Mechanical Response of Novel 3D Woven Flax Composites with Variation in Z Yarn Binding

ABSTRACT

This paper is focused on the development of novel 3D woven flax composites for improved mechanical performance. The 3D woven interlock fabrics were produced on dobby loom using novel weaving patterns, with variation in binding point density (four different levels). These fabric structures were then used to fabricate composites with green epoxy resin as a matrix. Tensile, flexural, short beam shear, impact (pendulum and drop weight) and compression after impact properties were characterized. It was found that 3D woven composites having higher binding point density showed overall improved mechanical behavior, i.e. the out-of-plane properties were enhanced whereas in-plane properties are either reduced or unaffected.     

间隔织物面层组织对其增强板材性能的影响

设计织造平纹、方平、2/2斜纹和1/3斜纹4种不同面层组织的间隔织物,并在间隔织物的空间结构中填充聚氨酯泡沫,再用环氧树脂对其表面进行复合,加工制成机织间隔织物复合材料板材.对加工出来的4种间隔织物的复合板材进行压缩和弯曲试验,探讨4种不同的面层组织对间隔织物复合材料板材性能的影响.     

曲面三维横编间隔织物复合材料的压缩性能

为研究曲面三维横编间隔织物增强复合材料的压缩性能,为后续低速冲击及剩余强度的研究提供实验数据,制作了满足要求的试样。将三维横编间隔织物织成平面与曲面2种,再分别制成2组不同曲率的复合材料。将不同曲率增强复合材料置于电子万能材料试验机上测试其压缩性能,分组比较其载荷与位移的曲线关系。结果表明：在其他条件相同时,不论是平面间隔织物复合材料还是曲面间隔织物复合材料,横向压缩载荷峰值都明显高于纵向;同组复合材料随着织物样片曲率的增大,压缩载荷峰值也呈逐渐增大趋势。     

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.     

三维机织预型件的织造技术

纺织复合材料预型件的生产工艺有多种,其生产路径主要由最终用途决定。三维机织物是通过对传统织造原理改进加工而成的。二维机织复合材料是一种由二维织物构成的层合材料,而三维机织复合材料是复杂几何结构的整体构件。三维机织复合材料预型件有许多优点,最重要的优点是它避免了二维层合材料的分层现象。介绍了三维机织预型件的织造方法,为纺织复合材料的开发提供了有益的借鉴。     

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.     

三维间隔织物复合材料的制备及拉伸性能研究

介绍三维间隔织物复合材料的制备方法,并采用Instron 5969型万能材料试验机对三维间隔织物复合材料的拉伸性能进行测试,重点分析间隔高度、经纬向等结构参数对三维间隔织物复合材料拉伸性能的影响。结果表明:三维间隔织物复合材料拉伸性能随间隔高度的增加而下降;纬向拉伸性能优于经向。     

二维与三维机织复合材料力学性能的实验研究

对超厚三维正交机织复合材料及二维要织层合板人别进行了拉伸和压缩实验,研究比较了两种复合材料刚度和强度特性的差异研究发现无论是三维机织材料的拉压还是二维层合板的拉压应力应变曲线都近似为直线,而且具有脆性破坏的特点;三维复合材料的拉压强度要高于二维层合板.这主要是由于材料不同的增强相结构及纤维含量造成;不同的破坏模式对材料强度影响很大.     

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。     

3D间隔织物增强聚氨酯基缓冲材料力学及舒适性研究

将3D间隔织物与聚氨酯基体相复合,制备成3D间隔织物增强聚氨酯基复合材料。对不同厚度、孔隙率和材料的3D间隔织物增强聚氨酯基复合材料试样进行了透气性、透湿性和压缩性能的测试,分析了参数对试样性能的影响。结果表明:孔隙率越高,厚度越薄,试样的透气性越好,而被间隔织物增强的试样透气性变差;孔隙率越高,厚度越厚,试样的透湿性越差,试样的屈服强度越低,抗压性能越差,更容易产生塑性变形,间隔织物可以增强聚氨酯基体的抗压性能。     

组合式3D机织物复合材料的拉伸性能

采用正交和角联锁结构进行组合设计,并使用玻璃纤维试织了2种不同结构的组合式3D立体机织物,经与树脂复合制成增强复合材料,对其拉伸性能进行了测试。结果表明,组合式3D机织物增强复合材料具有接近正交3D机织物增强复合材料的弹性模量和抗拉强度。     

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.     

Effect of alkali treatment on mechanical properties of woven jute composites

The effect of alkali treatment on the jute fabrics and its influence on jute composites properties has been studied. The plain woven jute fabrics were manufactured using handloom. The alkali treatment was optimized using Box and Benkhen experimental design using time, temperature and concentration as independent variables and water absorbency, weight loss percentage as dependent variables. The fabric treated with optimized condition of 5% NaOH for 4 h at 30 °C was made into a composite of [0°]₄ lay-up sequence by means of compression moulding technique using vinyl ester resin. The composites were characterized for various mechanical properties such as tensile, flexural and impact strength. It is observed from the results that the alkali-treated samples show increased mechanical properties of the composites which may be due to the better adhesion between the fabric and the resin because of the removal of lignin and hemicellulose.     

针刺复合羊毛面料的设计及其性能

为开发新型复合针刺羊毛面料,选用涤纶基布和羊毛为原料,利用现代无纺针刺机针刺复合面料,探究羊毛与涤纶基布以不同排列方式针刺后的效果对比,制作不同主题风格的创新面料;设计制作了不同羊毛含量、羊毛与面料不同排列组合的试样;通过测试试样的拉伸断裂强力、撕破强力、顶破强力来分析针刺面料的性能,以及影响这些性能变化的原因,探究其应用价值。结果表明:经过针刺复合后面料的力学性能比涤纶基布降低,但随着羊毛含量的增加,其力学性能提高,伸长率降低;针刺复合后面料纵向力学性能优于横向;羊毛平铺在双层涤纶布上针刺后复合面料的力学性能优于夹在双层涤纶布中间,且其针刺后的手感、图案表现效果最佳。     

3D woven green composites from textile waste: mechanical performance

Application of textile waste for development of value added green composites has been carried out in this work. Textile fabric waste is collected from various sources. These waste materials are garneted, so as to produce loose fibrous material, subsequently this fibrous material was converted into twisted strand for manufacturing of 3D woven preforms for production of composites. Twisted strands are converted into orthogonal 3D woven structure. The fibers extracted from waste material are combined with polypropylene in 60/40 proportion. Composites of various specifications are developed to examine their end-use applications. These composite materials are characterized for their mechanical behavior to find out the response against tensile loading, flexural stress, and impact force. The effects of moisture absorption on mechanical properties of composites are investigated. 3D woven fabric reinforced composites produced by using waste fiber yarn and normal cotton OE yarn do not exhibit any significant difference in the mechanical behavior of composite. This result confirmed that waste material can be safely used as reinforcing structure in green composite manufacturing.     

Investigation of mechanical behavior of woven/knitted hybrid composites

The objective of this research is to develop the woven/knitted hybrid composites for improved in plane as well as out of plane mechanical properties. Two different type of structures and two different materials were used in this study. Firstly, the woven and knitted fabrics were developed with glass and Kevlar yarn. Secondly, the laminated composite samples were fabricated with different stacking sequence of fabric plies. The epoxy resin was used as matrix. The cured samples were characterized for impact, tensile and dynamic mechanical properties. The behavior of composite materials was then analyzed with percentages of different fiber and fabric types. The samples with higher percentages of knitted reinforcement gave better impact strength but failed to provide better tensile properties. Moreover, the samples with higher percentages of woven structure and glass materials gives better modulus values.     

Electromagnetic shielding effectiveness of carbon/stainless steel/polypropylene hybrid yarn-based knitted fabrics and their composites

In this study, a range of conductive hybrid knitted fabrics and their composites have been investigated for shielding effectiveness in the frequency ranges of 50 MHz to 1.5 GHz (low frequency) and 4 to 8 GHz (C-Band). Carbon and stainless steel (SS) filaments were combined in Dref-3 spinning machine and different hybrid yarns were prepared. The plain- and rib-knitted fabrics were made in V-bed flat knitting machine from the prepared hybrid yarns. The composite laminate was prepared by sandwiching a ply of fabric between the polypropylene films in compression moulding machine at 180 °C for 5 min under a consolidation pressure of 12 bar. All the fabrics and composites were tested for shielding effectiveness (SE) in coaxial transmission line and C-band waveguide with the help of vector network analyser. It was observed that fabric having both conductive loop and inlaid yarns exhibited higher SE of 20.2 dB than other fabrics in low-frequency range. However, in the composite form, carbon composite with SS inlaid yarn showed better SE of 45 dB than other composites. In C-band frequency range, conductive loop fabric structures yielded high shielding effect in course direction compared to wales direction. Compared to fabric form, the composite showed higher SE for all frequency ranges. This study proposes that knitted fabrics and their composites can be utilized as electromagnetic shields in wide frequency ranges.     

Mechanical Properties of Composite Panels Reinforced with Integrally Woven 3-D Fabrics

An investigation is reported in which six three-dimensional cellular fabrics were designed and woven. They consisted of two facings connected by an integrally woven sinusoidal core. In lateral compression, the ratio of the cell-repeat distance to the fabric thickness determines the resistance of the fabrics to buckling. Composite panels were fabricated by impregnating the fabrics with resin. Formulae developed allow the cross-sectional area and second moments of area of the panels to be calculated. Tensile tests were performed on the panel facings and whole structures to measure the Young's moduli and strengths in the longitudinal (weft) and transverse (warp) directions. Flexural tests were made to measure the beam flexural rigidities. The structural analysis of the beam sections together with the tensile properties of the beams enables flexural properties to be accurately predicted. The properties of the 3-D beams in flexure are comparable to those of other engineering materials, but the fabric-based, cellular composites will have advantages as components in composite structures.     

间隔机织物的卷绕、切割和存储系统

描述了间隔机织物的新型卷绕、切割和存储系统的设计.这种系统的关键问题是间隔织物包含织物结构如间隔,即所谓的交联.为了防止玻璃纤维-聚丙烯混纺纱线中玻璃纤维被破坏,必须避免交联塌陷.这种织物被用作热塑性纺织增强复合材料模件的预型件.     

The mechanical performance of plain and plain derivative woven fabrics reinforced composites: tensile and impact properties

In this work, the mechanical performance of the plain and plain derivative woven fabric reinforced composites, were investigated. Tensile strength, modulus of elasticity, elongation at break and poison ratio values of the composites were found by tensile tests. In addition, drop-weight impact tests were performed at several impact energies: 15, 20, 25, 30 and 35 J in order to characterize the impact resistance, and damage mechanisms of the composite plates. The results reveal that the weaving pattern affects the tensile properties and the impact behaviour of the composites. It is observed that 2/2 matt woven fabric reinforced composite showed the best performance in tensile tests along warp direction; whereas, 2/2 warp rib woven fabric reinforced composite showed the best performance during tensile tests in weft direction. It is also observed that 3/1 matt woven fabric reinforced composite absorbs more energy for perforation than the others.