Study of tensile properties of plain-woven fabrics in all-directional using energy method,Part I: theoretical study

Abstract

In the first part of this series, a new mechanical parameter, that is, “Comprehensive Tensile Modulus (CTM)” is introduced and modeled to show the tensile behavior of plain-woven fabrics in the initial linear elastic region of the force-elongation curve subjected to tensile load and extended it simultaneously in all directions. Considering the initial load-extension behavior of fabrics, a mathematical-mechanical model is presented to predict the CTM of fabrics in the initial linear elastic region using Castigliano’s theorem. Based on the generated model, the initial sample length, dimension of the load imposed region, the geometrical shape created in the plain-woven fabric sample during tensile, the structural specification of these fabrics such as yarns sett, yarns crimp in fabric and mechanical properties of yarns such as bending rigidity in both warp and weft yarns affect in the comprehensive tensile modulus of fabric. In order to verify the conformity and accuracy of the model, a preliminary test was conducted on the prepared samples based on a novel tensile test method developed to measure load-extension curve of the fabric samples under the proposed loading condition. A reasonable agreement was found between theoretical and experimental results.     

Analysis of the tensile behavior of tubular braids using energy method,Part II: experimental study

In the first part of this series, an analytical model was proposed for predicting the tensile modulus of tubular braids using energy method. The aim of this study is to perform experimental effort to evaluate the previous generated model. For this purpose, two types of yarns namely monofilament and multifilament yarns were used to produce tubular braids. The bending rigidity and tensile modulus of yarns were obtained in order to be used in the mentioned model. Also, the geometrical parameters of braids, i.e. braid angle, length of the unit-cell, and length of the yarns in the unit-cell were measured. Using the proposed model, the tensile modulus of braids was calculated. On the other hand, the tensile modulus of provided samples was measured by means of INSTRON tensile tester and compared with theoretical values. The results showed that the proposed model in Part I of this series is capable of predicting tensile modulus of braids with different structure, adequately.     

Theoretical and experimental investigation of tensile properties of net warp-knitted spacer fabrics

Abstract

This work aimed to investigate the tensile behavior of net warp-knitted spacer fabrics using the experimental and theoretical approaches. Tensile behavior of the warp-knitted spacer fabrics is one of the fundamental parameters which rarely considered in the literature. Therefore, the net spacer fabrics were made with three different variables (fabric thickness, size of meshes, and the position of meshes of the outer layer with respect to each other) in order to study the effects of structural parameters on the tensile behavior. A 2D net-fabric which used for the outer fabrics was made for in-depth considerations and also the comparison between the 2D fabrics and spacer fabrics. The initial linear elastic modulus of the 2D fabrics and the initial linear elastic modulus of the spacer fabrics were selected for the assessment of the tensile characteristics. First, a mechanical model was developed based on the geometrical structures and material properties of the 2D fabrics using energy method and Castigliano’s theorem. Then, the effects of spacer yarns on the tensile behavior of spacer fabrics were taken into account. The latter model was proposed using the bending theory of a curved bar. Experimental data were compared with the values obtained from the theoretical approaches and the end results showed that the developed models can predict the modulus reasonably. Moreover, the results indicated that the tensile behavior of the spacer fabrics are independent of the position of the holes in the outer layer whilst the fabric thickness and size of meshes affect the tensile modulus.     

A novel method to investigate tensile properties of woven fabrics in all-direction

In this research, we propose a new method and instrument to measure load-extension curve of the fabric samples under all-directional extension. Using this method, fabric sample is loaded under extension in the warp, weft, and all other directions in between. Using this new method, we introduced a comprehensive tensile modulus which is affected by the fabric structures and densities. For this purpose different structures i.e. plain, Twill 2/2, Twill 1/3, and Twill 1/7 were produced with different densities. Then these samples were tested under the new method. Our results are then compared to those one would obtain under uniaxial tests, by performing independent uniaxial tests. It is shown that under all-directional test lowering the weft density decreases the tensile comprehensive modulus. Furthermore, a reduction in the floating yarns in the fabric structure decreases the tensile comprehensive modulus. It was found that among the samples tested here, plain fabric and Twill 1/7, respectively, possess the maximum and minimum comprehensive modulus. A similar trend was also observed through independent uniaxial extension, in warp or weft direction, test.     

Anisotropy in geometrical and tensile properties of plain weave fabric: verifying a semi-empirical model

Geometrical and mechanical behaviors of fabric are extremely anisotropic. Exploit of fabric in multiplicity applications is dependent on its behavior in differ directions. Thus, attempts had been made to study the behavior of fabric in off and on axis systematically. For this purpose, authority of a semi-empirical model, based on earlier work, was experimentally investigated. The model consists of a numerical way to estimate yarn path under axial and normal tension simultaneously. A test method to evaluate flattening of yarn was presented in this study. Moreover, to reduce stress concentration at the sample’s corners a modified griper was applied. On the basis of initial data of fabric and flattening behavior of constitutive yarns, the fabric geometry and tensile force–strain (TF–S) curve of a strip fabric in arbitrary direction are capable to estimate using stated model. The variations in density of warp and weft yarns, shear angle, and TF–S curve of a fabric in different directions were measured and are compared with theoretical values. It was found that the stated model is applicable to predict fabric geometry and tensile behavior of a plain weave fabric under stress in arbitrary direction. Experimental results indicated that the strength of fabric at 45 degree was 22.59% higher than the strength of fabric in average of principal directions. On the basis of semi-empirical model, it is anticipated that the maximum strength of presented fabric would be occurred at 60 degree with 27.99% higher than the strength of fabric in average of principal directions.     

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.     

Prediction of thermal resistance of woven fabrics. Part II: Heat transfer in natural and forced convective environments

The aim of the paper is to observe the effects of convection on the total heat transfer of the fabric. Convective heat transfer through textiles can be simulated with the help of computational fluid dynamics (CFD). The first part of this paper has dealt with the mathematical model for predicting the conductive and radiative heat transfer. The second part of the paper describes the use of CFD to simulate the wind tunnel of the instrument. The fabric has been subjected to natural and forced convection. The convective heat transfer coefficients obtained from the simulation were used to find the resistance due to convection. The final values obtained from the model were compared with the values obtained from the thermal resistance measuring instrument fabricated to measure the thermal resistance in natural and forced convective modes. The mathematical model gave excellent prediction in forced as well as natural convective mode when coupled with CFD results.     

Characterization and analysis of in-plane shear behavior for glass warp knitted non-crimp fabrics based on bias extension experiment

Abstract

In this article, the in-plane shear rigidity modulus of five commercially available fabrics of glass warp knitted non-crimp fabrics (WKNCFs) was experimentally investigated by uniaxial bias extension test (UBE). The aim was to characterize and compare the shear behavior of relatively high areal density fabrics, while these fabrics could have good potential to be widely used in the composites field. In this work, five fabrics were included: a uni-directional, 2 bi-axial, and 2 tri-axial fabrics. To characterize the shear properties, stress equations were established to deliver the in-plane modulus of shear rigidity as a function to shear angle. The fabric structure of uni-axial or multi-axial had a different influence on the shear resistance mechanics along with the influence of the stitching pattern; both were also presented in the comparison of deformation mechanisms. It was found that the shear behavior of all five fabrics was dissimilar to each other.     

用于VCM钢板单向拉伸实验的数字散斑相关法应变检测

针对板料传统拉伸实验中应变获取仅限于拉伸断裂之后的数值等问题,应用数字散斑测量技术计算了应变,分别以深冲VCM钢板、非深冲VCM钢板及其组分材料为研究对象进行了单向拉伸实验,应用XJTUDIC散斑测量设备进行了同步检测,获得了材料沿x向、y向2个方向的应变数据,并以5种材料的轧制45°方向试样为例,分析了5种材料沿x向、y向2个方向的应变关系.结果表明:2种VCM钢板的应变能力明显优于2种钢板基板,非深冲VCM钢板和深冲VCM钢板x向的最大应变为68.743%和48.632%,y向的最大应变为-2.657%和-15.381%,其力学性能介于钢板与VCM薄膜之间,其中深冲VCM钢板的力学性能要优于非深冲VCM钢板.     

Analysis of spinning process using the Taguchi method. Part IV: Effect of spinning process variables on tensile properties of ring,rotor and air-jet yarns

Abstract

The yarn samples prepared for migration study were tested for tensile properties. Furthermore, the effect of drafts of the spinning machines on yarn strength and breaking elongation (%) was studied. The effect of spinning position, doff position and material conditioning during testing on yarn tensile properties were also accounted for. The ring yarn was seen to have the highest tensile properties, whereas air-jet yarns the lowest. The low elastic recovery of viscose fibres is the cause of weakest and least extensible air-jet yarns.     

Ramie fibre: part II. Physical fibre properties. A critical appreciation of recent developments

This monograph critically reviews recent research work and developments in physical and related properties of ramie, a long vegetable bast fibre. The properties of the fibre at different stages of plant growth including topography, optical microscopy, electron microscopy, moisture regain, density, strength, tenacity, fineness and mechanical properties as well as thermal, infrared, FTIR and X-ray properties are discussed.     

Ramie fibre: part II. Physical fibre properties. A critical appreciation of recent developments

This monograph critically reviews recent research work and developments in physical and related properties of ramie, a long vegetable bast fibre. The properties of the fibre at different stages of plant growth including topography, optical microscopy, electron microscopy, moisture regain, density, strength, tenacity, fineness and mechanical properties as well as thermal, infrared, FTIR and X-ray properties are discussed.     

Phenolic Composition,Essential Oil,and Antioxidant Activity in the Aerial Part of Artemisia Herba-Alba from Several Provenances: A Comparative Study

This study characterized the phenolic, aroma compositions, and antioxidant capacities of four Artemisia herba alba accessions collected from north and center regions in Tunisia in order to select valuable origin with optimal bioactive compounds production. The total polyphenol and flavonoid contents varied between accessions with maxima contents observed in center regions. Kaempherol, apigenin, naringenin, p-coumaric, trans-cinnamic, and caffeic acids were the most abundant compounds with percentage varying depending on the considered accession. Significant changes on essential oil yields (0.4–1.2%) were found between accessions and three different oil chemotypes were distinguished: camphor, fenchol/α-thujone, and α-thujone/camphor. Cluster analysis of volatile and phenolic compositions grouped the accessions on different groups. Antioxidant activities of extracts were found to be higher than essential oils for the four provenances. The results suggested that the center regions have high potential for selecting varieties rich on essential oil, antioxidant phenolic acids, and flavonoids.