Total porosity,theoretical analysis,and prediction of the air permeability of woven fabrics

Air permeability is one of the most important properties of textile materials that ensure their comfort. For many materials for technical applications (filters, sails, vacuum cleaners, parachutes, etc.), this is one of the main properties that determine their quality. The air permeability of woven textile fabrics depends on many parameters of fabric. Thus, the determination of air permeability of woven fabric is highly complex and difficult. In this study, we attempted to establish a theoretical model for the porosity and predicted the air permeability of woven fabrics. A theoretical model was created to predict the total porosity and the air permeability of a fabric structure depending on the geometrical parameters such as pore size, warp density, weft density, fabric thickness, number of yarn, diameter of yarn, and fiber density. For the purpose, a theoretical model of porous systems on D’Arcy’s law was used, and the validity of the model was confirmed by experimental results using 100% cotton and 97/3 cotton/lycra woven fabrics. Since the amount of air passing through both the pores between yarns and the interstices in the fibers constituting the yarn structure was calculated, theoretical values of air permeability were obtained very close to the experimental values.     

Investigation of image registration method for the multi-directional image fusion of woven fabrics

Abstract

Traditional single-side scanning or single-vision image acquisition methods have the limitation of incomplete information caused by the existence of blind spots. To collect the complete texture information of fabric images, a new multi-vision image acquisition and the related fusion method is developed to solve this problem. However, linear addition of image sequences acquired from multiple directions cannot achieve a good result of image fusion, it is necessary to conduct the image fusion based on the image registration between images at pixel level. Therefore, a new multi-directional digital image acquisition system for woven fabrics is established in this article; one set of image fusion algorithm based on image registration is proposed for the image enhancement of fabric. Fabric texture images are digitized by means of multi-directional vision imaging instead of unidirectional imaging, the structural information of fabric texture could be enhanced using image registration and fusion technology and the indexing and localization of texture corresponding points could be controlled using matching points or control points. Our experimental results show that the proposed method could be used to merge the effective information from the multi-directional vision images completely, it has the potential application for the rendering of woven fabrics using image driven virtual reality enhancement.     

应用图像法的织物弯曲刚度计算

为评估虚拟服装所采用织物模型的准确性,有必要通过图像法全面对比虚拟织物和真实织物的弯曲性能,因此提出了基于图像分析的方法计算织物的弯曲刚度。为了采集织物在悬臂梁状态下弯曲形态的图像,设计了织物弯曲仪。真实织物在自重弯曲下边缘存在翘曲现象,必须从翘曲织物的侧面形态中确定一条可以代表其弯曲性能的曲线。分别计算了翘曲织物上、下边缘曲线的弯曲刚度,提出了采用中值曲线表示织物弯曲性能的方法。实验结果表明,通过中值曲线得到的弯曲刚度和KES法得到的弯曲刚度存在很好的线性相关度,且在45°和41.5°斜面上的测试结果也具有很好的一致性。     

Tensile characteristics and stress relaxation analysis of woven fabrics in terms of fabric direction

Abstract

Woven fabrics in various end uses are subjected to tensile loads in different directions, so investigation of the effect of fabric direction on the tensile behaviour and the stress relaxation performance of fabrics is important and needs to be considered. In this study, the tensile and stress relaxation properties of woven fabrics with five various weave structures have been analysed, in different directions. It was concluded that the tensile properties of fabrics such as Young’s modulus, breaking load and elongation and also the work of rupture were significantly affected by the fabric direction and weave structure. Moreover, it was determined that the fabric tensile stress relaxation (%) was considerably affected by the applied strain level, fabric direction and weave structure in the confidence range of 95% and it might well be expressed as a Gaussian function of sample direction.     

The mechanical performance of plain and plain derivative woven fabrics reinforced composites: tensile and impact properties

In this work, the mechanical performance of the plain and plain derivative woven fabric reinforced composites, were investigated. Tensile strength, modulus of elasticity, elongation at break and poison ratio values of the composites were found by tensile tests. In addition, drop-weight impact tests were performed at several impact energies: 15, 20, 25, 30 and 35 J in order to characterize the impact resistance, and damage mechanisms of the composite plates. The results reveal that the weaving pattern affects the tensile properties and the impact behaviour of the composites. It is observed that 2/2 matt woven fabric reinforced composite showed the best performance in tensile tests along warp direction; whereas, 2/2 warp rib woven fabric reinforced composite showed the best performance during tensile tests in weft direction. It is also observed that 3/1 matt woven fabric reinforced composite absorbs more energy for perforation than the others.     

基于图像光影重构的缎纹影光织物明度预测方法

为更准确获取缎纹影光组织织物的明度值,提出一种基于织物图像光影重构的明度预测方法。将织物图像分离为经纬图形层、阴影层和材质层,计算3层中不同因素的相对面积率,并赋予各图形面积以实际经纬纱线明度值,采用明度相加重构织物图像明度值,再将重构明度与织物实际测色数据进行拟合分析。选择经纬图形、投影和杂点面积率为自变量,建立经、纬两向加强织物的明度预测回归模型,并随机选取样本检验模型精确度。结果表明:经纬图形层重构明度与织物实测明度的接近度为0.15,依次增加阴影层和材质层明度,则接近度从0.76提升为0.89;模型预测的织物明度总体相对误差在±4%以内,预测结果可为影光组织织物设计提供参考。     

Finite element analysis of monofilament woven fabrics under uniaxial tension

Mechanical behavior of woven fabrics under tensile load is complex because their deformation could result from the combined effects of tension, compression, bending, and shear. In this study, the tensile behavior of woven fabrics is simulated using finite element method. The input parameters are the mechanical properties of constituent yarns obtained from tensile and friction coefficient tests and the geometry of woven fabric repeating unit. First, a 3D geometric model of the repeating unit based on Pierce’s model was built using computer-aided design tools. Then, finite element analysis which incorporates material properties, frictional contact, and periodic boundary conditions was implemented using ANSYS. A non-linear mechanical behavior was defined. Frictional contact algorithm for the cross-sectional zone of the repeating unit and periodic boundary conditions to the contour of the repeating unit was implemented. Numerical simulation data and experimental data were compared, which showed good agreement.     

织物毛细孔径分布与其组织结构及组分的关系

由于织物组织结构及组分对织物毛细孔半径及其分布有影响,采用质量分级法,测定5种组织结构的棉和涤/棉机织物的毛细孔半径分布。分别考察纱线线密度、织物经纬密和组分对织物毛细孔径分布曲线的影响。结果表明：这些织物的孔径分布曲线大都由4个区段构成;随着纱线线密度的减小,整个孔径范围明显扩展,其中最小孔径略有增加,最大孔径显著增加,最大比例孔径显著减小;随着经纬密的降低,分布曲线的部分区段被压缩甚至和其他区段归并,织物孔径分布趋于简单化和均匀化;织物的组分并不影响其孔径分布曲线的特征形状,只是在不同区段曲线略有压缩和伸展变形。     

Acoustic performance of woven fabrics in relation to structural parameters and air permeability

This work deals with the study of the acoustic characteristics of woven fabrics in relation to fabric structural parameters and air permeability. In order to achieve the objectives of the research, sound absorption coefficient of woven fabric samples was determined via impedance tube method. Samples with various pick densities and yarn twist were used. The effect of fabric thickness was analyzed using three and six layered test samples. Results showed that, while for all samples the minimum values of sound absorption were observed at frequency bands of 250 and 2000?Hz, the maximum sound absorption occurred at the frequency of 1000?Hz. Results also indicated that fabrics woven at pick density of 30?thread/cm exhibited higher sound absorption than fabrics woven at other pick densities. It was found that, noise reduction coefficient of three and six layered samples, woven at low pick densities showed significant increases in comparison to those woven at high pick densities. It was also established that samples woven with lower weft yarn twist absorb sound wave more efficiently. It was concluded that fabric air permeability can be used as a criterion of sound absorption behavior of woven fabrics.     

Application of discriminant analysis to parameters describing the drape for two types of woven fabrics

A total of 33 commercial drapery and lining fabrics were used to determine the drape indicators drape ratio and R-factor. The slope of a plot of one indicator against the other was found not to afford complete characterization of drape shape for fabrics of different commercial use. In this work, further six parameters describing the drape, proposed by the authors to discriminate drape shapes were also calculated. Discriminant analysis of the data revealed that a linear combination of various parameters allowed two types of woven fabrics (viz. drapery and linen) to be distinguished. The discriminant function used accurately classified 75.76% of the fabrics studied.     

基于ABAQUS的三原组织机织物拉伸力学性能模拟

为更好地了解平纹、斜纹和经面缎纹3种基本组织纯棉机织物抵抗外力拉伸变形的能力,在实际测量织物结构参数的基础上,提出一种评价和预测机织物拉伸性能的方法;借助专业纺织建模软件Texgen建立织物三维细观模型;利用有限元软件ABAQUS,依据织物拉伸环境设置材料属性、相互作用和边界条件等计算模型数值解;通过织物拉伸强力测试实验验证数值模拟结果的有效性。结果表明:平纹织物、斜纹织物和经面缎纹织物拉伸应力、应变模拟结果与实验测试结果差异率均在6%以内;在原料、经纬纱密度和捻度、织物经纬密都相同的条件下,平纹织物抵抗外力变形的能力更强。     

基于数码技术的机织物组织设计原理和方法

通过对机织物的结构特征及组织设计的特点进行分析,并结合数码设计技术的应用,提出一种机织物组织设计的新原理和方法。以全息组织替代传统单一组织的设计模式,设计的全息组织可以建立相应的组织库,组织库中的组织可以替代应用来改变织物效果,但不会改变机织物交织平衡的结构特征。以机织物的经纬交织平衡分析为基础,设计的织物结构能满足机织物大批量生产的技术要求,可以方便地应用于数码机织物的产品创新,特别是分层组合设计模式下数码提花织物的创新设计。     

Theoretical analysis of geometrical and mechanical parameters in plain woven structures

An analytic solution for the estimation of structural parameters and initial tensile modulus of plain woven fabrics under uniaxial tensile loading in their linear elastic domain of deformation is presented. For this purpose, a new approach in straight line geometry with a parallel segment to the fabric plane and an inclined segment at the weave intersection in 3D form is proposed which leads to the theoretical estimation of all the structural parameters of plain woven fabrics with saw-tooth geometry. Defining and applying of JJ₂ Ratio in the model enable us to modify the geometrical model and estimate the value of structural parameters considering the history of samples influenced mainly by its manufacturing process. The strain energy method and Castigliano’s theorem are used for the mechanical analysis of the structure. The elasticity, bending, shearing, and compression rigidity of yarns are incorporated into the model. It has been shown that predicting the geometrical and mechanical parameters of woven fabrics before production are possible if and only if the crimp value of the fabrics can be estimated before their production. The proposed theory is validated and compared by applying into some experimental data and a previous model.     

Effect of woven fabric structure on the air permeability and moisture management properties

In this study, six different woven samples were produced on air jet loom with two different weave designs (i.e. 3/1 twill and 1/1 plain), three different picking sequences (i.e. single pick insertion (SPI), double pick insertion (DPI) and three pick insertion (3PI)). All the woven samples were singed, desized, bleached and finished together at industrial scale, as a single lot. The effect of these factors on the wetting, wicking and air permeability (AP) of the fabric samples was analysed. It was revealed that the fabric weave design and picking sequence has statistically significant effect on fabric wetting time, water spreading speed and AP of the fabric. It was found that fabrics woven in twill weave design and with simultaneous 3PI give significantly better AP, shorter wetting time and better water spreading rate as compared to plain woven fabrics and those with double or SPI. It could be concluded that the thermophysiological comfort of woven fabrics may be significantly improved simply by selecting a suitable weave design and picking sequence.     

三维正交整体夹芯机织物的结构设计及织造

以正交结构为基本的三维结构单元,通过改变空心各边的长度和厚度,设计了多种经向截面为六边形的三维整体夹芯机织物结构,并在改造的普通织机上织造成功。在此基础上对试样的结构特点进行对比分析,同时探讨了三维正交夹芯机织物孔形尺寸的影响因素,比较了各种三维整体夹芯机织物试样的结构特点及织造方法。该研究为三维整体夹芯机织物的结构设计提供了参考,设计的多种三维夹芯机织物为蜂窝结构复合材料提供了性能良好的增强体。     

基于图像分析的织物外观质量综合评价

 针对织物外观质量主观评价结果不够准确的现况,本文构建一种基于图像灰度分析的方法,可数字化对织物外观质量进行描述及评价。通过构建灰度极差值、纹理均匀度、能量极差值、对比度极差值、粗糙度极差值等五个灰度特征描述织物各方面外观质量状况,给出一种基于数量级调整及可变权重的织物外观质量综合评价模型,将五种特征进行数字化综合计算,以精确对织物外观质量进行综合评价。实验及分析显示,该方法能较为合理的对织物外观质量进行数字化综合描述及评价,为织物外观质量的客观化、标准化评估提供了一种新的研究思路。     

机织物隔声性能的测试与分析

用自开发的一种针对纺织品的隔声性能测试系统,对机织物的隔声性能进行了测试。结果表明机织物具有的隔声性能以高密度多层结构织物的隔声效果最好。     

蛋白酶对羊毛机织物改性的可行性分析

分别利用诺和LanL、WSLnew及其复合酶对羊毛机织物进行改性处理,经正交实验得出:使用双氧水预处理后,将诺和LanL与WSLnew复合使用,处理羊毛机织物可得到优良的改性性能,经弱酸艳蓝RAW染色的上染速率明显提高,强力保留率可达87%左右.     

基于孔径分布图的高密织物防水透湿性能

为研究高密织物孔径分布对防水透湿性的影响,采用沸水收缩率分别为21.7%和10.2%、线密度比为1∶1.1的异收缩PET复合丝,通过丝的异收缩使织物蓬松,缩小织物中丝间孔径,增加丝内孔隙。测试分析了4种温度处理的织物孔径分布图与防水透湿的关系。结果表明,高密防水透湿织物的孔径分布图呈左偏不对称形态,分布图从右向左可分为平台区、缓增区、顶峰区和缓减区。随着复合丝收缩增大,各区域有合并的趋势,最大孔径减小,主体孔径向左偏移。收缩最大的孔径分布图中,表征丝内孔隙的顶峰区,孔径范围为4~6μm,小孔百分比达76.8%;表征丝间孔径的平台区,10~31.1μm的大孔所占比例只有8.9%。孔径分布图中缓增区和顶峰区也就是小孔的量对透湿性起主导作用,平台区也就是大孔对织物的防水影响显著。     

Effect of structural parameters of porous yarns and fabric on air permeability and moisture transfer of double-face woven fabrics

In this study, effect of fabric structural parameters of double-face woven fabrics including kind of porous yarn namely micro-porous yarn and hollow yarn, hole size of hollow yarn, percentage of these yarns in double-face woven fabric structure, and finally weft density on air permeability and moisture transfer of woven fabrics was evaluated. These yarns were produced by using water-soluble continuous polyvinyl alcohol filaments as core part for hollow yarns and as doubling yarn in micro-porous yarn. Results revealed the effect of kind of porous yarn, hole size of hollow yarn, and weft density on air permeability and moisture transfer of woven fabrics. The percentage of porous yarns as weft did not show obvious trend. Analysis of variance was used to study the effect of these variables on air permeability and moisture transfer of double-face woven fabrics statistically.