Properties of yarn pull-out in para-aramid fabric structure and analysis by statistical model

The aim of this study is to analyze and determine the pull-out properties of para-aramid woven fabrics. Para-aramid Kevlar29® and Kevlar129® woven fabrics were used to conduct the pull-out tests. They have high and low fabric densities. A yarn pull-out fixture was developed to test various fabric sample dimensions. Data generated from single and multiple yarn pull-out tests in various dimensions of Kevlar29® and Kevlar129® woven fabrics included fabric pull-out forces, yarn crimp extensions in the fabrics and fabric displacements. The regression model showed that yarn pull-out forces depend on fabric density, fabric sample dimensions and the number of pulled ends in the fabric. Yarn crimp extensions depend on the crimp ratios of the fabric and fabric density. Fabric displacements depend on fabric sample dimensions and the number of pulled yarns.     

Reinforcement of cementitious matrices by warp knitted fabrics

The efficiency of knitted fabrics for reinforcing cementitious composites was studied. Weft insertion warp kiitting fabrics of controlled structure were especially produced for this work consisting of high modulus (Kevlar and Polyethylene) and low modulus (Polypropylene) polymers. The performance of the fabrics was studied by evaluating the flexural properties of the composites and the bond to the matrix. The performance of the knitted fabrics was compared to that of the straight yarns from which the knitted fabrics were made, as well as comparison with woven fabric reinforcement. It was concluded that: (i) in the knitted fabric reinforcement greater efficiency was achieved in fabrics consisting of high modulus polymer yarns, which are made of bundles consising of a smaller number of filaments, (ii) the reinforcing effect of the knitted fabric is smaller than that of the individual straight yarns, (iii) the reinforcing efficiency of woven fabric reinforcement is better than that of the knitted fabric, due to the crimped structure of the yarns in the woven fabric. In view of these conclusions, it might be stated that the use of weft insertion warp knitting fabric for cement reinforcement is advantageous in the sense that the fabric can provide the means by which a composite can be produced with continuous and aligned yarns. However, with this kind of fabric some of the reinforcing efficiency of the individual yarns is lost. In contrast, the use of woven fabric can provide all of the above, with the added advantage of enhanced reinforcing efficiency over the straight yarns, induced by their crimping in the woven fabric.     

Micro-CT analysis of internal structure of sheared textile composite reinforcement

Simple shear is a deformation mechanism typical for a woven fabric during draping. The mesoscopic internal structure of the fabric differs between the non-deformed state and a sheared state. This paper presents an analysis of the internal structure of woven fabrics in a sheared state based on micro-CT (X-ray micro computed tomography) imaging of the internal structure of woven fabrics in a sheared state. Two methods for the analysis of the fabric geometry are used: automatic mapping of the local fibre directions based of the micro-CT image analysis and manual measurements of the yarns cross section shape, size and middle line coordinate of yarns on the micro-CT images. Changes of the fibre orientations within the yarns and of the yarn geometrical parameters in a carbon fibre twill woven fabric before and after shear deformation are quantified.     

Effect of hybrid woven fabrics structure on their electrical properties

The aim of this study is to investigate the influence of hybrid textile woven fabric structure on the electrical resistivity. Weave structure was varied by varying the weave pattern and the conductive yarn density in the woven fabrics. Electrical surface and volume resistivity were measured and compared to the fabric structural properties. Results showed that not only the conductive yarns percentage has an important effect on the electrical resistivity but also the weave structure. The most influencing structural parameter on surface resistivity was the woven fabric surface profile as it controls the contact quality between the conductive yarns and the measuring electrodes. A high surface resistivity was noticed when the contact quality was poor. When this contact quality was good, a linear correlation was found between surface electrical resistivity and the cover firmness factor, the apparent conductive fiber surface area as well as the conductive yarn floating length of the woven structures.     

柔性纺织电阻传感器的研究进展

纺织电阻传感器具有质量轻、柔性好和可拉伸等优良特性,在可穿戴电子产品领域具有很大的应用价值.文中根据近年来不同纺织材料基电阻传感器的研究进展,介绍了无捻纤维(束)基电阻传感器、纱线(长丝纱、短纤维纱、复合纱)基电阻传感器和织物(针织物、机织物、非织造织物)基电阻传感器的制备、性能及应用研究.在纱线基电阻传感器中,主要基...     

Friction core-spun yarns for electrical properties of woven fabrics

This paper reports a study to develop a spinning method of open-end friction core-spun yarn (OFCY) and its conductive fabric for shielding the electrostatic discharge and electromagnetic applications. To facilitate weaving of stainless steel (SW) and to reduce the material cost, initially OFCY yarn was made from SW core and polyester (PET) and stainless steel staple (SS) fibers, produced by a DREF III open-end friction spinning method. The core-spun yarns were woven into a variety of woven structures, which are made from semi-automatic loom, successfully. The conductive fabrics could be suitable for shielding home electronic and electrical appliances, cellular phones, and digital devices from electromagnetic fields. The variations of EMSE, and ESD of the woven fabric structure, and blend ratio of stainless steel yarns are also described. It has been shown that the EMSE and ESD attenuation of the woven fabric can be tailored in a number of ways including fabric structure, density, and the amount of conductive filler material.     

具有保温性能的电纺LA/PET纳米纤维复合织物的制备与表征

本文制备了电纺月桂酸(LA)/聚对苯二甲酸乙二醇酯(PET)纳米纤维/机织物的复合织物,并对其进行了表征.选用纯棉纱线、毛纱线、涤棉纱线、腈纶纱线和涤纶纱线分别作为经纬纱线,在实验室制备机织物小样,同时,通过静电纺丝法制备LA/PET纳米纤维,将LA包裹在PET基材之中.之后通过缝合的方式,将电纺LA/PET纳米纤维和机织物构造成三明治结构的复合织物.对纳米纤维的形貌和热性能进行了表征,并分别探究了LA/PET的质量比,机织物组织结构和机织物材料对复合织物保温性能的影响.结果表明:LA/PET纳米纤维呈圆柱形,具有光滑表面,LA和PET展现出良好的相容性,热焓值略低于理论值,但相变温度改变不大.复合织物的热保温性能测试表明,复合织物的保温性能都优于未加入相变材料的织物,同时展现出良好的热循环稳定性.     

Experimental identification of a lattice model for woven fabrics: Application to electronic textile

Lattice models employing trusses and beams are suitable to investigate the mechanical behavior of woven fabrics. The discrete features of the mesostructures of woven fabrics are naturally incorporated by the discrete elements of lattice models. In this paper, a lattice model for woven materials is adopted which consists of a network of trusses in warp and weft direction, which represent the response of the yarns. Additional diagonal trusses are included that provide a resistance against relative rotation of the yarns. The parameters of these families of discrete elements can be separately identified from tensile experiments in three in-plane directions which correspond with the orientations of the discrete elements. The lattice model and the identification approach are applied to electronic textile. This is a fabric in which conductive wires are incorporated to allow the embedment of electronic components such as light-emitting diodes. The model parameters are established based on tensile tests on samples of the electronic textile. A comparison between the experimental results of an out-of-plane punch test and the simulation results shows that the lattice model and its characterization procedure are accurate until extensive biaxial tensile deformation occurs.     

On the Poisson''s ratios of a woven fabric

Although it is undeniable that the Poisson's effect on the behavior of a woven fabric is crucial, there have been relatively few papers devoted to this subject. In this study, a mechanical model for a woven fabric made of extensible yarns is developed to calculate the fabric Poisson's ratios. Theoretical results are compared with the available experimental data. A thorough examination on the influences of various mechanical properties of yarns and structural parameters of fabrics on the Poisson's ratios of a woven fabric is given. The prediction of Poisson's ratios in this paper will enable more rigorous studies on such important issues of fabric bending and draping behaviors.     

涤纶基材表面沉积Ag/ZnO复合膜形貌结构及性能研究

以组织结构不同的纯涤纶非织造布、机织布、针织布作为基材,采用直流射频共溅法,在织物表面沉积Ag/ZnO复合膜,通过扫描电子显微镜、X射线衍射仪、X射线光电子能谱仪对镀膜织物的表面形貌以及结构成分进行分析,测试了镀膜织物的抗静电、抗紫外线性能。结果表明:沉积Ag/ZnO复合膜后,机织布表面最不平整,针织布表面最平整;纯涤纶非织造布的结晶度较低。X射线光电子能谱表征证明Ag以单质形式存在于纯涤纶非织造布表面;纯涤纶非织造布的抗静电性最差,针织布最好;机织布抗紫外线性能最好,纯涤纶非织造布最差。     

Lateral Compressive Properties of Spacer Fabric Composites with Different Cell Shapes

Spacer fabrics belong to the category of 3D hollow structures, and consist of two separate fabric layers that are connected with pile yarns or fabric layers maintaining hollow space between adjacent connecting yarns or fabric layers. In this study, spacer structures connected with woven cross-links having three different cross-sections of the hollow tunnels: rectangular, trapezoidal and triangular, along the weft direction, were produced using 600 tex E-glass tows. All the sections of the structures were plain 2D fabrics with all constituent layers having the same construction. These fabric structures were then converted to composites, with epoxy resin as matrix, using vacuum assisted resin infusion molding (VARIM) technique. The produced composite samples were characterized for their lateral compressive properties. This study provides an insight into the production of sandwich structures connected with woven cross-links, and their load bearing capabilities. The results indicated that the compressive strength of structure depends mainly on the thickness of the cell walls and its angle with the horizontal layer.     

Effect of Frictions on the Ballistic Performance of a 3D Warp Interlock Fabric: Numerical Analysis

3D interlock woven fabrics are promising materials to replace the 2D structures in the field of ballistic protection. The structural complexity of this material caused many difficulties in numerical modeling. This paper presents a new tool that permits to generate a geometry model of any woven fabric, then, mesh this model in shell or solid elements, and apply the mechanical properties of yarns to them. The tool shows many advantages over existing software. It is very handy in use with an organization of the functions in menu and using a graphic interface. It can describe correctly the geometry of all textile woven fabrics. With this tool, the orientation of the local axes of finite elements following the yarn direction facilitates defining the yarn mechanical properties in a numerical model. This tool can be largely applied because it is compatible with popular finite element codes such as Abaqus, Ansys, Radioss etc. Thanks to this tool, a finite element model was carried out to describe a ballistic impact on a 3D warp interlock Kevlar KM2? fabric. This work focuses on studying the effect of friction onto the ballistic impact behavior of this textile interlock structure. Results showed that the friction among yarns affects considerably on the impact behavior of this fabric. The effect of the friction between projectile and yarn is less important. The friction plays an important role in keeping the fabric structural stability during the impact event. This phenomenon explained why the projectile is easier to penetrate this 3D warp interlock fabric in the no-friction case. This result also indicates that the ballistic performance of the interlock woven fabrics can be improved by using fibers with great friction coefficients.     

Engineering Design and Mechanical Property Characterisation of 3D Warp Interlock Woven Fabrics

3D warp interlock fabrics have been used both in composite materials as fibrous reinforcement as well as in protective solutions against impact mainly due to their improved capacity to absorb energy by higher intra-ply resistance to delamination. However, depending on the type of architecture used, the binding warp yarns may provide different types of mechanical behaviour. By the same, the choice of the yarn raw material coupled with the suited 3D warp interlock architecture is still a challenge to solve due to the lack of knowledge on the optimized fabric parameters to be chosen. Thus, to fill this gap, we have designed, produced on same dobby loom and tested different types of 3D warp interlock architectures (O-T 4 3–4 Basket 3–3 and A-T 4 5–4 Twill 6) with different types of raw material (E-glass EC9 900 Tex, para-aramid 336 Tex and flax Tex 500 yarns). Thanks to these tests, it has been highlighted different mechanical behaviours of 3D warp interlock fabrics with the same weave pattern but with different types of yarns (E-glass, flax and para-aramid) both in the warp and weft directions. It has been also revealed that the warp shrinkage of warp yarns inside the woven structure has a major influence on the whole fabric behaviour.     

Modeling formability of multiaxial warp knitted fabrics on a hemisphere

The aim of this paper is to describe a model for the prediction of the formability of a multiaxial warp knitted (MWK) fabric to a 3D surface. For this purpose, we first characterized in detail the forming behavior of MWK fabrics containing two bias inserting yarns (TBMWK fabric). Through experimental observation, it was found that the two bias inserting yarns always tend to gather along the weft direction. The angle between the two bias yarns has a linear relationship with the perpendicular distance from the measured points to the longitudinal axis of the hemisphere during forming process. The slope of this linear relationship is also linear with the magnitude of radius of the pressing hemisphere provided that the radius is larger than 7 cm.Based on the above finding, a mathematical model is established for predicting the deformations of TBMWK fabrics during the hemisphere-forming process. The shape of flat TBMWK fabric that can yield the corresponding hemisphere during the forming process as well as local deformations can be calculated through this model. The hemisphere-forming experiments show that the present model is workable and accurate. The results from both the model and experiments suggest that the shape of flat TBMWK fabric that can yield the corresponding hemisphere which is close to a rectangular, not to a square as presented by woven fabric.The method developed in the paper has laid a foundation for further modeling of the forming behavior of MWK fabrics onto other 3D surfaces. More importantly, it is of great value to find that the two bias inserting yarns always tend to gather along the weft direction of the fabric which is a starting point for modeling of the forming behavior of MWK fabrics.     

Processing and Properties of Multifunctional Metal Composite Yarns and Woven Fabric

Multifunctional metal composite yarns made of crisscross-section polyester (CSP), antibacterial nylon (AN), and stainless steel wires (SSW) were manufactured using a hollow spindle spinning machine. The core yarn, the inner wrapped yarn, and the outer wrapped yarns were SSW, AN, and CSP, respectively. Process parameters such as wrapping material content obviously influenced the tenacity, elongation, and surface morphology properties of the manufactured multifunctional metal composite yarns. These yarns were then woven into fabrics using a rapier loom. Woven fabric WC-8 was evaluated in terms of its mechanical properties, antibacterial activity, and electromagnetic shielding effectiveness (EMSE). Results showed that the use of SSW and AN in the metal composite yarns improved the antibacterial and EMSE of the woven fabric. Thus, these metal composite woven fabrics can be used in manufacturing personal protective clothing to protect humans from electromagnetic radiation and bacterial cross-infection.     

Determining Effective Thermal Conductivity of Fabrics by Using Fractal Method

In this article, a fractal effective thermal conductivity model for woven fabrics with multiple layers is developed. Structural models of yarn and plain woven fabric are derived based on the fractal characteristics of macro-pores (gap or channel) between the yarns and micro-pores inside the yarns. The fractal effective thermal conductivity model can be expressed as a function of the pore structure (fractal dimension) and architectural parameters of the woven fabric. Good agreement is found between the fractal model and the thermal conductivity measurements in the general porosity ranges. It is expected that the model will be helpful in the evaluation of thermal comfort for woven fabric in the whole range of porosity.     

Tribological properties of woven para-aramid fabrics and their constituent yarns

The tribological behaviours of woven fabrics made from Kevlar® (DuPont's registered trademark) yarns of different linear densities were compared with the friction properties of their constituent yarns with different surface treatments. The latter were examined with a traditional friction meter, and the woven fabrics were studied with a pin-on-disc tribometer in alternate and continuous sliding mode. Scoured fabrics, a poly(tetrafluoroethylene)-coated fabric, and fabrics made of surface-treated yarns (polysiloxane oil, hydrophobic paraffin or ester oil lubricant) were compared. These treatments are not representative of commercial Kevlar® yarn finishes but are suitable models for simulating various tribological situations. Both the yarn texture and the surface treatment have an influence on friction coefficient values. Relative humidity affects the friction coefficient only in the case of hydrophilic surfaces, whereas hydrophobic surfaces exhibit fairly constant tribological characteristics. The largest impact on friction seems to be evidenced by the linear density factor. This comparative tribological analysis could lead the way to correlations between yarn friction, weaving performance and woven structure tribological characteristics.     

Free vibration analysis of orthogonal-woven fabric composites

This paper presents a study on the free vibration analysis of orthogonal-woven fabric composites. The fabrics are composed of two sets of mutually orthogonal yarns of either the same material (nonhybrid fabrics) or different materials (hybrid fabrics). We focus on the repeating unit of the woven structure, known as a `unit cell'. Based upon the one-dimensional (1D) elasto-dynamic analysis developed by the authors for such a woven fabric composite, the free vibration problem is formulated and solved for four basic boundary conditions. Natural frequency equations and natural modes are obtained analytically. For the special case of two bonded isotropic layers, closed-form solutions of natural frequencies and natural modes are given. It has been shown that numerical solutions can readily be carried out for woven fabric composites with arbitrary combinations of material and geometrical parameters. As an example, the first ten natural frequencies for plain weave composites based upon graphite/epoxy and glass/polyester are presented and discussed.     

Highly aligned flax/polypropylene nonwoven preforms for thermoplastic composites

A major challenge for natural fibre composites is to achieve high mechanical performance at a competitive price. Composites constructed from unidirectional yarns and woven fabrics are known to perform significantly better than composites made from random nonwoven mats, but unidirectional yarns and fabrics are much more expensive to manufacture than random nonwoven mats. Here, we report on highly aligned natural fibre nonwoven mats that can be used as a replacement for unidirectional woven fabrics. A drawing operation is added to the conventional nonwoven process to improve fibre alignment in the nonwoven preforms and the final composites. The modified nonwoven manufacturing process is much simpler and cheaper than the unidirectional woven fabric process because of the elimination of expensive spinning and weaving operations. The composites fabricated from the highly aligned nonwoven mats showed similar mechanical strength as the composites made from unidirectional woven fabrics.     

Woven fabric reinforcement of cement matrix

The performance of woven fabric reinforced cement was studied to resolve the influence of the structure of the fabric on its reinforcing efficiency. Special fabrics were produced for this study in which the longitudinal (warp) yarn density was kept constant and the perpendicular (fill) yarn density was varied, in the range of 0 to 22 yarns per centimeter. Specimens for flexural and pull out testing were produced from the fabrics and crimped yarns untied from the fabric. Scanning electron microscope tests were carried out to resolve the microstructure of the composite, in particular at the yarn-matrix interface. The results point to three main conclusions: (1) Woven fabric structure improved the bonding capacity as compared to polyethylene monofilament fibers and cement matrix. (2) The crimped structure of the yarns in the fabric plays an important role in this improvement of the bond, providing mechanical anchoring between the woven fabric and the cement matrix. (3) There is an optimal density of fill yarn in the fabric, which causes the higher flexural strength within the tested densities and matrix formulations. This optimum is achieved in the fabric with five fill yarns per centimeter, and it may be accounted for by the fact that at higher density the matrix does not penetrate efficiently into the spaces in the fabric.