三原组织织物拉伸力学性能有限元仿真

为使织物在设计前就可预估其拉伸性能,对织物拉伸过程进行了有限元模拟和试验验证。通过超景深数码显微镜对织物试样的细观照片进行尺寸测量,得到纱线的几何结构参数,借助AutoCAD绘图软件建立了三原织物单胞物理模型;基于纱线拉伸试验和织物周期边界条件理论,利用有限元分析软件ANSYS研究了三原织物的拉伸性能;并将有限元仿真结果与拉伸试验结果进行对比。结果表明：织物经向拉伸时,经向平均应力、经向平均应变、纬向平均应变和泊松比的有限元模拟结果与试验结果的差异均在5%左右;经向弹性模量的有限元模拟结果与试验结果的差异也在10%以内;证明有限元仿真的可行性。     

二维机织复合材料力学分析中的周期性边界条件研究

为了精确地进行二维机织复合材料力学性能的数值分析,需建立单胞模型的准确边界条件。基于周期边界条件理论,提出了简便通用的二维机织复合材料周期边界方程,并给出了周期边界条件下各弹性常数在有限元分析中的求解方法;为验证周期边界条件的正确性,建立了９ 个单胞构成的九宫格结构,取中央单胞作为参考单胞,对不同边界条件下独立单胞的变形和应力分布与参考单胞进行对比。研究结果表明：即使在单向拉伸载荷下,单胞各个边界面也不保持平面状态,而是出现凹凸翘曲变形,即存在边界周期性;通过边界周期性条件,可正确地获得二维机织织物的工程弹性常数。     

Finite element modelling of SMA textiles: superelastic behaviour

The paper describes guidelines for building a finite element model of a unit cell of a textile made of superelastic NiTi wires and illustrates the application of the model for woven and knitted textiles. The goal of the analysis is prediction of the tensile diagram of the textile based on the fabric structure and the superelastic tensile diagram of the wires. The differences between the superelastic behaviour of the fabrics and that of individual wires are discussed. Predictions for a knitted NiTi fabric are compared with experimental data.     

采用ABAQUS的粘胶机织物拉伸力学性能仿真

为预测织物拉伸性能,采用有限元方法对织物拉伸力学进行数值模拟分析。在实测织物几何结构参数的基础上,借助纺织建模软件Texgen建立了织物模型;利用有限元软件ABAQUS模拟织物拉伸环境,设置材料属性、相互作用和边界条件,得到织物拉伸变形后应力分布云图以及拉伸时应力—应变曲线图等数值模拟结果;最后通过织物拉伸强力测试实验对数值模拟结果进行了验证。结果显示：模拟所得应力—应变曲线和实验所得拉力—伸长曲线上升趋势大致相同;模拟所得最大拉伸应力与实验所得拉伸应力平均误差为3.03%,证明了采用ABAQUS有限元软件模拟粘胶织物拉伸力学性能的是可行的。     

石墨烯黏胶纤维机织物的功能改性研究

制备同规格的普通黏胶纤维机织物、石墨烯黏胶纤维机织物及不同不锈钢丝质量分数的石墨烯黏胶纤维/不锈钢丝机织物,对比它们的导电、防电磁辐射、防紫外线、抗静电、力学(拉伸、弯曲、耐磨)及透气等性能。结果表明:普通黏胶纤维经石墨烯改进后,所制成的石墨烯黏胶纤维机织物的导电、防电磁辐射、防紫外线、抗静电、力学(拉伸、弯曲、耐磨)等性能都有所改善,其中防紫外线与耐磨性能提高显著,透气性能下降明显;石墨烯黏胶纤维/不锈钢丝机织物的导电、防电磁辐射、防紫外线和抗静电、经向拉伸断裂强力、纬向抗弯刚度、透气性能都优于石墨烯黏胶纤维机织物,纬向拉伸断裂强力、经纬向拉伸断裂伸长率、经向抗弯刚度及耐磨性能不及石墨烯黏胶纤维机织物;随着不锈钢丝质量分数在7.0%~20.0%范围内的增加,石墨烯黏胶纤维/不锈钢丝机织物的导电、防紫外线、抗静电、经向拉伸断裂强力、纬向抗弯刚度及透气性能增强,纬向拉伸断裂强力、经纬向拉伸断裂伸长率、经向抗弯刚度、耐磨性能减小,不锈钢丝质量分数变化对防电磁辐射性能影响较小。当不锈钢丝质量分数为7.0%时,石墨烯黏胶纤维/不锈钢丝机织物的综合性能最佳。     

基于ABAQUS的筒状纬编针织物拉伸力学性能模拟

为更好地了解筒状纬编针织物抵抗拉伸变形的能力,基于对织物试样尺寸测量得到的几何结构参数,借助Rhino 3D建模软件建立了纬编针织物线圈模型和筒状纬编针织物模型;同时利用有限元分析软件ABAQUS在单位线圈和筒状织物2个方面研究了筒状纬编针织物的纵向拉伸性能;对织物拉伸过程进行有限元模拟和实验验证,并对针织物拉伸过程中...     

二维三轴编织复合材料预压单胞模型建立及其弹性规律数值预测

针对二维三轴编织复合材料预压参数化单胞模型建立困难的问题,结合变形后的预制件模型单元离散数据,采用体素法生成了参数化的单胞模型,同时利用周期三次样条曲线构造了纤维束路径,建立了纤维束任意一点处的材料方向计算方法,以及可以描述非对称透镜形平面曲线的参数方程,然后通过单元切割程序,获得了挤压变形的编织预制件网格模型。结合变形后的预制件单元离散数据,利用体素法生成了在界面上和单胞边界面上均位移连续的参数化单胞模型,分析了不同网格尺寸下有限元模型的收敛性,并验证了模型的计算精度。实验结果表明可利用该模型对实际预压条件下二维三轴编织复合材料的弹性规律进行预测。     

三维机织正交结构复合材料的参数化设计

为给三维机织正交结构复合材料的力学模拟分析提供一种模型,通过观察3层机织正交结构复合材料预制件的细观几何结构,分析其最小重复单元中纱线间的几何位置关系,探讨细观结构中的几何参数与宏观设计参数的关系。在此基础上,利用Pro/Engineer软件对复合材料预制件进行参数化设计,建立三维机织正交结构预制件的通用几何模型。通过对比制得的三维机织复合材料的实际结构与模型结构以及纤维体积分数,验证了该模型的合理性。     

基于ABAQUS的涤/棉混纺机织物起球过程有限元仿真

为更好地了解涤/棉混纺机织物起毛起球过程,基于对织物起球过程表面毛羽测量得到的毛羽分布特征,借助PYTHON语言建立了织物及其表面毛羽的几何模型,同时利用有限元软件ABAQUS研究了涤/棉混纺机织物表面毛羽的起球过程,分析了涤纶弹性模量对涤/棉混纺机织物起球过程的起球等级、能量吸收形式的影响规律,并将有限元仿真的起球结果和实测起球结果进行对比分析。结果表明:涤纶弹性模量的增加使得涤/棉混纺机织物的起毛起球等级降低;摩擦耗散能是涤/棉混纺机织物起毛起球过程的主要能量吸收形式,织物起毛起球等级的仿真结果与实验结果的差异在7.4%以内,证明有限元仿真的可行性。     

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.     

A Study of the Mechanical Properties of Woven Silk Fabrics. Part III: A Study of the Extensibility of Continuous-filament Woven Silk Fabrics in the Small-load Region

Continuous–filament woven silk fabrics have a very low tensile modulus in the small-load region compared with woven fabrics of other fibres having a similar structure. In the silk fabrics, there may exist a small gap between the warp and weft threads at their crossover points because of the sericin-removing treatment that is applied after weaving. The tensile behaviour of a fabric with such a gap is considered to consist of two stages. In the first stage, the bent yarn alone is stretched in the initial state of tensile deformation without any mechanical interactions between the warp and weft threads. Since the bending rigidity of silk yarns is small and the gap is relatively large, the tensile modulus of silk fabrics becomes very low in the initial tensile region. After the contact of the warp and weft threads, the soft lateral-compressional property of the silk threads leads to extensibility of the silk fabric. This stage is called here the second stage, in which the tensile and the lateral-compressional deformation properties are mainly concerned with the tensile behaviour of the fabric in this region. Silk–fibroin fibre has a small fibre crimp, and this crimp also makes the silk yarn compressible. In this paper, the extensibility of silk fabrics is analysed, with a theoretical estimation of the extensibility, and an experiment to explain the reason for the high extensibility of silk fabrics is reported.     

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.     

基于芳纶平纹织物微观几何结构的纱线抽拔力学性能分析

为研究芳纶平纹织物纱线抽拔力学性能及各参数的影响规律,建立纱线抽拔数学模型,为后续数值模型提供理论基础.采用数字单元法模拟芳纶平纹织物织造过程,获得其微观几何模型,并计算得出纱线轮廓.在此基础上,使用ABAQUS模拟单纱抽拔过程,建立纱线厚度方向单层网格划分准则和纱线材料属性,获得横向预紧力、纱线间摩擦因数对纱线抽拔力...     

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.     

Theoretical analysis of geometrical and mechanical parameters in plain woven structures

An analytic solution for the estimation of structural parameters and initial tensile modulus of plain woven fabrics under uniaxial tensile loading in their linear elastic domain of deformation is presented. For this purpose, a new approach in straight line geometry with a parallel segment to the fabric plane and an inclined segment at the weave intersection in 3D form is proposed which leads to the theoretical estimation of all the structural parameters of plain woven fabrics with saw-tooth geometry. Defining and applying of JJ₂ Ratio in the model enable us to modify the geometrical model and estimate the value of structural parameters considering the history of samples influenced mainly by its manufacturing process. The strain energy method and Castigliano’s theorem are used for the mechanical analysis of the structure. The elasticity, bending, shearing, and compression rigidity of yarns are incorporated into the model. It has been shown that predicting the geometrical and mechanical parameters of woven fabrics before production are possible if and only if the crimp value of the fabrics can be estimated before their production. The proposed theory is validated and compared by applying into some experimental data and a previous model.     

纯棉纱线合股数对织物性能的影响

为研究纯棉纱线合股数对织物力学性能和保形性的影响,采用线密度相同的单纱、双股线、3股线、4股线4种股线类型,以适当的经、纬密分别织制成平纹、斜纹、缎纹组织的织物。对织物的拉伸性能、撕裂强力、拉伸弹性、折皱回复性、悬垂性、弯曲性进行测试与分析。结果表明:3股线织物的断裂强力和撕裂强力较大,4股线织物的断裂伸长率较大,双股线织物的拉伸弹性回复率较大;平纹织物仅有双股线织物的折皱回复性优于单股线织物,斜纹和缎纹织物的折皱回复性随合股数的增加均变差;双股线平纹织物悬垂性相对较好,但均没有斜纹和缎纹织物的悬垂性好;单纱织物的弯曲性能比股线织物好。     

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。     

A finite element approach to the modelling of fabric mechanics and its application to virtual fabric design and testing

This work presents a detailed finite element approach for textile fabrics for mechanical analysis and simulation by combining yarn properties, inter-yarn interaction and fabric structures. The fabric geometries are generated using the TexGen geometric modelling schema developed at the University of Nottingham. This geometric model of the fabric is interfaced with a mechanics modelling environment, ABAQUS, to predict its mechanical properties. The major advantages over other approaches are that all issues arising from textile mechanics modelling are considered, physically measured data are used as inputs and the traditional requirement of user intervention during model creation is removed. The developed model and its implementation are validated using the Kawabata Evaluation System for Fabrics on commercial fabrics subjected to variety of external loadings. The presented validation shows good agreement between the simulations utilising the finite element model and the experiments. The modelling approach is used as a virtual fabric design/testing system which allows designers to input yarn details and geometric fabric structures and to predict how the performance of the fabric depends on textile structures and basic material properties. The virtual testing shows that fabric mechanical performance depends in a complex way on structural parameters, geometric data and loading conditions due to the interaction between various deformation mechanisms. The virtual testing also shows that the bending and shear properties are very sensitive to the cross-sectional shape of the yarns, which need to be modelled accordingly in order to obtain good mechanical predictions.     

聚四氟乙烯／芳纶破斜纹织物衬垫拉伸性能数值仿真

为了解自润滑关节轴承织物衬垫的拉伸性能,对其拉伸性能进行了数值仿真与试验验证。通过进行切片试验,利用激光共聚焦显微镜观测纤维截面形态,对截面形貌轮廓尺寸进行测量计算,得到了纤维束的几何参数,利用ANSYS有限元软件建立了织物衬垫增强相单胞模型;基于复合材料细观力学方法和周期性边界条件,研究了织物衬垫拉伸性能,利用ANSYS得出了聚四氟乙烯（ PTFE）／芳纶（ Kevlar）混织破斜纹衬垫的拉伸弹性常数;并将数值仿真分析结果与拉伸试验结果对比,结果相差约20％,在误差允许范围内。     

Finite element modelling the mechanical performance of pressure garments produced from elastic weft knitted fabrics

Compression garments mainly produced from elastic knitted fabrics have attracted many attentions due to their medical care performances. Components’ characteristics of the pressure garments such as yarn and fabric structure affect significantly the pressure applied on the human body. In this paper, it is aimed to simulate the effect of yarn’s mechanical properties as well as fabric structure on mechanical performance of the compression garment. For this purpose, a precise geometrical model for fabric structure is needed by which the pressure applied to the body could be predicted. Accordingly, double jersey knitted fabrics containing elastane weft yarns were produced on an electronic flat knitting machine and the fabric tensile properties were measured in course direction. Using equations governing the fabric structural unit-cell, a real geometric model was created in a finite element software environment. Considering the linear visco-elastic properties for elastane weft yarn, stress-strain curve was extracted. The results obtained from numerical simulation were compared with the experimental data in order to validate the proposed geometrical model. The findings demonstrate a good agreement between experimental and simulation results.