Modeling Locking Angle of the Multi-layered Biaxial Weft Knitted Fabric in Shear Deformation

This paper introduces the construction of the multi-layered biaxial weft knitted fabric （MBWK fabric） and studies the locking angle of this kind of fabric. Moreover, a locking angle model of the MBWK fabric is established for the first time according to its unique construction. Two kinds of locking angles are considered under different restraint conditions: the locking angle θ1 controlled by the inserting yarns and the locking angle θ2 controlled by the stitch yarns. It is concluded that the ultimate value of the locking angle θ is the larger one of the two angles.

Web-Based Interactive Simulation of Weft Knitted Fabric

In order to realize parametric simulation of three-dimensional(3D)fabric structure based on web,a 3D model describing a plain knitted fabric,in which the cross-section of the yarn is circular shape and the path of the yarn is cubic B-spline curve,is proposed in this paper.With this model,the 3D simulation of the loop and of the basic structures of the knitted fabric is realized by using Virtual Reality Modeling Language(VRML).The virtual simulation scene is suitable for network transmission with freely available VRML browsers and can be translated,scaled and rotated quite arbitrarily.By using Java and External Authoring Interface(EAI)technology,the web-based interactive simulation platform of weft knitted fabric is established.The user can input type of structures,basic fabric parameters,and yarn colors interactively to obtain a more realistic simulation result in real-time.A new approach is provided to imitate the knitted fabric 3D appearance on network.

Mechanical Properties of Weft-Knitted Spacer Fabrics Integrated with Silica Aerogels

The work investigated surface and mechanical properties of untreated and treated three-layered weftknitted spacer fabrics.In order to optimize the mechanical properties of weft-knitted spacer fabrics,silica aerogels(SAs)coating was employed.Scanning electron microscopy(SEM)images of untreated and treated spacer fabrics were analyzed to ensure the presence of SAs on the coated spacer fabrics.The basic properties of uncoated and coated weftknitted spacer fabrics were studied and compared.Tensile strength and initial modulus were studied according to the GB/T3923 test standard YG026 MB-250 by testing machine.Moreover,compression properties of spacer fabrics were also tested by HD026 G test instrument.In this testing,work of compression,the linearity of compression,recovery work of compression and other parameters were calculated from stress and strain curves.It was found that SAs coating has a significant influence on the mechanical properties of weftknitted spacer fabrics.The statistical analysis also verified the significant performance(P value smaller than 0.05)of treated fabric samples at the 0.05 level.

Tensile Properties of Weft Knitted Fabric Reinforced Composites

Seven kinds of weft knitted fabrics from glass fiber yarns were used as reinforcement to make fabric/epoxy composite laminates. Tensile tests were carried out to examine and compare the mechanical properties in course and wale direction of these composites. On the basis of experimental results, attempts have been made to analyze some main factors influencing stress-strain curve, ultimate tensile strength and initial elastic modulus of specimens.

Flexural Properties of Weft Knitted Fabric Reinforced Composites

Several different kinds of weft knitted fabrics from glass fiber yarns were used as reinforcement to make fabric/polyester composite laminates. Flexural tests were carried out to examine stress- deflection process and compare the mechanical properties in course and wale directions of these composites. The experimental results indicate that the numbers of load-bearing yarn in course and wale direction and the fabric density are the main factors influencing the ultimate tensile strength and initial elastic modulus of specimens.

Effect of Run - in Ratios on the Mechanical Properties of Two - Guide Bars Warp - Knitted Fabrics

Warp knitting technology gets rapid development at present and becomes one of the most important parts of the textiles.But it is less known how the parameters of warp knitting technology affect the mechanical properties of warp-knitted fabrics.This paper presents discuss a research on the relationships between run-in ratio and mechanical properties of the two-bar warp-knittedfabrics through the measurement and analysis of the mechanical properties of various samples with different run-in ratios.The optimal run一in ratios for the reasonable mechanical properties are obtained from above dis-

Effect of Aramid/Carbon Hybrid on the Tensile Properties of Multilayered Biaxial Weft Knitted Fabric Reinforced Composites

The effects of aramid/carbon on tensile properties of multilayered biaxial weft knitted( MBWK) fabric reinforced composites are analyzed by experiments. The tensile tests are inducted by the SHIMADZU AG-250 KNE universal material testing machine and Aramis V6 digital image correlation( DIC) technique.More specifically,the composite samples own four hybrid ratios(Na∶ Nc= 12∶ 0,8 ∶ 4,6 ∶ 6 and 4 ∶ 8). The results showed that the aramid/carbon hybrid MBWK fabric reinforced composites showed nearly linear response until reaching the maximum load and the inserting yarns distribution on the surface of MBWK fabrics reinforced composites had a great influence on the strain pattern distribution. Besides,the tensile strength,the tensile modulus and the elongation at breakage of 0° samples and 90° samples increased with the decreasing of aramid/carbon hybrid ratio. In a word,the changes of tensile strength, tensile modulus and elongation at breakage have a lot to do with the difference of aramid/carbon hybrid ratio.

Analysis of the Thermohydro - comfort Durability for Microfil - polypropylene Knitted Fabric under Grey System

Thin microfll - polypropylene knitted fabric that is knitted to use new single plated theory on large diameter circular weft knitting machine is a new functional fabric. After military use, the reflective opinions are that it is light, thin, soft, smooth - touch, and it has excellent elasticity, good air perviousness, large water vapor permeability . In this paper, an analysis is held to use grey system theory, and the thermohydro - comfort durability of this microfil - polypropylene knitted fabric is compared with that of common knitted fabrics. The analytical result proves the microfil - polypropylene knitted fabric is satisfactory under the climatic conditions that human body needs to eliminate or retain the quantity of heat. It can be use to seam up not only physical ability training uniform of serviceman but also civil sporty and sportswear et cetera.

A New Method for Measuring the Stitch Length of Weft Knitted Fabric in a Static Environment

It is essential to measure the stitch length of weft knitted fabric in a static environment for economy and improving productivity. The image inputted was dealt with the digital image processing techniques： the paper carried out the transformation of grey scale; then removed impurities with filtering; the characteristic of the stitch structure was abstracted by using the Fourier transform technique. To obtain the stitch length more accurately, we should establish ageometric medal of the stitch lined on the digital image processing, which provides a way to transform the stitch length in the two-dimenslon space into a three-dimension space. This study provides a new methed for measuring the stitch length without damaging the fabric.

Computer-aided Pattern Design of Multi-bar Warp Knitted Fabrics

To meet the development trend of multi-bar warp knit-ting machine towards high-speed,advanced technologyand computer control and the requirements of variousproducts with small quantity,there are many researcheson the computer-aided pattern design of multi-barwarp knitted fabrics.In terms of the special propertiesof the computer-aided pattern design of multi-barwarp knitted fabrics,the Object Oriented Program(OOP)programming-Object Windows class Library(OWL)programming is selected.According to thecharacters of the OWL programming,various functionsare defined.Pattern design and technical parameters canbe output,which offers a great convenience for the fac-tory.

3D Modeling and Simulation of Fancy Fabrics in Weft Knitting

Weft knitted fancy fabrics are widely used in knitted garment design. Due to the complexity of the structures, their modeling and simulation needs to be solved in three-dimensional (3D) CAD developments. In this paper, 3D loop geometrical models of weft knitted fancy structures, including tuck stitch, jacquard stitch, transfer stitch and fleecy stitch, were developed based on an improved model of plain loop, and their central axes as some 3D space curves were achieved by using Non-Uniform Rational B-Splines (NURBS). The 3D visual simulation programme was written in C++ programming language using OpenGL, which was a function library of 3D graphics. Some examples of weft knitted fancy fabrics were generated and practical application of 3D simulation was discussed.

Measuring Structural Parameters of Knitted Fabrics by Digital Image Processing Techniques

In the knitting industry the measurements of the stitch density and the stitch length are usually done manually, which may lead to lower efficiency and less definition and also bring subjective ideas into the test results. In order to improve the effect we can measure with Digital Image Processing Techniques. A piece of sample is scanned into computer and changed into a digital image, which is processed with media filtering. To acquire the power spectrum, the image in the spatial domain is converted into the frequency domain. Picking up the characteristic points describing the stitch density and the stitch length separately in the power spectra and reconstructing them, the values of the stitch density and the stitch length could be calculated. When measuring the stitch length, we should establish a geometric model of the stitch based en the digital image processing, which provides a method to transform the stitch length in the two-dimensien space into the three-dimensien space and to measure the value of the stitch length more accurately. This method also provides a new way to measure the stitch length without damaging the fabric.

纬编双面移圈织物多层弹簧-质点结构模型构建与实现

纬编双面移圈织物工艺结构复杂多变,现有系统在进行设计开发时难以直观地展示出织物的组织结构特点。为实现纬编双面移圈织物的组织结构模拟,本文提出了一种纬编双面移圈织物多层弹簧-质点结构模型。首先建立了成圈、集圈、移圈线圈几何结构模型,接着分析了纬编双面移圈织物结构特征,并在传统弹簧-质点模型的基础上构建了多层弹簧-质点模型,然后采用牛顿第二定律和Velocity-Verlet数值积分法求解了多层弹簧-质点模型的最终位置,最终提出了一种纬编双面移圈织物结构模拟的算法流程。本文建立的多层弹簧-质点结构模型能够反映纬编双面移圈织物的组织结构,具有较好的结构模拟效果。

Study of Single Plated Principle on Large Diameter Circular Weft Knitting Machine

A new theory and method that differs from the tradition-al single plated weft - knitting theory and method hasbeen expounded after theoretical analyzing and experi-mental proving. If the new method is used when platingstitch is knitted on large diameter weft knitting machine,the thorny problem of long standing that ground yarn iseasy to appear on the face side of fabric is solved. Thenew method, i.e, the production of physical ability oftraining uniform for serviceman has been used.

基于粒子群算法对纬编针织物Johnson-Champoux-Allard模型参数反分析研究

为快速获取纬编针织物JCA(Johnson-Champoux-Allard)模型参数,建立材料、结构与模型函数关系,实现吸声性能预估,提出迭代次数少、可快速达到全局最优解的粒子群算法对JCA模型进行反分析求解,并以吸声系数实验值和设定值差值平方和的最小值为适应度函数,设置约束,添加学习因子与惯性权重对反分析过程进行限制,多次迭代得到孔隙率、流阻率、曲折因子、黏性特征长度与热特征长度的数值;然后建立JCA模型参数(孔隙率与流阻率)与针织物结构参数(未充满系数)的函数关系,以达到快速获取不同结构针织物JCA模型参数,进而对其吸声情况进行预估的目的;最后,用有限元方法对快速获得的JCA模型参数准确性进行验证。结果表明:基于粒子群算法可精确获得针织物JCA模型的5种参数,迭代次数少于200;针对纬平针组织不同规格,未充满系数可直接换算结构参数(孔隙率与流阻率),结合已知材料参数(曲折因子、黏性特征长度与热特征长度)快速计算出纬平针组织和双反面组织的吸声系数曲线发现,吸声系数曲线拟合度较高,R^(2)分别为0.809和0.852。

基于交织点改进弹簧-质点模型的纬编针织物动态变形模拟

为了对不同线圈单元组成的纬编针织物进行动态变形模拟,从而预设织物结构形态和加速面料设计流程。首先通过建立三维结构模型,获得了线圈中心线型值点和交织点之间的关系,并基于交织点改进传统弹簧-质点模型,得到了与纬编针织物适配度更高的变形模型,然后以交织点为桥梁关联结构模型和变形模型,通过NURBS曲线反算原理绘制线圈中心线路径,采用力学求解方法不断更新织物形态变化,使用计算机工具展现了关联模型的动态模拟过程,并举例展示了不同织物组织的变形模拟效果。模拟效果表明,建立的三维结构模型具有合理性与真实性,改进的弹簧-质点模型具有极高的适配性,基于交织点关联两者为后续模拟提供了支撑,采用NURBS曲线并通过力学求解等方法实现纬编针织物的三维动态模拟具有可行性。

基于改进弹簧-质点模型的纬编织物三维模拟

为解决弹簧-质点模型在模拟组织结构复杂的纬编织物时模拟效果不真实、立体感不足等问题,对传统弹簧-质点模型进行改进,提出了立体化的弹簧-质点模型。改进的弹簧-质点模型能够很好地模拟组织结构较复杂的纬编织物,通过非线性的弹簧力模拟织物动态仿真中出现的超弹性现象。同时,采用Velocity-Verlet数值积分方法对质点的空间位移进行计算,实现了对纬编织物受到三维状态多外力作用时的动态模拟。所提方法计算速度快,实时性好。

接触电阻对导电纬平针织物柔性传感器的电-力学性能影响

采用Popper和Kawabata的针织物力学模型计算纬平针织物线圈中交叠纱线间的接触力,为了简化计算过程,采用两个弯曲的纱线相互钩套来模拟导电纬平针织物线圈中相互交叠的纱线,导电纱线间接触电阻和接触力的关系可用经验幂函数求得.由理论分析和试验研究可得:导电纬平针织物线圈中交叠纱线之间的接触电阻随接触力的增加呈幂函数减小;由接触电阻引起的电阻变化是影响导电纬平针织柔性传感器灵敏度的关键因素;导电纬平针织物电阻随应变的增加而线性减小.

等离子体-硅烷偶联剂改性芳纶纬平针织复合材料的力学性能研究

采用等离子体联合不同质量分数的硅烷偶联剂溶液对芳纶纬平针织物进行改性,再利用真空辅助树脂传递模塑成型(VARTM)工艺制备未改性及改性芳纶纬平针织复合材料。通过测试和分析芳纶纬平针织复合材料的拉伸、弯曲、压缩和冲击性能发现:改性芳纶纬平针织复合材料的拉伸、弯曲、压缩和冲击性能较未改性芳纶纬平针织复合材料的都有所改善;随着硅烷偶联剂质量分数的增加,改性芳纶纬平针织复合材料承受的最大拉伸载荷、最大弯曲载荷、最大压缩载荷和最大冲击载荷呈现先增加后减小的趋势,其中等离子体-硅烷偶联剂(w=1.5%)改性芳纶纬平针织复合材料各项性能改善最明显,其能承受的最大拉伸载荷、最大弯曲载荷、最大压缩载荷和最大冲击载荷较未改性芳纶纬平针织复合材料的分别提高了32.73%、38.03%、24.83%和35.10%。

芳纶-UHMWPE混杂复合材料力学性能研究

为探究不同混杂结构的芳纶-UHMWPE纬平针织混杂复合材料的力学性能,根据混杂比设计10种不同混杂结构的芳纶-UHMWPE纬平针织复合材料。采用电子式万能试验机、落锤法对其进行拉伸、冲击等测试,研究不同混杂结构拉伸性能和抗冲击性能的差异性。结果表明:层间结构的拉伸强度随UHMWPE织物层数增加而增大,在相同混杂比的情况下,UHMWPE(U)层夹芯芳纶(K)层时复合材料的拉伸性能较好;当K∶U=1∶3时,以芳纶织物为冲击面,混杂复合材料的抗冲击性能最佳;当K∶U=3∶1时,以UHMWPE织物为冲击面时,混杂复合材料的抗冲击性能最佳;所有混杂方式表现为正的混杂效应。