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.     

The influence of two bar warp-knitted structure on the fabric tensile stress relaxation Part I: (reverse locknit,sharkskin, queens’ cord)

Time-dependent mechanical behavior of textiles has particular importance. One of such behaviors is the stress relaxation. If a fabric is under tension over a period of time, some of the stresses in it will be relieved. During the manufacture and application of clothing and footwear, materials experience various long-lasting deformations, and relaxation process in materials arises. For example, if medical pressure garments such as compression stockings are under tension over a long period of time, some of their stresses will be relieved, with a consequent reduction in the skin and garment interfacial pressure. Thus, with theoretical and experimental study of the factors affecting stress relaxation, the ability to design and produce appropriate clothes will be increased. The aim of this study was to investigate the effect of fabric structure on the stress relaxation of two bar warp-knitted fabrics (reverse locknit, sharkskin, queens’ cord), as well as to find the effect of strain value and loading direction on the stress relaxation of the fabrics. The results reveal that the fabric structure, strain, and loading direction are important factors affecting the stress and stress relaxation percent of the fabrics. By increasing the strain and the length of underlap in the back guide bar, stress will be increased, but stress relaxation percent will be decreased. Also, stress relaxation percent in wale direction is more than course direction for reverse locknit and sharkskin3, but this is reversed for sharkskin4 and queens’ cord. Finally, among the mechanical models used to describe the stress relaxation behavior of the fabrics, three-component Maxwell’s model with parallel-connect nonlinear spring showed the best agreement with the experimental relaxation curve of the analyzed fabrics.     

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.     

An analysis of the bending rigidity of warp-knitted fabrics: a comparison of experimental results to a mechanical model

This study focuses on the bending rigidity of warp-knitted fabrics as a function of knit structure (underlaps length), density (wale and course spacing) and yarn bending properties. Seven standard warp-knitted fabrics are produced with three different densities (Tricot, Locknit, three and four needles Satin, Reveres Locknit, three and four needles Sharkskin). The bending rigidity of the fabrics is measured using a Kawabata evaluation system and an automatic cyclic bending tester. Results show that the bending rigidity increases for the fabrics with a higher density and underlaps length of the front and back guide bars. In addition, a new mechanical model for the bending behaviour of warp-knitted fabrics using an energy method is presented. In this model, the knitted loop structure is assumed to consist of a series of straight and skew yarns simulating legs and underlaps while considering a rigid region lying in the direction of bending. Experimental results show that there is a reasonable agreement between the calculated and measured values for both wale and course directions.     

衬垫用经编间隔织物的压陷性能

为获得具有良好支撑性和压力分布的衬垫用经编间隔织物,对不同规格的经编间隔织物的压陷性能进行研究。在双针床拉舍尔经编机上,通过改变织物纵密、间隔丝垫纱角度、间隔丝直径以及脱圈板距离,试织了13种经编间隔织物试样。测试了试样的压缩应力与应变曲线,并以25%和65%压陷硬度和支撑因子作为评价织物压陷性能的指标。探讨间隔丝密度、垫纱角度和直径以及织物厚度对经编间隔织物压陷性能的影响。研究结果指出：织物屈服阶段是研究织物压缩性能的重要阶段;通过各种结构参数的合理配置,可以获取具有理想压缩特性的经编间隔织物衬垫材料。     

A relationship between dry-relaxed warp-knitted fabric structure and curling distance

This study provides us information about relationship between curling and knitted structure and density of two-guide bar warp-knitted fabrics. Five standard warp-knitted fabrics are produced with three densities (Tricot, Locknit, three-needle Satin, Reveres Locknit and three-needle Sharkskin). Certain cut lengths of sample fabrics in both wale and course direction are analyzed through image processing to define curling value. A mechanical model, a function of fabric structure and yarn parameters, is also suggested to predict the curling force. The results of experimental and theoretical results show a greater curling value for course-wise cut in comparison to that of wale-wise in all warp-knitted structures and densities. The lowest curling value is found for three-needle Sharkskin structure in both directions and all densities.     

经编无缝筒形织物的计算机辅助设计

针对双针床经编无缝筒形织物常用人工经验法设计,工作量大、效率低、易出错的问题,在分析无缝筒形织物组织结构、垫纱数码和穿经循环的基础上,建立全新的表示垫纱数码和穿经循环的无缝筒形织物数学模型.对筒形织物的前片、后片以及筒身边缘的设计方法作了详细的数学描述,重点阐述筒身边缘组织的垫纱运动规律、编织筒身边缘所需的梳栉数、筒身...     

氨纶经编平纹布送经量的影响因素

针对氨纶经编平纹织物更换品种时送经量设置困难的问题,前梳采用33、44、55dtex的涤纶长丝、锦纶长丝,后梳采用44dtex的氨纶丝为原料,分别在卡尔迈耶HKS2-3 E经编机和利巴COP2 KE经编机上进行上机实验,考察了牵拉密度、原料线密度及种类、机号以及机型等参数对经编弹力织物前梳送经量的影响,并利用回归分析得出各影响因素与前梳送经量的关系。结果表明,以上参数均对氨纶经编弹力织物的前梳涤纶或锦纶的送经量有影响。其中,牵拉密度、机号是影响前梳送经量的高度显著性因素。     

组织结构对涤纶经编织物卷边性的影响

为减少织物卷边对后道工序带来的影响,对各把梳栉的组织结构配置以及牵拉密度的选择进行了探讨。以55.5 dtex 24 f涤纶全牵伸丝(FDY)为原料,生产出7种不同组织和4种不同牵拉密度的两梳经编织物,对其卷边量进行测试,并结合显微镜下的线圈图进行分析。结果表明：随着牵拉密度的增大,经编织物横、纵向卷边量均不断减小,其中牵拉密度对横向卷边的影响要明显大于纵向卷边;两梳同向编织的织物横向卷边性要明显好于反向编织;当前梳组织不变,增加后梳延展线长度时,织物的横、纵向卷边量均不断减少,尤其是横向卷边量下降明显;而当后梳组织不变,增加前梳延展线长度时,织物的横、纵向卷边量均不断增加。     

经编导电织物弹性对传感性能的影响

为探讨经编导电织物弹性与传感性能的关系,将镀银基锦纶纱线作为导电纱线分别与氨纶包覆纱线和氨纶裸丝在特里科经编机上交织,制备了具有不同弹性的3种经编导电织物。测试了3种织物在一定拉伸范围内的应力大小与电阻变化,并根据实验数据计算出弹性性能和静态评价指标,得出弹性与传感性能的关系。结果表明:弹性导电织物的电阻随应变呈线性变化,原料越粗则电阻变化的速度越快;弹性模量随着织物弹力的增大而减小,弹性伸长与织物弹力的大小成正相关;在中小应变范围内,弹性模量越低、弹性伸长越大的导电织物传感性能越优。     

Design and manufacturing of warp-knitted filterable fabric with PET/PVDF fiber

In this paper, the filtering effect on fine particle of warp-knitted mesh fabrics was investigated. Polyester yarn (PET) and polyvinylidene fluoride (PVDF) fiber were used as materials to knit the fabrics with five different structures on KS4 tricot warp-knitted machine. After knitting, the fabrics were treated with tourmaline liquid with five different concentrations of tourmaline. Then, the filtration efficiency of samples was tested by the comprehensive test machine. By comparing the filtration efficiency of samples with different concentrations of tourmaline and different structures, the optimal process parameters were obtained that the concentration of tourmaline liquid was 30% and the structure of fabric was one by two insertion. The experimental data of the comprehensive test also revealed that the application of the PVDF and tourmaline did have effects on the promotion of the filtration performance of the warp-knitted fabrics.     

Application of warp-knitted spacer fabrics in car seats

Polyurethane foam is commonly used as padding in car seats despite some problems concerning comfort and recycling. Compared with polyurethane foam, textile seat padding is easier to recycle; so textile padding is a good candidate to substitute foam padding as regulations on recycling have become more stringent on car manufacturers. With the available textile option, warp-knitted spacer fabrics are likely a good substitute for polyurethane foam as padding in car seats. Warp-knitted spacer fabric structures can be designed to be quite flexible in a variety of thicknesses. Warp-knitted spacer fabrics can be very resilient and may display good breathing properties. The current work presents a study on the application of warp-knitted spacer fabrics as cushion in car seats. The results show that, relatively to polyurethane foam, warp-knitted spacer fabrics demonstrate better recovery to compression, thermal properties and breathability. Furthermore, warp-knitted spacer fabrics retain their original thickness for longer time and can be easily recycled.     

宏弯光纤应变传感经编织物的设计

为开发一种利用宏弯原理测量人体呼吸和心跳的光纤传感织物,设计了以棉纱编织的经绒斜为地组织,以直径为1 000μm的聚合物光纤为衬纬纱的经编衬纬复合织物。通过光纤弯曲实验研究了光纤弯曲曲率半径与光信号衰减之间的关系,确定了衬纬光纤的初始弯曲曲率半径为10 mm,选择传感循环单元数为2;通过比较分析双梳经编织物组织的特点,确定了传感织物的地组织。在此基础上设计了织物垫纱运动图和线圈密度,并在手动经编小样织机上编织出传感织物;最后对这些织物进行了测试。结果表明,传感织物可通过电压值变化的形式反映出拉伸过程中光信号相对于织物形状的变化。     

用作汽车座垫的两种经编间隔织物性能比较

介绍了间隔织物的结构、试验所用原料及复合工艺，比较了海绵座垫与间隔织物座垫的压缩性曲线，说明间隔织物不仅环保而且在压缩性上优于海绵，更适合做汽车座垫。     

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.     

经编贾卡提花间隔织物编织工艺探讨

在对专业生产经编提花间隔织物的RDPJ系列双针床拉舍尔经编机结构特征、编织原理、提花原理、设计与仿真原理进行分析的基础上,对经编贾卡提花间隔织物的原料、组织结构等编织工艺进行探讨,并列举了一款该类织物用作功能性鞋子面料的编织工艺,最后结合经编贾卡提花间隔织物的优异性能,指出其在功能性鞋子面料及文胸罩杯等高性能服装面料领域的广阔应用前景。     

An explanation of warp knitted fabric deformation under uni-axial tension by a novel index as shape ratio

Although the Poisson’s ratio (PR) can predict the deformation of engineering materials under uniaxial tension, but seems that it cannot predict well the deformation of structures such as fabrics. It can be attributed to the lack of continuity among constituent elements that leads to some distortion of them during tension. Therefore, the PR is not a suitable tool to explain precisely the deformation of structures such as fabrics. For this reason, a new geometrical index was defined to quantify the deformation of fabrics in order to use instead of PR. This index named shape ratio is obtained by division of the variation of squared perimeter to the area of a printed square on the fabric under uniaxial tension. To check the defined index, warp-knitted fabrics with various structures such as Tricot, Locknit, and Three- and Four-needle satin were produced and tested using tensile tester. The results show that shape ratio can predict the deformation of warp-knitted fabrics as an orthotropic structure rather than the PR.     

经编双针床方格绒织物织造工艺的探索

本文根据西德ＫａｒｌＭａｙｅｒ公司，ＲＤ６ＤＰＬＭ／１２，１６Ｅ双针床短毛绒经编机的工艺原理设计出经编双针床方格绒织物织造工艺，并投入生产。     

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.     

Three-Dimensional simulation of metallic two-bar warp-knitted mesh based on loop structure geometry

In order to predict the appearance and porosity of the metallic two-bar warp-knitted mesh, a three-dimensional (3-D) loop model was developed by some key points on loop, and then based on the model meso structure of mesh was simulated. Firstly, a two-dimensional (2-D) loop geometry in metallic warp-knitted mesh was established. The loop geometry was described on the basis of the yarn property effect to loop sharp. And the underlap geometry was taken as an arc. To describe the 2-D loop geometry, coordinates of key points called databases were established. Then databases in 2-D loop geometry were relocated through the loop offset by stress distribution. Secondly, the 3-D loop geometry was ensured according to the yarn diameter, the angle between loop plane and fabric plane as well as the type of loops (front bar loop or back bar loop), etc. Finally, the coordinates of databases were imported to TexGen software to simulate the 3-D meso structures of the metallic mesh. By comparing simulation images with actual fabrics, the 3-D loop geometry model was fitted well for metallic two-bar warp-knitted mesh. And the simulation results demonstrated that the predicted porosity of mesh was in good agreement with experimental values.