Warp-knitted Spacer Fabrics Research Articles

Preparation and properties of shear thickening fluid (STF) capsule filled graded buffer composites

In this study, we prepared a graded buffer composite by using shear thickening fluid (STF) capsules, polyurethane (PU) foam, and low-melting point PET fabric or spacer fabric with improved energy absorption performance. Various graded buffer composites are fabricated including STF capsule/PU foam covered with PET fabric (SC/PU/PET-CM) and STF capsule/PU foam covered with warp-knitted spacer fabric (SC/PU/WKSF-CM). The thermal stability and the mechanical properties of the graded buffer composite were tested. After adding STF capsules, PU foam still has good thermal stability whose weight- loss temperature reaches 200 ℃; and the compression energy and buffer performance both increases. The compression energy of S4-STF/PU is 2.26 times than that of S4-PU and 5.65 times than that of pure PU foam. Among SC/PU/PET-CM samples, HP-STF/PU graded foam composite showed the lowest impact force (3833 N). Comparatively, among SC/PU/WKSF-CM samples, the buffer performance of S4-STF/PU shows the best, and the impact value is reduced to 3921 N, which is 848 N lower (17.7%) than that of PU foam. The composites can be used as an alternative material in the field of protection.

Warp-Knitted Spacer Fabrics: A Versatile Platform to Generate Fiber-Reinforced Hydrogels for 3D Tissue Engineering.

Mesenchymal stem cells (MSCs) possess huge potential for regenerative medicine. For tissue engineering approaches, scaffolds and hydrogels are routinely used as extracellular matrix (ECM) carriers. The present study investigated the feasibility of using textile-reinforced hydrogels with adjustable porosity and elasticity as a versatile platform for soft tissue engineering. A warp-knitted poly (ethylene terephthalate) (PET) scaffold was developed and characterized with respect to morphology, porosity, and mechanics. The textile carrier was infiltrated with hydrogels and cells resulting in a fiber-reinforced matrix with adjustable biological as well as mechanical cues. Finally, the potential of this platform technology for regenerative medicine was tested on the example of fat tissue engineering. MSCs were seeded on the construct and exposed to adipogenic differentiation medium. Cell invasion was detected by two-photon microscopy, proliferation was measured by the PrestoBlue assay. Successful adipogenesis was demonstrated using Oil Red O staining as well as measurement of secreted adipokines. In conclusion, the given microenvironment featured optimal mechanical as well as biological properties for proliferation and differentiation of MSCs. Besides fat tissue, the textile-reinforced hydrogel system with adjustable mechanics could be a promising platform for future fabrication of versatile soft tissues, such as cartilage, tendon, or muscle.

Introduction and Optimization of a Novel Nonlinear Model for the Free Vibration of Warp-knitted Spacer Fabrics

The aim of this study is to present a nonlinear model that can describe the free vibration damping behavior of 3D knitted fabrics. A fabric is considered as a single degree of freedom model which consists of a nonlinear spring paralleled with a dashpot both in series with a mass. The differential equations of the system motion are solved using the multiple scales method. Damped frequency ωd and damping coefficient $$\widehat\mu $$ are determined using the approximate analytical method, the Imperialistic Competitive Algorithm (ICA) and linear methods to estimate the system response. The obtained system response is then compared with experimental results. The results of the study show that, in comparison with analytical solutions and linear models, ICA can predict the behavior of spacer fabrics more accurately. It is also found that the difference between experimental and predicted models is explained by errors of 8.3 %, 13.7 % and 16.2 % for ICA, approximate analytical and linear model respectively.

Moisture and Thermal Transport Properties of Different Polyester Warp-Knitted Spacer Fabric for Protective Application

Abstract Warp-knitted spacer fabrics are generally used for sportswear, functional clothing, protective clothing, and other applications. This article studied the heat and mass transfer properties of polyester warp-knitted spacer fabrics from low thickness (2 mm) to high thickness (20 mm), from low mass (247.34 g/m2) to high mass (1,585.9 g/m2), and surface structure in plain or mesh construction. Water vapor permeability, air permeability, water absorption, and thermal insulation property were conducted to evaluate the spacer fabrics. The results revealed that with increasing volume density the water vapor permeability of spacer fabrics decreased, but the water absorption ratio increased. The water vapor permeability of fabrics increased when thickness decreased and volume density increased. It was further found that spacer fabrics with mesh worn nearby the skin and plain structure worn far from the skin could facilitate water vapor and air transmission. The difference of 8.82% for water vapor permeability and 14.19% for air permeability were found between testing mesh side up and down for the spacers (2.56 and 3.37 mm), respectively. Thermal insulation ratio was highly and significantly correlated with heat transfer coefficient at −0.958 and with thickness at 0.917. Thermal insulation ratio is highly and significantly correlated with air permeability at 0.941.

Development and characterization of warp knitted spacer fabrics for helmet comfort liner application

The inner padding layer of the motorcycle helmet is one of the important components that control the factors of comfort during wearing the helmet and provides a perfect fit and stability of the helmet on the head. The inner padding consists of a low-density flexible polyurethane layer attached to a soft fabric layer that is in direct contact with the head. The present study aims to replace foam in the comfort liner of a helmet with spacer fabrics to avoid the risk of heat stress during the use of the helmet. In this work, 9 warp-knitted spacer fabrics were produced by varying the course/cm (10, 12 & 14) and thickness (3, 3.5, and 4 mm). Air permeability, thermal, and water vapour resistance of the developed spacer fabrics were characterized along with compression properties and compared with commercially available standard liner. The results showed that warp-knitted spacer fabrics had better energy absorption compared to the standard liner. Also, the developed spacer fabrics had better breathability and evaporative heat transfer compared to the standard liner.

Preparation of auxetic warp-knitted spacer fabric impregnated with shear thickening fluid for low-velocity impact resistance

This paper reports the preparation of auxetic warp-knitted spacer fabric impregnated with shear thickening fluid and studied its impact behavior under low-velocity impact loading. The shear thickening fluids have been prepared by mechanically dispersing 12 nm silica particles with weight fraction of 10, 15, 20, and 25% in various carriers (PEG200, PEG400, and PEG600). Rheological results indicate that shear thickening fluid experiences shear thickening transition at a specific shear rate. The critical shear rate reduces, and initial viscosity and maximum viscosity increase with the increase of silica weight fraction. The higher molecular weight of polyethylene glycols can lead to lower critical shear rate. The impact process of composite under impact loading can be divided into three stages. The warp-knitted spacer fabric with different negative Poisson’s ratio has a significant effect on the impact behavior. The warp-knitted spacer fabric with better auxetic performance endows composite better impact resistance, the specific performance is the deformation depth, and energy absorption and peak load increase with the increase of auxetic effect of fabric. The silica weight fraction of shear thickening fluid can increase the energy absorption of composite due to the shear thickening transition of shear thickening fluid. Shear thickening fluid has a synergistic effect with the auxetic warp-knitted spacer fabric on impact resistance of composite. The various carriers have no obvious influence on the overall energy absorption and impact load of composites.

Spring-like sandwich foam composites reinforced by 3D Concave–Convex structured fabric: Manufacturing and low-velocity cushion response

In order to solve the problems of poor mechanical properties and incapable reuse for single cellular foam, this study proposed low-cost spring-like sandwich flexible foam composites (SFFCs) with a 3D resilient concave–convex structured fabric core (RCFC) and two gradient-structured styrene-ethylene/butene–styrene copolymer (SEBS)-g-maleic anhydride (MAH)-filled polyurethane (PU) foam faces through two-step foaming. RCFC plied with different sizes and distances constituted warp-knitted spacer fabrics (WKSF) sealed between two layers of low-melting polyester nonwovens through thermal bonding. The effects of SEBS-g-MAH content and volume content of RCFC cubes on compression and dynamic low-velocity impact properties were explored at different impact energy levels. At 3:4 (wt%) ratio of the upper-to-lower SEBS-g-MAH content faces and at 0.4 ratio of WKSF-to-PU volume ratio, the resultant SFFCs showed a compression stress of 68.4 kPa (40%) and absorbed up to 98% of impact energy under 16 J. After five cycles of impact, this sandwich foam composite maintained 98% absorption of impact energy, demonstrating excellent spring-like dynamic-impact-recovery property. Overall, this study provided a novel structure design for lower cost, higher-performance recycling cushion materials in industrial construction, transport packaging, and sports fields.

Characterization of a 3D Auxetic Warp-knitted Spacer Fabric by Synchrotron Radiation X-ray Computed Tomography

Auxetic fabrics have many potential applications in technical textiles. Auxetic 3D warp-knitted spacer fabric can be produced by adoption of some special geometrical configuration. Characterization of the geometrical configurations is of vital significance to understand their auxetic property. In this paper, a typical 3D auxetic warp-knitted spacer fabric was studied by synchrotron radiation x-ray computed tomography (SR-CT). Fiber distribution in the fabric was clearly obtained and different types of yarn were extracted separatively. 3D image reconstructed by synchrotron radiation X-ray computed tomography was consistent with the designed geometrical configuration. Besides, 3D model reconstructed lays the foundation for further numerical analysis by FEA.

Seat cushions made of warp knitted spacer fabrics influence seat transmissibility

The aim of this study was to compare the application of different warp knitted spacer fabrics on a car seat shell to a standard seat in terms of vertical seat transmissibility. Furthermore, the results obtained by human subject tests were compared to results of an anthropodynamic dummy test. Experiments were conducted on a vertically actuated platform under laboratory conditions with 16 human subjects and an anthropodynamic dummy. Seat Effective Amplitude Transmissibility of the seat pan and the seat backrest were calculated to evaluate ride quality. Seat transmissibility ranged between 73.6% for backrest and 177.7% for pan. Based on the results of statistical tests, the hypothesis that the transmissibility of a seat would be influenced by seat cushion conditions was accepted (p < 0.05). It was also shown that an anthropodynamic dummy test could replace tests with human subjects (r2 = 0.907) if the target population was matched sufficiently.

Evaluation of air permeability behaviour of warp knitted spacer fabrics

The porosity and air permeability of 3D polyester warp knitted spacer fabric has been determined by optimizing the structural parameters and using Box and Behnken experimental design. Spacer fabrics are developed by using polyester multifilament of 80 - 120 denier on the face layer and 30 - 70 denier on the bottom layer. Polyester monofilaments of 20 - 40 denier are used in the middle layer, deciding the third dimension of the fabric. Porosity and air permeability are estimated with respect to the linear density of polyester filaments, and response the surface design is used to predict the optimum linear density. Better air permeability and porosity are observed at the face layer denier of 100 and middle layer denier of 20. The statistical analysis proves that the degree of correlation of F values is 12.44 between the filament linear density and air permeability.

Low-velocity impact properties of composite reinforced by auxetic warp-knitted spacer fabric

Auxetic warp-knitted spacer fabric composite is famous for its excellent mechanical properties and has been applied in many potential fields, such as automobile industry, aerospace field, and so on. Four kinds of composites with different negative Poisson’s ratios were used for low-velocity impact tests. The influence of different negative Poisson’s ratio effect and initial impact energy on the impact resistance and energy absorption ability of composites are studied. Result shows that the peak impact load, energy absorption, and impact resistance of composites increase with an increase in the auxetic effect of reinforcement. The composite with better auxetic effect shows lower damage level after low-velocity impact. And the higher initial impact energy can easily weaken the impact resistance ability of composites.

Sound absorption of warp knitted spacer fabrics based on knit structure and nanofiber enhancement

In this work, the sound absorption properties of warp knitted spacer fabrics enhanced with nanofiber were studied. The angle of connecting yarns at two different spacing was considered as knit structure variable. Also, the effect of layering on the sound absorption performance was studied. Besides that, the effect of polyacrylonitrile nanofiber enhancement on sound absorption coefficient of such structures were considered. The polyacrylonitrile nanofibers were manufactured by a single-nozzle electrospinning device using a rotating cylindrical collector. The main variable for the nanofiber enhancement was its deposition amount on the front surface of spacer fabrics. The sound absorption coefficient was measured by using the method of impedance tube. For this purpose, the samples were prepared according to the requirements, and the tests were performed at the frequency range of 500–6000 Hz on single-layer and multi-layer samples. The results showed that increasing the spacing and the angle of connecting yarns will enhance the sound absorption coefficients of samples through increasing their areal mass, thickness and porosity. Moreover, layering will significantly affect the sound absorption performance of samples. Furthermore, nanofiber enhancement increased the absorption of sound at all frequencies.

3D Spacer Fabric Structure for the Prevention and Care of Pressure Ulcers

Many pressure wound protection products, such as pressure redistribution supports and exuding wound dressings, are made of polyurethane sponge. However, polyurethane sponge does not possess a desirable combination of air permeability, moisture management and mechanical properties required by pressure redistribution supports and exuding wound dressings. This study explores the optimization of a 3D warp-knitted spacer fabric (WKSF) structure for pressure ulcer protection. The influence of construction and material parameters on the compression performance and air permeability of WKSFs was investigated by numerical simulation and then validated with experiments. The moisture transport and wetting properties of WKSFs were characterized by a moisture management tester. The numerical simulation and experimental results indicate that the WKSF structure can be tuned to achieve compressional properties, air permeability, and moisture management performance that are more suitable for pressure ulcer protection than polyurethane sponge. WKSFs constructed with a low-density surface layer, coarser spacer yarns, and larger spacer yarn inclination-angle are more suitable for pressure redistribution support surfaces, while WKSFs constructed with dense surface layers and coarse spacer yarn can better meet the performance requirements of exuding wound dressings.

Three-Dimensional Deformation of Warp-Knitted Spacer Fabrics Under Tensile Loading

Abstract This paper puts forward a new method for measuring the three-dimensional deformation of warp-knitted spacer fabrics under tensile stress. The three-dimensional deformation mechanisms of warp-knitted spacer fabrics have been analyzed using stress–strain curves. Poisson’s ratio of the three-dimensional deformation has also been analyzed. The stress–strain curves obtained for tests in the warp-ward direction and weft-ward direction show a characteristic initial large deformation, followed by minimal-to-no deformation. The stress–strain curves obtained for tests in the thickness direction exhibit different characteristics due to the differences in stretch directions. In the weft-ward direction, the curve shows an approximate linear change with minimal strain. In the warp-wise direction, the curve shows a large stress with small strain, and subsequently, a small stress yielded a large strain. During the stretching process, the surface deformation perpendicular to the direction of tensile force is greater than the tensile deformation, and the deformation in the thickness direction is also minimal compared to that in the direction of the tensile deformation.

An effect of fabrics thickness and structure on moisture management properties of 3D spacer fabrics

PurposePolyester multifilament is used to produce the face and back layer of warp knitted spacer fabric (WKSF) and these two layers are connected by polyester monofilament as a middle layer. This fabric has unique and extraordinary characteristics, and different possibilities of fabric structure and the middle layer thickness are tried to find out the moisture management properties. The paper aims to discuss these issues.Design/methodology/approachThis study investigates the influence of fabric thickness and structure on moisture management properties.FindingsPolyester monofilament quickly up takes the water molecule from the water reservoir and transfers it by capillary action. The gravitational force and the availability space between the two outer surface layers restrict the movement of water molecules, although the pressure develops to push the molecules from the water reservoir. As a result, all the spacer fabric samples attain the equilibrium state very quickly. WKSF and the hexagonal net structure prove to be better in vertical wicking.Originality/valueThe liquid movement is quick in the front side of the spacer fabric, and the rate of wicking is higher in open structure than in the closed structure. It confirms that the hexagonal net structure produces high pore size on fabric and it reaches maximum wicking values. Fabric thickness does not have much influence on the vertical wicking properties of all fabric samples, and the rate of liquid movement produces a similar trend. In in-plane wicking, the polyester monofilament in the middle layer of spacer fabric plays a major role rather than the outer surface layers of fabric.

Compressive mechanics of warp-knitted spacer fabrics

This paper aims to identify the underlying physical mechanism for the compression deformation of a warp-knitted spacer fabric with a typical structure with experimental and theoretical studies. Compression tests were carried out to measure the load–displacement relationship of the fabric. The structural features of the spacer yarns were photographed by a microscope at different displacements during the compression test. A theoretical model based on elastica theory was developed to describe the compression behavior of the fabric by introducing the effect of complex geometry of the spacer yarns. A comparison between the experimental results and theoretical calculations was also conducted. Four distinctive stages including initial stage, elasticity stage, plateau stage and densification stage were identified and their underlying physical mechanisms were explained based on experimental observations and theoretical calculations. The model could provide an in-depth understanding on the deformations of spacer yarns of spacer fabrics under compression.

Investigation of the flexural behavior of self-consolidating mortars reinforced with net warp-knitted spacer fabrics

This work intended to study the flexural properties of self-consolidating mortars (SCM) reinforced with net warp-knitted spacer fabrics (WKSF). The effects of fabric structural parameters namely mesh size, the position of the meshes in the outer layers with respect to each other, and the fabric thickness on the properties of the composite materials were investigated. The uniaxial tensile tests were conducted to evaluate the influence of the fabric variables on the fabric elastic modulus. The cement-based specimens were made by casting in three forms: 1) plain SCM as the control specimen, 2) SCM reinforced with two 2D fabrics, and 3) SCM reinforced with the 3D spacer fabrics. Three-point bending tests were carried out. The mode of fracture was investigated through microscopic analysis using a Scanning Electron Microscope. Furthermore, the condition of the prepared SCM from porosity viewpoint was evaluated using the water absorption test with and without fabric inclusion. The tensile tests indicated that the modulus of fabrics in the wale direction is more than the modulus in the course direction. Fabrics with larger mesh and also thicker fabrics have lower modulus than the fabrics with smaller meshes and lower thickness. The fabric modulus was independent of the position of the meshes. The experimental results of the flexural tests showed the significantly better performance of the spacer fabrics owing to the presence of spacer yarns and their contribution towards the thickness reinforcement. Stiffness, strength, and strain capacity of the composite materials were improved using the spacer fabrics. Furthermore, SCM reinforced with 2D fabrics had better mechanical properties than the plain SCM. The flexural bending tests indicated that the composite materials which reinforced with larger mesh have better mechanical performance owing to the easier penetration of the matrix through the fabrics and making reasonable interfaces. There is an increase in the volume fraction of the reinforcement using thicker fabrics with longer spacer yarns which were resulted in higher modulus and strain capacity. The SEM images indicated that matrix cracking and then the breakage of the outer layers of the spacer fabrics are the major causes of the composite failure.

Fabrication of bamboo-structure hollow polyester monofilaments for extraordinary compression properties

Owing to its special structure, bamboo can withstand larger load in nature. The novel structure of bamboo is a great example for exploring materials with excellent mechanical properties, though limited research in this area has been reported so far. In textiles, monofilaments with outstanding compression property are desired in the development of warp-knitted spacer fabrics for a range of applications. Herein, we use 3D printing method to fabricate polyester (PET) bamboo-structure monofilaments and study their compression properties. It has been found that bamboo-structure hollow monofilament undertakes more load per unit mass than solid and continuous hollow monofilaments, and the value of load per unit mass increases with the increase of the hollow part. FEM analysis has discovered that the compression behavior and the compression properties of the bamboo-structure monofilament are in accordance with that of spacer monofilament in warp-knitted spacer fabrics. Warp-knitted spacer monofilaments prepared from bamboo-structure hollow monofilament with a high percentage of hollow part undertake more load per unit mass, providing new opportunities on the design and development of warp-knitted spacer monofilament towards different applications.

Characterization of Warp Knitted Spacer Fabric for Application in Sports Bra

Women's breasts contain limited anatomic support. Sporting activities create an excessive movement of breasts. It causes generation of continuous stress on the cooper ligaments. Excessive stress on cooper ligaments creates discomfort, pain, embarrassment and also causes the breasts to sag. The effectiveness in reducing breast movement depends on various factors. The factors are related to breast sizes, breast stiffness, running and jumping speed of sport woman and fabric structural parameters by which sports bra are made. However, no work has investigated and characterized spacer fabric based on the curvature of inner body parts under the bra. Characterization of spacer fabric is required on the basis of the real life simulation. The reaction force acting on the breasts during spherical compression of spacer fabric needs to be analyzed. Air and moisture transmission through the fabric, thermal resistance and moisture management properties also need to be characterized along with compression properties. Samples were developed to characterize spacer fabric for the above requirement. This paper analyzes to understand the behavior of warp knitted spacer fabric for spherical compression with different diameter of the spheres and its thermal, air and moisture related comfort characteristics. Finite Element Analysis (FEA) is also done for compression properly of spacer fabric. It is concluded that spacer fabric may be considered as a very effective component of sports bra for controlling breast movement without compromising with comfort of sports women.

Theoretical and experimental investigation of tensile properties of net warp-knitted spacer fabrics

This work aimed to investigate the tensile behavior of net warp-knitted spacer fabrics using the experimental and theoretical approaches. Tensile behavior of the warp-knitted spacer fabrics is one of the fundamental parameters which rarely considered in the literature. Therefore, the net spacer fabrics were made with three different variables (fabric thickness, size of meshes, and the position of meshes of the outer layer with respect to each other) in order to study the effects of structural parameters on the tensile behavior. A 2D net-fabric which used for the outer fabrics was made for in-depth considerations and also the comparison between the 2D fabrics and spacer fabrics. The initial linear elastic modulus of the 2D fabrics and the initial linear elastic modulus of the spacer fabrics were selected for the assessment of the tensile characteristics. First, a mechanical model was developed based on the geometrical structures and material properties of the 2D fabrics using energy method and Castigliano’s theorem. Then, the effects of spacer yarns on the tensile behavior of spacer fabrics were taken into account. The latter model was proposed using the bending theory of a curved bar. Experimental data were compared with the values obtained from the theoretical approaches and the end results showed that the developed models can predict the modulus reasonably. Moreover, the results indicated that the tensile behavior of the spacer fabrics are independent of the position of the holes in the outer layer whilst the fabric thickness and size of meshes affect the tensile modulus.