A three-dimensional biomechanical model for numerical simulation of dynamic pressure functional performances of graduated compression stocking (GCS)

The beneficial effects of graduated compression stockings (GCS) in prophylaxis and treatment of venous disorders of human lower extremity have been recognized. However, their pressure functional performances are variable and unstable in practical applications, and the exact mechanisms of action remain controversial. Direct surface pressure measurements and indirect material properties testing are not enough for fully understanding the interaction between stocking and leg. A three-dimensional (3D) biomechanical mathematical model for numerically simulating the interaction between leg and GCS in dynamic wear was developed based on the actual geometry of the female leg obtained from 3D reconstruction of MR images and the real size and mechanical properties of the compression stocking prototype. The biomechanical solid leg model consists of bones and soft tissues, and an orthotropic shell model is built for the stocking hose. The dynamic putting-on process is simulated by defining the contact of finite relative sliding between the two objects. The surface pressure magnitude and distribution along the different height levels of the leg and stress profiles of stockings were simulated. As well, their dynamic alterations with time processing were quantitatively analyzed. Through validation, the simulated results showed a reasonable agreement with the experimental measurements, and the simulated pressure gradient distribution from the ankle to the thigh (100:67:30) accorded with the advised criterion by the European committee for standardization. The developed model can be used to predict and visualize the dynamic pressure and stress performances exerted by compression stocking in wear, and to optimize the material mechanical properties in stocking design, thus, helping us understand mechanisms of compression action and improving medical functions of GCS.     

Comparison of bending properties Co-woven-knitted and Multi-layered biaxial Weft-knitted fabric reinforced composites

Co-woven-knitted (CWK) fabrics and multi-layered biaxial weft knitted (MBWK) fabrics were prepared using glass filaments as both the warp and weft yarns and high tenacity polyesters as the stitch yarns with the same stitch length. Then the polyethylene resin was injected into the fabrics by vacuum assisted resin transfer molding to produce composites. Specific bending stress-displacement curves in the course and wale directions of the CWK fabric reinforced composites and the MBWK fabric reinforced composites were analyzed and their bending properties were also compared. Results indicate that the initial segments of all the specific bending stress-displacement curves for the CWK and the MBWK fabric reinforced composites are linear; then the specific bending stresses decrease with the displacements in a wave-like manner until sample destruction. The CWK fabric reinforced composites show plastic failure in course and wale directions, while the MBWK fabric reinforced composites show first fragile failure then plastic failure in course direction and show plastic failure in wale direction. Bending properties in the course direction of the CWK and the MBWK fabric reinforced composites are different from those in their wale direction, respectively. The CWK fabric reinforced composites are of smaller anisotropy than the MBWK fabric reinforced composites. By designing the buckling and distribution of the warp and weft yarns, the axial properties difference can be shortened.     

Technical knitting and ergonomical design of 3D seamless compression hosiery and pressure performances in vivo and in vitro

The present study was conducted from a new and innovative view to analyze pressure performances of elastic compression hosieries (ECHs) based on a technical knitting and ergonomic design and development methodology. ECHs with pressure classes I and II have been designed and developed. Multiple influencing factors and their dynamic interaction involved in the working mechanisms of ECHs were analyzed and discussed in this study. Yarn properties, material combinations, knitting structural complex, and parameters setting of machinery elements determine the fabric elasticity, stiffness, hosiery configuration, pressure magnitudes and gradient distribution. A good agreement and significant correlation on pressure performances of the developed hosieries are present from positions B1 to D when being tested on the wooden leg model by using Medical stocking tester in vitro and on the studied subjects’ legs in vivo. A reasonable pressure gradient was presented on the leg model (i.e. 70–100 % pressure at B1 and 50–80 % at C compared with the pressure exerted at ankle B), which supported the technical knitting design methodology applied in this study. However, some differences at ankle region B existed between the in vivo and in vitro values due to differences of anatomic structures that existed on the tested ankle areas. The location of testing points and body postures being undertaken by the wearers also significantly influenced the pressure profiles in vivo. More stretch deformations in hosiery fabric are produced, as assessed by static stiffness index evaluation, at the ankle when the body posture changes from standing to supine. The developed ECHs with pressure classes I and II received positive feedback on pressure and comfort perceptions on testing spot. More explorations are needed to elevate the consistency of the in vitro and in vivo pressure values at ankle region and to investigate their long-term pressure performances in practical wear through innovative knitting technical design with considerations of ergonomic factors and conducting larger scale of wear trials in future studies.     

Changes of pulling-out length and shrinkage ratio in polyester/spandex power net warp knitted fabrics

Power net fabric is one of the highly extensible two-way fabrics. Power net structure shows special characteristics in the wearing of final functional clothes. This research evaluated effects of treatment temperature on proportional extensibility and shrinkage ratio of spandex at a given wale length. As treatment temperature increased, extensibility increased proportionally to the standard length of the sample and the shrinkage ratio in the direction of course and wale increased. The pulling-out length increased proportionally to the standard length of the sample. However it was affected by the effect of treatment time and temperature due to the thermal properties of spandex filament yarn.     

Physical and comfort properties of the hoisery knit product containing intermingled nylon elastomeric yarn

There are several studies related with knitted fabric containing elastomeric yarn. These studies have been carried out only on fabrics containing naked elastomeric yarn, i.e., without intermingling. And most of them have focused on dimensional and extension-recovery properties of the fabric. Of course, intermingling yarn parameters such as number of knots and draw-ratio will affect the properties and performance of the fabrics. This paper presents a study about the effect of draw-ratio and number of knots, which are important parameters in intermingled nylon-elastomeric yarns, on the physical and comfort properties of hosiery knit products. To see the relationship and significance, bivariate correlation analysis and analysis of variance have been carried out. It has been seen that increase of draw ratio and number of knots lead to an increase in dimensional change, stitch density, fabric weight, and lead to a decrease in fabric spirality, abrasion, fabric wicking (wickability in course direction is less than that of wale direction). Fabric thickness increases with an increase in draw ratio and a decrease in number of knots. The number of knots and the draw-ratio do not affect the fabric drying rate. However, an increase in the draw ratio and the number of knots result in an increase in initial water content before beginning the drying process. But, an increase in initial water content is not so high as to affect the drying rate.     

Flexural stiffness of core spun cotton/spandex weft knitted structures under relaxation and machine washing treatments

In this research work, behavior of flexural stiffness of core spun cotton spandex single jersey, 1x1 rib and interlock fabrics was studied under relaxation and machine washing treatments. Results are compared with similar fabrics made from 100 % cotton. Fabric weight density increased with the progression of treatments and it is proportionate to the fabric tightness factor (stitch length^?1). Even though both types of fabrics had same machine set stitch lengths, cotton/spandex fabrics have shown the higher fabric weight densities than that of 100 % cotton fabrics. Although 1x1 rib and single jersey fabrics knitted with the same machine set stitch lengths, rib fabrics have given higher fabric weight densities than single jersey fabrics. Among the three knitted structures, interlock fabrics with higher machine set stitch lengths gave the higher fabric weights. Fabric stiffness and flexural rigidity have given higher values under the progression of treatments and it was found that higher values of stiffness have given by cotton/spandex knitted fabrics compared to their cotton fabrics. Fabric stiffness and flexural rigidity in wale direction were higher than that in course direction, but it is only observed in single jersey fabrics. However, 1x1 rib and interlock fabrics have shown an opposite behavior. It was also observed a positive correlation between TF (i.e.: stitch length^?1) and bending length/flexural rigidity in both fabric types. Lower flexural rigidities reported with single jersey structures and highest values gave with interlock structures of cotton/spandex and cotton fabrics.     

Porosity and capillarity of weft knitted spacer structures

A geometrical model of weft knitted spacer structures made with mono-filament yarn has been analysed to understand the spacer yarn path. Theoretical models have been created to predict the porosity and the radius of the capillaries of a knitted spacer structure depending on their geometrical parameters, such as course spacing, wale spacing, stitch length, fabric thickness, count of yarn and fibre density. Polyester knitted spacer fabrics were produced with different parameters; their porosity was determined by measuring the weight and compared with the theoretical porosity. The validity of the model was confirmed by experimental results. The porosity of knitted spacer structures made out of mono-filament yarn can be maintained above a certain level by adjusting the fabric parameters such as fabric thickness, course spacing and wale spacing.     

Dimensional and physical properties of plain knitted fabrics made from 50/50 bamboo/cotton blended yarns

In this study, the dimensional and some physical properties of plain knitted fabrics made from 50/50 bamboo/cotton blended yarns are investigated. In order to see the differences and similarities, the results are then compared with those for similar fabrics knitted from 50/50 conventional viscose/cotton and 50/50 modal/cotton blended yarns. Each fabric type was produced with three different stitch lengths. After all fabrics were dyed under identical dyeing conditions, they were subjected to dry and full relaxation treatments. For dimensional properties of fabrics, course, wale and stitch densities were measured. Then, by calculating statistically best-fit lines passing both through the experimental points and the origin, dimensional constants i.e. k values were predicted in terms of the fiber types. The result show that each fabric type knitted from bamboo/cotton, viscose/cotton and modal/cotton blended yarns behaves in a similar manner. However, in both dry and fully relaxed states, the modal/cotton knitted fabrics tend to have slightly higher k values than the bamboo/cotton and viscose/cotton knitted fabrics. For physical properties, fabric weight per unit area, thickness, bursting strength, air permeability and pilling were evaluated. The results show that the weight, thickness and air permeability values are independent of the fiber type. Plain knitted fabrics from modal/cotton blended yarns have the highest bursting strength values. Plain knitted fabrics from bamboo/cotton blended yarns tend to pill less.     

Comparison of tensile properties of co-woven-knitted and multi-layered biaxial weft-knitted fabric reinforced composites

The co-woven-knitted (CWK) fabric and multi-layered biaxial weft-knitted (MBWK) fabric were produced using glass filaments as warp and weft inserted yarns and high tenacity polyester as stitched yarns. Vacuum Assisted Resin Transfer Molding process was used to produce the two composites. Tensile tests were carried out in the course, wale and slanting directions of the composites, respectively. Specific stress-strain curves and failure modes of the two composites were investigated and compared. Results reveal that tensile strengths and elastic moduli of the two composites in the course and wale directions are better than those in the bias direction. All the composite samples fracture in the brittle damage mode. Furthermore, the buckling due to different inserted ways of the warp and weft yarns has a few influences on the tensile properties of the two composites. This research may lay a foundation for the establishment of the process windows for the co-woven-knitted reinforced composites.     

Empirical modelling of tensile strength of woven fabrics

Aesthetic properties of fabrics have been considered as the most important fabric attribute for years. However, recently there has been a paradigm shift in the domain of textile material applications and consequently more emphasis is now being given on the mechanical and functional properties of fabrics rather than its aesthetic appeal. Moreover, in certain woven fabrics used for technical applications, strength is a decisive quality parameter. In this work, tensile strength of plain woven fabrics has been predicted by using two empirical modelling methods namely artificial neural network (ANN) and linear regression. Warp yarn strength, warp yarn elongation, ends per inch (EPI), picks per inch (PPI) and weft count (Ne) were used as input parameters. Both the models were able to predict the fabric strength with reasonably good precision although ANN model demonstrated higher prediction accuracy and generalization ability than the regression model. The warp yarn strength and EPI were found to be the two most significant factors influencing fabric strength in warp direction.     

Using artificial neural network to predict colour properties of laser-treated 100% cotton fabric

In this paper, artificial neural network (ANN) model was used for predicting colour properties of 100 % cotton fabrics, including colour yield (in terms of K/S value) and CIE L, a, and b values, under the influence of laser engraving process with various combination of laser processing parameters. Variables examined in the ANN model included fibre composition, fabric density (warp and weft direction), mass of fabric, fabric thickness and linear density of yarn (warp and weft direction). The ANN model was compared with a linear regression model where the ANN model produced superior results in prediction of colour properties of laser engraved 100 % cotton fabrics. The relative importance of the examined factors influencing colour properties was also investigated. The analysis revealed that laser processing parameters played an important role in affecting the colour properties of the treated 100 % cotton fabrics.     

Analysis and off-axis tensile characterization of air-entangled textured polyester woven fabrics depending on unit cell interlacing frequency

The aim of this study is to analyze and determine the off-axis tensile properties of air-entangled textured polyester fabrics based on unit cell interlacing frequency. For this purpose, continuous filament polyester air-entangled textured yarn was used to produce plain, ribs and satin woven fabrics. The fabrics were cut from the warp direction (0°) to weft direction (90°) at every 15° increment, and tensile tests were applied to those of the off-axis samples. The strength and elongation results were introduced to the statistical model developed, and regression analyses were carried out. Hence, the effects of off-axis loading and interlacement on the directional tensile properties of the fabric were investigated. The regression model showed that off-axis loading influences fabric tensile strength. On the other hand, interlacement frequency is the most important factor for fabric tensile elongation. The results from the regression model were compared with the measured values. This study confirmed that the method used in this study as can be a viable and reliable tool. Future research will concentrate on multiaxially directional fabric and the probability that it will result in homogeneous in-plane fabric properties.     

Handle,fit and pressure comfort of silk/hybrid yarn woven stretch fabrics

Hybrid yarn was produced by twisting silk with nylon covered lycra yarn. Silk of 20 D in warp and hybrid yarn in weft was woven to develop lustrous woven stretch fabrics for sari blouse. Silk and hybrid yarn fabrics were produced in three different weaves namely plain, crepe and sateen. An in-depth study was carried out to understand the effect of weave on thermal comfort; low stress mechanical properties, total hand value and stretch properties. Nine blouses (3 samples× 3 figures) were constructed from three different woven stretch materials for fit assessment and objective pressure comfort test. The effect of fabric weave, low stress mechanical properties, total hand value and stretch properties on fit and pressure comfort of silk/hybrid yarn stretch fabrics were analyzed. Sateen weave silk/hybrid yarn stretch fabric shows higher total hand value, stretch properties and better thermal comfort properties. Sateen and crepe weave stretch fabrics provided good fit. Sateen weave fabric exerted lower clothing pressure value in the range of 3-12 mmHg at all body locations in standing position and in different postures.     

Effect of fiber and fabric constructional parameters on dynamic behavior of compression athletic wear

Compression athletic wear (CAW) is used in number of active sports like jumping, running and power lifting etc. to enhance the performance of an athlete. Compression efficiency is mainly determined by interface pressure exerted by it but pressure reduces with time due to prolonged stretching and deformation of fabric. In this study, compression behaviour was evaluated by measuring the interface pressure drop and recovery characteristics of CAW. Interface pressure over a long duration of time was measured using a dynamic leg segment prototype. Recovery characteristic was evaluated by measuring the residual shrinkage at different time interval using cyclic fatigue test. The effect of filament cross sectional shape, Lycra® linear density and fabric tightness on compression properties was found to be statistically significant by ANOVA. Fabric with high tightness factor, coarse Lycra® and profiled polyester was observed to have better recovery and compression efficiency as compared to other fabrics under study.     

Drape simulation of three-dimensional virtual garment enabling fabric properties

This study analyzes how the silhouette of virtual garments applied to virtual avatars is altered according to various virtual fabric properties. This study measures the properties of real fabrics that include a charmeuse (#F1) and gabardine (#F2) using the Fabric Analysis by Simple Testing system; in addition, the material properties of different real fabrics were applied to that of the virtual fabric. It then evaluates the drape stiffness and silhouette of the virtual garments according to the different fabrics. This study also compared the virtual garment silhouette of sample fabric #F1-S that changed only the stretch property of the sample fabric #F1 with the virtual garment silhouette of sample fabric #F1. The results show that the fabric properties including bend, thickness, weight, stretch, shear values affect the drape stiffness, silhouette, and fit of the virtual garment simulated on virtual avatars and may be used for the realistic virtual garment technology.     

Changing porosity of knitted structures by changing tightness

A geometrical model of plain knitted structures is discussed in depth to understand the yarn path in a knitted loop. A theoretical model has been created to predict the porosity of a knitted structure depending on the geometrical parameters, such as course spacing, wale spacing, stitch length, fabric thickness, count of yarn and fibre density. Polyester and nylon plain knitted fabrics were produced to different tightness, and porosity was determined by measuring the weight. The validity of the model was confirmed by experimental results, using different plain knit fabrics. The porosity of a knitted structure can be changed by reducing the yarn thickness and the stitch length; however this would influence the courses and wales per unit length in the structure.     

Effect of washing cycles on behavior of core spun cotton/spandex interlock structures

Effect of machine washing on structural behavior of core spun cotton/spandex interlock fabrics made with high, medium and low tightness factors has been investigated. Results are compared with those for similar fabrics knitted from 100 % cotton. Structural behavior of cotton/spandex and cotton fabric samples was observed under full relaxation and washing treatments up to 10th cycle. Based on these data, dimensional constants (U-values) were predicted under 95 % significance level. Higher course and wale densities, stitch densities, dimensional constant values, linear and area dimensional shrinkages are reported with cotton/spandex interlocks. After treatment levels, cotton/spandex showed the dimensional constants with lesser CV %. With increasing fabric tightness, decreasing of length shrinkages and area shrinkages and increasing of width shrinkages are reported in cotton/spandex interlock structures. Cotton/spandex interlocks showed longitudinally and highly deformed shapes after treatments. Fabric tightness affects significantly on structural behavior of cotton/ spandex and cotton structures during relaxation.     

Investigation on hydrostatic resistance and thermal performance of layered waterproof breathable fabrics

Waterproof breathable layered fabrics allow water vapor passing through, but resist liquid water to pass. This ability of the fabrics to protect rain and snow water while allowing sweat vapor to evaporate from inside to outside atmosphere, leads them to be used as outdoor sportswear or protective clothing. The big challenge of enhanced hydrostatic resistance of these fabrics with proper breathability and thermal comfort has widened the research scope. This study presents an experimental investigation on hydrostatic resistance and thermal behavior of layered waterproof breathable fabrics. Six different types of hydrophobic and hydrophilic membrane laminated layered fabrics were evaluated by varying different fabric parameters in the experiment. Hydrostatic resistance and water vapor permeability of the laminated fabrics were measured by SDL ATLAS Hydrostatic Head Tester and PERMETEST respectively. Thermal properties were evaluated by ALAMBETA instrument. Moreover, FX-3300 air permeability tester was used to measure air permeability which represents the porosity of the fabrics and computer based See System software was used for water contact angle measurement on the outer fabric surface in order to determine the hydrophobic and hydrophilic properties. This experiment clearly discusses the influence of different fabric characteristics and parameters on hydrostatic resistance and thermal properties of the breathable laminated fabrics. The results show that fabric material composition, density, thickness, and hydrophobic and hydrophilic membranes have significant effects on hydrostatic resistance, breathability and thermal properties of different laminated fabrics.     

Mechanical characterization of flocked fabric for automobile seat cover

In this study, the tensile and tearing properties of substrate, substrate with adhesive and flocked fabric were studied with developed regression model which explains the relationships between fabric forms and tensile and tearing strength of the flocked fabrics. Warp and weft tensile strengths of wet flocked fabric are generally higher than the warp and weft tensile strengths of dry flocked fabric due to the high wet properties of cotton yarn. Weft tensile elongation of the flocked fabric is generally higher than warp tensile elongation due to the higher crimp ratio of the flocked fabric in the weft direction. Warp and weft tearing strengths of wet form substrate with adhesive and flocked fabric are higher than those of dry forms of substrate with adhesive and flocked fabric. One of the reasons could be the decrease of inter-yarn frictional forces due to the lubrication effect of the wet form of acrylic adhesive in substrate with adhesive fabric. Generally, tearing strength of flocked fabric is low compared with substrate. It was concluded that the regression model used in this study could be viable and reliable tools and flocked fabric could be considered as an alternative seat cover material to use in automotive industry.