of a theory, an extension of authors’ earlier proposition. The geometrical quantities necessary to reproduce the yarn path, i.e. the inclination angle made by the yarn against a disk surface, the length along which the yarn runs on the disk, etc., are estimated from the CCD image of the yarn configuration. The twisting tension, the inter-disk yarn tension, and the untwisting tension of the running yarn are also detected. It is revealed that the theoretical analysis can successfully elucidate and predict the inter-disk yarn tension as well as the relation between the twisting tension and the untwisting tension only if the yarn configuration is observed. This study will give a novel and useful clue to the manufacturing technology related to false-twist processing using multi-disk spindles.

3—THE MECHANICS OF STAPLE-FIBRE YARNS PART II: ANALYSIS AND RESULTS

The governing equations of the staple-fibre-yarn model presented in Part I are formulated and solved by utilizing the finite-element method. Major features added to Hearle's work are the incorporation of changes in yarn configuration due to slippage, non-linear material behaviour, and a more realistic representation of the lateral contraction of the yarn. A number of specially spun yarns were used to evaluate the staple-fibre-yarn analysis.

Length distributions of filament yarns in 3-ply cord.

The distributions of yarn lengths are investigated for some commercial 3-ply cords with different number of yarns. The results are compared with those calculated by Treloar's theory. There is no general agreement between the measured and calculated values. The range of measured values has a tendency to be smaller than the calculated values. This proves that the yarn migration occurs along the ply axis and that the yarn configuration in the ply is distored. Furthermore, the results of measurements suggest that the yarn length distribution in commercial cords may be an index of cord quality.

20—THE DESIGN AND DYNAMICS OF NON-LINEAR CAMS FOR USE IN HIGH-SPEED WEFT-KNITTING MACHINES PART II: THE ANALYSIS OF KNITTING-YARN TENSIONS WITH NON-LINEAR CAMS AND NEGATIVE FEED

A model of loop formation in the knitting zone of a non-linear weft-knitting system is described. The yarn tensions developed in this zone are analysed for the condition of negative yarn-feeding only. Detailed geometries of the yarn configuration in the initial stages of loop formation are proposed, to allow for accurate predictions of maximum yarn-knitting tensions.

1—THE MICROSCOPICAL EXAMINATION OF BENT FABRICS

Microscopical examinations of fabric-crease cross-sections at progressively higher curvatures, made to investigate the changes in structure involved in the formation of a crease mark, are reported. Measurements made include the radius of the maximum fabric curvature, the length of fabric in a bend, the thread-spacinbg, and the yarn configuration.

18—SOME ASPECTS OF YARN STRUCTURE

Yarn geometry, when the number of constituent filaments is small, is studied here with particular reference to yarn configuration, retraction, diameter, and packing factor. It is shown how, for twist factors within the range 20–40, yarn configuration and therefore yarn diameter remain more or less constant. A new approach to the definition of yarn diameter is put forward and corroborated by experimental evidence. A new formula for yarn retraction on twisting is determined for yarns having filament numbers in the range 1–37, and experimental evidence is given to show how it is more applicable than Treloar's formula when the number of filaments is fewer than 37. Two new definitions of packing factor are considered.