Knitted Loop Research Articles

Bionic design and mechanical performance of spiderweb-inspired mesh fabrics

The mesh structure is widely applied due to its unique structure and exceptional performance, especially spider web structural materials, which have attracted widespread interest. However, the existing flexible spider web structural materials face problems such as low production efficiency and structural defects, constraining their practical application. This study proposed two types of no-knot mesh fabrics according to the topological structure of spider web and explored their mechanical properties. Both knitted loop divergent and ring spiral mesh fabrics showed excellent mechanical performance, with the ring spiral fabric demonstrating higher maximum failure forces (2217 N in tensile and 5738 N in bursting tests) and superior impact performance in terms of maximum impact force and energy absorption. Both fabrics exhibited similar creep behaviors and could withstand 70 J impact energy with an energy absorption rate around 90 %. This work may provide new strategies and inspiration for the preparation of high-performance flexible mesh materials and further helps in developing applications of spiderweb-inspired mesh fabrics in engineering fields.

Ultralight air-filled hollow yarn fabrics for efficient thermal insulation and its heat and mass transfer mechanism

Fibrous thermal insulating materials rely on retaining stationary air in their porous structure for effective insulation. However, hollow fibers lose their insulation when turned into textiles due to compression. In this study, we developed connected knitted loop sheaths to create stable hollow yarns. This direct formation allowed immediate use in fabric weaving, avoiding flattening during spinning. Comprehensive experimental analyses examined hollowness, porosity, mass density, and thermal resistance of air-filled hollow (AFH11AFH: air-filled hollow.) yarn fabrics. Results showed remarkable hollowness (41.62%) and porosity (87.509%), effectively trapping stagnant air and enhancing insulation while maintaining a lightweight structure. Computational Fluid Dynamics (CFD) revealed that minor temperature gradients and negligible airflow within the hollow structure minimized heat transfer, resulting in superior thermal insulation performance. These insights aid in designing textiles with hollow yarns for desired insulation and thermal comfort.

Comparative Analysis of Structural Effect of Single Jersey and its Derivative Fabrics on Mechanical and Comfort Properties of Knitted Fabric

The physical, mechanical, and comfort properties of knitted fabrics depend on the type, shape, and number of loops per unit area. Physical properties, namely areal density depend on the ratio of knit, tuck, and miss stitches. The higher the ratio of touch stitches, the higher would be the areal density of the knitted fabric. Double Lacoste had a higher ratio of touch stitches and single jerseys had a zero ratio of tuck stitches. Noticeably, the double Lacoste had the highest areal density, whereas the single jersey had the lowest areal density among all knitted fabrics. Therefore, areal density was inversely proportional to the loop length. Mechanical properties such as tensile strength and bursting strength also depend upon the type and length of the loop. The knit loop had the highest tensile and bursting strength, which decreased as the ratio of touch stitches increased. Air permeability increased with the increasing ratio of tuck stitches and reduced when the fabric contains 100% of the knit loops.

Image-based analysis of single jersey loop parameters

Quality Control is crucial when it comes to fine and technical knits. Digital Twins are common in product design and are necessary for heat and mass flow simulations of textile fabrics. In both cases primarily, the exact geometry of the knitted loop is necessary for following processes. Wale spacing W and course spacing C are the essential geometrical characteristics of the representative unit cell of single jersey fabrics. The loop parameters can be obtained manually by counting loops per unit length or by microscopic measurements, which both are time consuming and are not applicable in integrated digital processes. Therefore, a new method for automatic extraction of major loop geometry parameters is described. A state-of-the-art method, which analyzes the microscopic images automatically, works with Fourier-Transformation of the image brightness and is used as a benchmark. The new loop-based method extracts the geometrical data from the distances between the center points of the loops. The methods are evaluated on single jersey fabrics of three different yarns. In addition, the impact of magnification on the measurement is shown for one fabric. The new method gives same results as manual measurements and even more precise results as the benchmark method.

Studies on thermal and moisture properties of novel Eri silk knitted structures

PurposeEri is a short-stapled fibre that possesses an excellent soft feel and warmness to the wearer. Investigation of thermal comfort and moisture properties of Eri silk fabric provides the enhanced commercial scope for Eri silk-based clothing.Design/methodology/approachTo examine the impact of process factors on thermal and moisture properties, three different single knit Eri silk structures were made, each with a different loop length and yarn count. Three different linear densities of Eri silk spun yarn (15, 20 and 25 tex) were selected. Three distinct knitted constructions, including plain jersey, popcorn and cellular blister, were created, along with two different loop lengths.FindingsThe novel cellular blister structure has shown appreciable thermal comfort properties than the other two structures. Yarn fineness and loop length were significant with most of the thermal comfort properties.Research limitations/implicationsIn recent times the Eri silk production is completely domesticated, so the new demand can easily be met by the producers. This research will create a new scope for Eri silk fibres in sportswear and leisure wear.Originality/valueThis study was conducted to explore the influence of knit structure, loop length and yarn count on the thermal comfort properties of the clothing.

A waffle structured composite for RCS reduction via absorption and scattering mechanisms

A radar absorbing material named waffle structured composite (WSC) was proposed based on the periodic structure element formed by one-step double-sided knitting process with the advantage of continuous manufacture. The unique waffle structured pattern shaped by the knitted loops achieved the integration of structure and function. By realizing the collaborative mechanisms of absorption and scattering, the radar cross section (RCS) below −10 dB was achieved in the range of 6–8 GHz and 12–18 GHz towards the wale and course directions, respectively, and RCS reduction peak reaches to −30 dB. Through the S-parameter analysis and electromagnetic simulation, it can be revealed that the low-frequency RCS reduction in the wale direction was mainly dominated by the absorption mechanism, and the high-frequency RCS reduction in the course direction was led by the scattering mechanism. Furthermore, to further explore the scattering and absorption mechanism, phase difference, dielectric loss and magnetic loss were investigated in details. It was verified that the absorption of WSC is mainly originated from dielectric loss with slight magnetic loss, and Debye relaxation plays the important role in dielectric loss. The WSC proposed in this paper is equipped with characteristics of good RCS reduction and continuous large-scale manufacture, which is promising in practical engineering application of radar stealth.

Studies on low stress mechanical properties of Eri silk knitted fabric

PurposeEri silk fiber has superior thermal insulation behavior, better softness than cotton fiber. However, Eri silk’s use in the commercial arena has not yet taken off. The purpose of the study is to explore the comfort properties of the fabric, which enhances the commercial acceptance of Eri silk clothing.Design/methodology/approachIn this investigation, three different single knit Eri silk structures were produced with different loop lengths and yarn counts to analyze the influence of process variables on low-stress mechanical properties. To execute the research work, Eri silk spun yarn of three different linear densities (15 tex, 20 tex, 25 tex) were chosen. Three different knitted structures were produced, such as single jersey, popcorn and cellular blister, and two different loop lengths were also selected.FindingsThe cellular blister structure has shown appreciable low-stress properties next highest position was attained by the popcorn structure. Yarn fineness and loop length were significant with most of the low-stress properties.Research limitations/implicationsThe findings of this research will contribute to a greater awareness of Eri silk knitted fabric and its process parameters in relation to its commercial utility.Originality/valueThis study was conducted to explore the influence of knit structure, loop length and yarn count on the low-stress properties of Eri silk-based thermal clothing.

Clinical application of titanium nickelide knitwear based on the quantitative assessment of rheological similarity to soft biological tissues

Samples of metal knitted mesh made of the 40 μm, 60 μm and 90 μm diameter TiNi wires are studied by uniaxial tension to rupture and uniaxial cyclic tension. It was found that the metal knitted TiNi mesh behaves like a hyperelastic material under uniaxial tension in contrast to the superelastic wire from which it is made. Using the rheological models of Gent, Neo-Hookean, Mooney–Rivlin and Bergstrom-Boyce, the calculation of the cyclic tension of the knitted mesh was carried out. The similarity of the mechanical behavior of knitted mesh and biological tissues is shown. Criteria for quantitative assessment of the biomechanical compatibility of a knitted mesh implant for plasty of hyperelastic biological tissues are proposed.The main criteria for the rheological similarity of knitted mesh and soft tissues are the ultimate tensile strength, elastic modulus and the range of low-modulus and high-modulus elastic strain under loading and unloading; the residual strain value during cyclic tension.It has been found that knitted mesh made of superelastic TiNi wire exhibits a rubber-like behavior characteristic of hyperelastic materials under soft zero cyclic tension. At the same time, in the most loaded contact areas of the superelastic TiNi wire, the martensitic transition did not affect the tension cycles is due to friction, which counteracts the recovery of elastic strain during unloading. It has been established that the Bergstrom–Boyce model is closest in terms of the stress–strain diagram to the knitted mesh and biological tissues. Knitted mesh implants made of nickeide titanium wire were used for plasty of soft tissues and musculoskeletal complexes. The developed method for quantitative assessment diagram of the hyperelastic knittes mesh. The residual strain during the first two tension of the biocompatibility of the implant and biological tissue make it possible to choosу knitteв mesh with a certain wire diametre, focusing on the forces developed by the knitted mesh and the variable elasticity modulus. The knitted mesh was applied without additional fixation, using elastic self-fixation of knitted mesh loops into soft tissues.

Comparative Moisture Management Studies of Single Jersey Knitted Soya Bean Fabrics

ABSTRACT In recent times, due to increased environmental awareness, the usage of sustainable, eco-friendly textile products has gained momentum. In this respect, the Soya bean protein fiber (SPF) based fabric structure is considered a potential product. Single Jersey and Single Pique knitted structures were developed by changing the yarn count and loop length using Soya bean fiber for next-to-skin applications. Multidimensional moisture management properties were measured using MTT tester to understand the influence of process parameters (fabric structure yarn count and loop length). Further to this, physical properties and wetness comfort properties of the SPF knitted fabrics were also studied. It was found that the OMMC properties of most of the SPF knitted samples were highly rated. The influence of knit structure, yarn count, and loop length on moisture properties was studied through ANOVA. Similarly, the correlation between the physical parameters and moisture properties was also investigated. The Single Pique structure with finer yarn count and higher loop length configuration showed higher moisture management properties. The fabric thickness was correlated with all the moisture management properties. However, the fabric tightness factor was correlated with all the moisture management properties except MWR and AOTI.

Development of 3D Models of Knits from Multi-Filament Ultra-Strong Yarns for Theoretical Modelling of Air Permeability

The work is devoted to the study of the geometric parameters of a knitted loop. It has been found that the optimal model is a loop model detailed at the yarn level, which considers the change in the cross-sectional shape and sets the properties of the porous material in accordance with the internal porosity of the yarn. A mathematical description of the coordinates of the characteristic points of the loop and an algorithm for calculating the coordinates of the control vertices of the second order spline, which determine the configuration of the yarn axes in the loop, are presented in this work. To create 3D models, Autodesk AutoCAD software and Structura 3D software, developed in the AutoLisp programming language, were used. The simulation of the air flow process was carried out in the Autodesk CFD Simulation environment. For the experimental investigation, plane knits from 44 tex × 3 linear density ultra-high molecular weight polyethylene yarns were produced, and their air permeability was tested according to Standard DSTU ISO 9237:2003. The results obtained during the laboratory experiment and simulation differed by less than 5%.

Flexible Theoretical Calculation of Loop Length and Area Density of Weft-Knitted Structures: Part I.

This work presents a simple and flexible method for theoretical calculation of the main structural parameter of weft-knitted fabrics’—the loop length and one of the main characteristics of textile fabrics—area density, which combines physical and economical aspects. It helps to predict many physical properties and the mechanical behaviour, which is especially important for protective textiles, and allows predicting potential yarn consumption for knitting of one square meter of the fabric. The main idea of the proposed method, based on Čiukas geometrical model, is to calculate different parts of the knitted loop separately, which gives a great flexibility of such modelling. The proposed theoretical formulas can be used for various weft-knitted structures, give very low errors to empirical calculations, and are easy to use. It is a big advantage because known geometric models only allow a loop length of some particular pattern to be calculated, usually of single jersey or rib 1 × 1.

ОСОБЛИВОСТІ 3D МОДЕЛЮВАННЯ СТРУКТУРИ ТРИКОТАЖУ У МАКСИМАЛЬНО РОЗТЯГНУТОМУ СТАНІ

The study aims at the development mathematical basics for software for automated construction of three-dimensional geometric models of knitwear in the most stretched state due to uniaxial stretching along the wale or course direction. Methodology. The research methods of theoretical analysis, spline theory, methods of three-dimensional geometric modeling and parameterization, computer graphics tools, programming tools were used. Findings. During the research, it was assumed that in the maximally stretched state, the tangent to the centerline of the loop at the interlacing point is located at an angle of 45º to the vertical line oriented along the wale direction. Mathematical expressions are proposed for determining the co-ordinates of the characteristic points of the loop in three-dimensional space. An algorithm and its software implementation have been developed as a separate module of the Structure 3D program, designed to create models of knitwear in a stretched state. To verify the algorithm, samples of weft knitted fabrics were made with a 8th gauge flat-bed knitting machine of para-aramid and high-molecular polyethylene threads of linear density 58.8x2 tex and 44x3 tex, respectively. The parameters of the loop structure of the samples in dry-relaxed state and under maximum uniaxial stretching along the wale and the course directions. Tensile testing of specimens was performed on the machine KaoTieh KT-7010AZ. The maximum stress state of the samples was recorded using a Micro Capture Pro microscope to further determine the changes of the loop structure parameters under the action of tensile deformation. The obtained values of the the loop structure parameters of the samples were used as input data for the construction of three-dimensional models. The deviation of the value of the length of the spline representing the centerline of the thread in the loop model from the length of the thread in the loop obtained during the analysis of the samples does not exceed 5%. Scientific novelty. An algorithm for the automated construction of 3D models of knitted structures, undergoing maximum deformations coursed by uniaxial tension along the wales or course directions, has been developed. Practical value. A separate module of the 3D Structure program has been created for the automated construction of a knitted loop undergoing maximal stretching under has been developed.

Geometry of compact plain knitted structures

Purpose The purpose of this paper is to develop mathematical relationships to calculate the loop length to knit compact plain knitted fabrics and to validate the model using the fabric parameters of commercial fabrics. Design/methodology/approach Ellipse defines the shape of the head of a knitted loop and straight lines define the arms of a knitted loop. The mathematical relationships developed relate the yarn count to the loop length of compact knitted fabrics. The experimental data and the data from previous similar research validate the accuracy of the mathematical model. Findings The model can calculate loop lengths to knit compact plain knitted fabrics in terms of thickness of the yarn and the coefficient defined to express the ratio of minor axis to major axis of the ellipse that defines the shape of the head of the loop. The mathematical model can deliver several loop lengths to produce compact plain knitted fabrics for different values of this coefficient. For commercial fabrics the error of the model was 0.53%. Originality/value The present model defines the head of the loop as an ellipse. The uniqueness of the present model is that several ellipses can exist for any given yarn thickness for a range of values assigned to the minor axis of the ellipse. The accuracy of the model against experimental data ascertains that the model is closer to the reality for commercial fabrics and proves the uniqueness of the model. Further, this model is an ideal and a simple model to introduce knitted loop configurations in teaching knitted fabric geometry.

Determination of corrugated core sandwich panels elastic constant based on three different experimental methods and effect of structural integrity on flexural properties

This study deals with the investigation of flexural stiffness and transverse shear rigidity in the direction of corrugation of the integrated and non-integrated corrugated core sandwich panels with the rectangular core. The non-integrated sandwich panels were reinforced with conventional 2-D fabrics in which resin provides the bond between core and skins. The integrated sandwich panels were reinforced with 3-D weft knitted fabrics in which bonding of the core wall to skins was carried out by combined efforts of knitted loop and resin. Using weft knitting technical capabilities, samples of the integrated and non-integrated structures were manufactured with the uppermost degree of resemblance in terms of geometry and mass. Flexural stiffness and transverse shear rigidity of the structures based on the known and unknown facing modulus of ASTM D7250 standard and Nordstrand–Carlsson methods were calculated. The estimated elastic constants based on unknown facing modulus and the Nordstrand–Carlsson methods were found to be highly compatible. However, the unknown facing modulus method is prone to disclose the statistical significant differences between the elastic constants of the structures with fewer tests. Regarding the unknown facing modulus method, it was found that the flexural stiffness and transverse shear rigidity of the non-integrated structure in the direction of corrugation were higher than those of the integrated structure. Results also indicated that the load-carrying capacity in the direction of corrugation was significantly higher in case of the non-integrated rectangular core structure compared with that of the integrated structure.

Impact of the Presence of the Loop at Different Location on Fabric Width and Areal Density of a Weft Knitted Structure

Knitted structures are progressively built up from row after row of knitted intermeshed loops known as knitted loops. Apart from this knitted loops, tuck or miss loops may be produced by varying the timing of the intermeshing sequence of the old loop and new loops. These loops are main and prominent part of the design of the weft knitted structures. Structures having float or miss loop exhibits many noticeable characteristics. The fabrics renders better surface appearance or color pattern. Dimensional stability is significantly improved. Fabric width is reduced and areal density is also increased considerably due to the presence of float loops in the structure. Therefore, the dimensional and physical features of different knitted structures having knit-miss loops may be studied carefully to find the influence of float stitch or loop on fabric width and areal density. In this project work, such an attempt has been made to specify some specific single jersey structures, which will be ensured as an effective tool for product research and development as well as for meeting up customer’s quality requirements of high class products.

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.

In-situ strain- and temperature-control X-ray micro-diffraction analysis of nickel–titanium knitted architectures

The reversible phase transformation between B2 austenite phase and B19’ martensite phase is the governing mechanism behind the exciting active and passive capabilities of Nickel–Titanium (NiTi) knitted architectures. NiTi knitted architectures are manufactured from a monofilament fiber of originally-straight NiTi wire that is bent into an interlocking network of adjacent loops. Depending on the thermo-mechanical load path, NiTi knitted architectures can provide excellent isothermal energy-absorption using the superelastic effect (SE) or function as large-deformation actuators that respond to thermal inputs using the shape memory effect (SME). The magnitude of NiTi knitted architecture characteristic performance metrics is dependent on the ability of the knitted architecture to undergo the reversible phase transformation, which is a function of the material stresses, strains, and temperature. This research quantifies the NiTi knitted architecture austenite phase fraction of the highly stressed filament surface in X-ray diffraction experiments as a function of the measurement position on the knitted loop and applied thermo-mechanical loading conditions. A Bruker D8 Discover 2D micro-diffractometer was equipped with a custom tensile straining- and temperature-control device. The Direct Comparison Method was employed to derive the austenite phase fraction from the X-ray diffraction patterns. This research establishes novel in-situ strain- and temperature-control X-ray micro-diffraction experiments and provides understanding of the governing deformation modes in NiTi knitted architectures.

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.

Resistive network model of the weft-knitted strain sensor with the plating stitch-Part 1: Resistive network model under static relaxation

The resistive network model of the weft-knitted strain sensor with the plating stitch under static relaxation is studied based on the knitted loop structure and circuit principle. The prepared sensors are divided into the sensing area and the non-sensing area. The former consists of the conductive face yarn and the insulated elastic ground yarn, while the latter includes the normal face yarn and the same ground yarn. The loop of conductive face yarn not only produces length-related resistance but also causes the jamming contact resistances along the width and length direction. Besides, the elastic ground yarn has a potential impact on the contact situation of the conductive face yarn at the interlocking point, determining whether the interlocking contact resistance exists. Therefore, two resistive network models have been established accordingly. In addition to the length-related resistance, the first model focused on both the jamming and interlocking contact resistances, while the second one only dealt with the jamming contact resistance. In the case of applying voltage along the two ends of the course, the theoretical calculations of the corresponding network models were performed using a series of equivalent transformations. Finally, the correctness and usability of the two models were verified through experiments and model calculations. It was found that both models can predict that the equivalent resistance increases with the conductive wale number and decreases with the conductive course number. It was implied that the first model’s calculating resistances are closer to the experimental data and lower than those of the second model. The difference in the calculating resistances of the two models would become smaller as the course number increases. Thus, the investigation indicates that the jamming contact resistance has a more considerable influence on the resistive network than the interlocking contact resistance.

Auxetic deformation of the weft-knitted Miura-ori fold

Negative Poisson’s ratio (NPR) material with unique geometry is rare in nature and has an auxetic response under strain in a specific direction. With this unique property, this type of material is significantly promising in many specific application fields. The curling structure commonly exists in knitted products due to the unbalanced force inside a knit loop. Thus, knitted fabric is an ideal candidate to mimic natural NPR materials, since it possesses such an inherent curly configuration and the flexibility to design and process. In this work, a weft-knitted Miura-ori fold (WMF) fabric was produced that creates a self-folding three-dimensional structure with NPR performance. Also, a finite element analysis model was developed to simulate the structural auxetic response to understand the deformation mechanism of hierarchical thread-based auxetic fabrics. The simulated strain–force curves of four WMF fabrics quantitatively agree with our experimental results. The auxetic morphologies, Poisson’s ratio and damping capacity were discussed, revealing the deformation mechanism of the WMF fabrics. This study thus provides a fundamental framework for mechanical-stimulating textiles. The developed NPR knitted fabrics have a high potential to be employed in areas of tissue engineering, such as artificial blood vessels and artificial folding mucosa.