Mechanical Properties of Three-Dimensional Fabric Sandwich Composites

Three-dimensional( 3 D) fabric composite is a newly developed sandwich structure,consisting of two identical parallel fabric decks woven integrally and mechanically together by means of vertical woven fabrics. In this paper,six types of 3 D fabric sandwich composites were developed in terms of compressive and flexural properties as a function of pile height( 10, 20 and30 mm) and pile distance( 16, 24 and 32 mm) in pile structures. The mechanical characteristics and the damage modes of the 3 D fabric sandwich composites under compressive and flexural load conditions were investigated. Besides,the influence of pile height and pile distance on the 3 D fabric sandwich composites mechanical properties was analyzed. The results showed that the compressive properties decreased with the increase of the pile height and the pile distance. Flexural properties increased with the increase of pile height, while decreased with the increase of pile distance.

MODELING OF LIGHT SPECULAR REFLECTION FROM PLAIN-KNITTED FABRICS: A THREE-DIMENSIONAL ANALYSIS

The paper applies a mathematical model[1] for specular reflection to plain-knitted fabrics by using a three-dimensional analysis. Computer simulation of goniophotometric curves is generated based oa the model. Correction factors are introduced by taking into consideration of geometry of the instrument used. Comparison between the simulated and the measured curves of a straight monofilament yarn with various orientation angles is carried out and reasonable agreement has been obtained.

Investigation on the Dimensional Properties of Relaxed Plain Knitted Fabrics

A geometric model of relaxed plain-nitted fabric isproposed.A method based on the model for predictingthe loop length from the course spacing,wale spacing offabric and the diameter of yarn is deduced,as well as a computer program is developed to graphically represent the structures of plain knitted fabric with various struc-tural parameters.

Fabrication of Two-dimensional Monolayer and One-dimensional Wire of Zn-tetra-[3,5-di-t-butylphenyl]-porphyrin on Cu(100) Surface

We describe in this paper the fabrication of two- and one-dimensional nanostructures with organic molecular beam epitaxy （OMBE） principle based on controlled selfassembly by using adsorbate-substrate and intennolecular interactions that are important in molecular fabrication. Cu（100） single crystal was used as substrate in fabricating molecular nanostructures. Scanning tunneling microscopy （STM） experiments confirmed that Zn-tetra- [3,5-di-t-butylphenyl]porphyrin-molecules can be used to fabricate both monolayer and molecular wire on Cu（100） surface simultaneously, and the latter is arranged on the terrace edges. We herein briefly discuss the selectivity in terms of a mechanism in which the highest occupied and lowest unoccupied molecular orbitals （HOMO and LUMO） of the molecules interact with the surface.

Fabrication and formation mechanism of NbC_x-C three-dimensional netted fibers

Micrometer NbC_x-C three-dimensional netted fibers were synthesized by thecarbothermal method under 0.1 MPa of N_2 ambient atmosphere at a relatively low temperature. Rawmaterials were commercial powders of Nb_2O_5 (99.95 percent), reactive carbon (99.99 percent), NaCl(99.95 percent) and sucrose (99.94 percent). The relationship of the fabrication processing with thecomposition, crystal structure and morphology of fibers was investigated. The formation mechanismwas also proposed and discussed.

Low-Temperature Growing Anatase TiO2/SnO2 Multi-dimensional Heterojunctions at MXene Conductive Network for High-Efficient Perovskite Solar Cells

A multi-dimensional conductive heterojunction structure,composited by TiO2,SnO2,and Ti3C2TX MXene,is facilely designed and applied as electron transport layer in efficient and stable planar perovskite solar cells.Based on an oxygen vacancy scramble effect,the zero-dimensional anatase TiO2 quantum dots,surrounding on two-dimensional conductive Ti3C2TX sheets,are in situ rooted on three-dimensional SnO2 nanoparticles,constructing nanoscale TiO2/SnO2 heterojunctions.The fabrication is implemented in a controlled lowtemperature anneal method in air and then in N2 atmospheres.With the optimal MXene content,the optical property,the crystallinity of perovskite layer,and internal interfaces are all facilitated,contributing more amount of carrier with effective and rapid transferring in device.The champion power conversion efficiency of resultant perovskite solar cells achieves 19.14%,yet that of counterpart is just 16.83%.In addition,it can also maintain almost 85%of its initial performance for more than 45 days in 30–40%humidity air;comparatively,the counterpart declines to just below 75%of its initial performance.

3D Modeling and Simulation of Fancy Fabrics in Weft Knitting

Weft knitted fancy fabrics are widely used in knitted garment design. Due to the complexity of the structures, their modeling and simulation needs to be solved in three-dimensional (3D) CAD developments. In this paper, 3D loop geometrical models of weft knitted fancy structures, including tuck stitch, jacquard stitch, transfer stitch and fleecy stitch, were developed based on an improved model of plain loop, and their central axes as some 3D space curves were achieved by using Non-Uniform Rational B-Splines (NURBS). The 3D visual simulation programme was written in C++ programming language using OpenGL, which was a function library of 3D graphics. Some examples of weft knitted fancy fabrics were generated and practical application of 3D simulation was discussed.

Investigation on relations between grain crushing amount and void ratio change of granular materials in one-dimensional compression and creep tests

Grain crushing plays an important role in one-dimensional (1D) compression and creep behaviors of granular materials under high stress. It is clear that the macro-properties of granular materials are closely related to the micro-fracture properties of grains in 1D compression and creep tests. In this paper, a series of 1D compression and creep tests were performed on Ottawa sand to investigate the deformation and grain crushing properties of granular materials, and it shows that the void ratio is correlated to the grain crushing amount (the quantity of crushed grains) for granular materials subjected to grain crushing. The test results, combining with the existing test data related to grain crushing of granular materials, were used to verify the relation. Moreover, the implications of these relations on the yield of granular material, and the equivalent effect of stress and time in changing soil fabric are presented.

碳纤维多层立体织物平行打纬构型的设计建模与仿真

为提升碳纤维立体织物各层打纬力分布的均匀性,通过机构串联对共轭凸轮与平面四连杆进行功能配置,设计了一种适用于多层立体织造的组合式平行打纬构型。根据修正梯形加速运动规律,在Matlab环境中对主、副凸轮理论廓线进行数值分析与编程反求,提出了适用于多层立体织物的打纬阻力计算方法,构建了基于Adams/View的高精度平行打纬系统数字化仿真模型,并针对其运动特性、共轭精度及接触碰撞等进行了动态模拟与分析。结果显示:钢筘在前死心位置(凸轮轴转角为72°时)附近能够很好地实现水平打纬运动;摇轴与摆臂具有较高的角运动匹配精度,且两者负角加速度在前死心处均达到瞬时最大,有利于同步打紧各层纬纱;当凸轮机构存在共轭间隙时,摇轴角位移、角加速度会产生明显的偏离与振荡,同时主、副凸轮与滚子之间亦存在高频次接触和碰撞,并将导致摇轴与筘座发生振动,不利于提升平行打纬动力精度。文章为高品质多层立体织物打纬构型的设计与应用提供了借鉴。

石英纱线/石英纤维毡三维织物的设计及其隔热性能

为充分利用石英纱线及其纤维毡良好的隔热效果制备隔热性能优异的石英纱线/石英纤维毡三维织物,采用石英纱线和纤维毡在小样织机上进行三维立体编织,针对石英纱线/石英纤维毡三维织物不易编织等诸多问题,对织机综丝综框进行降低摩擦处理;然后采用控制变量法和实验对比法,对所得石英纱线/石英纤维毡三维织物在热环境下的隔热性能进行测试表征,对其加热状态下的温度和外观形状的变化趋势和规律进行探讨。实验结果表明:石英纱线/石英纤维毡三维织物在300~700℃时,平均隔热保留率是相等厚度普通石英纤维织物的4倍,验证了石英纱线/石英纤维毡三维织物的优越隔热性能。确定了石英纱线/石英纤维毡三维织物具有良好的整体性能和隔热性,能够作为航天飞行器的外部隔热材料抵挡高温冲刷,因此对石英纱线/石英纤维毡三维织物性能的研究具有深远意义。

血管支架预制件的六角形三维虚拟编织

为解决六角形三维编织血管支架的编织工艺复杂、开发周期长的问题,提出了基于MatLab编程的支架三维虚拟编织方法,以快速完成编织工艺开发。首先,基于六角形编织机底盘的结构特点,对底盘单元进行坐标数值化,从而可将支架编织的工艺和工序转换为不同时刻下携纱器在底盘上的XY平面坐标和运动信息以及纱线在芯棒上的高度坐标z值,并应用数值计算方法进行连接和拟合,建立纱线空间轨迹的数学模型,得到虚拟支架的三维基本形态。然后,将编织支架的三维形态展开为二维形态,分析二维平铺形态下单向支架沿螺旋方向缠绕的特点,应用线性方程组求解纱线的交织点坐标,并通过层内和层间的纱线交织关系判断得到各交织点的交织类型。最后,通过方程修正得到具有六角形编织特征的纱线波动方程,进一步建立了具有纱线立体交织特征的虚拟支架实体化数学模型。经不同编织工艺的支架虚拟仿真实验,将虚拟支架与其实物进行比较发现,虚拟支架均能准确直观地表达实物的几何特征和交织特征。由此验证了虚拟仿真建模的正确性,有利于六角形三维编织工艺的快速开发。

三维圆筒织物的织造工艺研究

为解决织造大直径三维圆筒织物时存在的边缝、缺经等问题,提出了一种三维圆筒机织法。根据三维圆筒织物结构,设计添经工艺,绘制纹板图,并在三维圆筒织机上进行织造。结果表明:采用三维圆筒机织法,应用弧形分布开口机构中的综眼和打纬优化后的纬密,并合理设计不同层的经纱数量,能够较好地织造出大直径的三维圆筒织物。认为:织物的尺寸以及规格由工艺结构、每次的卷曲长度、经纱纬纱数量及规格等决定,可以应用于大型筒状结构预制体的规格化、连续化生产。

基于多综眼的纬向T型结构多筋机织物的设计与织造

为了解决传统织机织造效率低下以及异型织物织造难度大的问题,设计了一种基于多综眼的纬向T型结构多筋机织物的织造工艺。通过研究整体T型结构机织物的成形技术,采用多层角联锁结构为基础,结合多综眼织机的特性,设计经向截面图并绘制纹版图,通过机织方法织造了梁高和基座厚度相同的纬向T型结构多筋机织物。结果表明:采用五综眼织机相较于单综眼织机织造效率提升了5倍,织造基于多综眼的纬向T型结构多筋机织物是可行的。

面料性能对A字裙坐姿起皱形态的影响

着装褶皱对服装外观有重要影响,常见的褶皱评价指标及传统的二维图像处理技术无法准确、全面反映三维起褶状态。因此,文章利用三维扫描技术对坐姿下A字裙形成的褶皱从褶皱区域、褶皱类型、褶皱大小和褶皱尖锐度四方面建立了一系列新指标,运用单因素方差分析比较了不同种类面料间的褶皱形态差异,并探究了面料性能与褶皱形态指标之间的相关性。研究结果表明,不同面料成分的A字裙在坐姿下形成的褶皱形态各异,其中棉类与其他面料之间各方面差异最为明显。此外,经密、抗弯刚度、褶皱回复性等面料性能对褶皱形态各指标有着不同程度的影响。研究结果可为面料选择及服装三维仿真提供参考。

基于线圈结构的双针床经编毛绒织物三维仿真

为实现高效率、低成本双针床经编毛绒织物开发,在分析了双针床经编毛绒织物形成及运动规律的基础上构建了垫纱数码数学模型、穿经数学模型,由数学模型自动生成垫纱运动轨迹。探讨了成圈及衬纬结构形成的毛绒织物的编织规律及其工艺,在研究其线圈结构及毛绒形态的基础上,建立了理想状态下的成圈及衬纬毛绒线圈模型,结合毛绒仿真关键因素及生成工艺参数,利用C#和JavaScript程序设计语言在Visual Studio平台上进行编程,实现了双针床成圈型及衬纬型毛绒织物的三维仿真。通过与实物图对比,验证了该模型可以真实模拟实物花色效果,仿真效果相似度高,可有效解决毛绒花型设计局限性的问题,降低设计难度和生产成本,解决设计周期长的问题,提高了生产效率,使双针床经编毛绒织物的应用得到广泛推广。

海水老化下类填充微穿孔板结构水下吸声材料的性能及其寿命预测

针对现阶段潜艇用水下吸声材料的低厚度强低频吸声的性能诉求,基于三维间隔织物,将兼具多孔和共振吸声特性的类填充微穿孔板(F-MPPL)结构引入常规空心微珠填充水下吸声材料(HBF复合材料)中,设计出新型三相复合水下吸声材料(F-MPPL复合材料)。鉴于海中复杂环境对水下吸声材料声学性能的影响,采用人工海水浸泡的方法对F-MPPL复合材料进行海水老化,结果发现老化12个月后的F-MPPL复合材料平均吸声系数下降了13.6%。同时,基于海水老化下孔隙率和穿孔率的变化对最终宏观模型仿真结果的影响,对F-MPPL复合材料的水下吸声性能寿命进行预测发现,模型可准确预测材料吸声峰值的位置,但对材料吸声系数峰值的大小预测稍有偏差。研究结果可为各类水下吸声材料的吸声性能老化研究提供实践经验,并为F-MPPL结构在海水老化下的长期寿命预测及性能优化提供理论参考。

抗菌保暖羊绒立体肌理针织面料的开发

为了丰富织物的类型和提升织物性能,采用羊绒纱线为主要原料,辅以抗菌锦纶高弹丝和涤纶低弹丝,通过立体化织物组织设计,在纬编针织电脑圆机上成功开发出了2种具有立体肌理的针织面料,测试了针织面料的保暖性能和抗菌性能。结果表明:开发的针织面料具有挺括的表面质感、凹凸分明的肌理和褶皱效果,同时兼具舒适的弹性和柔软的触感以及一定的抗菌性,适用于多种秋冬季节的衣物,可通过改变织针排列和纱线颜色变化设计不同风格的针织面料,为功能性纺织品的开发提供了新的思路和方法。

三维超高分子量聚乙烯纤维/苎麻混杂轮胎防滑织物的设计与制备

为改善传统防滑链笨重、噪音大、易损伤轮胎等缺点,基于干、湿摩擦因数的差异通过三向正交混杂织物结构设计,制备超高分子量聚乙烯/苎麻混杂织物轮胎防滑套,分析测试了其摩擦因数、耐磨性能和实际路面效果。结果表明:混杂织物轮胎防滑套干湿摩擦因数的转变使车辆制动距离可缩短20.5%;其摩擦因数比市场商用防滑套增加了116%;由于层间间隔结构织物防滑套的苎麻含量最高,织物结构更紧密,混杂效应更明显,其防滑性能和耐磨性能均最好;通过吸湿性能测试,进一步揭示了该新型防滑织物防滑机制。本文研究成果可减少防滑链对车体损伤,拓展三维织物的应用领域,具有重要的实用价值。

三维间隔织物编织工艺及应用

三维间隔织物是一种具有特殊结构的新型纺织材料。文章介绍了经编和纬编间隔织物的编织工艺和织造方式,归纳了间隔织物作为新型材料在垫用、服用、车用、建筑、农用、过滤、包装等方面的常规应用,重点讲述了三维间隔织物在可穿戴领域的研究现状和研究成果,包括传感器、电容器、发电机、纺织天线等智能器件,为间隔织物在可穿戴领域的应用和发展提供了参考。

变厚度三维机织复合材料的抗冲击性能

为解决变厚度层合复合材料受到载荷时易分层导致其力学性能变差的问题,使用800 tex玄武岩纱线作为经纬纱,采用分层角联锁结构设计并织造了整体性优异的连续变厚度三维机织物,并采用树脂传递模塑工艺制备了树脂基变厚度三维机织复合材料,同时织造了同纬铺层和同经铺层2种不同结构的层合复合材料进行对比测试。然后对变厚度层合复合材料分别进行25、50、75、100 J的不同冲击能低速冲击实验,并通过单独分析冲击能为100 J时3种复合材料的损伤面积探究其损伤机制。结果表明:在冲击能为25、50、75 J时,变厚度三维机织复合材料与同纬铺层结构复合材料的刚度退化呈现高度一致性,二者抗冲击能力均优于同经铺层结构复合材料,变厚度三维机织复合材料损伤载荷大于2种铺层复合材料;层合材料受到冲击损伤时,因其层间无纱线连接,能量在材料层间传播时消耗,从而产生较大范围的分层损伤;而变厚度三维机织复合材料具有层间连接的经纱,受到冲击时应力在材料经纱连接作用下内部不断传播导致材料整体受载,因此具有更高的损伤容限。