基于3D打印的竹节结构中空单丝制备及其压缩性能

为研究竹节结构中空单丝内部结构对其压缩性能的影响,以聚酯为耗材,利用3D打印技术制备了长度为100 mm、外径为2 mm的竹节结构中空单丝和实心单丝,测试了单丝的抗压性能,利用有限元分析探讨了竹节结构中空单丝作为间隔丝对经编间隔织物抗压性能的影响。结果表明:单丝的压缩性能受其内部结构影响,竹节结构中空单丝单位质量承受载荷的能力优于实心单丝;竹节结构中空单丝中空部分所占比例越大,单丝单位质量承受的载荷越大;织物的压缩性能与间隔丝内部结构有关,作为间隔丝的竹节结构中空单丝中空部分所占比例越大,织物单位质量承受的载荷越大。     

Mathematical modeling of spacer fabrics under impulsive loading

In this research, a model has been provided to predict the damping behavior of spacer fabrics against impact forces. These fabrics were modeled as lumped mass and spring system. Because of damping force in mechanical systems, a dashpot has been added to the system for producing the damping force. Therefore, mathematical modeling of the vibration system led to a differential equation. By solving this equation, the displacement of the system was obtained. Consequently, by the application of the second law of Newton, the resulting force of impulse was calculated as a function of time. In addition, the damping behavior of multi-layer spacer fabrics was analyzed by extending the model used for a single layer. Finally, to evaluate the accurateness of the obtained model, a set of standard impact tests were designed and performed on spacer fabric samples. The results of statistical analyses showed that there is no significant difference between theoretical and experimental outputs. Altogether, the results of impact tests show that by decreasing the fineness and length of monofilaments and increasing their density, the force transmitted to the projectile is increased.     

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.     

纬编间隔织物的编织工艺与压缩性能探讨

采用涤纶单丝作为间隔纱和低弹涤纶长丝作为表层纱,在双面圆纬机上编织了几种不同规格的纬编间隔织物,并探索了编织工艺.对这些织物的压缩性能进行了测试,分析了压力-变形曲线和影响压缩变形和回复性能的因素.实验结果表明,在其它条件都相同时,间隔纱细度、织物密度、筒口距离的增加,有利于减小织物的压缩变形和提高回复性能.     

Permeability and impact properties of warp-knitted spacer fabrics for protective application

An experimental investigation was carried out to study the effect of interlining material on the comfort and dynamic deformation characteristics of body armour. Suitable plies of interlining materials were selected based on the fabric comfort properties and the impact resistance specified for ballistic application. Kevlar woven fabric was used to block the projectile, and the spacer fabric was used as an interlining material to ensure wearing comfort and for imparting impact resistance. The yarn denier of the middle and bottom layers of the spacer fabrics was maintained constant, and three different deniers were used for the face layer. Three different plies of spacer fabrics were analysed by means of thermophysiological comfort properties to select the suitable interlining material for body armour. The experimental results confirm that the number of plies of spacer fabrics has significant influence on the ballistic armour characteristics than the face layer denier as proved by two-way ANOVA. The substantiated spacer fabric was used as an interlining material, and the depth and area of deformation were analysed. The research findings demonstrated that the three-plied warp-knitted polyester spacer fabric produced better results than single- and five-plied spacer fabrics. One-way ANOVA and Turkey’s HSD also confirmed the influence and interaction of different plies of spacer fabrics.     

Investigation on production,analytical models,and characteristics of monofilaments/staple fibers composite yarn

This study aims to develop a composite yarn comprising monofilaments/staple fibers with distinctive structures and performance. A modified ring spinning system was proposed for producing the composite yarn with three monofilaments and staple fibers. The spinning mechanism was analytically modeled, and the structures of composite yarn were studied by scanning electron microscopy and optical microscopy. The characteristics of polyester monofilaments/cotton composite yarns and the conventional cotton yarns were compared. Analytical and experimental results showed that three monofilaments were distributed around the yarn center forming a 3D spiral, and the staple fibers interlaced inside and wrapped outside of the composite yarn. Experimental results showed that the composite yarn had better tensile properties, less hairiness, and stronger abrasion resistance. As a result, the composite yarn exhibited a remarkable improvement over the conventional yarn, which could be a valuable proposition for specific purposes, such as offering fabrics with shape preservation based on good yarn’s rigidity, and even electromagnetic shielding effectiveness with metal monofilaments in yarns.     

Thermal and water vapor transmission through porous warp knitted 3D spacer fabrics for car upholstery applications

This paper deals with water vapor transmission and thermal properties of various warp knitted spacer fabrics. In this work, thermal and water vapor permeability of different spacer fabrics have been evaluated by varying the structure, areal density, thickness, type of raw materials, etc. The air permeability and water vapor transmission of the fabrics were measured using the Textest FX-3300 air permeability tester and PERMETEST. The thermal behavior of fabrics was evaluated by Alambeta instrument. Analysis of Variance (ANOVA) was performed using new statistical software in order to compare the influence of different fabric parameters on thermo-physiological behavior of samples. This study established that the raw materials, type of spacer yarn, density, thickness, and tightness of surface layer have significant influence on thermal conductivity in spacer fabrics. The parameters which mainly influence the water vapor permeability of these fabrics are porosity, density, and thickness. The empirical model for thermal conductivity calculation shows very high accuracy when compared with experimental results. The statistical model for spacer fabrics also predicts the thermo-physiological properties with very high accuracy. These findings are important requirements for further designing of spacer fabrics for car seats and back supports.     

Experimental and computational analysis of acoustic characteristics of warp-knitted spacer fabrics

Abstract

As a kind of porous medium, textiles have recently received increased attention for acoustic applications due to their high profitability and low cost and environmental impact. 3D knitted spacer fabrics stand out as a unique class of textile materials. These materials simultaneously are soft, voluminous and highly porous and therefore are expected to be suitable for sound absorbing applications. This article aims to investigate the acoustic performance of 3D warp-knitted spacer fabrics. To this end, acoustic behavior of warp-knitted spacer fabrics was experimentally measured using the impedance tube method. In order to predict the sound absorption behavior of fabrics, a simple geometrical model was created. Flow resistivity was calculated by numerically solving incompressible laminar Newtonian flow through the 3D pore space of generated structure. The frequency-dependent sound absorption coefficient of the warp-knitted spacer fabric was predicted using the empirical models of Delany and Bazley, Garai and Pompoli and Dunn and Davern. The results showed that the Dunn and Davern model can predict sound absorption characteristics of warp-knitted spacer fabrics in the mid-to high-frequency ranges. At low frequency ranges; however, none of the empirical models can reasonably predict sound absorption behavior of the fabrics.     

Investigation on thermo-physiological and compression characteristics of weft-knitted 3D spacer fabrics

The thermo-physiological comfort and compression properties of knitted spacer fabrics have been evaluated by varying the different spacer fabric parameters. Air permeability and water vapor transmission of the fabrics were measured using the Textest FX-3300 air permeability tester and PERMETEST. Thermal behavior of fabrics was evaluated by (TCi) thermal conductivity analyzer and overall moisture management capacity was evaluated by moisture management tester. Spacer fabrics compression properties were also tested using KES-FB3. In the KES testing, the compression resilience, work of compression, linearity of compression, and other parameters were calculated from the pressure–thickness curves. Analysis of variance was performed using new statistical software named QC expert trylobite and Darwin in order to compare the influence of different fabric parameters on thermo-physiological and compression behavior of samples. This study established that the raw materials, type of spacer yarn, density, thickness, and tightness of surface layer have significant influence on both thermal conductivity and work of compression in spacer fabrics. The parameter which mainly influences the water vapor permeability of these fabrics is the property of raw material i.e. the wetting and wicking properties of fibers. The Pearson correlation between moisture capacity of the fabrics and water vapor permeability was found.     

Impact resistance behaviour of silicone coated warp knitted spacer fabrics used for protective clothing

This paper aims to analyse the effect of coating, fabric layers and structural parameters on the impact resistance behaviour of warp knitted spacer fabrics used for protective clothing. For this purpose, six warp knitted spacer fabrics were produced by varying thickness and mesh structure and were coated with a silicone substrate. A drop-weight impact tester was used to determine the impact resistance characteristics of the samples. The results indicate that, the impact resistance properties of warp knitted spacer fabrics can be improved considerably by coating as reducing approximately 10 kN of the peak transmitted force. Also, the structural parameters such as fabric thickness and mesh structure have significant effects on impact resistance behaviour of the samples. The fabrics with higher thickness and smaller size mesh on the outer layers have better impact resistance properties. Additionally, the lamination of spacer fabrics can effectively improve the impact resistance characteristics of the spacer fabrics. The warp knitted spacer fabrics can be used as an energy absorbing material for body protection by varying their structural parameters, fabric lamination and/or by coating.     

经编间隔织物多层复合材料的防刺性能

针对目前国内防弹防刺复合插板的防刺性能仍需加强的要求,本文通过采用传统层压复合工艺将间隔织物与现有警用防弹防刺插板中材料(芳纶无纬布/芳纶机织布)相结合,在涂覆不同的黏合剂后,考察其在准静态与动态穿刺状态下的防刺性能。实验结果表明：芳纶平纹机织布由于其紧密的结构特征,可以被用来作为间隔织物的上表面进行有效防刺,同时间隔织物的下表面设计需较为紧密,这样有利于阻止刀尖的持续下刺,另外间隔织物的间隔丝可以有效将刀尖锁住,起到抗刺作用。研究也发现黏合剂对间隔织物及其夹层结构的防刺性能影响较大,采用强度、韧性、和粘结度高的胶有利于材料的防刺性能提高。     

经编间隔织物的冲击性能

为探讨间隔织物在一定冲击能量下对人体(支撑物)的保护性能。采用的原料为在拉舍尔双针床经编机上编织的6种不同结构(不同间隔丝梳栉横移针距、间隔丝直径和织物厚度)的间隔织物。分析了不同织物在一定冲击能量下的应力、能量和能量吸收效率特征。实验结果表明,随着间隔丝梳栉横移针距数的减小、间隔丝直径的增大,冲击产生的应力峰值减小,吸收的能量和能量吸收效率峰值增加,但间隔丝过于接近垂直的织物容易发生倒伏,不利于人体保护。较厚的织物产生的应力峰值小、吸收的能量多,中等厚度的织物能量吸收效率峰值高。刚度或厚度大的织物由于产生的应力峰值小有利于人体保护,但在选择织物结构时还需考虑人体穿着的舒适性。     

Application of warp-knitted spacer fabrics in car seats

Polyurethane foam is commonly used as padding in car seats despite some problems concerning comfort and recycling. Compared with polyurethane foam, textile seat padding is easier to recycle; so textile padding is a good candidate to substitute foam padding as regulations on recycling have become more stringent on car manufacturers. With the available textile option, warp-knitted spacer fabrics are likely a good substitute for polyurethane foam as padding in car seats. Warp-knitted spacer fabric structures can be designed to be quite flexible in a variety of thicknesses. Warp-knitted spacer fabrics can be very resilient and may display good breathing properties. The current work presents a study on the application of warp-knitted spacer fabrics as cushion in car seats. The results show that, relatively to polyurethane foam, warp-knitted spacer fabrics demonstrate better recovery to compression, thermal properties and breathability. Furthermore, warp-knitted spacer fabrics retain their original thickness for longer time and can be easily recycled.     

Prototyping and analyzing physical properties of Weft knitted spacer fabrics as a substitute for wound dressings

In this research, the required physical properties of weft knitted spacer fabrics, as an alternative for wound dressings have been investigated. For this purpose, weft knitted spacer fabrics with five different fabric structures have been produced on the electronic flat knitting machine. Moreover, in order to compare the properties of the produced fabrics with available wound dressings in the market, two kinds of wound dressing have been prepared from the market. Then, the physical properties of the spacer fabrics and the wound dressings such as air permeability, water vapor permeability, thermal conductivity, compressibility and absorbency have been measured and compared. The results show that in weft knitted spacer fabrics with the same fabric structure of the outer layer and different inclination angle (the angle formed between the outer layer and the spacer yarn), by decreasing the inclination angle, the fabric air permeability, water vapor permeability and absorbency decrease and the thermal conductivity and compressibility increase. Moreover, the use of tuck stitches in the outer layer of the spacer fabric leads to an increase of air permeability, water vapor permeability, absorbency and thermal conductivity and decrease of compressibility. The wound dressings also exhibit less air permeability and compressibility than weft knitted spacer fabrics. On the other hand, they possess higher water vapor permeability and absorbency. According to the results, among the examined weft knitted spacer fabrics in this research, the fabric with the tuck stitches in the outer layer is specified as the most appropriate alternative for wound dressing, in case of wounds with low exudates.     

经编间隔织物的缓压性能

为探究经编间隔织物的缓压性能与结构参数之间的量化关系,从理论上分析了经编间隔织物压缩过程中人体受力与间隔织物之间的相互作用机制,以及人体所受压强与其结构参数之间的关系,获得间隔丝直径、间隔丝排列密度以及间隔织物的厚度等结构参数与间隔织物缓压性能的规律方程。采用自行设计球形压头对不同结构参数的间隔织物样品进行压缩实验,验证分析间隔织物的缓压性能与这3个主要影响因素之间的关系,并得出了各自的回归方程。研究结果表明,间隔织物压缩过程中人体所受压强与间隔丝直径呈幂函数变化,与织物的厚度和间隔丝的排列密度分别呈反比和正比函数关系。     

纬编间隔床品面料的结构及性能分析

采用3.3 tex涤纶单丝为间隔纱,8.3 tex涤纶和2.2 tex氨纶交织为表层,制备4种不同密度、厚度及间隔纱连接方式的纬编间隔织物。分析织物组织结构和编织工艺,并测试力学性能和热湿舒适性能,分析面料厚度、密度与各项性能关系,用数学模糊分析法对面料进行综合分析。结果表明,间隔纱连接方式对面料拉伸断裂性和顶破性有一定影响,对透气透湿性无明显影响;厚度、密度较小且间隔纱交叉连接的织物综合性能最好;选择床垫面料时考虑厚度、密度及间隔纱连接方式对面料性能影响。     

形状记忆合金尺寸对消防服面料防护性能的影响

为提升嵌入形状记忆合金消防服面料组合的防护性能,构筑了3种形变高度和3种排列方式的面料组合以分析形状记忆合金尺寸对其性能的影响。在高温热接触和低辐射热灾害环境下分别测试不同面料组合的防护性能。研究结果表明：形状记忆合金有效地提高了消防服面料的防护性能,合金弹簧的形变高度影响组合面料层间空气层厚度,从而改变其防护性能;在不同的排列方式下弹簧形变高度也不同,可能与弹簧形变产生的空气层形状及分布有关;在不同的热源条件下,不同排列方式的面料组合的防护性能呈现出不同的规律,即在 2 种热源条件下,1 个合金弹簧中心排列与 3 个合金弹簧对角排列方式下全高型试样的隔热性能均明显优于减半型,而 2 个合金弹簧对角排列方式下 2 种弹簧试样隔热性能的差异较大。     

单纤维柔软性的新型测试方法与优化

针对目前测量单纤维柔软性的方法中公式复杂、测量误差大和测量范围受限等问题,设计了一种新型的单纤维柔软性测试方法。详细描述了所设计的模具并阐述了制样方法,测试了不同弯曲刚度的聚乳酸和聚丙烯单纤维的压缩力,以表征单纤维的柔软性能;探讨了不同的制样根数及压脚直径对该测试方法精准性的影响程度,并对测试参数进行了优化。结果表明:本文方法可通过压缩力的大小有效地表征单纤维的柔软性,具有测试方法简单、适用范围广的优点;同时根据单纤维柔软性测试参数得出,压脚直径为10 mm,制样根数为10时,可更好地减少试验误差。     

Design and fabrication of novel auxetic weft-knitted fabrics with Kevlar yarns

For the purpose of fabricating three kinds of auxetic weft knitted fabrics, three different geometrical structures namely rotational structure, foldable structure and double-headed arrow topological structures with three different knit loop lengths were produced using computerized flat knitting machine. Experimental results show that all three different weft knitted fabrics have auxetic effect. The Poisson’s ratio values of the three fabrics are inversely proportional to knit loop lengths. However, differences exist between the curves of Poisson’s ratio relative to strain. With regards to the rotational and double-headed arrow topological structures, the curves tend to be monotonic, whilst that of the foldable structure takes the form of a parabola. This research thus confirms the possibility of producing auxetic fabrics based on several geometrical structures using flat knitting technology     

经编间隔织物的应用及其发展

介绍经编间隔织物的特性,指出经编间隔织物在座椅包覆、鞋材、箱包和床垫等方面的常规应用及其优势,并根据当前经编间隔织物结构和原材料的发展,详述经编间隔织物在时装面料、成型鞋材、卫浴产品、建筑增强材料、农业无土栽培和包装材料等方面的新应用,得出经编间隔织物的三个未来发展方向——个性产品、功能产品和智能产品。