基于数字图像相关法的纱线和织物微观变形测量

为连续、精确地测量纱线和织物组织单元的拉伸变形量,结合数字图像相关法(DIC),提出一种微观尺度下的单轴拉伸变形测量方法。首先选取4种织物,从织物中抽取纱线、裁剪织物试样,并制作合理的散斑。然后对纱线和织物试样分别进行单轴拉伸实验并用相机记录整个过程。最后在DIC测试软件中添加引伸计,计算拉伸过程中单纱分段线应变以及织物单元结构在经、纬方向上的线应变。结果表明：单纱拉伸过程中,各处线应变增长速率不同;织物微小变形下内部结构呈非均匀变形,其中纬编针织物线圈变形不均匀性更为明显。基于DIC的微观变形测量方法揭示了纱线和织物生产、应用中的微量变形规律,为智能可穿戴电子纺织品的设计与应用提供指导。     

镀银锦纶电磁反射面织物的力学性能

对镀银锦纶电磁反射面织物材料进行拉伸、撕裂、顶破力学性能测试,得到了材料的抗拉强力、撕裂强力、顶破强力、双轴拉伸弹性模量和泊松比。实验结果表明:反射面织物材料拉伸性能符合机织物拉伸性能特点;双轴拉伸求得的织物弹性模量较小;织物的经向撕裂强力大于纬向;顶破试样裂口形式表现为纬纱的断裂。     

具有负泊松比效应经编织物的制备及其力学性能

负泊松比效应材料结构具有优良与独特的力学性能,而针织结构是制备负泊松比效应材料的最佳结构之一,为此,对经编机上生产负泊松比效应织物的组织结构和力学性能进行了研究。首先,对负泊松比效应织物的结构进行设计,确定其编织工艺,并在KS4特里科经编机上进行上机编织操作;然后,对织物分别从0°、45°、90°和135°方向进行拉伸性能试验,通过绘制不同方向的应力与应变曲线及泊松比与应变曲线研究其力学性能,同时分析了几种织物不同方向上拉伸的最终破坏形态。结果表明,不同织物在不同方向上存在力学性能差异。     

广角机织物的织造工艺及其偏轴拉伸力学性能

为开发适用于不同应用领域的产业用纺织品,在对原有普通剑杆织机改进的基础上,探讨了广角机织物的织造工艺,织造了经纱和纬纱夹角为120°的涤/棉平纹广角机织物。借助万能材料试验机研究了普通涤/棉正交织物和广角机织物不同偏轴方向的拉伸力学性能,获得了其应力-应变曲线和特征值变化规律,并分析了其变形及失效模式。结果表明:对于普通正交机织物和广角机织物,其拉伸断裂强力均呈现出明显的极轴特性;在断裂强力相同的情况下,与普通正交机织物相比,广角机织物纬向的断裂伸长率提高了30%,经、纬向弹性模量分别提高了42%和79%,展现出优异的强度和变形特征。     

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。     

基于数字图像相关法研究某织物增强橡胶基复合材料的力学性能

随着现代社会经济科学技术的发展,织物增强橡胶基复合材料应用越来越广泛,其力学性能备受关注。本文基于数字图像相关法的原理研究了某织物增强橡胶基复合材料的力学性能。实验采用两台高分辨率(2 4 4 8×2048)工业CCD相机记录某织物增强橡胶基复合材料拉伸试样的变形过程,对采集到的图片进行分析得到试样表面的二维位移/应变场数据,并对其应力、应变数据进行线性拟合得到表征织物增强橡胶基复合材料力学性能的弹性模量和泊松比。     

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。     

基于数字图像相关法的针织物泊松比测定

为解决针织物因其各向异性,传统泊松比测定方法不适用的问题,结合数字图像相关法对针织物进行单轴拉伸测试,提出了一种以纬平针织物试样整体作为研究对象且在其较大形变下测试其泊松比的方法。实验选取3种纬平针织物,首先录制试样单轴拉伸的整个过程,导出每1帧图像,将图像转化为灰度图后,在MatLab软件中用数字图像相关法进行位移分析,用SPSS软件对载荷方向拉伸的计算值与实际拉伸值进行t检验,验证了可行性,计算所得泊松比在正常取值范围内,避免了织物颈缩问题,且每秒可提取30帧图片进行位移分析,提高了精度,为研究针织物的泊松比提供新思路。     

棉针织物结构与拉伸收缩性能的关系

探讨了棉针织物结构与拉伸收缩性能的关系。利用图像法测试6种不同纱支、组织结构、织物密度的棉针织试样在10%、30%、50%、70%定伸长条件下的拉伸收缩性能。利用Auto cad软件处理试样横向收缩的实物图片后,分析在同一拉伸伸长率下不同结构针织物的横向收缩分布规律。结果表明:针织面料布边收缩曲线可由抛物线模拟,抛物线开口越大,面料布边收缩越严重;织物纵向拉伸得到的布边曲线的弯曲程度要大于织物横向拉伸后得到的布边曲线的弯曲程度;纱线根数越多,织物密度越大,横向收缩越小,织物保形性越好;罗纹组织结构面料保形性能优于半畦编组织和纬平针组织织物。     

机织物增强双层柔性复合材料拉伸异向性能及其失效准则

为了进一步研究织物增强双层柔性复合材料的力学性能,对偏轴向试样的单向拉伸性能进行了实验分析,研究了材料的拉伸破坏机理,并比较了两种强度失效准则下的预测值。结果表明：与机织物膜结构材料相比,该种材料表现出更加明显的各向异性;同时发现,相对于Tsai-Hill 强度失效准则,调和余弦级数强度失效准能较好地适应各种破坏模式下失效强度的预测,且该种材料的拉伸性能指标之间表现出非同相特性。     

纺纱方式对织物抗皱性能及拉伸弹性的影响

为开发天然抗皱免烫衬衫面料,探讨纺纱方式对拉伸弹性及抗皱性的影响,用聚酯(PET)长丝与纯棉纱通过全聚纺、全聚纺包芯、全聚赛络纺包芯、全聚赛络纺双丝包芯、全聚纺包芯合股5种纺纱方式,开发了5种线密度为14.8 tex的纱线,并织造了相同规格的5种织物,对织物的抗皱性、尺寸稳定性、刚柔性、拉伸变形性等进行测试与分析。 结果表明:纤维的急弹性变形比例、初始模量越大,织物的弹性及折皱回复性越好;纱线的毛羽少、表面光洁、条干均匀、初始模量大,则织物抗皱性好;全聚赛络纺包芯纱、全聚纺包芯双合股纱的抗皱性、尺寸稳定性、拉伸弹性回复性均较好,织物的外观平整度均为3.5级;全聚赛络纺包芯纱比全聚纺包芯纱双合股纱生产流程短,成本低,更适合用于开发高保形免烫衬衫面料。     

Deformation characteristics of flexible PU-coated multi-axial warp knitted fabrics under uniaxial tensile

Based on the characteristics of high tenacity, low density, flexible design, the coated fabric has emerged as a promising construct for tensile test. Here, it reports the deformation mechanism of a PU-coated multi-axial warp-knitted fabric under uniaxial tensile via a digital image correlation system. Specimens produced by us are chase in three fibre-reinforced directions namely 0°, 45° and 90°, respectively. The result shows that the crease does not have an effect on the deformations in the small deformation range (strain < 5%), and the deformation was evidently occurred near the fixed end lags because of the faster movement of specimen at the loading end, and the transverse shrinking at the edges is faster than that in the middle of the specimen. In the large deformation range, the strain fields are inconsistent at the same displacement revealing that the deformations of this kind of flexible coated fabric is in-homogeneous under tensile.     

Study of tensile properties of plain-woven fabrics in all-directional using energy method,Part II: experimental verification

Abstract

In the previous part of this series, ‘Comprehensive Tensile Modulus (CTM)’ was introduced as an important modulus to express the force-elongation behavior of plain-woven fabrics when the force is imposed on the fabric and extended it simultaneously in all directions. A theoretical model was presented to predict this modulus in the initial elastic region. In order to verify the accuracy of the model, a novel tensile test method was developed to measure load-extension curve of the fabric samples under the proposed loading condition. Thereafter, six plain-woven fabrics were produced with different raw materials and densities then were washed and dried to reach the relaxed state. Fabric samples were tested using the new method. The fabric’s experimental Comprehensive Tensile Modulus (CTMs) were determined from the results of the tests in all directions by the nine-point central difference method, and the calculated data were analyzed statistically to obtain the experimental CTM of fabrics. Reasonable agreement between theoretical and experimental results confirmed that the generated model is capable to predict the CTM index as a tensile property of plain-woven fabrics, adequately. The comparison between results of the theoretical model and experimental test shows that maximum error of prediction is 8.5% which is recorded for the grey fabric sample constructed from the OE Cotton yarn with nominal yarn count 24 Ne. Also, maximum experimental comprehensive tensile modulus (17.9 N/mm) is for the grey fabric sample constructed from the high tenacity continuous filament of Nylon with nominal yarn count 900den, in one millimeter extension with maximum modulus in warp and weft directions, that is, 5.6 N/mm and 6.6 N/mm in the same extension in the initial linear elastic region, respectively.     

Tensile characteristics and stress relaxation analysis of woven fabrics in terms of fabric direction

Abstract

Woven fabrics in various end uses are subjected to tensile loads in different directions, so investigation of the effect of fabric direction on the tensile behaviour and the stress relaxation performance of fabrics is important and needs to be considered. In this study, the tensile and stress relaxation properties of woven fabrics with five various weave structures have been analysed, in different directions. It was concluded that the tensile properties of fabrics such as Young’s modulus, breaking load and elongation and also the work of rupture were significantly affected by the fabric direction and weave structure. Moreover, it was determined that the fabric tensile stress relaxation (%) was considerably affected by the applied strain level, fabric direction and weave structure in the confidence range of 95% and it might well be expressed as a Gaussian function of sample direction.     

面料拉伸性能对经编无缝服装服装压的影响

通过对经编无缝服装面料的拉伸性能测试和经编无缝服装的服装压测试,探讨了面料拉伸性能与经编无缝服装压的关系,研究表明,服装压与弹性回复率、断裂强力和弹性模量呈正相关关系,与塑性变形率呈负相关关系;在原料、织物密度不变情况下,组织结构是影响面料拉伸性能的主要因素。研究成果对经编无缝服装设计和生产有指导意义。     

芯丝种类对织物抗皱性及抗变形性的影响

文章采用全聚纺纺纱方式生产了JC/PET、JC/PTT、JC/SPH、JC/T400四种包芯纱和一种纯棉纱,利用这五种纱线织造了规格相同的五种机织物。分别利用客观与主观评价法,评价织物的抗皱性及平整度等级,同时测试了织物的拉伸弹性回复率,以研究芯丝种类对织物抗皱性及抗变形性的影响。结果表明:芯丝的加入可以改善纯棉织物的平整度;长丝的初始模量、弹性影响织物的抗皱等级,SPH的初始模量最高、T400的弹性回复性最好,因此JC/SPH和JC/T400包芯纱织物抗皱等级最高,可以达到3. 5级;且这两种长丝的表面均有沟槽,截面为异形,起到毛细管作用,其织物具有较好的吸湿排汗作用,是开发高保形免烫衬衫面料的理想选择。     

An explanation of warp knitted fabric deformation under uni-axial tension by a novel index as shape ratio

Although the Poisson’s ratio (PR) can predict the deformation of engineering materials under uniaxial tension, but seems that it cannot predict well the deformation of structures such as fabrics. It can be attributed to the lack of continuity among constituent elements that leads to some distortion of them during tension. Therefore, the PR is not a suitable tool to explain precisely the deformation of structures such as fabrics. For this reason, a new geometrical index was defined to quantify the deformation of fabrics in order to use instead of PR. This index named shape ratio is obtained by division of the variation of squared perimeter to the area of a printed square on the fabric under uniaxial tension. To check the defined index, warp-knitted fabrics with various structures such as Tricot, Locknit, and Three- and Four-needle satin were produced and tested using tensile tester. The results show that shape ratio can predict the deformation of warp-knitted fabrics as an orthotropic structure rather than the PR.     

Study of tensile properties of plain-woven fabrics in all-directional using energy method,Part I: theoretical study

Abstract

In the first part of this series, a new mechanical parameter, that is, “Comprehensive Tensile Modulus (CTM)” is introduced and modeled to show the tensile behavior of plain-woven fabrics in the initial linear elastic region of the force-elongation curve subjected to tensile load and extended it simultaneously in all directions. Considering the initial load-extension behavior of fabrics, a mathematical-mechanical model is presented to predict the CTM of fabrics in the initial linear elastic region using Castigliano’s theorem. Based on the generated model, the initial sample length, dimension of the load imposed region, the geometrical shape created in the plain-woven fabric sample during tensile, the structural specification of these fabrics such as yarns sett, yarns crimp in fabric and mechanical properties of yarns such as bending rigidity in both warp and weft yarns affect in the comprehensive tensile modulus of fabric. In order to verify the conformity and accuracy of the model, a preliminary test was conducted on the prepared samples based on a novel tensile test method developed to measure load-extension curve of the fabric samples under the proposed loading condition. A reasonable agreement was found between theoretical and experimental results.