Effect of Weft Binding Structure on Compression Properties of Three-Dimensional Woven Spacer Fabrics and Composites

With the wide use of three-dimensional woven spacer composites(3DWSCs),the market expects greater mechanical properties from this material.By changing the weft fastening method of the traditional I-shape pile yarns,we designed three-dimensional woven spacer fabrics(3DWSFs)and 3DWSCs with the weft V-shape to improve the compression performance of traditional 3DWSFs.The effects of weft binding structures,V-pile densities,and V-shaped angle were investigated in this paper.It is found that the compression resistance of 3DWSFs with the weft V-shape is improved compared to that with the weft I-shape,the fabric height recovery rate is as high as 95.7%,and the average elastic recovery rate is 59.39%.When the interlayer pile yarn density is the same,the weft V-shaped and weft I-shaped 3DWSCs have similar flatwise pressure and edgewise pressure performance.The compression properties of the composite improve as the density of the V-pile yarns increases.The flatwise compression load decreases as the V-shaped angle decreases.When the V-shaped angle is 28°and 42°,the latitudinal V-shaped 3DWSCs perform exceptionally well in terms of anti-compression cushioning.The V-shaped weft binding method offers a novel approach to structural design of 3DWSCs.

水峰抑制(WEFT)技术在~1H NMR中研究糖类化合物的变旋现象

在FX-100型核磁共振仪器上,将WEFT技术用于观察糖类化合物六元环结构中与氧原子直接联结的C_1上的α、β构型质子峰高的变化,从中获取糖类化合物在水溶液中的变旋行为信息,得到α、β构型的平衡时间,以及最后平衡浓度α、β各占的百分比;通过变旋的动力学过程,跟踪了一般~1H NMR无法观察到的C_2位质子峰的化学位移。

An Analysis of the Orthogonal Crank-rocking Lever Spatial Mechanism for the Weft Insertion in Rapier Looms

On the basis of the analysis of typical orthogonal crankrocking lever spatial mechanism for the weft insertion in rapier looms, the rules of the outputting lever motion and the mechanism pressure-angle variety are studied when the maximum swing angle of rocking lever and the length of outputting lever have different values, and the optimum parameters suitable for motion transmission can be chosen. At the same time some existing shortpoints of the mechanism are also pointed out.

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.

Kinematic Modeling and Characteristic Analysis of Eccentric Conjugate Non-circular Gear & Crank-Rocker & Gears Train Weft Insertion Mechanism

A novel weft insertion mechanism named eccentric conjugate non-circular gear & crank-rocker & gears train weft insertion mechanism was proposed in order to better meet the requirements of rapier loom's weft insertion mechanism as well as reduce the manufacturing difficulty. Meanwhile, based on the working principle of this mechanism, kinematical mathematic models of this mechanism were established and an aided analysis and simulation software was compiled. The influences of eccentricity ratio, deformation coefficient, and other important parameters on the kinematics characteristics of this mechanism were analyzed by using the software. A group of preferable parameters which could meet the requirements of weft insertion technology were obtained by means of human-computer interactive optimization method. The maximum velocity, maximum acceleration, and variation of acceleration of this mechanism are smaller than those of the conjugate cam weft insertion mechanism applied on TT96 rapier loom under the conditions of the same unilateral total stroke of rapier head and the same rotary speed of loom spindle; meanwhile the other demands of weaving technology can be met by this novel weft insertion mechanism.

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.

Reverse Solution and Parametric Design of the Conjugate Cam Weft Insertion Mechanism Based on VB.NET and UG

In order to realize the parametric design of the conjugate cam weft insertion mechanism,according to the necessary parameters of weft insertion process,ideal kinematic curves of the weft insertion mechanism were given,and the mathematical model of reverse solution for this mechanism was established.The parameters of this mechanism were obtained by reverse solution on the basis of the given ideal kinematic curves and kinematic requirements.The parametric design platform which was integrated with the functions of parametric reverse solution,motion simulation,three-dimensional modeling and virtual assembly was developed based on VB.NET and Unigraphics(UG) NX.After entering the technological parameters of weft insertion process and essential structural parameters by users,three-dimensional drawing of the main parts such as the conjugate cam and shaft,can be obtained by this platform,also the processing data of the cam can be calculated.This platform provides a rapid approach for parametric design of weft insertion mechanism.

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.

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.

Simulation and Analysis of Spatial Weft Insertion Mechanism Considering Flexibility and Clearance

A 3D model of the spatial four-bar weft insertion mechanism was built with unigraphics NX(UG) according to the actual requirement,and dynamics simulation was carried out by importing the model into ADAMS.Without considering the clearance,the motion characteristic curve of the sword belt was generated through ADAMS combined with MATLAB.In this paper the hinge between the rod and the sector gear was selected as an example with different values of clearance,outputting the motion characteristic curve of the sword belt.Finite element analysis(FEA)was conducted,the flexible body was generated by importing the forked frame into ANSYS,and flexible dynamics simulation was carried out by importing the flexible body into ADAMS to replace the rigid rod.A comprehensive comparison of the output characteristics of the sword belt was conducted in the consideration of the clearance or flexible.Analysis of the force on the left hinge of the rod was carried out with the ADAMS post processing module.With the same clearance,considering the flexibility,amplitude of fluctuation of the force on the hinge increased obviously.

STATISTICAL ANALYSIS OF YARN APPEARANCE IN SINGLE PLATED WORK KNITTED ON LARGE DIAMETER CIRCULAR WEFT KNITTING MACHINE

In this paper the significance analysis has been made of the factors influencing the yarn appearing of single plated weft-knit fabrics knitted on large diameter machine by a mathematical statistical method. By means of orthogonal test and variance analysis, it is known that the feeding tension is the significant factor influencing the yarn appearance and the ground yarn tension should be larger than the face yarn tension. Through comparison, it is also known that the drawing off force should be regulated suitably, the carrier should be near the first closed needle, and the sinker should be out late slightly.

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.

DYNAMIC PROBLEMS OF WATER JET FOR WEFT INSERTION

In recent years, China has imported thousands of water jet looms. In order to master thetechniques and to develop the variety of products, the dynamic problems of this jet device hasbeen discussed in this paper briefly. It contains 1. Introducing the rotary plunger pumps and the open-type jet nozzles. 2. Establishing the fundamental equations of the dynamic analysis for water jet device. 3. An illustrating example to show the jet speed, and the rate and time duration for the jetflow varies with different pipe resistance, cross section area of the nozzle outlet, and the springcompressive deflection etc. It is useful for research and production references.

A THEORETICAL ANALYSIS OF WORKING CHARACTER OF WEFT TENSION COMPENSATOR IN NEEDLE LOOMS

Based on the analysis, according to the principle of vibration, of the working character of weft tension compensator in needle looms, the paper studied the principle of tension compensation and introduced the idea of compensating coefficient. The paper also discussed some factors affecting the effect of tension compensation.

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.

COMPUTER SIMULATION FOR THE-INFLUENCE OF WEFT-COMPRESSIBILITY ON WEAVING RESISTACE AND PICK-SLIPPING UNDER THE BALANCED-SHED

Based on the privious model,this paper discusses the effect of the compessed property of the weft on the weaving-resistance and picks slipping under unbalanced -shed.after giving a short description about the privious work.The discussion is made.under both situation of constant- cloth- tension and variable- cloth- tension respectively.

Effect of Knitted Structures and Yarn Count on the Properties of Weft Knitted Fabrics

This paper is focused on change in shrinkage, GSM, Wales per Inch and Course per Inch due to structure and count variation and state variation. This work was carried out with 12 samples of single jersey, single lacoste and weft lock knit fabrics of different counts which were scoured with NaOH. After pretreatment process the samples were tested for widthwise shrinkage, width, GSM, Wales per Inch and Course per Inch and compared between different states like grey state and finished state. The result obtained in this research indicated that physical properties like structures with tuck stitch possess higher value of widthwise shrinkage, width, GSM and Wales per Inch and Course per Inch value lowers prominently in those structures having float or miss stitches. In both cases i.e. grey state and RFD state values of those properties are high in coarser yarn and low in finer yarn. During project knitted fabrics specification along with machine specification and major factors which are necessary to calculate different types of variation and variables on which the whole fabric construction depends were managed to watch carefully. Main efforts were to develop a dependable way so that the resulting fabric specifications with required configuration can be easily visualized and be forecasted. A great emphasization was provided to the adjustable points on which fabric GSM, stitch length, fabric width and shrinkage percentage directly or indirectly depends.

Dynamic Modeling of Variable Stiffness and Damping for Spatial Linkage Weft Insertion Mechanism with Clearance

In order to further analyze the influence of clearance on the kinematic performance of spatial linkage weft insertion mechanism,it is necessary to study the dynamic characteristics of contact impact force model with the variable stiffness and damping coefficient.Firstly,the parameters in the output process of the system are solved by describing of the flexible joint clearance.Then,based on Lankarani-Nikravesh contact force model,the contact impact stiffness and damping coefficient is modified from fixed values to time-varying coefficients.The dynamic model of spatial linkage weft insertion mechanism with modified clearance is established by Lagrange method,and the dynamic characteristics of the system are calculated.The results show that the joint clearance can directly affect the output performance of the mechanism.With the increase of the clearance value,the curve fluctuations of acceleration,driving torque and collision force are obvious,and it will be further intensified with the increase of spindle speed,which greatly affects the stability of mechanism and fabric quality.Finally,the virtual prototype is established by the SolidWorks software and simulated by the ADAMS software.The simulation results are compared with the numerical results,which verifies the accuracy of the modeling method in this paper.

Impact of the Presence of the Loop at Different Location on Fabric Width and Areal Density of a Weft Knitted Structure

Knitted structures are progressively built up from row after row of knitted intermeshed loops known as knitted loops. Apart from this knitted loops, tuck or miss loops may be produced by varying the timing of the intermeshing sequence of the old loop and new loops. These loops are main and prominent part of the design of the weft knitted structures. Structures having float or miss loop exhibits many noticeable characteristics. The fabrics renders better surface appearance or color pattern. Dimensional stability is significantly improved. Fabric width is reduced and areal density is also increased considerably due to the presence of float loops in the structure. Therefore, the dimensional and physical features of different knitted structures having knit-miss loops may be studied carefully to find the influence of float stitch or loop on fabric width and areal density. In this project work, such an attempt has been made to specify some specific single jersey structures, which will be ensured as an effective tool for product research and development as well as for meeting up customer’s quality requirements of high class products.

Design of Electronic Weft-Insertion System for Three-Dimensional Loom

The motion laws for rapier weft insertion mechanism are analyzed. According to the special requirements on rapier loom's weft-insertion system for weaving three-dimensional( 3-D) fabric,a new rapier electronic weft-insertion system is presented. The design principle for 3-D loom's weft insertion system is introduced,including the design of the motion law of electronic weft-insertion system,the driving system's hardware configure,and its software's controlling principle. The weft insertion system is computer-controlled and servocylinder driven so as to control the rapier's movement to insert the weft into the multi-shed while 3-D weaving. This method greatly simplifies the weft-insertion system,achieves weft-insertion with variable travel,and improves the flexibility and reliability. The weft insertion system has been applied in a 3-D loom successfully.