Optimization of textile parameters of plain woven vascular prostheses

This paper investigates and reports the effect of some textile parameters (yarn and fabric parameters) on the main performances of plain woven vascular prostheses in order to enhance their overall quality. We weaved tubular structures with different fabric densities using texturized Dacron® polyester filament yarns with different linear densities and filament counts, in warp and weft directions. The performances of the manufactured samples, such as wall porosity, water permeability and mechanical features, have been tested. By adopting a two‐level fractional factorial design of experiments, the responses were fitted to predictive models using a multiple linear regression method. The models were tested by variance analysis and validated by correlation between measured and predicted values. We determined the optimum settings of main textile parameters enhancing plain woven vascular prosthesis quality by contour plots method.     

平纹机织物空间参数化模型及仿真

在Peirce模型的基础上,采用圆弧和切直线描述纱线的屈曲形态,采用圆形描述纱线截面形状,基于坐标变换原理,建立了平纹机织物空间三维形态的数学模型。在此基础上,采用MATLAB语言编程,对平纹机织物进行参数化建模,实现平纹机织物在不同经纬纱线直径、不同经纬纱线密度、不同结构相下的三维仿真,并通过颜色插值、添加光源等改进模拟效果。     

Computer simulation of plain woven fabric appearance from yarn photographs

This article proposes a method for simulating plain woven fabric appearance based on photographs taken by still camera of actual yarns along their lengths. The survey mathematically models the transformation of yarns from a straight circular cylinder to a flattened and crimped form in the fabric structure. The simulation is performed by yarn images that are obtained by image processing techniques and resized according to mathematical models developed by means of the software prepared. Transforming circular yarn cross-section to elliptical one for simulating yarn flattening and modelling the crimped shape of yarn by an elastica curve are both convenient and realistic. The simulation of plain woven fabric can be performed by a method based on raster graphics. This article provides a model for yarn shape in fabric structure as well as a method for simulating plain woven fabric appearance. This method may be used in textile industry for design and quality control.     

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.     

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.     

Theoretical and experimental analysis of bending rigidity of plain and twill woven fabrics

The study of bending behavior of woven fabrics is an important issue in textile scientific researches and its industrial applications. Different behavior of fabrics such as drape, comfort, and handling can be understood by this study. Bending rigidity of fabric depends on several factors such as weave geometry, bending rigidity of yarn, and yarn density. In this study, estimation of bending rigidity of woven fabric with different twill and plain structures, have been carried out using energy method. Generally, the woven fabric structure is divided into three different section lengths i.e. rigid, semi-rigid, and flexible sections. Thereafter, bi-component and tri-component models for predicting bending behavior of plain and twill woven fabric have been presented. Then, bending properties of fabric based on Shirley apparatus as well as weight per area as a physical property were measured. Good agreement between measured and predicted values, validated our theoretical models for obtaining bending rigidity, except considerable differences observed between experimental and predicted values using bi-component model of plain fabric. Therefore, using assumptions in calculation of the ratio of rigid section length to flexible section length (R₁), the modified model of plain fabric has been proposed.     

基于频域特征点提取的素色机织物密度识别算法

通过计算机图像处理技术对织物图像进行分析,利用傅里叶变换技术将织物图像从空间域转换到频率域,并采用对比度拉伸、高斯低通滤波等图像预处理手段来增强图像质量,然后使用阈值处理技术对织物频谱图进行处理,得到包含织物密度信息的特征点坐标。通过频谱图上特征点坐标和空间域周期的对应关系,经计算最终得到织物经纬密度。实验结果表明,织物密度识别最高误差为2.8%,此方法可以实现三原组织素色织物的经纬密度的自动识别。     

基于芳纶平纹织物微观几何结构的纱线抽拔力学性能分析

为研究芳纶平纹织物纱线抽拔力学性能及各参数的影响规律,建立纱线抽拔数学模型,为后续数值模型提供理论基础.采用数字单元法模拟芳纶平纹织物织造过程,获得其微观几何模型,并计算得出纱线轮廓.在此基础上,使用ABAQUS模拟单纱抽拔过程,建立纱线厚度方向单层网格划分准则和纱线材料属性,获得横向预紧力、纱线间摩擦因数对纱线抽拔力...     

平纹织物纱线截面形态经典理论探析及其泛化

平纹机织物内部纱线的截面一直被业界视为某种固定的形态,但应用可视化技术发现,基于经典的双凸截面模型存在问题,即使用微积分思路解决问题过程中,发现纱线截面变化的规律.研究结果表明,无论是单层机织物还是多层机织物,其纱线截面均呈现多元性,而非单一形态.特别是对于接结多层纬纱的经纱,其截面沿纱线长度方向按凹凸交变的规律呈周期性变化.这一研究成果对"织物纱线恒定截面论"提出了异议,对研究纱线的真实截面形态及织物外观模拟具有参考价值.     

中低密度机织平纹织物中纱线压扁变化规律

摘 要 为了探讨真实描述平纹织物结构中纱线截面的几何形状,需要测量沿纱线中心线方向的压扁程度。设计并织造了经向紧度和纬向紧度分别为34.72%、43.4%、52.08%的9块中低紧度布样,用Keyence数码显微镜获得布样上经或纬组织点图片,非破坏性地实际测量组织点不同位置处纱线直径。利用Excel和Origin软件对测量数据的输入与处理、绘制测量位置与压扁系数的点线图,分析沿纱线中心线方向纱线截面的变化规律和不同紧度的织物中经纱或纬纱的压扁程度。发现纱线截面的压扁系数与组织点的中心位置距离呈现高度线性相关,距离越近,压扁程度越大;中低织物紧度条件下,紧度对纱线压扁系数影响不明显。     

Study of graphite/silicon carbide coating of plain woven fabric for electrical megawatt absorbing properties

In this paper, plain woven fabric was selected as the base fabric. Graphite and silicon carbide were the surface layer and underlying layer absorbents, respectively. The influence of the content of the graphite and silicon carbide absorbent and coating thickness on the real part and the imaginary part of the dielectric constant, and the loss tangent are discussed. Through the optimization of electromagnetic parameters, graphite/silicon carbide double-coated polyester woven fabric absorbing materials with the best wave absorption performance were prepared.     

基于有限单元法的平纹织物复合材料强度预测：1. RVE的有限元模型

 为更准确预测平纹织物复合材料的强度,基于平纹织物层合板内纱线的细观分布,建立具有双凸结构的特征体积单元RVE(representative volume element)有限元模型。模型内纱线浸渍体为弹性体,物性值随纱线走向变化,树脂为塑性体。利用有限元分析软件ANSYS,使用20节点solid单元分别对纱线、树脂进行离散,通过数值分析计算复合材料模量,并根据复合材料内纤维与基体的失效准则预测单胞强度。结果表明：通过有限元模拟得到的弹性模量值同理论计算值及实测值均一致,且预测的单胞强度同复合材料实际强度值相吻合;RVE有限元模型支持参数化建模,对平纹织物复合材料的强度预测有很好的应用价值。     

Determinants of electrical resistance change of in situ PPy-polymerized stretch plain woven fabric under uniaxial tensile strain

Although the conductive stretchable woven fabric has been widely used as the sensitive material of strain sensors monitoring human motion, it is lack of a deep understanding of the determinants of its electrical resistance change under uniaxial tensile strain. This study chose two kinds of typical stretchable plain woven fabric, i.e. cotton/spandex core-spun yarn fabric and polyester/spandex filament yarn fabric, and they were coated by in situ polymerization of polypyrrole. Their electromechanical responses under certain uniaxial tensile loadings were measured and compared. Meanwhile, by a multi-architecture analysis, i.e. the intrinsic resistance of yarns, the contact resistance of interlacing yarns and the contact resistance of adjacent yarns in parallel, several hypotheses were proposed and tested to determine the determinants of electrical resistance change under tensile strains. The results showed that the resistance change in woven fabric with in situ polymerization of polypyrrole mainly depends on the contact resistance of the adjacent conductive yarns in tensile direction, and the electromechanical responses of the cotton/spandex core spun yarn are significantly different from those of the polyester/spandex filament yarn. It was concluded that the conductive yarn density and fabric structure are critical parameters of woven fabric as resistive strain sensor.     

The influence of the type and concentration of oxidants on the dielectric constant of the polypyrrole-coated plain woven cotton fabric

The influences of the type and concentration of the oxidant on the real and imaginary parts of the dielectric constant, the loss tangent, and the surface resistance of the polypyrrole-coated plain woven cotton fabric were investigated. Subsequently, exterior morphologies were analyzed. The results showed that the type and concentration of the oxidant had a major influence on the real and imaginary parts of the dielectric constant, the loss tangent, and the surface resistance of the polypyrrole-coated plain woven cotton fabric. The composites showed good performance in terms of the dielectric properties, and conductivity. The ability of coupling is relatively good in the group whose molar ratio of the dosage of oxidant and pyrrole is 2:3. The dosage of oxidant has a major influence on the resistance of the polypyrrole-coated plain woven cotton fabric. When the initial molar ratio of the iron (III) chloride and pyrrole is 3:2, the value of the surface resistance is at its smallest, and the electrical conductivity is at its best.     

基于有限单元法的平纹织物复合材料强度预测:2.复合材料层合板拉伸过程的有限元分析

针对实际使用中平纹织物复合材料铺层角度问题,将0°/45°/90°/-45°铺层的层合板作为有限元分析对象,研究其犬骨试验件在单向拉伸作用下的响应。分析过程中,将试样视作宏观均匀的弹性材料,利用已得出的平纹织物复合材料的物性值,以8节点块单元对模型进行离散,通过分步施加载荷,得到复合材料的应力与应变曲线。与实测值作对比发现,仿真结果同实测结果相吻合。将节点反力作为复合材料单胞模型的边界条件,对复合材料进行失效预测。结果表明:角度铺层设计可以减弱细观结构的开裂和分层;且在承受相同的拉伸应力下,铺层复合材料单胞内树脂单元失效的数量少,因此具有更高的强度。     

Effect of misalignment on shear response of plain woven fabric in picture frame test: experiments and finite element modelling

Picture frame test on woven fabrics is not completely controlled and misalignment is one of the tremendous factors. The aim of this study was to investigate the effect of misalignment on the shear response of plain woven fabric in picture frame test. Misaligned and aligned specimens of plain woven fabric were tested, and digital image correlation (DIC) technique was applied to map the strain displacement fields. Unit cell models of misaligned and aligned specimens were built to simulate the mechanical behaviours during the shear test. Simulated and experimental results showed reasonable agreement. Strain fields mapped by DIC and averaged strains obtained by FEM simulation both demonstrate that tension or compression is introduced by misalignment. Deformation mechanism of misaligned fabric is discussed.     

纯棉机织物生物酶前处理

采用退浆酶CTA-AL1和煮练酶A、B对纯棉机织物进行前处理,对退煮漂三步法和退煮-浴后氧漂工艺中酶的选择,及其用量、pH值、温度、时间等工艺参数进行正交试验分析。试验表明,退浆酶和煮练酶的相容性好,退煮-浴法和退煮漂三步法生物前处理效果与传统方法基本相当。退煮-浴法的煮练酶用量1.0g/L,退浆酶CTA-AL1用量3.0g/L,精练漂白剂ST-09用量1.0g/L,在pH值为8.0下处理50min,而后进行漂白;退煮漂三步法则先用退浆酶CTA-AL13.0g/L处理20min,而后用1.0g/L的煮练酶B处理50min,最后进行漂白。     

机织物计算机模拟方法

分析现有的织物CAD软件在模拟素色织物时存在的不足,给出了纱线的数学模型,根据织物表面浮长线反光的原理,建立了织物浮长线上各点反光亮度计算的数学模型,该数学模型考虑了纱线屈曲、捻向、截面形状等因素对浮长线上各点反光亮度的影响。给出了根据上述数学模型计算并生成织物模拟效果图的方法,依据该方法在计算机上生成了素色织物模拟效果图。经过对上述数学模型的进一步优化,可使织物模拟效果图具有良好的真实感效果。     

角联锁织物的组织设计

提出一种简单的方法来表达角联锁织物组织。通过对角联锁织物组织进行研究分析,利用组织中各参数的关系,得出用分式来表达任意一根经纱交织规律的方法,从而得出多层角联锁织物的组织图和上机图,用这种方法可替代根据示意图画组织图和上机图的传统方法,不仅省时,而且准确可靠,同时为CAD设计打下基础。     

Theory of multilayer woven structures

Multilayer woven fabrics are conventionally represented with the usual weave notation of black and white squares. This notation is based on the top view of the woven fabric. Side view of multilayer woven fabrics contains more important information, namely the routes of warp yarns between layers of weft yarns. In this study, possibilities of woven structures with any numbers of layers and corresponding warp and weft yarns are described. Formulas are derived to describe horizontal, vertical, and diagonal symmetries which lead to identify the fully independent structures. The results serve as the theoretical ground to determine all the possible mechanical properties by using woven reinforcements.