Modelling of ageing effects on crack-bridging behaviour of AR-glass multifilament yarns embedded in cement-based matrix

This article focus on modelling of ageing effects on crack-bridging behaviour of AR-glass multifilament yarns embedded in cement-based matrix. In the first step, age-dependent changes in the crack-bridging behaviour of AR-glass multifilament yarns were investigated at the meso and micro levels. Two cementitious matrices were considered where the binder contained Portland cement clinker and ground granulated blast furnace slag cement, respectively. Mechanical characteristics of the bond between matrix and multifilament yarns after accelerated ageing were measured by means of double-sided yarn pullout tests. In these tests the multifilament yarns bridged a single crack in the matrix arising in a notched area of the specimen. Losses in performance with increasing age differed widely depending on matrix material composition. The essential cause of such losses was discovered to be the microscopic densification of the fibre-to-matrix interface. This led to increased bond intensity and restricted slip-ability of the filaments. Subsequently, these micro-structural phenomena were related to the mesoscopic material behaviour by means of a phenomenological bond model. This cross-linkage model describes the crack-bridging effect of the entire multifilament yarn at the single filament level. According to the model, each filament possesses a specific deformation length depending on its position in the cross-section of the yarn. This deformation length depends on bond characteristics between single filament and cementitious matrix, which vary with age. Characteristic values of the model were computed from load-crack width curves obtained from the yarn pullout tests. The changes in the microstructure were represented by the characteristic values of the model.     

Pre-tensioning of fabrics in cement-based composites

This paper studies the effects induced by applying a pre-tension load during the production of fabric-cement composites. The flexural behavior as well as the bonding between the different fabrics and the cement matrix was examined, as a means for characterizing the processing parameters. Microstructure characteristics of the fabric-matrix interface as well as the viscous elasticity properties of the fabrics were also explored and correlated with the mechanical properties of the composite. It was found that pre-tensioning of fabrics and the time at which the tension is removed can significantly influence the performance of the composite depending on yarn properties, mainly the viscous-elastic properties, and fabric geometry.     

Surface property modification of aromatic polyamides by microwave plasmas

Various microwave plasma treatments were applied to Kevlar in the form of multifilament fabric and single fiber. Plasma-modified fabrics were used to construct two-ply laminates using a triazine resin adhesive. Very significant increases in the bond strength of laminates may be attributed to the plasma treatments; the effectiveness of plasma treatment is best utilized by reducing to a minimum the time interval between plasma exposure and contact of treated substrate with impregnating (adhesive) fluid. Mechanical properties of single Kevlar fibers seem to deteriorate somewhat on plasma exposure, but the cohesive strength of multifilament cloth is enhanced by the same treatments.     

Establishment of a color tolerance for yarn-dyed fabrics from different color-depth yarns

Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔE_CMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns.     

涤纶浸胶帘子布(帆布)的技术经济分析

本文首先介绍了国内外涤纶帘子线(布)发展情况、主要生产厂家及规模、各种骨架材料应用范围及其性能比较及涤纶帘子线技术指标等。第二介绍了涤纶树脂增粘、纺丝制帘子线及其生产工艺流程。第三介绍了涤纶帘子布厂的建厂规模、单位产品的投资数及成本、涤纶工业丝产品单位成本的测算和比较、涤纶浸胶帘子布单位成本的测算和比较。第四介绍了各种化纤工业丝比价、涤纶工业丝和民用丝比价、涤纶工业丝与帘子布的比价及浸胶帘子布与轮胎比值、最低售价的测算等。最后提出核定价格的几个原则及其建议价格。     

Determining the dependence of colour values on yarn structure

The colour values of knitted cotton fabrics made from single and plied ring and compact yarns were investigated before and after dyeing. The fabric samples were knitted under the same constructional properties and then dyed with direct and reactive dyes. It was found that fabrics with ring yarns had high lightness and low chroma and colour strength values compared with fabrics with compact yarns. Also colour strength and colour difference values of dyed fabrics were assessed after increasing abrasion cycles (2500, 5000, 7500 and 10 000). The main changes in colour strength values were observed at 2500 abrasion cycles. The effect of abrasion on colour difference values of fabrics having ring yarns was more obvious than fabrics having compact yarns.     

A note on permeability simulation of multifilament woven fabrics

A conventional approach for modeling permeability of multifilament fabrics is to consider their warps and wefts to be individual thick filament made of homogeneous porous media and solve the flow equations for such monofilament fabrics. In this work, for the first time, the full 3-D geometry of an idealized multifilament woven fabric, wherein the filaments are packed in hexagonal arrangement, is generated to compute its permeability and compare with the homogeneous anisotropic lumped model of Gebart (1992. Permeability of unidirectional reinforcements for RTM. Journal of Composite Materials 26(8), 1100-1133). While a relatively good agreement is obtained, our results indicate that Gebart's model slightly underestimate the permeability of multifilament fabrics even at high yarn's solid volume fractions.     

防刺机织物的设计与研究进展

介绍了机织物防刺机制、测试方法及防刺性主要评判指标的研究进展,并以织物的防刺机制为理论依据,从纤维原料、纱线、织物、后整理四方面分析了提高机织物防刺性的设计方法。     

Influence of textile treatment on mechanical and sorption properties of flax/epoxy composites

The aim of the present work is to study the effect of conventional textile treatments of woven flax on the mechanical properties and the water sorption of flax/epoxy composites. The flax fabrics are standard 2/2 twills. Various treatments are carried out on fabric such as mercerization, bleaching, and leaching for long fibers or on yarn such as leaching for short fibers. A model, based on a modified rule of mixture applied to composite reinforced with woven fabric, is developed to include the effect of fiber and porosity volume fractions on composite stiffness and strength. Most treatments improve tensile stiffness and strength of flax/epoxy composite and reduce composite water sorption. We prove by X‐ray fluorescence analysis, thermogravimetric analysis, and tensile tests of dry fabric that it is due to an improvement in the interfacial bonding between fibers and matrix. The best performances are achieved with bleaching and mercerization treatment. The weakest performances are obtained with the composites made with leached yarns. POLYM. COMPOS., 34:1761–1773, 2013. © 2013 Society of Plastics Engineers     

Measuring linear density of threads in single‐system‐mélange color fabrics with FCM algorithm

According to the color yarns in the fabric, the fabrics can be divided into three categories: solid color fabrics, single‐system‐mélange color fabrics, and double‐system‐mélange color fabrics. The density of solid fabrics can be inspected with gray‐projection method or Fourier analysis method. But the methods cannot be applied to yarn‐dyed fabrics directly. A method for detecting the density of single‐system‐mélange color fabrics will be discussed in this article. By analyzing the pattern and color characters of single‐system‐mélange color fabrics, fuzzy C‐means algorithm is proposed to classify the colors in the fabric image based on CIELAB color space first. With the color segmentation results, the fabric can be divided into different blocks. The yarns can be located in different blocks with different average gray‐levels, and then the number of yarns can be counted in each block. The linear density of threads can be obtained by counting the yarns in a unit length finally. The experiment proved that the algorithm proposed in this study can inspect the density of single‐system‐mélange color fabric successfully. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 456–462, 2013     

用于轮胎帘布层的芳纶帘子布的开发

采用芳纶1414纱线和聚酰胺66包芯纱织造芳纶帘子布,通过调整帘子布的密度,设计出了4种不同紧度的帘子布,并对织造过程中遇到的影响帘子布质量的相关问题进行分析,提出了相应的解决方案。同时,对帘子布进行力学及阻燃性能测试分析,结果表明:所设计的帘子布的抗冲击性和阻燃性能良好,可较好地应用于轮胎帘布层。     

Effect of carbon fabric type on the mechanical performance of 2D carbon/carbon composites

A stabilized PAN fabric was carbonized and graphitized from 800°C to 2500°C. Two-dimensional (2D) carbon/carbon composites were made using the stabilized PAN fabric, carbonized fabrics, and a resol-type phenol-formaldehyde resin. These composites were heat-treated from 600°C to 2500°C. The influence of different heat-treated fabrics and heat treatment on the fracture and flexural strength of these composites was also studied. The composite reinforced with higher heat-treated fabrics showed a lower weight loss than that with lower heat-treated fabrics. When the composites were graphitized at 2500°C, the loss was 49.7 wt% for the composite made with stabilized PAN fabric and 26 wt% for that with carbonized fabric at 2500°C. Those composites also have a higher density than composites produced by other methods. Composites made with stabilized PAN fabric exhibited a strong bonding in the fiber/matrix during pyrolysis. This composite showed catastrophic fracture and a smooth fracture surface with no fiber pullout. Composites made with higher carbonized fabrics exhibited a weak interface bonding. These composites showed a pseudo-plastic fracture pattern with fiber pullout during pyrolysis. Composites made with carbonized fabrics at 2000°C and 2500°C showed the highest flexural strength at the prolysis temperature of 1000°C. Composites made with carbonized fabric at 1300°C showed the highest flexural strength above 1500°C to 2500°C. The composite made with stabilized PAN fabric exhibited the lowest flexural strength during pyrolysis.     

A novel method for weft and warp yarn segmentation in multicolour yarn‐dyed fabric images

This paper proposes a novel method for segmentation of weft and warp yarns in multicolour yarn‐dyed fabric images. A multicolour yarn‐dyed fabric is cross‐woven by weft and warp yarns with different colours. When a multispectral imaging system is used to measure the colour of a multicolour yarn‐dyed fabric image, its weft and warp yarns need to be detected before analysing their colours. Detection of interstices between weft and warp yarns is firstly conducted. A modified K‐means clustering approach is then utilised to separate weft and warp yarns. The number of clusters is fixed to 2. The metric to measure the distance between a pixel and the mean of a cluster is the CIELAB colour difference. The initial means are determined by the expected values of fitted Gaussian distributions to CIExyY colour histograms. Experimental results show that the proposed method is promising for the segmentation of weft and warp yarns in multicolour yarn‐dyed fabrics, with an improved segmentation accuracy and much faster processing speed than K‐means clustering in CIEXYZ and CIELAB spaces.     

Effect of reinforcement with carbon fabrics impregnated with nanoparticles on the tensile behavior of cement-based composites

The objective of this work was to modify the microstructure of carbon fabrics with mineral or organic fillers absorbed between the filaments of the fabric strands in order to optimize the composite tensile properties. The obtained mechanical properties of all composites with fillers were superior to those of the reference composite. In mineral fillers, the improvement in mechanical properties was attributed largely to an increased sleeve/core ratio, resulting mainly from a pozzolanic reaction between filler (silica) and calcium hydroxide of the cement paste products. In organic fillers, the improvement was attributed largely to good filling and the ability of the polymer to bind all the filaments within the bundle to form a single unit, such that the load is efficiently carried by all the filaments. However, these composites suffered from delamination. Silica-based fillers should be given special consideration since they provide good bonding with the cement matrix without suffering delamination.     

Automatic detection of layout of color yarns of yarn‐dyed fabric. Part 3: Double‐system‐Mélange color fabrics

Automat layout detection of color yarns is necessary for weaving and producing processes of yarn‐dyed fabrics. This study presents a novel approach to inspect the layout of color yarns of double‐system‐mélange color fabrics automatically, which is Part III of the series of studies to develop a computer vision‐based system for automatic inspection of color yarn layout for yarn‐dyed fabrics. The inspection of single‐system‐mélange color fabrics has been realized in Part I of the series of studies. Integrating the projection‐based region segmentation method proposed in Part I and the FCM‐based stepwise classification method proposed in Part II, the proposed approach is composed of three steps: (1) fabric region segmentation, (2) fabric region selection, and (3) layout of color yarns recognition. In the first step, the fabric regions are segmented by the projection‐based region segmentation method. In the second step, the reasonable fabric regions are selected by analyzing their color histograms and comparing their weft color's frequency. In the third step, the layout of color yarn is recognized by the FCM‐based stepwise classification method, and the precise layouts of color warps and wefts are produced. The experimental analysis proved that the proposed method can recognize the layout of color yarns of double‐system‐mélange color fabrics correctly by testing four different color fabrics and three pieces of same yarn‐dyed fabrics. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 250–260, 2017     

The production of soft, durable, and electrically conductive polyester multifilament yarns by dye-printing them with carbon nanotubes

Carbon nanotube based dyestuffs were prepared by dispersing aggregates of multiwalled carbon nanotubes in water using a blend of zwitterionic surfactants with anionic surfactants. Using a dye-printing approach, the carbon nanotubes were directly applied to polyester multifilament yarns to form an electrically conductive layer over each filament of the multifilament yarn. Yarns having electrical resistivity ranging from 10³ to 10⁹ ohm/cm were obtained. Yarn with a resistivity of 10³ ohm/cm could be used to form flat, soft, and portable electrical heaters by vertically weaving the yarns into fabrics. The 10⁵ ohm/cm yarns could be used for anti-static clothing, and the 10⁹ ohm/cm level yarns for brushes for photocopying machines.     

Comparison of mechanical and ballistic performance of composite laminates produced from single‐layer and double‐layer interlocked woven structures

Textile structures have become quite popular as reinforcement materials in composite laminates due to their high impact‐damage tolerance and energy absorption ability. The impact performance of textile composites is not only affected by the type of fiber/matrix but also by the fabric structure used as reinforcement. The aim of this study was to compare the mechanical and ballistic performance of composite laminates reinforced with single‐layer and double‐layer interlocked woven fabrics. Kevlar^®−29 multifilament yarn was used for preparation of all the fabric structures and epoxy resin was used as the matrix system. The composites were produced using a hand lay‐up method, followed by compression molding. The mechanical and ballistic performance of composites reinforced with single‐layer and double‐layer interlocked woven fabrics was investigated in this study. The energy absorption and mechanical failure behavior of composites during the impact event were found to be strongly affected by the weave design of the reinforcement. The composites reinforced with double‐layer interlocked woven fabrics were found to perform better than those comprising single‐layer fabrics in terms of impact energy absorption and mechanical failure. POLYM. COMPOS., 35:1583–1591, 2014. © 2013 Society of Plastics Engineers     

Impact response of 3-D woven composites reinforced by consolidated rods

This paper examines the impact response of three-dimensionally woven fabric composites using consolidated rods in the axial direction. The material processing includes fabrication of the 1-mm rods by pultrusion, formation of the fabrics, and impregnation of the resin. A weaving setup incorporating the rods in the axial direction has been developed. Using the setup, three types of orthogonal fabrics with varying the tow sizes have been made. The microgeometry of yarns and the distribution of fibers were examined. Impact tests were carried out using an instrumented drop-weight impactor. Matrix cracks and rod debonding are the principal damage modes on the top and bottom surfaces. However, the crack configurations on these surfaces are very different. Formation of these damage modes and the associated influencing factors have been discussed. One feature not found in conventional composites is rod pull-in, which is a result of rod debonding and sliding. The pull-in creates a zone of holes on the specimen edge, revealing how the stress wave propagates from the impact to the non-impact sides. It is found that the pull-in is more pronounced near the non-impact side. The load-time and energy-time histories have been examined and related to how the specimens respond to the impact.     

Some issues on impregnation in manufacturing of thermoplastic composites by using a double belt press

The manufacturing of thermoplastic composite intermediates by a continuously running double belt press (System of Held Comp., Germany) has become one of the most effective techniques for high quantity production. The process of combining thermoplastic materials and reinforcing fabrics during the manufacturing results in impregnation phenomena of the reinforcing layers distinct from one in resin transfer molding (RTM). Here, the work is focused on the clarification of the impregnation process that occurred in such a continuous manufacturing process. A composite intermediate of 50 wt% fibers consisting of E-glass fabrics and nylon 66 films (Zytel, DuPont) was produced at different processing conditions to exhibit the influence of the degree of impregnation on mechanical properties and damage patterns of thermoplastic composites. It can be proved that because of strong inhomogeneity in the fabric concerning the permeability of the yarns and the weaving structure, respectively, the time required to impregnate the fabrics is governed by transversal micro-flow into the fiber bundles rather than macro-infiltration of the polymer into the fabric structure. Imperfect impregnation resulted in specific damage pattern in the center of the compressed yarns after flexural loading. The results are to be applied to guide the optimization of the manufacturing process with respect to material selection and preselection of processing conditions.     

三维纺织结构增强复合材料的几何模型

基于对织物断面显微照片的观察和分析，首先建立了三维正交织物的单元结构模型，并以此为基础建立了正交接结织物的单元结构模型；利用几何模型公式推导建立几何结构特征参数与编织工艺参数之间的理论关系；在此基础上计算了纱线长度、接结经与经纱的取向角和纤维体积含量；通过几何极限条件定义了织物紧度，为进一步研究其力学性能奠定基础。