纺织工程中的分形应用研究

在简要介绍分形图形生成方法的基础上,综述了分形在纺织工程中应用的两个方面:一是将分形图形用于纺织图案设计、纺织纹样设计等;二是基于分形理论对织物性能进行分析,包括机织物渗透率分析、织物瑕点检测、织物表面纹理分析等.分形图形的应用为纺织图案设计提供了新的创作思路,分形理论是解决纺织工程复杂问题的有力工具.     

利用分形分析理论求解针刺非织造材料水平渗透系数

根据涤纶短纤针刺非织造材料的孔隙具有的分形特点,通过建立其纵向几何结构模型,介绍了一种利用分形分析求解针刺非织造材料水平渗透率的方法,进而预测有关非织造材料的水平渗透系数。     

分形在纺织中的应用

分形是人们在自然界和社会实践活动中所遇到的不规则事物的一种数学抽象，被广泛应用于数学、计算机科学、力学、物理学、化学、生物科学、地质科学、社会科学、人文科学以及艺术等各个领域，随着科技的发展，分形方法在纺织领域中对织物疵点检测、分形涤纶开发、求解纤维集合体的渗透率、分析织物表面形态、纤维结构分析等方面的应用也日益增多。     

LCM中碳纤维织物结构对横向渗透性的影响

为研究液体模塑成型加工过程中,树脂流体在厚型织物预型件厚度方向的横向流动渗透情况,采用基于超声波传感监测技术的3D渗透率测试装置,对厚型结构织物增强体内部流动渗透情况进行实验研究。结果表明：不同结构的斜纹、双轴向、单向的碳纤维织物内部流动行为和渗透性差异显著。相同结构中,面密度小而层数的增加会对流动通道产生更多阻碍作用而降低横向渗透性。低的纤维体积分数时,双轴向织物较斜纹织物厚度方向上的渗透率低;而在紧密织物结构中,双轴向比斜纹织物的渗透率要高。单向织物中面内层内流动容易,而厚度方向的渗透率非常低,相比其他两种结构的要低1-2个数量级。     

应急热防护织物有效导热系数分形模型

运用分形理论对应急热防护织物的内部微结构进行分析研究,结果表明分形维数与纤维体积分数是影响热防护织物传热的2个重要参数。根据等效热阻法建立预测高温下热防护织物有效导热系数的分形模型,求出基于分形理论的热防护织物的有效导热系数表达式,所得理论结果与实验值保持良好的一致性,同时合理反映出高温热辐射在织物传热中的重要作用。     

分形涤纶/棉织物的染整

分形涤纶织物由天然纤维（羊毛、羊绒、棉、麻、丝）和少量分形结构的涤纶织造而成。分形涤纶具有与天然纤维相同模式的扭曲基因，该基因经数控分形放大，产生与天然纤维相似的自然扭曲，从本质上改变了合成纤维单调死板的风格。分形涤纶织物的中芯是保形性极佳的分形涤纶，外层为柔软舒适的天然纤维，实现了天然纤维与合成纤维优良特性的结合。文中针对分形涤纶织物的染整加工特点，探讨了溢流染色和热溶染色工艺。     

经编四轴向玻璃纤维织物的渗透行为和渗透率

为研究经编四轴向玻璃纤维织物的渗透行为同织物结构的关系,采用径向法和单向法对不同铺层数和铺层角度的预制件进行面内渗透率以及单向渗透率的测试,并结合复合材料横截面切片对织物凹凸表面效应对流动的阻碍作用进行分析。采用以体积分数为自变量的经验公式对多层铺层织物的单向渗透率进行预测。实验结果表明：对于低铺层数的预制件,渗透率和纤维体积分数无直接关系,与织物表面在压缩作用下形成的平行于流动方向的流道数量密切相关;对于铺层角度不同的预制件,平行流道数目最多的预制件具有最大的渗透率;经验公式较Kozeny-Carman公式更能准确的预测经编四轴向织物的单向渗透率。     

重力对凝析油气相对渗透率曲线的影响研究

在凝析油气藏的开发中,相对渗透率和临界凝析油饱和度是很重要的参数。以已知分形解析模型的饱和度和相对渗透率数学表征出发,引入表征重力影响的无量纲参数邦德数(Bond数),数学推导出凝析油气相对渗透率和Bond数之间的关系,进而分析重力对凝析油气相对渗透率的影响。研究表明Bond数越大,对应的凝析油气相对渗透率越大;多孔介质越复杂(分形维数DL越大),临界凝析油饱和度越大。     

基于格栅法的绉织物灰度曲面分形特征的研究

文章通过MATLAB对绉织物表面图像进行处理,根据分形理论对绉织物表面的灰度曲面进行分形特征分析,利用格栅法计算灰度曲面的分形维数,以此评定绉织物表面纹理的粗糙度和起绉程度。实验结果表明：绉织物表面图像的灰度曲面具有显著的分形特征,分形维数与绉织物表面纹理的粗糙度和起绉程度有关。     

基于L系统的3×3平纹分形组织设计应用方法

为探讨分形组织在织物设计中的具体运用途径,根据3×3平纹变化组织点分布简单、均衡与对称等特点,运用L系统的链式语言生成规则与计算机图形方法,生成具有4级自相似结构的分形组织,并在此基础上讨论其分形组织的主要变化形式及其设计应用方法.重点研究通过填充组织的变化,配合分形组织获得一类新型的组织结构,进而探索设计产生新的织物...     

Fractal calculation of air permeability of nonwoven fabrics

A fractal permeability model for nonwoven fabrics is developed based on the fractal characteristics of pores within them. The fractal permeability is found to be related to pore area fractal dimension, tortuosity fractal dimension, size of fibers, the maximum and minimum pore sizes, fabric thickness, and the effective porosity of a medium. To verify the validity of the proposed model, experimental work was conducted on a set of nonwoven fabrics, and the predicted air permeability was compared with the experimental results. Good concordance was found between them. Meantime, the model was also compared with the existing models and is proved to be more accurate.     

Total porosity,theoretical analysis,and prediction of the air permeability of woven fabrics

Air permeability is one of the most important properties of textile materials that ensure their comfort. For many materials for technical applications (filters, sails, vacuum cleaners, parachutes, etc.), this is one of the main properties that determine their quality. The air permeability of woven textile fabrics depends on many parameters of fabric. Thus, the determination of air permeability of woven fabric is highly complex and difficult. In this study, we attempted to establish a theoretical model for the porosity and predicted the air permeability of woven fabrics. A theoretical model was created to predict the total porosity and the air permeability of a fabric structure depending on the geometrical parameters such as pore size, warp density, weft density, fabric thickness, number of yarn, diameter of yarn, and fiber density. For the purpose, a theoretical model of porous systems on D’Arcy’s law was used, and the validity of the model was confirmed by experimental results using 100% cotton and 97/3 cotton/lycra woven fabrics. Since the amount of air passing through both the pores between yarns and the interstices in the fibers constituting the yarn structure was calculated, theoretical values of air permeability were obtained very close to the experimental values.     

Investigation of pore parameters of woven fabrics by theoretical and image analysis methods

Fluid permeability property is an important performance feature of fabrics and must be considered during the designing processes of products. Since the rate of fluid flow through a textile is a function of viscosity, density, pressure gradient of fluid, and the pore properties of fabric, it is necessary to define pore properties by controlling the structural parameters of fabric for a certain area of use. Due to the complexity of fabric structure, modeling of pore structure and predicting the pore parameters are difficult. In this study, the interyarn porosity, pore size, and pore-size distribution of cotton woven fabrics were calculated by using two-dimensional (2D) and three-dimensional (3D) geometrical pore models and image analysis method. The effect of weave types and weft settings on the pore parameters and air permeability of fabrics were investigated, and the advantages of 2D, 3D geometrical pore models and image analysis method were compared.     

篷网织物网孔参数对篷内温变性能的影响

在帐篷外给帐篷"穿衣"可以调节帐篷内的热环境,以改善人在帐篷内的居住环境。经过测试多种织物的透气量、孔隙率、孔径大小,确定出在相关参数上具有同等梯度差的篷网织物;采用对比试验法研究篷网透气量和孔径分布两个参数对帐篷内温度变化的影响,以确定降温性能、保温性能优良的篷网织物所具有的结构参数。     

PLA表面温敏性互穿网络水凝胶的UV接枝及其透湿性

为制备一种温度响应型智能调湿织物,采用丙烯酸间苯二酚二缩水甘油酯在聚乳酸(PLA)非织造布表面通过热处理引入不饱和双键,在紫外光照射下引发聚丙烯酰胺/聚(N-异丙基丙烯酰胺)(PAAM/PNIPAAM)互穿网络水凝胶体系接枝于PLA非织造布表面。分析接枝后织物的化学结构、形貌,探究PNIPAAM用量在不同温度下对织物透湿性的影响。结果表明,PLA非织造布表面不饱和双键预处理-紫外光接枝两步法可以成功实现温敏性互穿网络水凝胶与PLA非织造布的接枝,所构建的织物表面具有丰富的孔隙结构,互穿网络中PNIPAAM质量分数为4.5%、AAM质量分数为10%时,接枝织物在24℃下的透湿量为1731 g/(m²·d),在38℃下的透湿量高达3601 g/(m²·d),赋予PLA非织造布温度可控的智能透湿性能,将其应用于伤口敷料领域可在低温低透湿性时保持伤口湿润、高温高透湿性时降低创面温度。     

Air permeability of multilayer woven fabric systems

A model to predict the air permeability of a multilayer woven fabric system from the air permeability and construction parameters of a single fabric has been developed. A new factor to account for the distortion of the threads in the fabric due to the flow of air through the layers of the fabric is proposed. This model incorporates the fabric cover factor (determined using an image‐processing method) and the proposed distortion factor (determined based on yarn linear density and fabric structure). The performance of the proposed model has been successfully validated by using it to predict the air permeability of other multilayer woven fabric systems and comparing it to experimentally determined values. The model can thus be used as a valuable tool in the engineering design of multilayer woven structures with desired air permeability performance requirements.     

涂层过程中织物拉伸对膜材料拉伸性能的影响

针对机织基布涂层前后结构相变化所导致的拉伸力学性能的变化,建立了膜材料拉伸力学的空间桁架模型,旨在讨论涂层过程中织物经向拉伸对膜材料拉伸性能的影响。建模过程中分别考虑了以经纬纱屈曲转换为主及纱线拉伸伸长为主的变形机制,用最小二乘法分段线性拟合来描述织物拉伸性能的非线性,用PVC/PES膜材料的拉伸试验验证模型的可靠性。结果表明:通过控制织物在涂层过程中的应变量,可以由涂层前织物的拉伸行为预测涂层后膜材料的拉伸性能。     

非织造材料孔隙结构的定量表述

利用计算机图像处理技术,提取了孔隙尺寸、孔隙形状和纤维取向分布等直观表达非织造纤维材料结 构的参数;利用新的几何学———分形几何,对非织造纤维材料的孔径分布情况进行分析,获得孔径分 布分形维数。在此基础上研究纤维网单位面积质量和特征长度对纤维网结构的影响,以及孔径分布 分形维数与通透性能之间的关系。