Volume 18, Issue 2

Direct conversion of nanofibers into a yarn formed by electrospinning has begun to draw attention recently while pioneering attempts in fact go back to 1930s. Once nanofiber yarns are spun successfully by electrospinning, obviously, this would open new gates for many different applications. However, this is still a challenging task and there is no system accepted universally yet. There are more than 20 different approaches available so far but with serious limitations. In this review, they were categorized as (i) systems for production of parallel bundle of nanofibers and (ii) systems for production of twisted nanofiber yarns, presenting potential applicability of each with a critical point of view. The results show that some of the attempts mainly present basic conceptual ideas only. There are some works to produce real twisted nanofiber yarns continuously while mainly funnel, disc, or ring collectors have been used as the twisting element. However, there is limited information regarding stability of spinning system or control of yarn properties. This review also analyses the technical properties of electrospun nanofiber yarns summarizing the available data in terms of yarn properties such as fiber fineness, twist, production speed, mechanical properties, polymer types, and other important parameters available.

Owing to twisting of filament fiber bundle, the structure and consequently various parameters and properties of a fiber bundle are changed. The aim of the work is to verify the effect of multifilament yarn twist (or twist coefficient) on selected mechanical properties such as multifilament tenacity, breaking elongation, and coefficient of fiber stress utilization in the yarn. Furthermore, the influence of twist on structural parameters such as the angle of peripheral fibers, the packing density, and the substance cross-sectional area of fiber bundle is observed. Two multifilament yarns with different filament cross-section shape and material were used for the experiment. Experimentally obtained data was compared with the known model dependencies derived decades ago based on the helical model. It can be stated that multifilament yarn retraction can be predicted based on the angle of peripheral fibers using the Braschler’s model. The coefficient of fiber stress utilization in the multifilament yarn determined experimentally corresponds with a theoretical curve, constructed according to Gégauff and Neckář, in the area of Koechlin’s twist coefficient α > 54 ktex 1/2 m −1 . Results as well as possible causes of deviations of experimental data from the theoretical one are discussed in this work.

This paper presents the experimental and numerical analysis of the potential of a braided fabric for flexor tendon repair. Numerical models of tubular braided fabrics were generated using a python script interface and imported into ABAQUS ® while Flexor tendon models were represented as silicone rubber rods. Experimental tests and Finite Element Modelling (FEM) of the flexor tendon repair was undertaken by deploying two tendon ends from opposite sides of a tubular braided fabric. This was done such that the tendon ends meet at the midpoint within the fabric. The tendons were tightly held to emulate a realistic repaired tendon. A displacement driven uniaxial loading was induced on the tendon-fabric assembly sufficient to cause a 2mm gap between the tendon ends. Numerical analysis of the repair potential of a braided fabric in tendon repair was done by analyzing selected fabric parameters that were crucial in tendon repair applications. The results show that changing the parameters of the braided fabrics significantly affected the potential of the fabrics during tendon repair.

The extra-large parachutes were different from the common parachutes because of their size and opening process. Some undesirable inflation phenomena such as canopy winding and whipping usually appeared in their pre-inflation process. However, the mechanical mechanism of these phenomena was very difficult to be explained by experimental means. In this paper, the pre-inflation process in finite mass situation of an extra-large parachute was calculated by explicit finite elements. According to the results, the pre-inflation process can be subdivided into symmetric inflation stage, undesirable inflation stage, and stable inflation stage. The canopy winding and whipping mainly occurred in the second stage. With the continuous deceleration of parachute-payload system, the top of canopy without effective constraints would appear winding and whipping under the function of inertia force. The canopy winding and whipping increased the difficulty of canopy expanding and then caused asymmetric inflation. The above undesirable phenomena had a great influence on the deceleration effect and were easy to cause the recovery failure. The actual airdrop experiments also proved that the lack of effective constraints on the canopy top will cause undesirable inflation phenomena. The conclusions in this paper can also provide a reference for extra-large parachute design and research.

The aim of the study is to show how the washing process, while considering the type of washing agent and number of wash cycles, determines the durability of hydrophobic finishes of laminated fabrics. The samples of material were subject to multiple wash cycles in clear water and with the use of two types of washing agents, namely, an ordinary washing powder and a detergent recommended by manufacturers of functional clothing. The washed materials were subject to spray test and its waterproofing and degree of surface wetting were evaluated. The tests have shown that waterproofing of membrane laminates with DWR (durable water repellent) coating become deteriorated during washing treatment and the use of special detergent does not guaranty the maintenance of better coating properties than an ordinary washing agent.

Seven drape indicators and four of the parameters assessed in the UPC ring test were determined by using canonical correlations in 15 commercial drapery fabrics of variable composition, aerial weight and weave type. A regression equation relating drape ratio (%DR) and parameter h in the ring test was thus established. Based on the results, the ring test provides a useful tool for the routine industrial assessment of drape in finished drapery fabrics without the need for additional equipment to determine the drape.

This study examined the mechanical properties of a para-aramid filament according to the processing conditions of air-jet textured yarns (ATY). The specimens were prepared by changing the yarn speed, over feed ratio, air pressure, and heater temperature, which are important processing factors in the ATY process. The basic physical properties of the ATY, such as denier, tenacity, breaking strain, and initial modulus, were measured and their thermal shrinkage, such as dry and wet shrinkage, were measured to determine the thermal stability of the aramid ATY. In addition, the instability of para-aramid ATY were measured and assessed with the loop formation of ATY, according to the ATY process parameters. An examination of the effects of process parameters on the physical properties of aramid ATY revealed the core overfeed and air pressure to be the main factors. A high core overfeed and air pressure make the aramid ATY crimpy in the yarn core and entangle the fluffy loops on the yarn surface, resulting in an increase in the yarn linear density and breaking strain as well as a decrease in the tenacity and initial modulus. In contrast, these yarn physical properties were unaffected by the yarn speed, heater temperature, and wetting treatment. In addition, the dry and wet thermal shrinkage were unaffected by the process parameters of ATY. On the other hand, the instability decreased with increasing core overfeed and heater temperature and increased with increasing air pressure. These results showed that a high core overfeed makes the aramid ATY crimpy with an entangled yarn structure, and high air pressure helps provide small loops on the yarn surface. Finally, a high heater temperature makes the crimpy ATY structure more stable due to the strong heat set, which results in low instability.

The main aim of this research was to implement appropriate Statistical Process Control (SPC) techniques for quality characteristics on sewing floor of garment Industry. Among different SPC quality improvements tools, control charts have been selected. After analyzing and selecting different critical parameters based on company and customer requirements, the X-bar and R charts for variable and c-charts for attribute quality characteristics have been identified and implemented in the trouser sewing lines for quality improvement. The check points for selected control chart implementation have also been designed. Remedial action plans for the occurred special cause variations and process stability were developed. The project incorporated theoretical and on-job training schemes for different quality team members, to understand the SPC concept and its implementation procedure. After implementation, significant improvements in the sewing section were achieved. The four months analysis before and after implementation of the SPC tools showed that the rejection percentage was reduced from 9.141% to 6.4%. Successful implementation of the result of this project can significantly improve process performance of other similar manufacturing units with appropriate modification.

The objective of this study was to model the physical and mechanical properties of 100% cotton slub yarns commonly used in denim and other casual wear. Statistical models were developed using central composite experimental design of the response surface methodology. Yarn’s linear density, slub thickness, slub length and pause length were used as the key input variables while yarn strength, elongation, coefficient of mass variation, imperfections and hairiness were used as response/output variables. It was concluded that yarn strength and elongation increased with increase in linear density and pause length, and decreased with increase in slub thickness and slub length. Yarn mass variation and total imperfections increased with increase in slub thickness and pause length, whereas yarn imperfections and hairiness decreased with increase in slub length. It was further concluded that due to statistically significant square and interaction effects of some of the input variables, only the quadratic model instead of the linear models can adequately represent the relationship between the input and the output variables. These statistical models will be of great importance for the industrial personnel to improve their productivity and reduce sampling.

There are many kinds of medical textiles, such as woven textiles, non-woven textiles, braided textiles and knitted textiles. Non-woven medical textiles constitute more than 60% of the total medical textiles used, but are almost disposable ordinary medical textiles. While knitted fabrics forms a small part of the medical textiles, but are greatly applied in high-tech medical textiles, containing artificial blood vessels, hernia patches, cardiac support devices, knitted medical expandable metallic stents and tendon scaffolds. Knitting structures, including weft knitting structure and warp knitting structure. The knitted textiles are popular for their loose structure, greater flexibility, higher porosity, more flexible structure and better forming technology. The present article will introduce some knitting structures and materials applied in the medical textiles in accordance with non-implantable, implantable, extra-corporeal textiles and healthcare and hygiene products.

The aim of presented work was to design the cotton woven fabrics which ensure thermal resistance higher than standard cotton fabrics of basic weaves. It was done in order to combine the excellent hygienic properties of cotton fibers with thermal insulation. Three variants of two-face cotton woven fabrics of different structure were designed and manufactured. Next, they were measured in the range of their basic structural, mechanical, and comfort-related properties. The results obtained were analyzed in the aspect of properties influencing the utility comfort of user wearing clothing made of the investigated fabrics.

A novel wool absorption board was prepared by using a traditional non-woven technique with coarse wools as the main raw material mixed with heat binding fibers. By using the transfer-function method and standing wave tube method, the sound absorption properties of wool boards in a frequency range of 250-6300 Hz were studied by changing the thickness, density, and cavity depth. Results indicated that wool boards exhibited excellent sound absorption properties, which at high frequencies were better than that at low frequencies. With increasing thickness, the sound absorption coefficients of wool boards increased at low frequencies and fluctuated at high frequencies. However, the sound absorption coefficients changed insignificantly and then improved at high frequencies with increasing density. With increasing cavity depth, the sound absorption coefficients of wool boards increased significantly at low frequencies and decreased slightly at high frequencies.