Fumei Wang

Predicting the Shearing Rigidity of Woven Fabrics

In this paper, we analyze the mechanical interaction of warp and weft yarns in shearing deformation, and establish theoretical equations expressing the relationship between the shearing rigidity and the fabric structures. To avoid calculating the rate of friction change during shearing deformation, we use KES data for twenty-seven worsted fabrics to create the empirical equations that describe the relationship between the rate of friction change and the contact area of yarns. By combining the theoretical and experimental equations, we develop equations for predicting the shearing rigidity of short-float worsted fabrics based on simple fabric structural data. Another set of worsted fabrics is used to validate the prediction equations.

Elasticity of woven fabrics made of polytri-methylene terephthalate/ polyethylene terephthalate bicomponent filaments

Polytri-methylene terephthalate (PTT)/polyethylene terephthalate (PET) filaments are self-crimping, highly elastic polyester bicomponent fibers. In this paper we studied the influences of important structural variables on the elasticity of woven fabrics made of PTT/PET weft filaments by testing 33 samples with different weave structures, PTT/PET contents, weft densities, and yarn twists. Fabric elasticity is described by two parameters: fabric strain and resilience in tensile testing. The experimental results indicate that twill and satin weaves have greater potentials in obtaining high elasticity than a plain weave. Fabric elasticity increases with the increase of the PTT/PET content in the weft yarn, but the change becomes insignificant after the PTT/PET content exceeds 66.7%. Increase in weft density has a negative effect on fabric elasticity, while the weft twist limits crimp formation of PTT/PET filaments and thus undermines the fabric’s elasticity noticeably. The PTT/PET filaments in fabrics can only realize about 6% of the elastic potential of the original PTT/PET filaments, because the crimp configurations of the filaments are dictated by not only the shrinkage differential of the two components, but also the weave structure and the yarn twist.

The novel frequency selective fabric and application research

There have been various efforts on frequency selective surface in recent years, and of course, some research progress has been made, especially in numerical calculation and simulation field. However, it seems that less work is done on the processing and forming methods. Soft fabrics are periodic and have advantages over the rigid materials in lightweight, softness, low bending rigidity, which make it possible and meaningful to study their filtering property as the medium in electromagnetic field. In this paper, a kind of electromagnetic functional textile based on frequency selective surface was proposed specifically for 10 GHz, dominant frequency of X-band radar. The full-wave simulation software, HFSS v14, was used for theoretical simulation and optimization, and two complementary cross-shaped unit cells with optimum size were obtained. Then, the frequency selective fabrics were manufactured through silk-screen-printing technology and measured using transmission method. It showed that the measured and simulated results had good consistency, and the fabricated frequency selective fabrics had ideal band-stop or band-pass performance. Finally, according to the analysis of S21 curve and transmission line equivalent circuit modal, the filtering mechanism was explained and the great potential in practical application of frequency selective fabrics was further illustrated.

Factors affecting crimp configuration of PTT/PET bi-component filaments:

In this paper, we explored factors that affect the crimp configuration of polytri-methylene terephthalate (PTT)/polyethylene terephthalate (PET) filaments. We selected three PTT/PET filaments that have approximately identical monofilament fineness but different cross-sectional shapes to study how crimp configuration is influenced by the elastic modulus ratio and differential shrinkage between PTT and PET components. The average elastic modulus ratio was obtained from the stress—strain curves and the cross-sectional measurements of the three PTT/PET filaments. The crimp curvature expressions of the three fibers were used to determine that the differential shrinkage of the two components, which was in the range of 6.8—10.01%. It was found that as the elastic modulus ratio (m) increased, the crimp curvature increases rapidly when the m increases from 0 to 0.5, and then approaches to a stable value when m is larger than 0.5. The crimp curvature increased continuously as the differential shrinkage increased. T...In this paper, we explored factors that affect the crimp configuration of polytri-methylene terephthalate (PTT)/polyethylene terephthalate (PET) filaments. We selected three PTT/PET filaments that have approximately identical monofilament fineness but different cross-sectional shapes to study how crimp configuration is influenced by the elastic modulus ratio and differential shrinkage between PTT and PET components. The average elastic modulus ratio was obtained from the stress—strain curves and the cross-sectional measurements of the three PTT/PET filaments. The crimp curvature expressions of the three fibers were used to determine that the differential shrinkage of the two components, which was in the range of 6.8—10.01%. It was found that as the elastic modulus ratio (m) increased, the crimp curvature increases rapidly when the m increases from 0 to 0.5, and then approaches to a stable value when m is larger than 0.5. The crimp curvature increased continuously as the differential shrinkage increased. The crimp curvature of the PTT/PET filament with a dumbbell-shaped cross-section was higher than that of the other two fibers with gourd-shaped and round cross-sections.

Configuring the spinning technology of PTT/PET bicomponent filaments according to fabric elasticity

This paper studied the configuration of spinning technology of PTT (polytrimethylene terephthalate)/PET (polyethylene terephthalate) bicomponent fiber via measurements obtained from the elasticity testing of fabrics made of them. The effects of four main spinning parameters on the elasticity of two series, named Z and Q, of interwoven fabrics were explained, including different ways of binding, intrinsic viscosity differences, and the percentage contents of PTT and the temperature of the hot plate. The experimental results indicated that the elongation ratios of the fabrics, which were made of PTT/PET bicomponent filaments spun by the parallel bound method, with larger differences in the intrinsic viscosity of the two ingredients and a higher temperature of the hot plate, were much larger than that of its corresponding counterparts. The elastic modulus ratio (m) and the PTT contents exhibited a cross-impact on crimp curves of PTT/PET bicomponent filament fabrics. The elongation ratios of fabrics made of PTT/PET bicomponent filaments would augment effectively as the hot plate temperature increased within a temperature range under the same posttreatment.

Structural design and physical characteristics of modified ring-spun yarns intended for e-textiles: A comparative study:

E-textiles based on yarn-based sensors have been a topic of intense research. In our previous paper, a straightforward way for fabricating tri-component elastic-conductive composite yarns (t-ECCYs) with a unique architecture applicable to yarn-based sensors was proposed using a modified ring-spinning frame. Herein, a comparative analysis of the physical characteristics of t-ECCY, bi-component elastic composite yarn (b-ECY), bi-component conductive composite yarn (b-CCY), and single rayon yarn (s-RY) are presented, in detail, in terms of tensile behavior, elastic recovery, electrical resistance, unevenness, and hairiness. In particular, a systematic study of the tensile and conductive properties of yarns appropriate for e-textiles, that is, t-ECCY and b-CCY, are highlighted. In addition, a non-invasive structure verification technique is conducted to identify the dispositions of constituents inside the yarn. It is found that the t-ECCY exhibits a remarkable improvement over the other yarns, having robust tensile properties, super elasticity, stable electrical durability, lower unevenness, and hairiness. A simple tensile model has been proposed to predict the t-ECCY’s tensile strength, and the substantial improvement in the tensile properties of t-ECCY compared with the b-CCY can be associated with the distinctive yarn structure. The stretch-deformation mechanism of coils in the t-ECCY is, initially, separation of adjacent surfaces of coils and gradual unwinding till free. Benefiting from its superior conductivity and elasticity after single/cyclic stretch tests as well as other properties, the t-ECCY itself can serve as a sensing element, which could be a highly valuable use for specific purposes in smart textiles.

The frequency response characteristics of planar frequency selective fabrics (FSFs) with cross-shaped units

In this paper, a computer-based carving experiment was conducted to make frequency selective fabrics (FSFs) with cross-shaped units. Different samples with varying frequency selective fabric types, structure parameters, conductive layers, base fabrics and unit shapes were prepared and the transmission characteristics were tested using the Shielding Room Method. The reflection characteristics under different electromagnetic (EM) wave incidence angles were also tested to study the angle stability. Experimental results showed that in the given frequency range of 4–14 GHz, two types of frequency selective fabrics had good complementary transmission characteristics, with ideal bandwidths and resonance peaks, and the aperture frequency selective fabrics showed certain stability to small electromagnetic wave incidence angles. Structure parameters played a very important role in determining frequency response characteristics and base fabrics with different effective dielectric constant could also exert a great influence. However, the change of electrical conductivity within a certain extent would not affect the transmission characteristics and related work should be continued to explore the effect rule. Through rational control of the unit shape to increase or decrease the conductive material mass, broad-spectrum shielding or passing-through properties could be obtained. In the paper, the experimental results were discussed and analyzed in detail aiming at different parameters, and internal causes were further investigated, which could provide reference values for the relevant design and product development process.

Compressibility of the kapok fibrous assembly

In this paper we study the compressibility of kapok fibrous assemblies via scanning electron microscopy (SEM) image observations on kapok microstructures and measurements obtained from Kawabata Evaluation System (KES) compression testing. The assemblies, made of slightly carded kapok fibers, were treated in different levels of relative humidity (dry or wet) and pressure (0 or 100 kPa) conditions. The SEM images of the treated samples revealed that kapok fibers were initially hollow and circular, but could be crushed partially or totally to become thin ribbons after being pressed with a 100 kPa pressure. Over 80% of the fibers in the wet-pressure-treated assembly appeared to be crushed. In the KES testing, the compressional resilience, bulkiness and other parameters of the kapok assemblies were calculated from the compression curves. The results showed that the compressional resilience of the dry-treated kapok assemblies was better than that of the wet-treated assemblies; the bulkiness of both the dry- and wet-treated assemblies was reduced after the pressure treatment, but in the wet assemblies kapok hollow structures and interspaces among fibers were much easier to be squeezed than those of the dry assemblies.

A study on the quality of kapok blended yarns through different processing methods

In this paper, 14 types of kapok blended yarns and four types of cotton yarns manufactured through different spinning technologies and processing methods were selected in order to explore the most efficient spinning technology for kapok fiber. Four yarn characteristics were measured: yarn fineness/unevenness, yarn defects, yarn hairiness, and breaking tenacity. According to Uster Statistics 2007, GB-T/398-2008, and FZ12001-1992 standards, the analytical results of the four characteristics showed that the quality of kapok blended yarns achieved a higher level with the improvement of spinning technology. The compact spinning and processing technology IV was a preferred way to spin high-quality kapok blended yarn, which lent support to widening the application of kapok fibers in various end-use products.

Improved Computation Formula of Thermal Conductivity of Fibrous Porous Materials

For the complexity of convective term, the interior heat transfer is important for the engineering testing of heat conduction of fibrous porous materials. In this paper the heat transfer through the body of fibrous porous materials was simulated with finite volume method. By the simulation, it is found that the total heat flux through the body of fibrous porous materials is a linear function of the thermal conductivity when it is measured by the guarded plate, and some constants in the linear function are related with the thickness and permeability coefficient of the sample. The simulated data are employed to fitting the variation curves of the total heat flux with thermal conductivity, thickness and permeability coefficient, respectively. The improved calculating formula of thermal conductivity for fibrous porous materials is established based on the fitting estimation. Through the experimental, it is demonstrated that the improved calculating formula is more accurate than the original one, which is based on the assumptions of single component continuum material and one dimensional heat transfer.