Knitted Structures Research Articles

A study on porosity related aspects of cotton knitted fabric with single jersey structure for improved comfort application for garment

Knitted fabrics are the preferred structures in athletic wear in which demand for comfort is a key requirement. Heat and liquid sweat generation during athletic & exercise activities must be transported out and dissipated to the atmosphere. A key property influencing such behaviors is porosity. Two parameters that characterize it are pore size and pore volume. One of the objectives in this research was to come up with models that can predict inter yarn pore size and pore volume for simple weft knitted structures, from fabric particulars, such as courses and Wales, count, yarn size, stitch density, thickness and other geometrical details of the fabric, which characterize the structure. Such a model was developed that was based on the geometry of the unit cell of a single loop. The experimental work in this project involved using a set of 16 knitted fabrics that differ in course count and examining their pore structure and porosity related characteristics. The values of pore size and pore volume were calculated, those of pore size were measured with image analysis, and other parameters. The effects of course count and washing on stitch density, stitch length, fabric thickness and pore size are examined in details.

Identifying the active sites and multifunctional effects in nitrogen-doped carbon microtube interlayer for confining-trapping-catalyzing polysulfides

Abstract Lithium-sulfur batteries (LSBs) are recognized as promising energy storage devices for their high theoretical energy density. However, the unresolved “shuttle effect” limits the practical performance. The conventional strategies to inhibit lithium polysulfide (LiPS) shuttles including physical blocking and chemical anchoring are easy to hit the ceiling, which is mainly due to the sluggish sulfur redox kinetics. Herein, we report a self-standing nitrogen-doped carbonized cotton cloth (N-CCC) interlayer with macroscopic knitted structure and microscopic carbon microtubes for confining-trapping-catalyzing LiPS simultaneously. In situ/Operando characterization (including electrochemical impedance spectroscopy, shuttle current measurement and Raman spectroscopy) and theoretical calculation synergistically demonstrate that the multifunctional active sites of Pyrrolic N and Pyridinic N on N-CCC accelerate catalytic reaction kinetics and inhibit the “shuttle effect”. With the multifunctional N-CCC interlayer, a high capacity of 998 mAh g−1 at 2 C and high stability with a retention of 76% after 400 cycles are realized. Moreover, N-CCC based LSBs display competitive performance even at high current density (596 mAh g−1 @10 C) and high sulfur loading (795 mAh g−1 @4 mg cm−2 at 1 C). This research demonstrates a rational mechanism analysis for sulfur redox kinetics for practical high-energy/power density LSBs.

Energy absorption from composite reinforced with high performance auxetic textile structure

The objective of this study is to analyze the impact behavior on the basis of energy approach of weft knitted structures, namely a jersey composite and an auxetic composite using high performance yarns. Weft knitted fabrics were produced with the same structural and machine parameters, using 100% para-aramid and hybrid (47% para-aramid and 53% polyamide) structure. Composite fabrication was achieved through hand lay-up using epoxy resin. Negative Poisson ratio of the reinforcing auxetic fabric was transferred from the fabric to the composite developed. Results obtained by drop weight dart impact test show that the impact experiment with different impact loads confirmed the auxetic composites, regardless de material composition, have an increase in the total energy absorption compared to jersey reinforced composite, approximately 2.5 and 4 times more for para-aramid and hybrid composite, respectively. Auxetic composites developed within this work present great potential for applications in different areas, mainly where energy absorption is a key factor to be considered, such as in protection, sports among others.

Ultra-Strong Knits for Personal Protective Equipment

This work focused on the development of ultra-strong knitted fabrics for personal protective equipment used for protection against mechanical damages. Such knits have to have enhanced mechanical strength properties, which strongly depend on knitting pattern and structural characteristics. Six variants of weft knitted structures were developed and knitted from ultra-high molecular weight polyethylene and additional elastomeric component. The elastomeric component was used to increase the elasticity and toughness of knits; however, it had a high influence on mechanical properties, as well. The performed mechanical tests allowed us to identify dependence of mechanical properties, such as breaking force and elongation at break and resistance to abrasion, tearing, cutting and puncture, on architecture and structural parameters of the knits. Obtained results demonstrate that elastomeric component has high influence on mechanical properties knits and can change the principal mechanical behaviour of knits.

Moisture management and antimicrobial performance of collagen peptide enriched knitted fabrics

Knitted fabrics made of natural, synthetic and regenerated fibres are presented to the final consumers at different fabric constructions. Reason to select different fibre types, fibre blends, and knitting constructions utilisation is to optimize consumer demands of comfort, functionality, fashion and price. Continuous fibre improving studies are one driving factor behind the fabric and clothing design possibilities. Collagen peptide added fibres are one recent fibre type in the regenerated cellulosic fibre family. Collagen peptide addition to the regenerated cellulosic fibre has been reported to improve fibre properties of moisture management, thermoregulation, anti-static, ultraviolet protection, biodegradable properties which make the fibre preferable material for active wear clothes. This study involves with the influence of new fibre type addition on moisture management, antimicrobial, and air permeability properties of the plated knitted fabric structures. Within this work; one plain knitted fabric is knitted using 100% collagen peptide added regenerated cellulosic yarn and polyamide yarn grounded six different plated knitted fabrics were studied. Moisture management transport (MMT) properties, antimicrobial properties (against Escherichia coli, Staphylococcus aureus and Candida albicans) and air permeability properties of those knitted samples were evaluated comparatively. Gathered results are statistically evaluated using one-way Anova test; it was determined that there was a significant difference on MMT and air permeability properties of knitted samples at significance level of 0.05. Additionally, presence of collagen peptide added fibre exhibits considerable level of antimicrobial effect against included microorganisms. The results of the experimental work represent an initial phase towards a better understanding of the influence of different fibre blended yarn utilization on plated knitted fabrics which would be appropriate for active wear cloth manufacturing.

Simulation and characterization of the mechanical properties of knitted esophageal stents using finite element and mathematical models

Esophageal stents are used as a clinical method for the treatment of a wide variety of esophageal diseases. Knitted mesh stents have such advantages as high flexibility and ease of production. In this study, an analytical approach was applied to simulate the weft knitted esophageal stents and to investigate the mechanical behavior of these tubular structures against the axial and circumferential stresses by using finite element (FE) and mathematical models. Then, the mechanical properties of the knitted structures were evaluated while the simulated food bolus was passed through the stent channel. The results demonstrated that the FE model had a good performance in simulating the mechanical properties of the esophageal knitted stents. The error of the prediction performance of the FE models was between (10–16)% and (7–11)% for the longitudinal and circumferential directions, respectively. Simulation of the food bolus passage also demonstrated that the esophageal PGA stent wall could tolerate a 7.96 kPa force and a strain of 65% by food bolus; so, it could mimic the real state of esophagus during its application. This model could be applied to design and investigate the mechanical behavior of the knitted stents in clinical application conditions.

Development of Advanced Knitted Structures for Base Layer Clothing for Glacier Regions

The principal objectives of the present work were to improve thermo-physiological comfort and other essential functional features of the existing material. Several important thermo-physiological comfort characteristics, such as thermal resistance, air permeability and water vapour permeability in addition to the other essential functional features like bursting strength, surface resistivity, ultraviolet (UV) radiation protection and colour fastness to washing and perspiration of the knitted fabrics, which were developed for application in glacier regions were evaluated. These evaluated properties are discussed and also compared with existing Base Layer Clothing (BLC) for the selection of the best material for up-gradation of the same for soldiers deployed in glacier regions. Statistical analysis is carried out at 95 % significance level for different functional features to establish the specific trend exhibited by the knitted fabrics. While the existing BLC is made of polypropylene knitted fabric, the improved versions proposed in the present study were developed with polyester/lycra and blend of polyester/lycra and polypropylene/lycra knitted fabrics, made in terry pile (uncut) knit design. The characterization of different yarns used in preparation of these newer and existing knitted structures was carried out by analyzing their respective FTIR spectrums. The knitted structure made with blend of polyester/lycra and polypropylene/lycra was found to be superior in terms of thermal insulation, warm/cool sensation, water vapour permeability and surface resistivity. Several prototypes of BLC with both existing and modified materials were also fabricated, evaluated and the same are proposed for User Trials to bring out unambiguously the valuable merits and demerits.

DESIGN AND MANUFACTURING OF FABRIC REINFORCED ELECTROMAGNETIC SHIELDING COMPOSITE MATERIALS

There is an increasing need to develop new materials for shielding against electromagnetic pollution that result of the change in our life styles. In this study, a high performance textile based composite material that provides effective electromagnetic protection is presented to meet this demand. The base textile is a weft knitted fabric produced by using a hybrid yarn consists of polyamid and kevlar 49 yarn plied with a stainless steel wire on a winding machine. Various weft knitted structures were processed by a hot press to obtain 1.5-3.0 mm thin composite layer forms. The polyamid yarn is the matrix, the kevlar 49 yarn is the reinforcing and stainless steel wire is conductive material in the composite. The Electromagnetic shielding effectiveness (EMSE) measurement in 30-3000 MHz frequency band shown that a shielding performance of 20-50 dB can be achieved depending on the thickness and structure of the composites.

Effect of Chemical Treatment on the Mechanical Properties of Luffa Fiber Reinforced Epoxy Composite

Novel luffa fiber reinforced epoxy composites are prepared and their mechanical properties are investigated before and after chemical treatment. The unique natural knitting structure of luffa provides an excellent reinforcement to the epoxy matrix. Knowing that the fiber-matrix bond gets stronger and imparts more strength to the composite when chemical treatment is done on fibers, composites are manufactured by untreated and treated luffa fiber using epoxy as a matrix. Luffa fiber is treated using benzoyl chloride and NaOH. Tensile and flexural tests are conducted on composites to investigate the effect of chemical treatment. Test results have shown that the chemical treatment on fibers improved the tensile strength, tensile modulus, flexural strength and flexural modulus by 27.21%, 49.37%, 41.84% and 6.44% respectively. Tensile modulus of luffa fiber composite is found to be higher compared with commonly used natural fiber composites. The experimental investigation suggests that, chemically treated luffa fiber reinforced epoxy composites could be a potential lightweight material in various applications.

Iron-on carbon nanotube (CNT) thin films for biosensing E-Textile applications

Conductive carbon nanotube-thermoplastic polyurethane (CNT-TPU) composite thin films are patterned and integrated onto knitted textile substrates to form electronic textile (E-Textile) dry electrodes. Vertically aligned CNT arrays are mechanically drawn into thin CNT sheets and infiltrated with a TPU solution to form the CNT-TPU thin films. The CNT-TPU thin films are then heat laminated onto knitted textile substrates to form dry E-Textile electrodes. To understand the wearability of our CNT-TPU thin films we perform an in-depth analysis of the films’ electromechanical properties, electrical impedance, and electrocardiogram (ECG) sensing performance. The electromechanical coupling between the CNT thin films and knitted textile substrates show a strong anisotropic dependence between the CNT film alignment and textile knit structure. Further analysis into the CNT thin films reveal that larger electrode sizes with a larger number of CNT sheet layers in the film, lead to more favorable impedance behaviors and ECG sensing capabilities. As a wearable demonstration, we fabricate a textile arm sleeve integrated with CNT thin film electrodes to form an ECG sensing E-Textile system. The proposed E-Textile sleeve demonstrates the practicality of our CNT thin films and show promise for other E-Textile and wearable applications.

ВЛАСТИВОСТІ ЕЛАСТИЧНИХ ОСНОВОВ'ЯЗАНИХ БИНТІВ

The market analysis of knitted elastic bandages in Ukraine, the investigation of the parameters and properties of the most common products and their comparison as well as determination of compliance to requirements are the main purposes of this study. Methodology. Standard test methods were used to experimental study the raw material composition, type of interlooping, structure parameters and relaxation characteristics of elastic bandages. Results. As a result of the study of the elastic bandage structure, it is found that all tested bandages are produced on Crochet knitting machine using four yarn systems. chain stitch with closed loop from is a ground interlooping. The ground guide bar is partially threaded with polyester yarn depending on the manufacturer. The requested level of elasticity is provided by elastomeric threads, which are used as longitudinal in-lay yarn with incomplete threaded of the guide bar and a diff erent repeat of its shifting behind the needles. The other two yarns systems are cotton yarn in several ends, which is laid across the bandage's entire width at both sides of the elastomeric yarn, ensuring its overlap and the combination of individual chain wales into the fabric. Obtained experimental data of the parameters and elongation of elastic bandages of diff erent manufactures allowed to establish their compliance with standardized values. It ensures the products functionality during usage. It is indicated that the yarn composition specifi ed by the manufacturers correlated with experimental results. The percentage of the elastomeric thread content is not a determining characteristic of the bandage's stretchability since the elastic component of full deformation for all tested bandages exceeds 0.95. The residual component is less than 0.02. It is indicating high elastic properties and functionality. The practical signifi cance of the work is confi rmed by the possibility of evaluating a bandage of a particular manufacturer based on the resulting array of their properties data. The results of the work expand the knowledge about the infl uence of the knitted structure on the parameters and deformation properties of elastic bandage.

Effect of knitting structure and yarn composition on thermal comfort properties of bi-layer knitted fabrics

In this work, nine bi-layer knitted samples with varied knitting structures and made up of different yarn compositions were fabricated, and their thermal comfort properties were investigated. The thermal comfort properties were evaluated by breathability, water transfer properties, thermo-physiology properties and dynamic cooling properties, and their relationship with fabric knitting structure and yarn composition were investigated statistically. It was observed that bi-layer knitted fabrics with meshes at one side had better air permeability, moisture management properties, drying performance, thermo-physiological properties and dynamic cooling function, but lower wicking height than bi-layer knitted fabrics with trim and symmetrical structure (without meshes). The composition of nylon and polyester filaments with varied wettability as outer and inners layer of bi-layer knitted fabrics, respectively, improved the water one-way transport capacity significantly. In particular, bi-layer fabrics with asymmetric structure and made up of yarns with varied hydrophilicity as each layer have excellent moisture management capacity. Moreover, fabrics made up of yarns with finer fibers exhibited better thermal comfort properties.

Characterization and statistical analysis of the mechanical behavior of knitted structures used to reinforce composites: Yarn compositions and float stitches

Over the years, several studies were published on the application of knitted fabrics in textile composites. However, until moment, neither work studied the structural influence of float stitch (omitted), composition (100% cotton, 50% cotton / 50% polyester and 100% polyester) and length loop (0.98 cm, 0.84 cm and 0.71 cm) on the mechanical properties (stress, MOE and strain) of knitted used in composites. Then, article exhibit a statistical study (full factorial design) using response surface methodology (RSM) and analysis of variance (ANOVA) to investigate the mechanical behavior of Jersey knitted structures, which in turn, are one of the most used fabrics to reinforce materials textile composites. Cotton yarns are investigated because their use is considered an alternative for ecological reinforcement, as well as for hybrid reinforcement with polyester yarns in polymeric textile composites. Thus, in this investigation approached additional improvements on the tensile properties of Jersey knitted fabric structures. And finally, exhibit response on stress, MOE and strain mechanical behavior through effects of the interactions produced by variables and conditions using mainly determination coefficient (R2), value-F and significance probability (value-ρ). To provide validation of useful conclusions about mechanical behavior of knitted structures.

Experimental and CFD Analysis of Air Permeability of Warp-knitted Structures

Functionality of technical textiles and apparels in a wide spectrum of end-uses is intensely dominated by their air permeability, which in turn depends on fabric porosity and structure. This work aims to investigate air permeability of warp-knitted fabrics using experimental and numerical simulation methods. Samples of locknit, three-needle satin and four-needle satin two-bar warp-knitted fabrics at tight, medium and loose densities together with single-bar 1×1 and 2×1 warp-knitted fabrics were knitted. The effect of loop density, underlap length and fabric structure on air permeability was investigated. The 3D geometry of locknit and single-bar 1×1 and 2×1 warp-knitted fabrics was modeled using CATIA. The structural geometry of a knitted loop as the unit cell of warp-knitted fabrics was simulated based on Vassiliadis model. The geometry models then were coupled with a computational fluid dynamics (CFD) model for flow simulation. Fluid flow through the fabric structure was simulated by numerically solving incompressible creeping Newtonian flow through the pore space of generated knitted structures using Fluent. The results were then compared with experimental data. It was found that 1×1 single-bar fabrics have higher air permeability than 2×1 single-bar fabrics. It was also found that single-bar fabrics show significantly higher air permeability compared to two-bar warp-knitted fabrics. For the two-bar fabrics, the results point to higher air permeability of locknit fabrics, followed by three-needle satin and four-needle satin. The results also indicated that increase in underlap length and loop density leads to reduction of both pore size and fabric porosity and therefore decreasing air permeability. It was found that the experimental and numerical results are acceptability compatible with error of less than 16 %. It was concluded that the proposed model is potentially capable of prediction of air permeability of single-bar and two-bar warp-knitted fabrics.

Research of 3D weft-knitted fabrics designed to protect against mechanical risks and suitable for contact with skin

Eight different 3D weft-knitted fabrics, consisting of outer, binding, and inner layers, were designed and produced on E20 and E28 circular weft-knitting machines. First, in the outer layer, high molecular weight polyethylene multifilament yarns and steel wire (0.05 mm diameter), twisted with high molecular weight polyethylene multifilament yarns, were used because of their exceptional properties to resist the mechanical risks. Second, in the inner layer, hydrophobic polyester spun yarns were chosen for their suitability to be used in contact with skin. Finally, in the binding layer, synthetic elastic textured polyamide yarns were used to connect the outer and inner layers. Following the standard EN 388, diverse tests were conducted to determine the resistance of the developed 3D weft-knitted fabrics to mechanical risks, i.e., circular blade cut, puncture, abrasion, and tear. The analysis showed that the quantity of steel wire in knitted structure highly influences circular blade cut and abrasion resistance, and moderately influences tear resistance for all the investigated knitted fabrics. While a strong positive correlation between the quantity of steel wire and the puncture force was defined only for 3D fabrics knitted on an E20 circular weft-knitting machine. The findings of the research lead to the conclusion that the designed 3D weft-knitted fabric structures, where the outer layer ensures protection against mechanical risks, while the inner layer is designed for contact with skin, provide complex protection against diverse mechanical risks.

Nanocomposite-Coated Silk-Based Artificial Conduits: The Influence of Structures on Regeneration of the Peripheral Nerve.

In this study, silk filaments are coated with different concentrations (5, 7.5, and 10% w/w) of carbon nanofibers (CNFs) dispersed in poly-ε-caprolactone. The nanocomposite-coated silk filaments are subjected to knitting, braiding, and twisting. The tubular structures are covered with a silk fibroin/polyvinyl film for the nerve conduit application. Physical characterization of the developed nerve conduits demonstrates suitable mechanical properties comparable to native nerve tissue. Cell proliferation is confirmed through in vitro cell culture studies using Neuro 2a and rat primary cortical neural progenitor cells, which show that the proliferation happens along the interconnected macrochannels of the internal structure of the nerve conduit. The knitted structure presents better biological properties than the nerve conduits with other internal structures. The in vivo sciatic nerve implantation is performed in a rabbit model using the best conduit, i.e., 10% CNF-based nanocomposite-coated silk with a knitted inner structure without any biomolecules or tube filling gels. Regeneration of a 2 cm gap excised sciatic nerve is investigated by immunohistochemistry and histology of implanted nerve conduits removed after 30 days. Results suggest that the CNF-based conducting nanocomposite coating in this well-defined architecture of the conduit helps in signal transmission and neural growth during the regeneration of the transected nerve.

Tunable flow rate in textile-based materials utilising composite fibres

Fluid movement is critical in textile-based microfluidic devices with post-processing approaches commonly used to enhance the wicking rate of textile-based microfluidic devices. In this work, for the first time, we have demonstrated composite fibre approach as an effective, easy, tunable and cost-effective technique with long-lasting effect to change the fibres surface chemistry. This approach incorporates commercially sourced polyester yarns and a low-density polyethylene (LDPE) - liquid crystalline graphene oxide (LCGO) composite fibre integrated into a circular knitted structure. Our technique improves the mechanical properties of the resultant fibres and provides a facile route for tuning the wicking properties of textile-based microfluidics constructs. It was shown that the fluid moves up to six times faster in 3D knitted structures containing the composite fibre as compared to equivalent 3D knitted structures made of polyester yarns only, and the flow rate achievable was found to be proportional to the LCGO loading.

Three-dimensional simulation of warp knitted structures based on geometric unit cell of loop yarns

Warp knitted fabrics are typically three-dimensional (3D) structures, and their design is strongly dependent on the structural simulation. Most of existing simulation methods are only capable of two-dimensional (2D) modeling, which lacks perceptual realism and cannot show design defects, making it hard for manufacturers to produce the required fabrics. The few existing methods capable of 3D structural simulation are computationally demanding and therefore can only run on powerful computers, which makes it hard to utilize online platforms (e.g. clouds, mobile devices, etc.) for simulation and design communication. To fill the gap, a novel, lightweight and agile geometric representation of warp knitting loops is proposed to establish a new framework of 3D simulation of complex warp knitted structures. Further, the new representation has great simplicity, flexibility and versatility and is used to build high-level models in representing the 3D structures of warp knitted fabrics with complex topologies. Simulations of a variety of warp knitted fabrics are presented to demonstrate the capacity and generalizability of this newly proposed methodology. It has also been used in virtual design of warp knitted fabrics in wireless mobile devices for digital manufacture and provides a functional reference model based on this simplified unit cell of warp knitted loops to simulate more realistic 3D warp knitted fabrics.

Influence of structure and stretch on air permeability of compression knits

PurposeAir permeability has a valuable role in comfort parameters. It is known that air permeability of elastomeric yarns is firmly low. Despite that, usage of elastomeric inlay-yarns is the most common and the most effective way to generate compression for knitted textile. This study aims to investigate the influence of elastomeric inlay-yarn linear density, insertion density and elongation of the sample to the air permeability of compression knitted materials.Design/methodology/approachTwo different types of knitting patterns were investigated: rib 1 × 1 pattern with different elastomeric inlay-yarn linear density (four variants) and insertion density (without inlay yarn and with inlay-yarns inserted into every single, second or fourth course) and combined laid-in jacquard pattern. The air permeability test for these structures was performed without any deformation and at 10 and 20 per cent fixed transverse elongation.FindingsAccording to the investigation, insertion density of inlay-yarns has a huge impact on air permeability; however, air permeability of knitted material is not linearly proportional to the total amount of inlay-yarns. Also, it was found that air permeability increases by increasing elongation, regardless of knitting pattern and total amount of elastomeric inlay-yarn in the knitted structure. Alteration of the loop geometry at natural state and 20 per cent fixed elongation was established, and the increase of air permeability at fixed elongation may be dependent on changes of knitted material porosity.Originality/valueAccording to the obtained results, recommendations to perform air permeability measurement at least with minimal specific wear elongation are presented.

Thermal resistance of double jersey fabric knitted by different yarn raw material

The research was carried out on five double jersey knitted fabrics, knitted from cotton, Viscose®, Tencel®, Modal® and polyester ring spun yarns finesses of 20 tex. A circular double bed knitting machine gauge of E17 with the same production parameters was used for knitting all the fabrics. A change in all knitted fabric structure parameters was reflected through fabric mass per unit area, which ranged from 142 g m−2 to 165 g m−2. The minimum and maximum knitted fabric mass per unit area difference is up to 16 %. The lowest thermal resistance have polyester, while the largest have cotton knitted fabric. Thermal resistance of cotton fabric is higher for 36.7 % related to polyester knitted fabric. Considering basic knitted fabric parameters, knitting with same constructional parameters but different yarn raw materials doesn’t provide knitted fabric with same mass per unit area or thickness, i.e. thickness factor. It can be concluded that beside basic knitted fabric parameters, yarn raw material influence on thermal resistance.