Complex Yarns Research Articles

Numerical Investigation on the Thermal Characteristics of Lightweight Metal Mesh-Based Reflector Antenna with Various Knitting Conditions

Proper prediction of the temperature variation in a metallic wire mesh for spaceborne large deployable reflector antennas is essential for evaluating the dimensional stability of the antenna under extreme on-orbit thermal environments. However, predicting the temperature of a mesh is difficult because of its complex yarn configuration. To analyze the thermal behavior of the spaceborne mesh antenna reflector, the thermal optical characteristics with various knitting methods of the metallic mesh were obtained experimentally in this study. Subsequently, to analyze the thermal sensitivity of the reflector based on its optical properties, an on-orbit thermal analysis of the mesh reflector was performed based on measurements of the mesh specimen. We also investigated the influence of deployable solar panels on the thermal gradient of the reflector.

Multiscale modeling of woven composites by deep learning neural networks and its application in design optimization

Due to complex yarn geometries and multiscale nature, it is very challenging to predict mechanical properties and strength constants of woven composites in an accuracy and efficient way. In this paper, mechanics of structure genome (MSG) is employed to predict effective material properties and strength constants of woven composites. The microscale analysis is performed to compute the effective properties and strength constants of yarns based on a hexagonal packed microstructure. Then, the mesoscale analysis is performed to compute the effective material properties and strength constants of woven composites. The accuracy and efficiency of the MSG method are compared with the computational homogenization method. In addition, simulation data using the MSG model is generated to train deep learning neural networks (DNN) models. The trained models provide ultra-efficient surrogate models with high accuracy. The DNN models are further applied to a design optimization problem to tailor geometry parameters to enhance the mechanical performance of plain woven composites, and the optimization can be efficiently solved with gradients from the DNN models. The developed computational framework can be applied to general woven composites featuring complex microscale and mesoscale features.

ANALYSIS OF TEXTILE MATERIALS USED FOR PROTECTION AGAINST ELECTROMAGNETIC RADIATION

The article is devoted to the actual problem of developing a woven material that would protect against electromagnetic radiation and meets modern requirements for functional performance properties, as well as the technology of its manufacture. The analysis of the works revealed that this topic has not been sufficiently studied. To solve the problem posed in the work, it is necessary: to analyse the complex yarn obtained by connecting a ferromagnetic microwire with cotton yarn in order to determine the possibility of making fabric from it; methods for designing special fabrics with desired properties; to perform the design of a fabric for workwear, with military fabrics used as a prototype.

Study on the Tensile Behavior of Helical Auxetic Yarns with Finite Element Method

Complex yarns with helical wrapping structure show auxetic effect under axial tension and a wide perspective application. Experimental results suggested that initial helical angle was one of the most important structural parameters. However, the experimental method was limited and could not effectively explain the deformation behavior or auxetic mechanism. A finite element model of the helical auxetic yarn was built and used to analyze the interactive relationship between the two components and the stress distribution mode. The effectiveness and accuracy of the model was first verified by comparing with the experimental results. The simulation results showed that the complex yarn with initial helical angle of 14.5° presented the maximum negative Poisson's ratio of -2.5 under 5.0% axial strain. Both the contact property between the two components and the radial deformability of the elastic core filament were key factors of the auxetic property. When the contact surfaces were completely smooth and the friction coefficient μ was set to 0, the complex yarn presented non-auxetic behavior. When the Poisson's ratio of the core filament was 0, the complex yarn showed greater auxetic effect. During the axial stretching, the tensile stress was mainly distributed in the wrap filament, which led to structural deformation and auxetic behavior. A pair of auxetic yarns showed pore effect and high expansion under axial strain. Thus, it may be necessary to consider new weaving structures and preparation methods to obtain the desired auxetic property and application of auxetic yarns.

Design, Manufacture, and Characterization of Auxetic Yarns with Multiple Core/Wrap Structure by Braiding Method.

Auxetic textiles with a negative Poisson’s ratio show significant energy absorption and synclastic curvature characteristics and potential application value in sportsmen protection material. The stability and reliability of the structure and properties of auxetic textiles is also an important factor to assess and promote the application. Thus, auxetic yarns with multiple core/wrap structure were prepared by a 16-spindle braiding machine. It mainly focused on the axial stretching behavior and the relationship between the structure and auxetic effect of yarn samples. The maximum Poisson’s ratio of auxetic yarns was −3.26. The experimental results also showed that the complex yarns still presented an auxetic effect during 30 repeats of cycle stretching. According to the study about the repeatable stretchability and auxetic effect of complex yarns, it could be expected to provide more comfortable, safer, and smarter protective textiles.

Study on the tensile behavior of helical auxetic yarns by modeling and mechanical analysis

Two-component auxetic yarns with helical wrapping structure showed negative Poisson’s ratio under axial tension. It was the interaction force, especially the normal force, between the two filaments that led to the outer contour diameter of the complex yarn being expanded. Both the deformation behavior of structure and cross section presented greater effect on Poisson’s ratio and auxetic effect. However, the previous geometrical model that has been reported was without considering the interaction force between the two components. Mechanical model with axial tension and the normal force was carried out to theoretically calculate Poisson’s ratio of the complex yarn. The results showed that the cross section of the filament was from circular shape to elliptical shape under the normal force. Theoretical value from the mechanical model with considering the effect of normal force on the radial strain was in good accordance with the experimental results of Poisson’s ratio.

New Approach to Preparation of Heat-Resistant "Lola-M" Fiber.

A new approach to the synthesis of polynaphthoylenebenzimidazoles and heat resistant fiber spinning has been developed using an environmentally friendly and energy efficient method, which operates with solutions of pre-polymers based on 3,3’,4,4’-tetraaminodiphenyl ether and 1,4,5,8-naphthalenetetracarboxylic acid dianhydride in N-methylpyrrolidone. Rheological properties of polymer reaction solutions and appropriate coagulant mixtures were investigated for further wet spinning process. The coagulation process was investigated through microscopic observation of solution droplets which imitate jet/fiber cross section surrounded with coagulants of different composition. For the case of the most optimal viscoelastic properties of dopes the best coagulant was found to be a ternary mixture ethanol/water/NMP (20/10/70). Fibers were prepared through the wet spinning from pre-polymers of various molecular weight characterized by intrinsic viscosity. As a result, complex yarns were spun, and their morphology was characterized and mechanical properties were measured. The strength of ~300 MPa and elastic modulus of ~2 GPa and elongation at break of ~20% were reached for the best fibers at average diameter of ~20 µm. After heat treatment “Lola-M” fibers do not burn and do not support combustion in open flame.

Tensile Test Method for Basalt Roving

In the construction industry there is no method for tensile testing of materials of basalt complex filaments of small diameters and roving. The existing methods of testing fibers and roving presented in regulatory documents are intended for textile materials and materials based on fiberglass. The studies cited in the article were aimed at studying the strength properties of roving materials and a multifilament yarn based on basalt fibers, as well as working out methods for testing them. The article presents studies of the strength characteristics of roving and complex yarn based on basalt fiber, on which testing of basalt material samples was tested. The strength characteristics of various forms of basalt materials for various adhesive processing were obtained. The applied experimental test procedure was appreciated positively.

Construction of new enriched beam models accounting for cross-section deformation and pinching

The consideration of nonclassical beam theories beyond Timoshenko beam model is necessary in applications involving complex yarns subjected to transverse compaction, for which the section dilatation and in-plane shear require a detailed kinematic and static modeling. In the present work, new enriched beam elements with additional degrees of freedom are derived from the mechanics of generalized continua, allowing a representation of the in plane-shear and dilatation of sections. As a novel aspect, enriched beam model called macrodilatation, macroshear, and macrostrain have been constructed on the basis of generalized beam theories but with a more condensed kinematics, assuming uniform hyperstress tensor within the beam. The choice of the adequate extended continuum for a given beam depends on its macroscopic deformation mechanisms. As a result, the developed beam models include modified material parameters (the tensile, shear and bulk moduli for an isotropic beam) involving additional microstructural parameters. These macrobeam models are expected to better describe the in plane-shear and dilatation of the beam sections along its mean line in comparison to classical beam theories. Numerical illustrative examples show that the microdilatation beam model has the ability to capture the local deformation field around holes, in contrast to Timoshenko beam model. The parameters of the microdilatation beam model provide a very good estimate of the overall porosity.

A Novel Interlaced-helical Wrapping Yarn with Negative Poisson’s Ratio

The two-component complex yarn with helical wrapping structure has been reported with auxetic behavior and unique performance, however, the residual torque could lead to the slippage of the wrap component from the core in the natural state and poor stability and applicability. Therefore, this paper aims to introduce a novel interlaced-helical wrapping yarn with negative Poisson’s ratio, stable structure, practicability and continuous preparation. The differences in geometry and auxetic behavior between helical structure and interlaced-helical structure were presented and analyzed. Both the structure stability and auxetic effect of the interlaced-helical complex yarn have advantages over the helical wrap yarn with same materials and initial wrap angle. It can be shown that the interlaced-helical wrap yarns with lower initial wrap angle and bigger tensile modulus of the stiff yarns will produce better auxetic effect. Besides, the deformation mechanism and the manufacturing process were described in detail. Several kinds of yarns have been fabricated to discuss the effect of initial wrap angle and tensile modulus on the Poisson’s ratio of the structure. The maximum value of Poisson’s ratio for the yarns manufactured was -2.8. It is also expected that auxetic yarns with novel braided structure can prompt the applications of auxetic textiles.

GAS PRODUCTS OF ARGON PLASMA INTERACTION WITH POLYARAMID AND POLY(ETHYLENE TEREPHTHALATE)

Non-equilibrium plasma is widely used for surface modification of polymer materials. Reactions of plasma active species with polymers lead not only to the surface modification, but to the formation of gaseous products, which change the plasma composition and internal plasma parameters. It results in the dependence of surface etching and modification kinetics on the quantity of material been treated (on sample sizes in a reactor). These phenomena are known as so called “loading effect” and have been studied for the treatment of polypropylene and polyimide films, poly(ethylene terephthalate) films and fabrics in oxygen and air plasma. It can be expected that gas products of noble gas plasma action on polymers will change strongly plasma parameters and modification results. In this paper, experimental data are represented on composition of gas products and their evolution rates at the treatment of polyaramid films, fibers and poly(ethylene terephthalate) fabric in low-pressure argon plasma. Poly(ethylene terephthalate) textile fabric (PET) made of monofilament yarns (SAATI, S.p.A., Italy) and polyaramide (PA) films and complex yarns “Rusar®” (Termotex, Russia) were used in experiments. Direct current discharge was excited in a flow of argon (technical grade) in a glass tube reactor with 3 cm inner diameter. Fabric samples were placed as cylinders on the reactor wall in the discharge positive column. Square of PET samples was varied from 18 to 111 cm2. The PA yarns with the total length of 550 or 1020 cm were placed in the reactor on special holder with the length of 20 cm. Total gas pressure in reactor was varied from 30 to 300 Pa at discharge current of 20 – 110 mA. Gas flow rate in the reactor was kept constant and equal to 30 cm´s-1. Gas phase analysis was carried out by the methods of plasma emission spectroscopy and mass-spectrometry. Plasma emission spectra and mass-spectra show evolution of H2, CO and H2O molecules at the treatment of PA and PET in argon plasma. Evolution rates for different gas products and their mole fractions have been obtained as functions of total gas pressure. Increase in polymer sample square has been shown to result in changing the ratios between evolution rates for different gas products. Sum of CO, H2 and H2O mole fractions increases with polymer sample square and decreases with gas pressure. Dissociation of molecular gas products results in the changing plasma active species. Oxygen and hydrogen atom lines and OH emission bands are observed in plasma emission spectra. Alteration of intensity ratio for О(3p3P ® 3s3S0) and Ar (4p3D3 ® 4s3P2) lines (IO/IAr) versus time after discharge starting shows the possible participation of oxygen atoms in heterogeneous reactions with polymers. Evolution of molecular gas products of heterogeneous reactions influences plasma properties and rates of plasma chemical reactions. The data obtained will be used for the further analysis of mechanisms of heterogeneous reactions of plasma active species with polymers.

A computationally efficient model to predict the uniaxial tensile loading response for dry woven fabrics

Woven structure is an essential component widely used in composite materials, bio-materials and mechanical metamaterials. The mechanical response of the dry woven fabric, which is widely used as reinforcement in composite materials is studied in the present paper. Typically, for the dry woven fabric, the warp and weft yarns are weaved with each other. Each warp or weft yarn also consists of large amounts of small filaments. Because of this multiscale nature, a model that can predict the material response as a function of the underlying structure is important for the design of the dry woven fabric. Hence, a computationally efficient model to simulate the uniaxial tensile loading response for dry woven fabrics is proposed. The proposed model is able to predict the macroscopic loading-deformation response, the effective in-plane Poisson’s effect and the deformation of the thickness by taking into account the influence of the filaments, the weaving pattern and the surface contact at the crossover of the yarns. The accuracy of the model is validated by a digital image correlation (DIC) experiment. For the weaved yarns, complex yarn geometries can be easily modelled and different yarn curve assumptions can be conveniently incorporated in the proposed model. The high computational efficiency of the model makes it potentially helpful for designing woven materials with high mechanical performance.

Study on the structure formation and heat treatment of helical auxetic complex yarn

Currently, auxetic yarns consisting of a core filament and a wrap filament are generally utilized as complex materials, which are attributed to residual torque. Thus, the main content dealt with in this paper was to analyze the structure formation and effect of heat treatment of helical auxetic complex yarn spun by a modified ring-spinning system. Firstly, an orthogonal experiment with three factors and three levels was carried out to study the effects of diameter ratio, yarn twists and initial helical angle on the structure and Poisson’s ratio of complex yarn. Secondly, a heat treatment process with polyamide filament with low melting point (80℃) was conducted to improve the structural stability of auxetic complex yarn. It was found that the heat treatment process can not only improve the structural stability of complex yarn, but also promote the expansion effect. By comparing experimental and theoretical results, it was found that the variation of Poisson’s ratio with axial strain had good consistency. Therefore, the heat treatment method can effectively solve the slippage problem of helical auxetic complex yarn.

Preparation Technique and EMI Shielding Evaluation of Flexible Conductive Composite Fabrics Made by Single and Double Wrapped Yarns

Electronics products and communication equipment release electromagnetic (EM) waves in service. EM waves affect biological health and precision instrument accuracy. This study purposes to fabricate flexible conductive composite fabric which is made of complex yarn using metal (stainless steel, copper) fibers and PET filaments. Complex yarn is formed by a rotor twisting machine, at varying values of wrapped number (6.5-16 turns/cm) and lamination number (single-layer, double-layer). Results show that when the complex yarn was wrapped 16 turns/cm, volume resistivity reached 2.9 Ohm-cm and conductivity reaches 0.408 S/cm. Four layers of conductive composite plied with 0°/90°/ 0°/ 90° resulted in the optimum electromagnetic shielding effectiveness, up to 47.7 dB.

Dynamics of Elongation and Breaking of Complex Yarns and Its Dependence on Filament Properties in Modeling Semicyclic Deformations

The results of a study of dependence of elongation resistance of complex yarns on the same characteristics of filaments with reference to Orlon fibre are presented. The computer model developed for these purposes takes account of nonlinear type of elastic deformation of filaments, dynamics of deformation and breaking, and statistical scatter of breaking characteristics.

Neural network assisted multiscale analysis for the elastic properties prediction of 3D braided composites under uncertainty

The stiffness prediction of textile composites has been studied intensively over the last 20years. It is the complex yarn architecture that adds exceptional properties but also requires computationally expensive methods for the accurate solution of the homogenization problem. Braided composites are of special interest for the aerospace and automotive industry and have thus drawn the attention of many researchers, studying and developing analytical and numerical methods for the extraction of the effective elastic properties. This paper intends to study the effect of uncertainties caused by the automated manufacturing procedure, to the elastic behavior of braided composites. In this direction, a fast FEM-based multiscale algorithm is proposed, allowing for uncertainty introduction and response variability calculation of the macro-scale properties of 3D braided composites, within a Monte Carlo framework. Artificial neural networks are used to reduce the computational effort even more, since they allow for rapid generation of large samples when trained. With this approach it is feasible to apply a variance-based global sensitivity analysis in order to identify the most crucial uncertain parameters through the costly Sobol indices. The proposed method is straightforward, quite accurate and highlights the importance of realistic uncertainty quantification.

Detection of Violations of Technological Process Dynamics By Structural Analysis Method

An algorithm is proposed for analyzing non-stationary time series obtained by monitoring technological processes or properties of the developed unidimensional fibre products (yarn, sliver, roving, tow, complex yarn, etc.). The algorithm is based on the correlation, known from the theory of chaos dynamics, between the trend and the random variations of values and consists in simultaneous evaluation of the trend of average and a range of variations. It can be used to identify and predict the type of nonstationary state in terms of the mean level and variations. The information gathered with its aid will make it possible to predict possible structural changes (bifurcation) in the characteristic features of the trends of time series. The algorithm can be used in many areas of analysis, control, and prediction of technological and technoeconomic processes.

Comfort and Functional Properties of Far-Infrared/Anion-Releasing Warp-Knitted Elastic Composite Fabrics Using Bamboo Charcoal, Copper, and Phase Change Materials

Elastic warp-knitted composite fabrics with far-infrared emissivity and an anion-releasing property were prepared using bamboo charcoal (BC), copper (Cu), and phase-change material (PCM). The functional composite fabric, which was composed of self-made complex yarns with various twisting degrees and material composition, were created using a rotor twister and ring-spinning technique. The fabric structure was diversified by the feeding modes of weft yarn into a crochet-knitting machine. The twist number of complex yarns was optimized by tensile tenacity, twist contraction, and hairiness, and analysis showed that twisting at 12 twists per inch produced the highest tensile tenacity and appropriate twist contraction and hairiness. Comfort evaluation showed that the elastic composite fabrics with BC weft yarns exhibited higher water–vapor transmission rate and air permeability, reaching 876 g/m2∙ day and 73.2 cm3/s/cm2, respectively. Three structures of composite fabric with various weft yarns had >0.85 ε far-infrared emissivity and 350–420 counts/cm3 anion amount. The prepared elastic warp-knitted fabrics can provide a comfortable, dry, and breathable environment to the wearer and can thus be applied as health-care textiles in the future.

Chemical properties of reinforcing fiberglass in aggressive media

In this article describe reinforced fiberglass. Fiberglass – fiber or complex yarn, formed from glass. The main application area of fiberglass and fiberglass textile materials is their use as reinforcing elements of fiberglass plastics and composites. For its consideration, conducted laboratory tests were conducted. As a result of the research was chosen the best of the characteristics of fiberglass.

Influence of yarn folding on UV protection properties of hemp knitted fabrics

In the last years the media have highlighted the damage of the ozone layer and the resulting increase of ultraviolet radiation (UVR) reaching the earth?s surface. Prolonged and repeated, both occupational and recreational, sun exposure of the population causes some detrimental effects. Clothing is considered to be one of the most important tools for UV protection. It is generally accepted that synthetic fibres provide a high UV protection capability of textiles, while cellulose fibres (cotton, linen, hemp, viscose) have a low UV absorption capacity. However, natural pigments, pectin and waxes in natural cellulose fibers, and lignin in hemp fibers, act as UV absorbers having a favorable effect on UPF of grey-state fabrics. Bearing in mind the trend of reintroduction of hemp fibers as a source of eco-friendly textiles, there is a serious lack of study about the potential of hemp materials in terms of UV protection. Folded yarn is a complex yarn composed of two or more component yarns arranged parallel and twisted together to make a ?new quality? yarn. Folding of yarns is an operation undertaken in order to modify single-yarn properties to an appreciable degree. There are very few investigations concerning the relationship between the yarn properties and UV protection effectiveness of the fabric made there from. In addition, there is no any result in the scientific literature about the influence of yarn folding on UV protection properties of textile materials. Having this in mind, for our research the idea was to evaluate the effect of yarn folding in this regard. The plain knitted fabrics composed of single or two-folded hemp yarn were compared in terms of UV protection properties. The Ultraviolet Protection Factor (UPF), as the quantitative measurement of the material effectiveness to protect the human skin against UVR, was determined for the textile materials by in vitro test method according to the European standard EN 13758. The knitted fabrics construction and physical properties were also determined. Bearing in mind that plain knitted fabrics are particularly susceptible to relaxation, they were subjected to relaxation and shrinkage by wetting process, and testing procedure was repeated on the water-treated samples. The results obtained indicated that the folding operation influences UV protection properties of knitted fabrics through an influence on a loop configuration, i.e. the fabric openness. Relaxation and shrinkage of the knitted fabrics due to wet relaxation caused the reduction of macro-porosity increasing the UPF of the knitted fabrics. Although the knitted fabric produced from single hemp yarn was characterized by higher UPF, the UVR transmittance of the folded hemp yarn knitted fabric after wet relaxation placed it in the ?excellent UV protection category? (according to European Standard EN 13758-2). This fact together with the better thermal comfort manifested itself in higher air permeability, confirmed the potential of folding operation in terms of UV protection properties of textile materials.