负泊松比经编间隔织物的准静态拉伸性能

为探究织物受单向拉伸时的能量吸收性能与负泊松比之间的关系,测算和表征了基于旋转六边形结构设计和制备的4 种经编间隔织物的负泊松比,并分别对其进行经向和纬向的单向拉伸,通过应力与应变曲线积分换算得到各织物受单向拉伸时吸收的能量。结果发现：织物单向拉伸时的能量吸收性能由结构变形容量和纱线承载容量决定,其中纱线承载容量起主要作用,结构变形容量的影响较小,负泊松比的影响则包括在结构变形容量内;在纱线承载容量相同的情况下,织物受某一单向拉伸时的负泊松比越好,该方向上的能量吸收性能越好。     

Analysis of warp-knitted fabric structure. Part III: theoretical study on initial modulus of warp-knitted fabrics (reverse locknit,three- and four-needle sharkskin)

In the second part of this series, tensile properties of tricot structure were investigated. Then derived model was extended to locknit and satin as first group of fully thread two-needle bar warp-knitted fabrics. In the present study, tensile properties of second group of these warp-knitted fabrics, i.e. reverse locknit and three- and four-needle sharkskin, are considered using energy method and Castigliano’s theorem. For this purpose, the difference between the tensile properties of first and the second group of warp-knitted fabrics is attributed to the movement space and friction of back bar underlaps. Similar to previous part, free-body diagrams of elements are drawn to show the relative magnitude and direction of all forces acting upon an object in a given situation. Finally, the initial modulus of second group of warp-knitted fabrics is obtained.     

Experimental and computational analysis of acoustic characteristics of warp-knitted spacer fabrics

Abstract

As a kind of porous medium, textiles have recently received increased attention for acoustic applications due to their high profitability and low cost and environmental impact. 3D knitted spacer fabrics stand out as a unique class of textile materials. These materials simultaneously are soft, voluminous and highly porous and therefore are expected to be suitable for sound absorbing applications. This article aims to investigate the acoustic performance of 3D warp-knitted spacer fabrics. To this end, acoustic behavior of warp-knitted spacer fabrics was experimentally measured using the impedance tube method. In order to predict the sound absorption behavior of fabrics, a simple geometrical model was created. Flow resistivity was calculated by numerically solving incompressible laminar Newtonian flow through the 3D pore space of generated structure. The frequency-dependent sound absorption coefficient of the warp-knitted spacer fabric was predicted using the empirical models of Delany and Bazley, Garai and Pompoli and Dunn and Davern. The results showed that the Dunn and Davern model can predict sound absorption characteristics of warp-knitted spacer fabrics in the mid-to high-frequency ranges. At low frequency ranges; however, none of the empirical models can reasonably predict sound absorption behavior of the fabrics.     

Analysis of warp-knitted fabric structure. Part II: theoretical study on initial modulus of warp-knitted fabrics (tricot,locknit, and satin)

In the first part of this series, a 3D straight line model was presented for the geometry of two-guide-bar warp-knitted fabrics. In this part, first, the variation of unit cell geometry under uniaxial tension in the range of elastic deformation is investigated. In the present study, the energy method and Castiglianos's theorem were used to derive the fabric's initial modulus. Energy terms which are considered in this study are extension, bending, and compression energies. Also, the friction phenomenon is taken into account by using frictional energy term. For this purpose, the loop of each bar is divided into eight elements. Free-body diagrams of elements are drawn to show the relative magnitude and direction of all forces acting upon an object in a given situation. After obtaining the force details, strain energy of each element is calculated. Finally, the initial modulus of warp-knitted fabrics is obtained. To verify the model, samples of tricot fabrics were produced and tested. Results showed that the generated model can predict precisely the initial modulus of aforementioned warp-knitted structures.     

经编间隔织物的应用及其发展

介绍经编间隔织物的特性,指出经编间隔织物在座椅包覆、鞋材、箱包和床垫等方面的常规应用及其优势,并根据当前经编间隔织物结构和原材料的发展,详述经编间隔织物在时装面料、成型鞋材、卫浴产品、建筑增强材料、农业无土栽培和包装材料等方面的新应用,得出经编间隔织物的三个未来发展方向——个性产品、功能产品和智能产品。     

Study of tensile properties of plain-woven fabrics in all-directional using energy method,Part II: experimental verification

Abstract

In the previous part of this series, ‘Comprehensive Tensile Modulus (CTM)’ was introduced as an important modulus to express the force-elongation behavior of plain-woven fabrics when the force is imposed on the fabric and extended it simultaneously in all directions. A theoretical model was presented to predict this modulus in the initial elastic region. In order to verify the accuracy of the model, a novel tensile test method was developed to measure load-extension curve of the fabric samples under the proposed loading condition. Thereafter, six plain-woven fabrics were produced with different raw materials and densities then were washed and dried to reach the relaxed state. Fabric samples were tested using the new method. The fabric’s experimental Comprehensive Tensile Modulus (CTMs) were determined from the results of the tests in all directions by the nine-point central difference method, and the calculated data were analyzed statistically to obtain the experimental CTM of fabrics. Reasonable agreement between theoretical and experimental results confirmed that the generated model is capable to predict the CTM index as a tensile property of plain-woven fabrics, adequately. The comparison between results of the theoretical model and experimental test shows that maximum error of prediction is 8.5% which is recorded for the grey fabric sample constructed from the OE Cotton yarn with nominal yarn count 24 Ne. Also, maximum experimental comprehensive tensile modulus (17.9 N/mm) is for the grey fabric sample constructed from the high tenacity continuous filament of Nylon with nominal yarn count 900den, in one millimeter extension with maximum modulus in warp and weft directions, that is, 5.6 N/mm and 6.6 N/mm in the same extension in the initial linear elastic region, respectively.     

Study of tensile properties of plain-woven fabrics in all-directional using energy method,Part I: theoretical study

Abstract

In the first part of this series, a new mechanical parameter, that is, “Comprehensive Tensile Modulus (CTM)” is introduced and modeled to show the tensile behavior of plain-woven fabrics in the initial linear elastic region of the force-elongation curve subjected to tensile load and extended it simultaneously in all directions. Considering the initial load-extension behavior of fabrics, a mathematical-mechanical model is presented to predict the CTM of fabrics in the initial linear elastic region using Castigliano’s theorem. Based on the generated model, the initial sample length, dimension of the load imposed region, the geometrical shape created in the plain-woven fabric sample during tensile, the structural specification of these fabrics such as yarns sett, yarns crimp in fabric and mechanical properties of yarns such as bending rigidity in both warp and weft yarns affect in the comprehensive tensile modulus of fabric. In order to verify the conformity and accuracy of the model, a preliminary test was conducted on the prepared samples based on a novel tensile test method developed to measure load-extension curve of the fabric samples under the proposed loading condition. A reasonable agreement was found between theoretical and experimental results.     

Permeability and impact properties of warp-knitted spacer fabrics for protective application

An experimental investigation was carried out to study the effect of interlining material on the comfort and dynamic deformation characteristics of body armour. Suitable plies of interlining materials were selected based on the fabric comfort properties and the impact resistance specified for ballistic application. Kevlar woven fabric was used to block the projectile, and the spacer fabric was used as an interlining material to ensure wearing comfort and for imparting impact resistance. The yarn denier of the middle and bottom layers of the spacer fabrics was maintained constant, and three different deniers were used for the face layer. Three different plies of spacer fabrics were analysed by means of thermophysiological comfort properties to select the suitable interlining material for body armour. The experimental results confirm that the number of plies of spacer fabrics has significant influence on the ballistic armour characteristics than the face layer denier as proved by two-way ANOVA. The substantiated spacer fabric was used as an interlining material, and the depth and area of deformation were analysed. The research findings demonstrated that the three-plied warp-knitted polyester spacer fabric produced better results than single- and five-plied spacer fabrics. One-way ANOVA and Turkey’s HSD also confirmed the influence and interaction of different plies of spacer fabrics.     

负泊松比经编间隔织物的抗低速冲击性能

为研发具有不同负泊松比效应的经编间隔织物,对5 种负泊松比经编间隔织物试样进行落锤冲击实验,通过冲击载荷与时间和位移的关系曲线分析5 种织物在低速冲击载荷下的形态变化和能量吸收性能,研究负泊松比织物在低速冲击下的能量吸收性能与负泊松比值及初始冲击能量的关系。结果表明：织物的能量吸收性能随织物负泊松比值的增大而提高,织物的能量吸收性能越好,耐冲击性能也越好;初始冲击能量的大小也会影响织物的能量吸收速率和耐冲击性能,初始冲击能量越高,织物的耐冲击持久性越差,但对织物总的能量吸收影响不大。     

针织间隔导电织物的压力电阻传感性能

为了研究针织间隔导电织物的压阻传感性能,将镀银锦纶与锦纶/氨纶包覆纱在无缝成型内衣机上进行编织,制备了3种纬编导电织物,将其与经编间隔织物结合,测试并得到了电阻随应变的变化规律,分析了导电区域面积及压缩方式对电阻-应变传感性能的影响。结果显示:压缩面呈平面时,压缩过程分为电阻随应变的增加先缓慢减小、再急速下降两个阶段;曲面压缩时,压缩过程分为电阻微弱减小、缓慢上升、急剧下降三个阶段,其中曲面压缩阶段Ⅲ和平面压缩阶段Ⅱ均具有较好的线性度和灵敏度,且前者灵敏度优于后者;当传感面积为35 mm×35 mm,且从织物横列方向进行曲面压缩电阻的测量时,传感器的综合传感性能最佳。     

A modeling study on the lateral compressive behavior of spacer fabrics

Van Wyk’s equation was considered to study the lateral compressive behavior of spacer fabrics. To prepare the spacer fabrics, different monofilaments were fabricated between two solid spastic sheets, one centimeter apart. Two types of monofilaments and three different forms of arrangement were used. Compressive tests were carried out using a Zwick tensile tester set in compressive mode. The results show that there is a good linear correlation between the compressive force and inverse thickness cubed of spacer fabrics as long as the fibers behave elastically. It can be concluded that the Van Wyk’s equation can be adapted to predict the lateral compressive behavior of spacer fabrics with an acceptable accuracy. The results also revealed that the position and arrangement of the middle monofilament has significant effect on the lateral compressive behavior of the spacer fabrics.     

三维间隔织物复合材料的制备及拉伸性能研究

介绍三维间隔织物复合材料的制备方法,并采用Instron 5969型万能材料试验机对三维间隔织物复合材料的拉伸性能进行测试,重点分析间隔高度、经纬向等结构参数对三维间隔织物复合材料拉伸性能的影响。结果表明:三维间隔织物复合材料拉伸性能随间隔高度的增加而下降;纬向拉伸性能优于经向。     

经编间隔织物的冲击性能

为探讨间隔织物在一定冲击能量下对人体(支撑物)的保护性能。采用的原料为在拉舍尔双针床经编机上编织的6种不同结构(不同间隔丝梳栉横移针距、间隔丝直径和织物厚度)的间隔织物。分析了不同织物在一定冲击能量下的应力、能量和能量吸收效率特征。实验结果表明,随着间隔丝梳栉横移针距数的减小、间隔丝直径的增大,冲击产生的应力峰值减小,吸收的能量和能量吸收效率峰值增加,但间隔丝过于接近垂直的织物容易发生倒伏,不利于人体保护。较厚的织物产生的应力峰值小、吸收的能量多,中等厚度的织物能量吸收效率峰值高。刚度或厚度大的织物由于产生的应力峰值小有利于人体保护,但在选择织物结构时还需考虑人体穿着的舒适性。     

间隔机织物的卷绕、切割和存储系统

描述了间隔机织物的新型卷绕、切割和存储系统的设计.这种系统的关键问题是间隔织物包含织物结构如间隔,即所谓的交联.为了防止玻璃纤维-聚丙烯混纺纱线中玻璃纤维被破坏,必须避免交联塌陷.这种织物被用作热塑性纺织增强复合材料模件的预型件.     

玻璃纤维多轴向经编复合材料的制备及拉伸性能研究

以环氧树脂为基体,分别以玻璃纤维多轴向经编针织物和玻璃纤维机织物作为增强材料,通过手糊法制备复合材料,并通过试验对比研究两种复合材料的拉伸性能。结果表明,经编复合材料沿各个轴向的拉伸强度比复合前多轴向经编针织物及机织复合材料的强度均有明显提高,增幅均在50%以上,说明多轴向经编复合材料具有更优异的力学性能。这为进一步扩大玻璃纤维多轴向经编复合材料的应用领域提供了有力证据。     

废棉再生气凝胶/经编间隔织物复合材料的制备及其性能

针对废旧纺织品制备纤维素气凝胶存在强度低、脆性高、韧性差的问题,将废旧棉花溶解在氢氧化钠/尿素水溶液体系中得到棉纤维素气凝胶(CFA),然后将经编间隔织物(WKSF)与其进行原位复合,经冷冻干燥得到CFA/WKSF复合材料,并对其形貌、压缩和隔热性能进行分析与研究。结果表明:CFA/WKSF复合材料保持了气凝胶的多孔网状结构;WKSF的加入使CFA的力学性能得到提高,其中编链和衬纬结构WKSF的加入使得CFA的压缩弹性模量和屈服强度分别提高了180%和450%,六角形网孔结构WKSF的加入使得CFA的压缩弹性模量和屈服强度分别提高了70%和312%;加入六角形网孔结构WKSF后,CFA/WKSF复合材料的导热系数相比CFA仅增加5%,仍具有良好的隔热性。     

三维横编间隔织物的编织工艺及其性能

为开发适合不同应用领域的曲面复合材料,采用新型三维曲面间隔结构,在电脑横机上用芳纶纱编织了带有双层罗纹连接中间层的横编间隔织物,探讨了编织步骤和编织工艺。在此基础上通过在间隔织物纬向的2个表层衬入芳纶增强纱,改进了织物的力学性能。通过调整编织程序,开发出不同曲率的间隔织物。在英斯特朗电子万能材料试验机上测试有增强纱和无增强纱织物的横、纵向拉伸性能,比较分析这2种织物的应力应变曲线。结果表明,在其他条件相同时,有增强纱的三维横编间隔织物横向、纵向拉伸应力增加明显,变形较少,织物尺寸稳定。     

Experimental methods to determine in-plane material properties of polyurethane-coated nylon fabric

Experimental procedures have been developed to obtain the mechanical stiffness and strength properties of an orthotropic polyurethane-coated nylon fabric for use in a finite element analysis of an inflatable, deployable structure. A method that utilizes a specialized material test fixture and photogrammetry to collect the linear and angular displacement data has been employed. Different material holding methods were compared with the objective of producing strength values not influenced by gripping and that allow for use of machine displacement to estimate longitudinal strains during cyclic testing. A series of tension and bias tension tests provided material properties such as Young’s modulus in both warp and fill directions, Poisson’s ratios in plane and through the thickness, and shear modulus. Results obtained from the photogrammetry method show good correlation to machine readings using a pinched gripping method. Additionally, cyclic tests gave the continuous load–unload response and the hysteresis characteristics of the stress–strain in plane and indicated the degree of material degradation. The shear stress–shear strain behavior and shear modulus values are acquired using bias tension tests on 45° skewed specimens.     

Investigation on thermo-physiological and compression characteristics of weft-knitted 3D spacer fabrics

The thermo-physiological comfort and compression properties of knitted spacer fabrics have been evaluated by varying the different spacer fabric parameters. Air permeability and water vapor transmission of the fabrics were measured using the Textest FX-3300 air permeability tester and PERMETEST. Thermal behavior of fabrics was evaluated by (TCi) thermal conductivity analyzer and overall moisture management capacity was evaluated by moisture management tester. Spacer fabrics compression properties were also tested using KES-FB3. In the KES testing, the compression resilience, work of compression, linearity of compression, and other parameters were calculated from the pressure–thickness curves. Analysis of variance was performed using new statistical software named QC expert trylobite and Darwin in order to compare the influence of different fabric parameters on thermo-physiological and compression behavior of samples. This study established that the raw materials, type of spacer yarn, density, thickness, and tightness of surface layer have significant influence on both thermal conductivity and work of compression in spacer fabrics. The parameter which mainly influences the water vapor permeability of these fabrics is the property of raw material i.e. the wetting and wicking properties of fibers. The Pearson correlation between moisture capacity of the fabrics and water vapor permeability was found.     

Deformation characteristics of flexible PU-coated multi-axial warp knitted fabrics under uniaxial tensile

Based on the characteristics of high tenacity, low density, flexible design, the coated fabric has emerged as a promising construct for tensile test. Here, it reports the deformation mechanism of a PU-coated multi-axial warp-knitted fabric under uniaxial tensile via a digital image correlation system. Specimens produced by us are chase in three fibre-reinforced directions namely 0°, 45° and 90°, respectively. The result shows that the crease does not have an effect on the deformations in the small deformation range (strain < 5%), and the deformation was evidently occurred near the fixed end lags because of the faster movement of specimen at the loading end, and the transverse shrinking at the edges is faster than that in the middle of the specimen. In the large deformation range, the strain fields are inconsistent at the same displacement revealing that the deformations of this kind of flexible coated fabric is in-homogeneous under tensile.