Finite element modelling the mechanical performance of pressure garments produced from elastic weft knitted fabrics

Compression garments mainly produced from elastic knitted fabrics have attracted many attentions due to their medical care performances. Components’ characteristics of the pressure garments such as yarn and fabric structure affect significantly the pressure applied on the human body. In this paper, it is aimed to simulate the effect of yarn’s mechanical properties as well as fabric structure on mechanical performance of the compression garment. For this purpose, a precise geometrical model for fabric structure is needed by which the pressure applied to the body could be predicted. Accordingly, double jersey knitted fabrics containing elastane weft yarns were produced on an electronic flat knitting machine and the fabric tensile properties were measured in course direction. Using equations governing the fabric structural unit-cell, a real geometric model was created in a finite element software environment. Considering the linear visco-elastic properties for elastane weft yarn, stress-strain curve was extracted. The results obtained from numerical simulation were compared with the experimental data in order to validate the proposed geometrical model. The findings demonstrate a good agreement between experimental and simulation results.     

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.     

经编间隔织物的缓压性能

为探究经编间隔织物的缓压性能与结构参数之间的量化关系,从理论上分析了经编间隔织物压缩过程中人体受力与间隔织物之间的相互作用机制,以及人体所受压强与其结构参数之间的关系,获得间隔丝直径、间隔丝排列密度以及间隔织物的厚度等结构参数与间隔织物缓压性能的规律方程。采用自行设计球形压头对不同结构参数的间隔织物样品进行压缩实验,验证分析间隔织物的缓压性能与这3个主要影响因素之间的关系,并得出了各自的回归方程。研究结果表明,间隔织物压缩过程中人体所受压强与间隔丝直径呈幂函数变化,与织物的厚度和间隔丝的排列密度分别呈反比和正比函数关系。     

An investigation into the effect of fabric structure on the compressional properties of woven fabrics

Lateral compression is one of the most important mechanical aspects of fabrics, which reflects their handle. Fabric compressional features depend on the compressional characteristics of constituent yarns and the fabric structure. In order to consider the effect of fabric structural parameters on its compressional properties, woven fabrics with five different weave patterns (plain, hopsack 2/2, twill 2/2, twill 3/1, warp rib 2/2) were produced with three different nominal weft densities (12, 15, 18 cm^?1). The compressional properties of produced fabrics were evaluated at different pressure values using a conventional fabric thickness tester. It was observed that increasing the weft density leads to decrease in the dissipated compression energy as well as the compressibility of the fabric, while the thickness recovery of the fabric increases. Moreover, the plain woven fabric exhibited the lowest dissipated compression energy and compressibility, while the highest thickness recovery. Besides, at the low pressure level, the fabrics with the lower weft densities demonstrate the higher thickness. By increase in the pressure level, the fabric thickness decreases by decreasing the weft density.     

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.     

膝部防护用材料的静态缓压性能

为减少摔倒给老年人膝盖部位造成的伤害,编织了经编间隔织物试样,采用万能材料仪对聚氨酯泡沫材料和经编间隔织物的静态缓压性能进行测试,通过对比实际摔倒能量和缓压材料吸收能量的大小评估材料缓压性能的优劣。结果表明:聚氨酯泡沫材料和经编间隔织物的面密度是影响其缓压效果优劣的决定性参数,而间隔纱、面纱的直径及试样的线圈密度是决定间隔织物面密度的主要因素。当外界压强大于30 kPa时,厚度为20 mm、面密度为1 353 g/m~2的间隔织物试样线圈密度最大,缓压系数最小,缓压效果最好,压缩吸收能为259 kJ/m~2,该间隔织物试样从厚度、编织工艺、成本上来说是最佳的膝部防护用缓压材料。     

Modeling the mechanical and compression properties of polyamide/elastane knitted fabrics used in compression sportswear

A compression sportswear fabric should have excellent stretch and recovery properties in order to improve the performance of the sportsman. The objective of this study was to investigate the effect of elastane linear density and loop length on the stretch, recovery, and compression properties of the weft-knitted polyamide/elastane (PA/EL) stretchable fabrics used in sportswear. Two different tests were performed to study the stretch and recovery properties of the fabric 1st: under low power force and 2nd: cyclic loading under high tension force. Kikuhime pressure sensor was used to measure the pressure generated by different PA/EL knitted sample garment sleeves. It was found that with the increase in elastane linear density there is an increase in fabric course density, areal density, recovery percentage, and compression, and fabric stretch percentage and elongation percentage decreased in both course and wale direction. The results of fabric samples were analyzed in Minitab statistical software. The coefficients of determinations (R² values) of the regression equations showed good prediction ability of the developed statistical models.     

紧密机织物高气压下面外变形的机制

为指导设计新型防护面料,依据其防护过程,探索了紧密机织物在高气压下面外变形的机制。结合能量理论和板壳理论,建立了紧密机织物在高气压下面外变形的系统能量平衡方程(机制模型),从能量最小化的角度预测织物变形后的最大变形量和变形轮廓曲线。通过自行搭建的织物变形仪测量了2类不同紧密程度的机织物面外变形情况。结果发现织物变形程度与其弹性模量呈负相关性,随后对织物变形的实验值与理论预测值进行了比较,发现二者之间的误差小于20%。从而证明该数学模型可较为精确地用来预测其他紧密机织物高气压下的面外变形。     

医疗袜用弹力管状针织物的开发与性能测试

为解决医疗袜穿着适配性存在的局部截面压力不均匀问题,编织3种弹力管状针织物,每种织物选用3种规格衬垫纱线,针对脚踝、小腿、大腿3个不同部位进行袜机参数的4因素3水平L₉(3⁴)的正交试验设计;对织物进行截面周长、织物克质量、密度、厚度及接触压力测试。研究发现,同一织物,在相同测试部位,压力值随腿模型号增大而变大;不同衬垫纱织物,衬垫纱越粗,压力值越大;袜机编织参数相同,围度上由两种组织编织的弹力管状织物的压力值大于单一组织的织物。     

Analysis of warp knitted fabric structure. Part V: experimental study on the initial modulus of warp knitted fabrics

In the previous parts of this series, tensile properties of warp knitted fabrics were investigated using energy method. For this purpose, the geometry of fully threaded two-guide bar structures, i.e. tricot, locknit, reverse locknit, satin and sharkskin were modeled by considering the fabric density, yarn diameter and the number of front and back bar underlaps. Then, the theoretical models for the initial modulus of aforementioned structures were obtained. In the present study, the initial modulus of actual fabrics has been calculated using presented models in previous parts. Then, a new test method was defined for tensile testing of warp knitted fabric, specifically. Thereafter, the initial modulus of prepared samples has been measured by using tensile tester in order to compare with theoretical values, based on derived test conditions. Reasonable agreements between theoretical and experimental results showed that generated models are capable to predict the initial modulus of fully threaded two-guide bar warp knitted fabrics, adequately.     

Thermophysiological comfort characteristics of plated knitted fabrics

Thermophysiological comfort properties of polyester elastane-plated fabric have been studied by varying the polyester filament shape factor, elastane linear density, and fabric loop length. Thermal and evaporative resistances were measured using sweating guarded hot plate. Absorption and wicking properties were measured using M/K GATS. Moisture management properties were measured by moisture management tester. Multilinear regression equations were calculated for all the properties by using generalized linear model (GLM). The hypothesis tests were performed on estimated model (GLM) and the probability values (p-values) were calculated for each variable. Most of the heat and moisture transmission properties were found to be significantly affected by all three variables (i.e. filament shape factor, elastane linear density, and fabric loop length) at 95% level of significance.     

Effect of input tension of inlay yarn on the characteristics of knitted circular stretch fabrics and pressure generation

Stretch fabrics are used in manufacturing pressure garments to exert pressure over specific body parts in medical conditions like venous and lymphatic disorders, scar management, and bone and muscle injuries. The amount of therapeutic pressure required in each medical condition is different; therefore, there is a need to engineer the stretch properties of garments to match the requirements in each case. Limited information is available on the relationship between fabric properties and the pressure generated on the body. In this paper, an attempt has been made to study the effect of inlay yarn pre-tension at the time of manufacturing of stretch fabrics on the pressure generated by the garments. Results show that change in inlay pre-tension significantly changes the structural characteristics of the fabric but the load elongation behavior remains unchanged up to 100% extension. Pressure exerted on rigid cylindrical tubes increases with reduction factor of the fabric tube and the curvature of the cylinder.     

Drape Prediction by Means of Finite-element Analysis

The draping behaviour of fabric treated as an orthotropic shell membrane is predicted by using a geometric non-linear finite-element method, and the results are compared with actual behaviour. A drape tester employing photovoltaic cells was designed and constructed to determine the drape coefficient of fabric specimens of 10-in. diameter. The warp- and weft-direction tensile moduli of these samples were determined by using a Kawahata Tensile and Shear Tester, and literature values of Poisson's ratio were obtained. With this approach, excellent agreement between experimental and predicted drape coefficients resulted. For a 100% cotton plain-weave fabric, a drape coefficient of 68.4% was experimentally determined as compared with a predicted value of 71.0%.     

25—THE WRINKLING OF WOOL WORSTED FABRICS. PART I: FIBRE AND YARN DEFORMATION IN BENDING

Experiments are described in which the extensional, bending, and twisting strains of seven fibres were measured in a wool worsted fabric deformed in a multiple-pleat tester. The only significant strain appeared to be the bending strain.     

Analysis of piezoresistive behavior of polyaniline-coated nylon Lycra fabrics for elbow angle measurement

In this article, a textile-based strain sensor has been developed by in situ polymerization of aniline on nylon Lycra fabric. The tensile and repeatability characteristics of the nylon Lycra fabric were studied in Zwick/Roell Z010 tester to analyze the suitability of the fabric for sensor development. After polyaniline coating, the control and coated fabrics have been characterized by means of scanning electron microscopy and energy dispersive X-ray. The change in electrical resistance for the applied strain was studied to analyze the strain sensing behavior of the polyaniline-coated nylon Lycra fabric. From tensile and repeatability study, it was observed that the conditioning cycles are necessary for the nylon Lycra fabric before taking actual measurements in order to improve the stability of the sensor response. The developed fabric had the electrical resistance of 3.5 KΩ/square. The electrical resistance of the developed PANI-coated fabric decreases as the sample is strained and increases again as the strain is relaxed. The measurement of the conductivity change with strain shows that the developed fabric exhibits high strain sensitivity. When used in conjunction with a commercial goniometer, the polyaniline-coated nylon Lycra fabric responded well to the magnitude of bending deformations, demonstrating potential for remote the strain sensing applications.     

Modeling the effect of elastane linear density,fabric thread density,and weave float on the stretch,recovery, and compression properties of bi-stretch woven fabrics for compression garments

The aim of this study was to investigate the effect of elastane linear density, thread density, and weave float on the stretch, recovery, and compression properties of bi-stretch woven fabrics for compression garments. Fabric samples were produced using elastane core-spun cotton yarns both in the warp and weft. The elastane linear density, fabric thread density, and weave float size were used as input variables while fabric contraction, subgarment pressure, fabric stretch, and recovery were taken as response variables. Two different elastane linear densities, i.e. 44 and 78 dtex, two different thread densities, and three different weave designs, i.e. 1/1 plain, 2/2 z-twill, and 3/3 z-twill were used. The results of fabric samples were analyzed in Minitab statistical software. The coefficients of determinations (R-sq values) of the regression equations showed good prediction ability of the developed statistical models. The findings of the study may be helpful in deciding appropriate manufacturing specifications of bi-stretch fabrics to attain specific stretch, recovery, and compression properties.     

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.     

基于三维扫描的医疗袜压力分布预测模型研究

基于三维人体扫描获取的人体表面点云数据和拉普拉斯方程,建立医疗袜与腿部接触的服装压分布理论预测模型。选择常用的Ⅰ级、Ⅱ级、Ⅲ级医疗压力袜以及3名在校大学生进行试穿,按照建立的理论模型计算压力袜和腿部接触的压力分布,并采用AMI3037型接触式气囊压力测量系统测试受试者穿着医疗袜时的实际接触压力,验证预测模型的实用性。结果表明,理论值和实测值基本一致,在一定程度上表明基于非接触式三维人体扫描的医疗袜压力分布预测方法可行。     

色纺针织物紧密程度对颜色预测的影响

为优化颜色预测模型,引入织物紧密程度常数,探究色纺针织物紧密程度对颜色预测的影响。采用红和蓝2种色纤维织造不同紧密程度的织物,选用常用的Stearns-Noechel模型为颜色预测模型,求解模型中的待定参数M时,以拟合色差最小时的M值为最优参数,对比引入常数前后的预测结果。结果表明:未引入织物紧密程度常数时,所得到的M值较引入常数后得到的M_p小;当织物组织相同时,随着织物紧密程度逐渐变小,M值变化很小(0.226 5~0.221 6),而M_p值却有逐渐增大的趋势(0.292 1~0.347 1);当弯纱深度一致时,M值随着织物紧密程度的增加,有变大的趋势,但M_p值变化趋势却不明显;引入织物紧密程度常数后,预测平均色差都更小。     

Interface pressure generated by knitted fabrics of different direction,composition and number of layers in sport compression garments

The present study aimed to determine the effect of fabric direction, fabric composition and number of fabric layers on pressure generated by sport compression garments. Experimental fabric used in commercially available compression sport garments was chosen. Experimental fabric sleeves imitating a part of a pressure garment were assembled and placed on cylinders of different diameters, so that they provided different fabric direction, fabric composition of sleeve and number of layers in assemblies along the circumference of the cylinders. A Salzmann MST MK IV pressure-measuring device and Salzmann MST 2007 software were used to measure the interface pressure generated by the sleeves. It was established that different direction, fabric composition of sleeve and number of fabric layers in fabric assemblies influences the interface pressure.