Yarn Strain Research Articles

Understanding the sensing performance alteration mechanism of a Yarn-based strain sensor after encapsulation and an effective encapsulation structural designs

Microcrack-based yarn strain sensors with non-uniform and rough structures offer high sensitivity and flexibility, making them promising for wearable electronics. However, their low mechanical endurance limits their usability. Encapsulating is a common method used to protect the conductive network and enhance environmental stability, but its impact on sensing performance is poorly understood. This work investigates the effects of thickness and tensile modulus of conformal encapsulation layer on the performance of double-threaded conductive yarns (CNT/DTY), especially focusing on the thickness variation coefficient of the conformal encapsulation layer. The results showed that the encapsulation layer affects the mechanical and electrical properties of yarn sensors. The permeation of Ecoflex transforms the conductive layer into Ecoflex/CNT composites, increasing the sensor’s initial electrical resistance. The encapsulation layer changes the rate of strain transfer from the substrate to the conductive layer, slowing strain localization. Increasing the thickness variation coefficient of the encapsulation layer improves the maximum strain range, linearity and repeatability, while decreasing the sensitivity and electromechanical hysteresis. An encapsulation layer with higher tensile modulus significantly reduces sensitivity, linearity and increases electromechanical hysteresis. Optimizing the encapsulation layer not only provides the sensors with robust mechanical support and protection but also enhance its sensing properties, including excellent water resistance. Moreover, encapsulated yarn sensors showed good potential in joint motion monitoring in water, gait analysis, and gesture recognition for wearable applications.

Strain sensor based on polyurethane/carbon nanotube elastic conductive spiral yarn with high strain range and sensitivity

AbstractWearable flexible electronic strain sensor devices have gained significant attention in recent years due to their potential for detecting human motion in various scenarios. However, the development of strain sensors with high sensitivity across a wide range of strains remains a major challenge. We present herein a novel strain sensor based on a graded structure thermoplastic polyurethane (TPU)/carbon nanotube (CNT) composite yarn with significantly enhanced mechanical performance imparted by the designed structure. The twisted CNTs/TPU spiral yarn demonstrated a fracture elongation of up to 1066% while maintaining charge conductivity under high‐strain conditions. Moreover, it exhibited sensitive changes in resistance versus tensile strain, excellent repeatability, and stability. As a strain sensor, it achieved a gauge factor (GF) of 67.2 within a strain range below 50%, reaching 51.7 in a strain range exceeding 150%. With a fast response time of 0.12 s, it enabled accurate identification of movements in different body parts. These findings highlight the broad application potential of the designed spiral yarn strain sensor in areas such as human motion monitoring and human–computer interaction.Highlights Prepares a flexible strain sensor with graded‐structure (CNT‐fiber‐yarn). Shows high sensitivity and a wide strain response range Reveals the conductive model of strain sensor.

Highly Stretchable and Fluorescent Visualizable Thermoplastic Polyurethane/Tetraphenylethylene Plied Yarn Strain Sensor with Heterogeneous and Cracked Structure for Human Health Monitoring.

Smart wearable technology has been more and more widely used in monitoring and prewarning of human health and safety, while flexible yarn-based strain sensors have attracted extensive research interest due to their ability to withstand greater external strain and their significant application potential in real-time monitoring of human motion and health signals. Although several strain sensors based on yarn structures have been reported, it remains challenging to strike a balance between high sensitivity and wide strain ranges. At the same time, visual signal sensing is expected to be used in strain sensors thanks to its intuitiveness. In this work, thermoplastic polyurethane (TPU) and tetraphenylethylene (TPE) were wet-spun to fabricate flexible fluorescent fibers used as the substrate of the sensor, followed by the drop addition of polydimethylsiloxane (PDMS) beads and curing to produce a heterogeneous structure, which were further twisted into a plied yarn. Finally, a visualizable flexible yarn strain sensor based on solidified liquid beads and crack structure was obtained by loading polydopamine (PDA) and polypyrrole (PPy) in situ. The sensor exhibited high sensitivity (the GF value was 58.9 at the strain range of 143-184%), a wide working strain range (0-184%), a low monitoring limit (<0.1%), a fast response (58.82 ms), reliable responses at different frequencies, and excellent cycle durability (over 2000 cycles). At the same time, the yarn strain sensor also had excellent photothermal characteristics and a fluorescence crack visualization effect. These attractive advantages enabled yarn strain sensors to accurately monitor various human activities, showing great application potential in health monitoring, personalized medical diagnosis, and other aspects.

Stretchable piezoresistive textile yarn strain transducer for low deformation detection

Stretchable piezoresistive textile yarn strain transducer for low deformation detection

Mass production of carbon nanotube fibers and hybrid yarns for high-performance helical auxetic yarn strain sensors

With the spectacular physical properties of electrical conductivity, mechanical strength and thermal conductivity, carbon nanotube (CNT) fibers are favored in many fields such as energy storage devices, sensing, electromagnetic shielding and structural reinforcement, especially in flexible sensing devices. However, the lower tensile properties of CNT fibers limit their further application in stretchable strain sensors, especially when monitoring large deformation variables. Here, large-scale continuous production of CNT fibers has achieved through floating catalytic chemical vapor deposition (FCCVD) technology. In the meantime, the CNT fibers were hybrid with Kevlar fibers to obtain hybrid CNT yarns with the strength of 168.4 MPa and the electrical conductivity of 7.78 × 104 S m−1. The strength of the hybrid CNT yarns produced by this method is higher than that of 40 count cotton yarns, which is perfectly suited for the fabrication of textile devices. Through knitting with three-dimensional elastic fabrics, the textile-based sensors exhibit promising sensing ability, washability, weather tolerance and sweat resistance, owing to the excellent physical and chemical properties of the hybrid CNT yarns. Moreover, stretchable strain sensors exhibit fast response and cycle stability, which provides unique opportunities in designing smart textiles with fast response and environmental durability.

Large-scale fabrication of conductive yarn with synergistic conductive coating for high-efficient strain sensing and photothermal conversion

With the rapid development of wearable electronics, conductive yarn strain sensors have attracted much attention due to their excellent flexibility, conformability, and knittability. However, it is still a great challenge to prepare flexible conductive yarn strain sensors with high sensitivity and wide working range simultaneously. Here, a large-scale fabrication of conductive spandex yarn (SY) with synergistic conductive coating composed of lower stable carbon nanotubes (CNTs)-polyaniline (PANi) hybrid layer and upper ultrasensitive cracked PANi layer was successfully achieved via the simple solvent swelling, non-solvent-induced phase separation (NIPS), and in-situ reduction processes. Thanks to the synergistic effect of the double layered conductive coating and its tunable microstructure based on the PANi content, the assembled conductive SY strain sensor exhibits wide working range (0–321 %), high sensitivity (GF is 43, 950, and 2439 for strain range of 0–100 %, 170–270 %, and 280–321 %, respectively), ultralow detection limit (0.5 %), fast response/recovery time (140 ms/160 ms), and excellent fatigue resistance (4000 cycles). As a proof of concept, the strain sensor can be used for wearable applications to achieve the effective detection of full-range human motion and physiologic signals. Besides, it also displays great potential in human-computer interaction for reliable operation of remote-control manipulator and flexible electronic textile for spatial pressure distribution identification. Finally, owing to the excellent optical absorbing ability of PANi and CNTs, the conductive SY exhibits high-efficient and stable photothermal conversion capacity even under the stretching and bending states, endowing it with good wearing comfort. This study provides a convenient but effective strategy for the fabrication of high-performance wearable strain sensor with excellent thermal management capacity.

Braiding procedure and axial compressive behaviors of three-dimensional integrated braided composite three-way circular tubes

The three-dimensional braided composite multi-way tube is one kind of high strength joint with a unique seamless braided microstructure. Here we report a new method to prepare the three-way integrated braided preform. Quasi-static axial compressive damages and strengths of the three-way braided composite tubes were tested for revealing the effects of braided structure on the compressive behaviors. We have paid more attention to braiding yarn strain distribution at the connection region and have found the braided yarns are in a uniform braided structure in this region. Compressive strength and initial stiffness can be improved by reducing branch length or increasing braiding layers. The surface strain on the branch tube shows obvious periodicity related to the braided structure while that on the connection region is affected by the bulging movement due to the compression of the three branch tubes. The main damage mechanisms are yarn breakage, yarn debonding, and kink band. This uniform braided structure paves the way to form the seamless braided structure among three branch tubes with high compressive strength.

Large-scalable fabrication of liquid metal-based double helix core-spun yarns for capacitive sensing, energy harvesting, and thermal management

Yarn-based flexible sensors are the crucial components of intelligent wearable electronics. However, the mass fabrication of high-performance yarn sensors with multifunctional and wear-comfortable remains a challenge. Herein, liquid metal-based double helix core-spun yarns (DHCYs) can be massively produced via a facile friction core-spinning for human motion monitoring, energy harvesting and thermal management. Due to the stable double helix and hierarchical structure, the yarn and its fabric exhibit combined superiority of flexibility, breathability and washability. The yarn strain sensor demonstrates a good workable range (100%), high sensitivity, ultra-low hysteresis and high durability (6000 cycles). For energy harvesting, the plain-woven fabric exhibits the excellent triboelectric performance of 50 V open-circuit voltage (VOC), 500 nA short-circuit current (ISC), and 100 nC short-circuit transferred charge (QSC). Moreover, owing to the high electrical conductivity of liquid metal, the DHCYs present a fast temperature response and achieve a stabilized temperature from 16 ℃ to 45 ℃ within 80 s under 6 V. As proof of concept, we demonstrate the electrothermochromism and heat preservation of DHCYs, indicating its great potential in smart textiles, wearable devices and human-machine interfaces.

Uniaxial tensile strain correction of multi-axial warp-knitted fabric

This paper analyzes the error between the theoretical calculated and actual values of single inserting yarn strain of multi-axial warp-knitted fabric under the uniaxial stretching process, and the “open M-shaped curved surface” of error was obtained theoretically. The analysis results show that the error increases with the increase of fabric elongation. The error is smaller in the small deformation range (fabric maximum elongation is 5%) and larger in the large deformation range. In addition, the error is also related to the angle between the single inserting yarn axis and the uniaxial tensile direction. The error varies periodically with the angle ([Formula: see text]), reaching its maximum when it is close to [Formula: see text]. In order to realize the correction of the existing theoretical calculated formula of single inserting yarn strain, the error formula was fitted by combining the laws of errors. The correction of the single inserting yarn strain was successfully achieved by the fitted error formula. The correction equation can correct the inserting yarn at any angle in the fabric strain range of 0–50%. The correction equation has a larger range of use and more accurate results than the theoretical calculated formula for inserting yarn. Finally, the validation was carried out with bias inserting yarn at [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] angles and the results were very good. Therefore, the corrected equation can replace the actual value of bias inserting yarn strain.

Energy absorption analysis of STF/Kevlar composite fabric based on 3D morphology of impact basin under low-speed impact

A new method based on the impact basin morphology is proposed to quantitatively evaluate the energy absorption characteristics and the impact deformation state of the fabric . Low-speed nonpenetrating impact test was conducted on Kevlar 49 plain fabric and the oily clay was used to completely record the ultimate deformation of fabric. The 3D depth morphology of the impact basin was measured via fringe projection profilometry (FPP). The impact profile curve was extracted to analyze the impact deformation attenuation trends and output the yarn strain to calculate the strain energy. Shear thickening fluid (STF) was used to form STF/Kevlar composite fabric to enhance its energy absorption capacity and improve the resistance to deformation. The results show that neat fabric and STF/Kevlar composite have different impact deformation attenuation trends, the STF/Kevlar composite demonstrates better energy absorption and smaller impact deformation at same impact energy as that of the neat fabric.

Large-scale production of weavable, dyeable and durable spandex/CNT/cotton core-sheath yarn for wearable strain sensors

Yarn-based wearable sensors have attracted attention, but it is difficult to fabricate yarn strain sensors with large-scale production, weavability, dyeability and durability toward real applications as wearable electronics and smart textiles. Herein, we report a facile core spun strategy to fabricated spandex/CNT cotton yarns (SCCY) on an industrial spinning machine. For the first time, wearable sensor could be dyed through a simple dip dyeing process with different colors (red, yellow, blue and black). The unique core-sheath structure endowed the yarn with good sensitivity (gauge factor of 21.85 at 300% strain), broad sensing range (0%-300% strain), excellent durability (against dip dyeing, washing, acid and alkali) and abrasion resistance (resistance change 5% after rubber 100 cycles). The sensor yarn was also successfully woven/knitted into textiles and it could be sewn into a fabric. The weavable and dyeable core-spun yarn in the present work provide a feasible way for industrial-scale manufacture wearable sensors.

Recent advances on the fabrication methods of nanocomposite yarn-based strain sensor

Abstract Yarn-based strain sensor is an emerging candidate for the fabrication of wearable electronic devices. The intrinsic properties of yarn, such as excellent lightweight, flexibility, stitchability, and especially its highly stretchable performance, stand out the yarn-based strain sensor from conventional rigid sensors in detection of human body motions. Recent advances in conductive materials and fabrication methods of yarn-based strain sensors are well reviewed and discussed in this work. Coating techniques including dip-coating, layer by layer assemble, and chemical deposition for deposition of conductive layer on elastic filament were first introduced, and fabrication technology to incorporate conductive components into elastic matrix via melt extrusion or wet spinning was reviewed afterwards. Especially, the recent advances of core–sheath/wrapping yarn strain sensor as-fabricated by traditional spinning technique were well summarized. Finally, promising perspectives and challenges together with key points in the development of yarn strain sensors were presented for future endeavor.

Experimental Investigation of Transverse Loading Behavior of Ultra-High Molecular Weight Polyethylene Yarns

Ultra-high molecular weight polyethylene (UHMWPE) Dyneema® SK-76 fibers are widely used in personnel protection systems. Transverse ballistic impact onto these fibers results in complex multiaxial deformation modes such as axial tension, axial compression, transverse compression, and transverse shear. Previous experimental studies on single fibers have shown a degradation of tensile failure strain due to the presence of such multi-axial deformation modes. In this work, we study the presence and effects of such multi-axial stress-states on Dyneema® SK-76 yarns via transverse loading experiments. Quasi-static transverse loading experiments are conducted on Dyneema® SK-76 single yarn at different starting angles (5°, 10°, 15°, and 25°) and via four different indenter geometries: round (radius of curvature (ROC) = 3.8 mm), 200-micron, 20-micron, and razor blade (ROC ~2 micron). Additionally, transverse loading experiments were also conducted for a 0.30 cal. fragment simulating projectile (FSP) and compared to other indenters. Experimental results show that for the round, 200-micron indenter, and FSP geometry the yarn fails in tension with no degradation in axial failure strain compared to the uniaxial tensile failure strain of SK-76 yarn (2.58%). Whereas for the 20-micron indenter and razor blade, fibers fail progressively in transverse shear followed by progressive strength degradation of the yarn. Strength degradation of yarn occurs at relatively low strains of 0.6–0.7% with eventual failure of the yarn at approximately ~1.8% and ~1.5% strain for the 20-micron indenter and razor blade, respectively. Breaking angles (range of 10°–30°) are observed to have little effect on the failure strain for all indenter geometries.

Exploring the relationship between applied fabric strain and resultant local yarn strain within the elastic fabric based on finite element method

As kinds of unique textiles with high extensibility and elasticity, elastic fabrics are widely used for sportswear, medical textiles and electronic textiles. The tensile behavior of fabric is very important for post-processing and usage of fabric. However, there are very few studies on the resultant yarn strain subjected to the applied fabric extension, which is crucial for understanding the tensile behavior of elastic fabric and expanding its potential applications. In order to address the tensile behavior of elastic fabric, a mechanical model of fabric was built for the analysis of local yarn strain within the fabric through finite element method (FEM). The FEM models with full consideration of the tensile property of elastic yarns were built to predict the relationship between the applied fabric strain and the resultant yarn strain. An experimental study was conducted to characterize the yarn deformation behavior during the fabric stretching and compare with the FEM prediction. The FEM simulations show a good agreement with the experimental results. Based on the FEM models, the effects of fabric structural parameters on such a relationship were investigated for understanding the deformation mechanism and thus optimizing the tensile properties of fabrics. A yarn strain of 27.5% could be achieved under 60% fabric strain by adopting an optimized warp yarn spacing of 0.8 mm. The results not only shed light on the origin of high extensibility and elasticity of fabrics but are of great value to the design and development of elastic materials for various applications such as textile-based electronics.

3D network structure and sensing performance of woven fabric as promising flexible strain sensor

A flexible strain sensor was developed through weaving conductive yarns to 3D woven fabric. The relationship between the sensing performance of the woven fabric and its 3D network structure containing yarn shrinkage and arrangement density, as well as fabric interweaving, was investigated according to Pierce’s fabric geometry model and the assumption of elastic strain of yarn. Based on such models and assumption, the theoretical results were verified by the experimental data from uniaxial stretching, and the trends of both results were consistent. The sensitivity of woven fabric on its elastic strain is relatively small (GF < 2) and nonlinearity. With the deformation of fabric geometry structure (Stage I) caused by stretching on warp direction, the shrinkage of weft yarn (cw) and interweaving points (nw) decreased or the arrangement density of warp yarn (Nj) increased, resulting in improved sensitivity on warp direction. At yarn deformation stage (Stage II), the increase in interweaving points (nw) or the decrease in arrangement density of warp yarn (Nj) could improve the sensitivity on warp direction. All the results provide a theory basis for the design and development of flexible strain sensor with promising application as wearable electronic device.

Preparation of a Highly Sensitive and Stretchable Strain Sensor of MXene/Silver Nanocomposite-Based Yarn and Wearable Applications.

As a wearable device, highly sensitive and stretchable strain sensors should be integrated to monitor various daily actions, which include large- and small-scale strains, such as jumping, running, heartbeat, and pulse. At present, the method of preparing strain sensors is mainly to impregnate or load materials like graphene, carbon nanotube, and their union products on elastic substrates to obtain highly sensitive characteristics. Both well-known carbon-based and other single-dimensional nanomaterials do not have high flexibility and conductivity, which limits the improvement of sensitivity. However, a novel material MXene Ti3C2Tx has a two-dimensional (2D) sheet structure, which allows for higher electron and ion transmission rates. In addition, it is easier to be combined with other nanomaterials as a nanosubstrate, greatly improving malleability. Hence, we creatively prepared zero-dimensional (0D)-one-dimensional (1D)-2D multi-dimensional nanomaterials, which designed 0D silver nanoparticles (AgNPs) loaded on 2D MXene nanosheets and compounded with 1D silver nanowires (AgNWs). The method improves the elasticity and conductivity of traditional single-dimensional materials, wherein AgNPs built a bridge between AgNWs and MXene, which ensures continuity and a high gauge factor even at a large strain (200%) of yarn. The composite yarn strain sensor has a remarkably high strain and sensitivity, effectively monitoring the large and small deformations of various parts of the human body, whose fabric can be an electrothermal device. It has vital inspiration for the development of intelligent textiles, which would be used in medical devices, artificial skin, and other wearable fields.

Theoretical study of the effects on yarn strength in a modified ring spinning system

A modified ring spinning system using a dynamic twist-resistant device has been employed to produce yarn. The modified device blocks twist to propagate to the spinning triangle, which changes the distribution of twist in the spinning area and increases the height of the spinning triangle. In this paper, two kinds of yarn counts (30 and 40 Ne) are spun in the conventional and modified ring spinning with twist multipliers of 3.2, 3.6, and 4.0. The results show that the yarn spun by the modified ring spinning system possesses a higher strength compared with the conventional yarn except in the higher twist multiplier. The increase in yarn strength was theoretically analyzed according to the model of yarn strength. The yarn strength was calculated by considering the original fiber strain in the yarn and the fiber strain due to yarn strain. In the model, the fiber migration was considered and the fiber entanglement caused by fiber migration was ignored to simplify the calculation. Four potentially important parameters of the spinning triangle, the height of the spinning triangle, the migration coefficient, the inclination angle, and the spinning tension, were proposed and their individual and interaction effects on yarn strength were analyzed. The results demonstrate that yarn strength increased with the increase of height of the spinning triangle and the migration coefficient. The inclination angle and the spinning tension have a relatively small influence on yarn strength when the height of the spinning triangle is higher.

COMPONENTS OF MATHEMATICAL MODEL OF TEXTILE YARN EXTENSION TO A BREAK IN TECHNOLOGICAL PROCESSES

The idea that mathematical simulation of the process of textile yarn stretching which reveals new features of its destruction in technological processes is substantiated in the paper. Mathematical model should take into account textile yarn motion velocity in technological processes, acting external forces, and the reliable law of yarn strain under stretching. Secant moduli of cotton yarn strain were determined from experimental diagrams of cotton yarn stretching. A significant nonlinearity of the change in strain modulus depending on the strain value is shown. An account of this factor leads to physically nonlinear laws of cotton yarn strain. Therefore, as the basis of a mathematical model of the motion process, a physically developed nonlinear elastic-viscoplastic law of cotton yarn strain is proposed. The main properties of the proposed law and the methods for determining its support dependencies are discussed. An algorithm for using the law in a mathematical model of the process of yarn strain to a break is proposed.

Experimental and theoretical analysis of failure mechanism of UHMWPE Yarn under transverse cut loading

This paper is concerned with transverse cut resistant properties of UHMWPE yarns by the methods of experimental and theoretical analysis. Rheological theory of fabric was applied to evaluate relation of stress and strain of UHMWPE yarn, when the UHMWPE yarn is subjected to external cut force. The dynamic response of yarn and the contact volume of yarn and blade in the cutting have been identified to interpret cut failure mechanism of yarn. The experimental results show that yarn structure, blade edge, and test parameters have great influence on cut resistant property of UHMWPE yarn, and which are consistent with the theoretical analysis. It provides a theoretical basis for quantifying the cutting resistance of fabrics.

Effects of ply orientation and material on the ballistic impact behavior of multilayer plain-weave aramid fabric targets

Abstract Virtual testing of fabric armor provides an efficient and inexpensive means of systematically studying the influence of various architectural and material parameters on the ballistic impact behavior of woven fabrics, before actual laboratory prototypes are woven and destructively tested. In this finite element study, the combined effects of individual ply orientations and material properties on the impact performance of multi-layered, non-stitched woven aramid fabrics are studied using 2- and 4- sided clamping configurations. Individual ply orientations of 0°, ±15°, ±30°, and ±45° are considered along with three levels of inter-yarn friction coefficient. Functionally graded fabric targets are also considered wherein the yarn stiffness progressively increases or decreases through the target thickness while keeping the yarn strain energy density constant and with all other material and architectural parameters unchanged for consistency. For each target configuration, one non-penetrating and one penetrating impact velocity is chosen. The impact performance is evaluated by the time taken to arrest the projectile and the backface deformation for the non-penetrating impacts, and by the residual velocity for the penetrating impact tests. All deterministic impact simulations are performed using LS-DYNA. 2-sided clamped targets and lower inter-yarn frictional levels generally resulted in better impact performance. The functionally graded targets generally showed either similar or inferior impact performance than the baseline fabric target configurations for the non-penetrating shots. Some performance improvements were observed for the penetrating shots when the yarn stiffness was progressively decreased through the layers in a direction away from the strike face, with additional performance enhancements achieved by simultaneously reducing the inter-yarn friction.