Optimization of bending and shear rigidities of woven fabrics using desirability function

Abstract

Banding and shear properties influence the drape and handle characteristics of woven fabrics. As bending and shear rigidities of woven fabrics generally have high degree of association, it is difficult to design a woven fabric having low bending rigidity and high shear rigidity or vice versa. This paper deals with the optimization of bending and shear rigidities of woven fabrics using the desirability function approach. Low stress mechanical properties such as bending rigidity and shear rigidity have been combined to represent ‘the overall desirability’ which is varying from 0 to 1. The overall desirability has been maximized against the target values of shear and bending rigidities. It was possible to attain overall desirability of 0.684 resulting from individual desirability of 0.662 and 0.707 for banding and shear rigidities, respectively. Experimental validation confirms that the applied method can be effectively used to optimize the woven fabric mechanical properties at low stress region.     

Effect of misalignment on shear response of plain woven fabric in picture frame test: experiments and finite element modelling

Picture frame test on woven fabrics is not completely controlled and misalignment is one of the tremendous factors. The aim of this study was to investigate the effect of misalignment on the shear response of plain woven fabric in picture frame test. Misaligned and aligned specimens of plain woven fabric were tested, and digital image correlation (DIC) technique was applied to map the strain displacement fields. Unit cell models of misaligned and aligned specimens were built to simulate the mechanical behaviours during the shear test. Simulated and experimental results showed reasonable agreement. Strain fields mapped by DIC and averaged strains obtained by FEM simulation both demonstrate that tension or compression is introduced by misalignment. Deformation mechanism of misaligned fabric is discussed.     

Characterization of shear behavior of warp-knitted fabrics applied to composite reinforcement

Different types of textile fabrics are now widely used for reinforcing composite structural parts. In this work, three types of weft-inserted warp-knitted fabrics differing in stitch pattern and composed of glass roving were produced. The shear behavior of the developed fabrics was determined according to stitch type. Three basic stitch types were chosen: tricot, cord, and pillar. The shear behavior was examined by the picture frame test method. It was observed that the stitch type significantly affects the shear behavior of the fabrics. The deformation phases during the fabric shear test were analyzed. To estimate the changes in the shear stiffness of the fabrics, shear moduli were calculated as a function of the shear angle. In general, the fabric with the tricot stitch has the greatest shear resistance than that of fabrics with the cord and pillar stitches. The results of the characterization of shear behavior of the warp-knitted fabrics are presented and discussed.     

Geometry of plain weave fabric under shear deformation. Part I: measurement of exterior positions of yarns

Behaviour of woven fabrics in all directions is important in some fabric applications. Dealing with geometrical deformation of fabric under shear stress is the main attempt of this paper. A method for detecting exterior positions of yarns in fabric, namely variation in warp-weft yarns angle and sett of yarns is developed in the present part. For this purpose, the fast Fourier transform (FFT) method is modified for detecting exterior position of yarns in sheared fabric. In an empirical work, two kinds of plain weave fabrics, cotton and polypropylene, are considered and specimens are prepared in different dimensions with identical aspect ration. Exterior positions of yarns in certain elongations are computed by proposed method for each specimen. It was found that the modified FFT technique is valid for evaluating exterior positions of yarns in sheared fabric. Moreover, it is observed that there is a critical state in behaviour of woven fabric under shear deformation. In subsequent parts, the treatment of fabric under shear deformation will be simulated and compared with results of present part.     

28—THE BENDING AND CREASING OF MULTICOMPONENT VISCOELASTIC FIBRE ASSEMBLIES. PART II: THE MECHANICS OF A TWO-DIMENSIONAL ASSEMBLY OF LONG STRAIGHT FIBRES OF DIFFERENT TYPES

A model two-dimensional assembly of long straight viscoelastic fibres of many different types arranged in various directions is analysed in terms of bending, creasing, and associated recovery behaviour. The fibres are assumed to be viscoelastic in both bending and torsion and subject to frictional restraints in both these modes of deformation. It is assumed that the model is relevant to the bending and creasing behaviour of woven and non-woven fabrics composed of fibres of one or more types.     

家庭滚筒洗衣机洗涤温度对机织物外观平整性的影响

家庭滚筒洗衣机洗涤衣物时,水、洗涤温度的共同作用对织物外观平整性影响显著,合适的温度设定有助于洗衣机的参数优化。文中选取5种常见白色普通整理的机织物,在滚筒洗衣机温度分别为室温20、30、45、60、75 ℃条件下洗涤,测试其洗后外观平整度、洗涤前后弯曲刚度及剪切刚度等指标。研究发现,洗涤温度较低时,机织物外观平整度较好;洗涤温度增大时,机织物平整度降低,洗后弯曲刚度及剪切刚度减小。纯棉织物20℃与75℃洗后的平整度最大差值为1.6级;涤纶织物20℃与75℃洗后的平整度最大差值为3.8级,洗涤温度对涤纶织物平整度的影响较棉织物大。研究成果可为机织物家庭滚筒洗涤温度的设置提供依据。     

Ring frame process parameters and fabric comfort. Part I – low-stress mechanical properties of fabrics

Influence of ring frame process parameters, namely twist multiplier of yarn, spindle speed and ring frame draft, on some of the yarn characteristics has been studied. The low-stress mechanical characteristics of woven and knitted fabrics made out of these yarns have also been reported in the present paper. Yarn packing factor, which is directly related with the yarn diameter, has direct impact on fabric comfort related characteristics. All the studied ring frame process parameters, i.e. yarn twist, ring frame draft and spindle speed, have inverse effect on the yarn diameter, which means the yarn diameter reduces with the increase in one of the process parameters by keeping the other two parameters constant. The impact of draft on reduction in yarn diameter is found to be higher as compare to other two parameters. All these ring frame process parameters have significant impact on other yarn parameters also. The increase in yarn twist, spindle speed and draft result in increase in flexural rigidity, unevenness and imperfections of yarn and decrease in yarn hairiness. All the low-stress mechanical properties, i.e. tensile, shear, bending, compression and surface, of both woven and knitted are affected by the above ring frame parameters. The thickness of fabrics changes with the yarn compactness, i.e. with the reduction in yarn diameter. The study revealed that by changing the above ring frame process parameters, it is possible to manipulate the fabric handle characteristics without changing the fabric constructional parameters.     

A test apparatus to measure vertical wicking of fabrics – a case study on shirting fabrics

A test apparatus based on electrical conduction principle was designed and manufactured to overcome some difficulties and deficiencies in vertical wicking measurements of fabrics, which is one of the test methods used to determine liquid moisture transmission performance of fabrics. In order to test effectiveness of the apparatus, capillary time with regard to height was measured for woven shirting fabrics, which have different raw material, weave type and weft density. It was found that twill weave type and fabric looseness improved the wickability of fabrics. It was also revealed that raw material was an important factor for vertical wicking. The wicking rate of fabrics obtained from the new test apparatus correlated well with DIN 53924. Consequently, the test apparatus clearly demonstrated differences between the fabrics used in the study, and can be used to determine vertical wicking behaviour of fabrics.     

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.     

织物折皱回复角的计算

利用标准固体单元和滑块并联组成的模型,在织物摩擦约束力偶与其弯曲曲率成正比的假设下,对织物的弯曲和折皱回复进行了分析,并用纯弯曲实验得到的数据计算出织物的模型参数,从而计算出织物在不同时刻的回复角,平纹织物的理论预期与实测结果符合较好。     

剪切增稠液浸渍超高分子量聚乙烯织物的防锥刺性能

为提升超高分子量聚乙烯织物的防锥刺性能,采用剪切增稠液对织物进行浸渍复合,制备了柔性液体防 护材料。采用落锤实验测试了不同密度的超高分子量聚乙烯织物及与剪切增稠液复合后织物的防锥刺性能,研究了不同质量分数剪切增稠液的流变性能和浸渍后织物的纱线抽拔性能,并分析了织物复合后的增强机制。实验结果表明：剪切增稠液的增稠效果随着分散相质量分数的增加而增强,剪切增稠液浸渍后织物的纱线抽拔力提高了3.1倍,经剪切增稠液浸渍的织物具有更好的防锥刺效果。剪切增稠液显著提高了纱线的摩擦力,并限制纱线滑移,从而具有更好的防锥刺效果。     

A Study of the Mechanical Properties of Woven Silk Fabrics. Part I: Fabric Mechanical Properties and Handle Characterizing Woven Silk Fabrics

In order to investigate the soft handle of woven silk fabrics, their basic tensile, bending, shearing, compressional, and surface properties were measured on the KESF system. Fabric shear, compressional, and tensile properties distinguish continuous-filament silk fabrics from fabrics of other fibres. Shear stiffness and hysteresis in shear force are very small, and these fabrics are very deformable in their compressional and tensile properties at small strain levels.

High values of FUKURAMI are a characteristic of continuous-filament woven silk fabrics.     

A Study of the Mechanical Properties of Woven Silk Fabrics. Part II: Analysis of the Shearing Properties of Woven Silk Fabrics

The gap between the warp and weft threads at their crossover points in woven silk fabrics is responsible for the very low values of shear stiffness and hysteresis of shear force in these fabrics. The existence of this gap is proved by using shear–deformation theory and making experiments on silk fabric. A quantitative determination of the gap is obtained by using strip–biaxial–extension experiments and measuring the retardation strain. The gap observed for woven silk fabrics is 6–7 μm. Since microscopical observation of the cross–section of silk fabrics does not show the gap, the gap measured by mechanical methods is called an “effective gap”. The gap has a strong effect on the mechanical properties of silk fabrics, especially their shear properties. It also emphasizes the good handle of silk fabrics.     

层-层正交角联锁机织物及其复合材料的结构及其层切破坏机制研究

采用无损高分辨率X射线成像(显微X-CT)技术对层-层正交角联锁机织物以及复合材料内部结构进行分析,并研究了层间剪切强度与结构之间的关系;通过三维重构展现了机织物的层-层正交角联锁的微观结构,观察到机织物内部的单丝扭转、挤压现象;依据机织复合材料中孔隙和高密度杂质在三维空间的分布,计算了其相应的占比。结果表明：层间剪切实验后的机织复合材料虽然宏观形貌保持了良好的完整性,但内部存在孔隙变形、分层、纤维弯曲、片层断裂等现象;层-层正交角联锁机织结构有效提高了复合材料的层间力学性能,内部的缺陷对复合材料的力学性能有较大的影响;无损高分辨X射线成像技术是研究纤维增强复合材料内部复杂结构特性的有利手段。     

Acoustic performance of woven fabrics in relation to structural parameters and air permeability

This work deals with the study of the acoustic characteristics of woven fabrics in relation to fabric structural parameters and air permeability. In order to achieve the objectives of the research, sound absorption coefficient of woven fabric samples was determined via impedance tube method. Samples with various pick densities and yarn twist were used. The effect of fabric thickness was analyzed using three and six layered test samples. Results showed that, while for all samples the minimum values of sound absorption were observed at frequency bands of 250 and 2000?Hz, the maximum sound absorption occurred at the frequency of 1000?Hz. Results also indicated that fabrics woven at pick density of 30?thread/cm exhibited higher sound absorption than fabrics woven at other pick densities. It was found that, noise reduction coefficient of three and six layered samples, woven at low pick densities showed significant increases in comparison to those woven at high pick densities. It was also established that samples woven with lower weft yarn twist absorb sound wave more efficiently. It was concluded that fabric air permeability can be used as a criterion of sound absorption behavior of woven fabrics.     

Dynamic fabric modelling and simulation using deformable models

This paper proposes a modelling of the dynamic behaviour of textile fabrics based on a new formulation of deformable models. Deformable models such as those that were introduced by Terzopoulos in 1987 for modelling and simulation of deformable objects in computer graphics are reformulated to simulate textile woven fabrics. This investigation tends to produce simulations of textile fabrics showing the dynamic aspect of their behaviour while remaining faithful to the physical reality of material. The developed model takes into account several mechanical and physical parameters of textile fabrics. Numerical resolution of partial differential equations controlling the behaviour of textile fabrics is made by using the finite element method. Several simulations are carried out and compared with the experimental results. A drape‐meter test is simulated and the results are strongly correlated with those obtained in experiments.     

43—ASPECTS OF SEAM-STRENGTH PREDICTION: PART I

Methods of sample preparation and test to assess fabric and seam strength in woven fabrics are described. In general, the samples examined were constructed so that the warp threads ran at an angle of bias to the loading direction. An initial analysis of experimental results is discussed, and physical and mathematical models of strength behaviour are postulated for plain-weave square-sett fabrics. Modifications to the mathematical model to cover non-square-sett, non-plain-weave fabrics are suggested.     

An experimental investigation into structure and properties of 3D-woven aramid and PBO fabrics

Three-dimensional (3D) fabrics are the focus of recent developments due to their versatile physical, structural attributes, and application scopes. These fabrics can be manufactured in various architectures which offer a great deal of opportunity to modify the weight, physical and mechanical properties, and cost of the various products. The potential usage of 3D woven fabrics in the ballistic protection applications was the main motivating factor of this research work. Thus, interest has been focused to investigate the structure and properties of 3D woven orthogonal fabrics with aramid fiber and PBO fiber in comparison with 2D fabrics. The investigation of ballistic properties of these fabrics showed that 3D woven fabrics are superior in terms of breaking load and energy absorption as compared to those of 2D woven fabrics. The specific ultimate tensile strength of 3D woven fabric was observed to be lower than 2D fabrics, which may be due to less number of load bearing yarns in the loading direction. The crimp percentages of the load bearing tows in 3D fabric are very less than that of 2D fabrics. Owing to the higher values of work at peak and load at peak, in knife penetration test, it is revealed that 3D fabrics offer better protection than 2D fabrics.     

Inspecting anisotropy in wrinkle recovery angle of woven fabric

In this paper, the anisotropic wrinkle recovery properties of plain and twill fabrics are explored by studying the variations of the wrinkle recovery angle with sample orientation angle. Orientation angle is the angle measured counterclockwise from the weft direction to the sample’s long axis, that is, the crease direction. This study focused on inspecting anisotropy in wrinkle recovery to find more effective test angles for different woven fabrics. A dynamic wrinkle recovery tester was used to measure the recovery angles of specimens automatically which were cut in various directions. The trend of plain fabrics shows that its recovery angle generally increases at first and then decreases with the increase in the orientation angle. The trend of twill fabrics differs in folding ways. The experimental results revealed that the wrinkle recovery angles of the woven fabrics had the lowest values near the orientation angles of 0° and 90°, i.e. the warp and weft directions, and therefore these two traditionally used directions in the standard test method did not best reflect the wrinkle recovery yielded from both warps and wefts. The diagonal direction (45°) was proven to be the optimal orientation angle for a balanced plain fabric, while the two orthogonal directions, i.e. the twill direction and its perpendicular direction, were found to be more relevant for a twill fabric. Optimal orientation angles used to test the wrinkle recovery angle of a woven fabric should be associated with its structure.     

近红外（NIR）光谱在长丝纱和机织物浆料检测中的应用

通过对上浆及已退浆的机织物试样和从织物中分离的经纬和纬纱的测试研究,探索了近红外（ＮＩＲ）光谱鉴定长丝纱与机织物上浆料的可能性与局限性,证实了近红外光谱可用于对纱线与织物上有机物（此时为浆料）的定性分析中,但必须有一个完整的数据库。每一次试验中必须得出清晰明了的试样鉴定结果,以便在数据库中提取具有相近特性的对照试样的数据相对照,最后,必须保证试样在准备和制作时条件一致。