Electrical and impact properties of the hybrid knitted inlaid fabric reinforced polypropylene composites

A range of conductive knitted fabric reinforced polypropylene composites have been developed and their electromagnetic shielding effectiveness (EMSE), electrostatic discharge (ESD) and impact properties have been investigated. Carbon and aramid fibers are used as the reinforcement phase in the composites, while copper and stainless steel wires are incorporated as conductive fillers to provide the ESD and EMSE properties of the composite materials. The hollow spindle spinning system has been used to make SS/PP, Cu/PP, SS/C/PP, Cu/C/PP and Cu/K/PP uncommingled yarns. The double plain knitted fabric and its inlaid fabrics were fabricated from the yarns using a 5G traverse knitted machine. Changing the yarn composition, fabric knit structure, and stitch density varies the amount of copper and stainless steel conductive fillers in the composites. 4 layer cross-ply laminates were laid-up by hand, then formed into 3-mm thick conductive thermoplastic composites using a compression molding. It was observed that the EMSE and ESD of the composites increase with increasing the incident frequency, especially at higher frequency range. The effects of inlaid ends, materials and yarn constitutions on the EMSE of the conductive thermoplastic composites were investigated. The results indicate that the composites can be used for the purpose of electromagnetic shielding and ESD attenuation, as well as for some microwave applications.     

Processing and Properties of Multifunctional Metal Composite Yarns and Woven Fabric

Multifunctional metal composite yarns made of crisscross-section polyester (CSP), antibacterial nylon (AN), and stainless steel wires (SSW) were manufactured using a hollow spindle spinning machine. The core yarn, the inner wrapped yarn, and the outer wrapped yarns were SSW, AN, and CSP, respectively. Process parameters such as wrapping material content obviously influenced the tenacity, elongation, and surface morphology properties of the manufactured multifunctional metal composite yarns. These yarns were then woven into fabrics using a rapier loom. Woven fabric WC-8 was evaluated in terms of its mechanical properties, antibacterial activity, and electromagnetic shielding effectiveness (EMSE). Results showed that the use of SSW and AN in the metal composite yarns improved the antibacterial and EMSE of the woven fabric. Thus, these metal composite woven fabrics can be used in manufacturing personal protective clothing to protect humans from electromagnetic radiation and bacterial cross-infection.     

Evaluation of electromagnetic shielding effectiveness of multi-axial fabrics and their reinforced PES composites

The usage of electrical and electronic equipments has been increasing in daily life, which has a potential hazardous impact on humans and other living organisms. In this paper, multi-axial fabrics containing steel yarns and carbon filaments, and their polyester (PES) resin-reinforced composites have been prepared for electromagnetic shielding applications. The electromagnetic shielding effectiveness (EMSE) of these structures was determined by using coaxial transmission line measurement technique. There were eight different multi-axial fabrics constructed. It was observed that the amount and the orientation of carbon and stainless steel yarns influenced the EMSE performances of multi-axial fabrics and their reinforced PES composites. The structures containing both carbon filaments and stainless steel yarns exhibited better EMSE than the ones including only one type of conductive yarns or filaments. Also, the EMSE performance of multi-axial fabrics was found better than their reinforced composites. The best EMSE results were obtained for the fabric, including two layers of yarns (steel and carbon) on top of each other in the centre with the angle of 45 and ?45°.     

Electromagnetic shielding effectiveness of copper/glass fiber knitted fabric reinforced polypropylene composites

The main objectives of this research work are to develop conductive knitted fabric composite materials and to determine their electromagnetic shielding effectiveness (EMSE). Polypropylene is the matrix phase and glass fibers are the reinforcement phase of the composite material. Copper wires are incorporated as conductive fillers to provide the electromagnetic shielding properties of the composite material. The amount of copper in the composite material is varied by changing the yarn composition, fabric knit structure and stitch density. The EMSE of various knitted fabric composites is measured in the frequency range of 300 kHz to 3 GHz. The variations of EMSE of knitted fabric composites with fabric structure, stitch density and yarn compositions are described. Suitability of conductive knitted fabric composites for electromagnetic shielding applications is also discussed.     

Electromagnetic and electrostatic shielding properties of co-weaving-knitting fabrics reinforced composites

The rotor twister successfully fabricated a series of hybrid conductive yarns. Copper wire and polyamide filament were used as the core yarn, and stainless steel wire was used as the wrapping yarn to fabricate the loop yarns for knitting structure. The nonwoven selvedge served as the core yarn, and the conducting wire was used as the wrapping yarn, to fabricate the weft-inlaid yarn. The co-weaving-knitting machine was used successfully in this study to fabricate the conducting co-weaving-knitting fabrics (CWKFs) with the hybrid yarn. The conducting materials of the hybrid yarn were copper wire and stainless steel wire, taken as the wrapping and core yarn, respectively. The CWKFs were laminated with various angles in four layers, and then were heat pressed for 3 mm in thickness. This study examined the surface resistivity, electromagnetic shielding effectiveness and electrostatic discharge attenuation percentage of the CWKFs reinforced composites.     

Processing of metallic fiber hybrid spun yarns for better electrical conductivity

This research was aimed at processing of metallic fiber hybrid spun yarns consisting of polyester/stainless steel and viscose/stainless steel staple fibers to achieve better electrical conductivity. Conventional ring spinning machine and ring twister machine were used to produce the single and plied yarns respectively. The linear electrical resistance of yarns was analyzed with reference to the three levels of twist multiplier (TM) for same yarn count, three levels of yarn fineness (Ne) at the same TM level, and number of plies for the same final yarn count. These results showed that by increasing twist, the electrical conductivity of yarn was increased. However, yarn fineness was in inverse relation with the electrical conductivity of yarns. The effect of yarn plying and twisting to produce the Ne 10s yarn was also found critical in governing the electrical properties. The electrical conductivity of viscose and stainless steel hybrid yarn was found more sensitive to increase with an increase in relative humidity contrary to that of polyester and stainless steel hybrid yarns. The findings of the study are significant to produce the hybrid spun conductive yarns for their potential applications in a variety of tailor-made functional, protective and smart textiles.     

Electromagnetic shielding effectiveness of thin film with composite carbon nanotubes and stainless steel fibers

Using the polymer blending method, conductive materials and waterborne polyurethane (WPU) were mixed to fabricate conductive composite films for application in electromagnetic shielding. First, nitric acid was used to purify the multi-walled carbon nanotubes (MWCNT). Second, sodium dodecyl sulfate (SDS) was utilized to disperse the carbon nanotubes, and then they were mixed with 8 microm diameter and 2 mm long stainless steel fibers (SSF) in the WPU by the polymer blending method. Finally, the thickness of 0.25 mm of conductive composite film was fabricated by means of coating. According to the ASTM D4935-99 standard, a coaxial transmission line was used to measure the electromagnetic shielding effectiveness (EMSE) of conductive composite film within the range of 50 MHz approximately 3.0 GHz. Moreover, the influence of the prior and posterior dispersion of carbon nanotubes dispersed on electromagnetic shielding was dealt with in the paper. Results demonstrated that the conductive composite film, within 50 MHz approximately 3.0 GHz, fabricated by the 15 wt% of the multi-walled carbon nanotubes and 30 wt% of the stainless steel fibers can achieve the maximum of the electromagnetic shielding effectiveness, 34.86 dB, and its shielding effect, 99.9%.     

Effect of hybrid woven fabrics structure on their electrical properties

The aim of this study is to investigate the influence of hybrid textile woven fabric structure on the electrical resistivity. Weave structure was varied by varying the weave pattern and the conductive yarn density in the woven fabrics. Electrical surface and volume resistivity were measured and compared to the fabric structural properties. Results showed that not only the conductive yarns percentage has an important effect on the electrical resistivity but also the weave structure. The most influencing structural parameter on surface resistivity was the woven fabric surface profile as it controls the contact quality between the conductive yarns and the measuring electrodes. A high surface resistivity was noticed when the contact quality was poor. When this contact quality was good, a linear correlation was found between surface electrical resistivity and the cover firmness factor, the apparent conductive fiber surface area as well as the conductive yarn floating length of the woven structures.     

柔性纺织电阻传感器的研究进展

纺织电阻传感器具有质量轻、柔性好和可拉伸等优良特性,在可穿戴电子产品领域具有很大的应用价值.文中根据近年来不同纺织材料基电阻传感器的研究进展,介绍了无捻纤维(束)基电阻传感器、纱线(长丝纱、短纤维纱、复合纱)基电阻传感器和织物(针织物、机织物、非织造织物)基电阻传感器的制备、性能及应用研究.在纱线基电阻传感器中,主要基...     

Tribological properties of woven para-aramid fabrics and their constituent yarns

The tribological behaviours of woven fabrics made from Kevlar® (DuPont's registered trademark) yarns of different linear densities were compared with the friction properties of their constituent yarns with different surface treatments. The latter were examined with a traditional friction meter, and the woven fabrics were studied with a pin-on-disc tribometer in alternate and continuous sliding mode. Scoured fabrics, a poly(tetrafluoroethylene)-coated fabric, and fabrics made of surface-treated yarns (polysiloxane oil, hydrophobic paraffin or ester oil lubricant) were compared. These treatments are not representative of commercial Kevlar® yarn finishes but are suitable models for simulating various tribological situations. Both the yarn texture and the surface treatment have an influence on friction coefficient values. Relative humidity affects the friction coefficient only in the case of hydrophilic surfaces, whereas hydrophobic surfaces exhibit fairly constant tribological characteristics. The largest impact on friction seems to be evidenced by the linear density factor. This comparative tribological analysis could lead the way to correlations between yarn friction, weaving performance and woven structure tribological characteristics.     

Effect of Frictions on the Ballistic Performance of a 3D Warp Interlock Fabric: Numerical Analysis

3D interlock woven fabrics are promising materials to replace the 2D structures in the field of ballistic protection. The structural complexity of this material caused many difficulties in numerical modeling. This paper presents a new tool that permits to generate a geometry model of any woven fabric, then, mesh this model in shell or solid elements, and apply the mechanical properties of yarns to them. The tool shows many advantages over existing software. It is very handy in use with an organization of the functions in menu and using a graphic interface. It can describe correctly the geometry of all textile woven fabrics. With this tool, the orientation of the local axes of finite elements following the yarn direction facilitates defining the yarn mechanical properties in a numerical model. This tool can be largely applied because it is compatible with popular finite element codes such as Abaqus, Ansys, Radioss etc. Thanks to this tool, a finite element model was carried out to describe a ballistic impact on a 3D warp interlock Kevlar KM2? fabric. This work focuses on studying the effect of friction onto the ballistic impact behavior of this textile interlock structure. Results showed that the friction among yarns affects considerably on the impact behavior of this fabric. The effect of the friction between projectile and yarn is less important. The friction plays an important role in keeping the fabric structural stability during the impact event. This phenomenon explained why the projectile is easier to penetrate this 3D warp interlock fabric in the no-friction case. This result also indicates that the ballistic performance of the interlock woven fabrics can be improved by using fibers with great friction coefficients.     

Modelling inter‐yarn friction in woven fabric armour

The effects of inter‐yarn friction on the ballistic performance of woven fabric armour are investigated in this paper. Frictional sliding between yarns is implemented in a computational model of the fabric that takes the form of a network. Yarn crimp and its viscoelastic properties are taken into account. Ballistic experiments are performed to verify the predictions of the model. Parametric studies show that the ballistic response of woven fabric is very sensitive to yarn friction when the friction coefficient is low but insensitive beyond a certain level. The results also show that very high inter‐yarn friction can lead to premature yarn rupture, thus reducing the ability of the fabric to absorb impact energy. Copyright © 2005 John Wiley & Sons, Ltd.     

Early prediction of the failure of textile-reinforced thermoplastic composites using hybrid yarns

In this study, the manufacturing of core-sheath hybrid yarns consisting of steel fibres and glass filament yarn (GFY) using a friction spinning technique and their usability for failure prediction in composites is reported. With the DREF-2000 friction spinning technique, it is possible to manufacture hybrid yarns having a core-sheath structure. Steel fibres are used as the sheath and the GFY is used as the core of the yarns. These hybrid yarns are embedded between two layers of glass/polypropylene (GF/PP)-based knitted fabric composites. By varying the steel fibre content, it is possible to adjust the initial resistance as well as the sensitivity of the hybrid yarns to measure the interphase strain in the thermoplastic-based knit composite during tensile loading. The hybrid yarns with lower steel fibre content are found to be more sensitive in the prediction of the early damage in the composite. By performing a quasi-static and gradual increase of loading during the tensile tests, it is possible to identify the critical load for the composite. The before mentioned hybrid yarns show their suitability for the structural health monitoring and the potential to be integrated into thermoplastic-based composites by textile processing.     

Ballistic impact modeling of woven fabrics considering yarn strength,friction, projectile impact location,and fabric boundary condition effects

The combined effects of yarn tensile strength, inter-yarn friction, projectile impact location, and fabric clamping conditions on the probabilistic impact response of flexible woven Kevlar KM2 fabrics are studied using a 0.22 caliber spherical projectile. The statistical nature of yarn tensile strength is accounted for by mapping Weibull strength distributions onto the individual yarns of the fabric model. Variability in projectile impact location relative to the yarns at the impact site is accounted for by randomly selecting one of 25 predetermined impact locations around a warp-fill yarn cross-over location at the center of the fabric. Five different inter-yarn friction levels are deterministically implemented, ranging from 0.0 to 0.4. Two boundary conditions are considered, 4-sided clamped and 2-sided clamped. Forty impact simulations are used to generate a probabilistic impact response (PVR) curve for each test case, describing the probability of fabric penetration as a function of projectile impact velocity. The fabric V₅₀ velocity and impact performance variability were observed to decrease with increasing inter-yarn friction levels for the 4-sided clamped cases, while they increased for the 2-sided clamped cases.     

Effects of Woven Fabric Geometry on the Bonding Performance of Cementitious Composites: Mechanical Performance

The effect of the geometry of woven fabrics on the bond between monofilament polyethylene yarns and cement matrix was studied in the present work. The fabrics were all plain weave, with varied fills density: 5, 7, or 10 fills per cm; the warps’ density was kept constant at 22 warps per cm. The interfacial bond was evaluated by pullout tests. To characterize the influence of the fabric’s geometry on bond performance, the influence of different parameters of the fabric’s geometry that may affect bond were separated: (1) pullout of a single crimped yarn untied from the fabric to characterize the influence of the shape of the individual crimped yarn; (2) pullout of a single yarn from free fabric (not embedded in the cement matrix); and (3) pullout of a yarn from a fabric embedded in the cement matrix. Straight yarns were also tested for comparison. It was found that the woven fabric provided a considerably better bond to the cementitious matrix than the bond of a single straight yarn. The crimped geometry of the yarn in the fabric was found to have a significant influence on increasing the bond between the woven fabric and the cementitious matrix.     

A numerical investigation of the influence of friction on energy absorption by a high-strength fabric subjected to ballistic impact

A finite element analysis was conducted to study the influence of friction during ballistic impact of a rigid sphere onto a square fabric panel that was firmly clamped along its four edges. Projectile-fabric friction and yarn–yarn friction were investigated. Modeling indicates that friction dramatically affects the local fabric structure at the impact region by hindering the lateral mobility of principal yarns. Reduction of lateral yarn mobility allows the projectile to load and break more yarns so that fabric possessing a high level of friction absorbs more energy than fabric with no friction. The projectile-fabric friction delays yarn breakage by distributing the maximum stress along the periphery of the projectile-fabric contact zone. The delay of yarn breakage substantially increases the fabric energy absorption during the later stages of the impact. The yarn–yarn friction hinders the relative motion between yarns and thus resists de-crimping of fabric weave tightness. It induces the fabric to fail earlier during the impact process. The overall influence of projectile-fabric friction and yarn–yarn friction cannot be calculated by simply adding their individual effects.     

Micro-CT analysis of internal structure of sheared textile composite reinforcement

Simple shear is a deformation mechanism typical for a woven fabric during draping. The mesoscopic internal structure of the fabric differs between the non-deformed state and a sheared state. This paper presents an analysis of the internal structure of woven fabrics in a sheared state based on micro-CT (X-ray micro computed tomography) imaging of the internal structure of woven fabrics in a sheared state. Two methods for the analysis of the fabric geometry are used: automatic mapping of the local fibre directions based of the micro-CT image analysis and manual measurements of the yarns cross section shape, size and middle line coordinate of yarns on the micro-CT images. Changes of the fibre orientations within the yarns and of the yarn geometrical parameters in a carbon fibre twill woven fabric before and after shear deformation are quantified.     

A homogenization procedure for the numerical analysis of woven fabric composites

The paper presents a procedure for the numerical evaluation of the mechanical properties of woven fabric laminates. Woven fabrics usually present orthogonal interlaced yarns (warp and weft) and distribution of the fibers in the yarns and of the yarns in the composite may be considered regular. This allows us to apply the homogenization theory for periodic media both to the yarn and to the fabric. Three-dimensional finite element models are used in two steps to predict both the stiffness and the strength of woven fabric laminates. The model includes all the important parameters that influence the mechanical behavior: the lamina thickness, the yarn orientation, the fiber volume fraction and the mechanical characteristics of the components. The capabilities of the numerical model were verified studying the elastic behavior of a woven fabric laminate available in the literature and the ultimate strength of a glass fabric laminate experimentally investigated. The procedure, that can be implemented into commercial finite element codes, appears to be an efficient tool for the design of textile composites.     

亚麻/聚丙烯复合材料板材的制备及其冲击性能

以亚麻纱线作为增强体,与聚丙烯（PP）纤维按六种质量比进行混合,制备PP长丝包覆的包覆纱,利用机织工艺织成二维机织布作为复合材料的预制铺层,采用热压法进行层合热压,制备出亚麻增强聚丙烯复合材料板材。通过对板材冲击性能的测试及分析,研究了制备工艺、纱线结构及纤维含量等因素对复合材料冲击性能的影响。结果表明,本试验中当亚麻质量分数为68%时板材的冲击性能最好;＂三明治＂铺层方法制备的板材体现出较好的冲击性能;0°/0°板材在受到冲击时比0°/90°板材吸收的冲击能更多,体现出较好的耐冲击性。     

Determining Effective Thermal Conductivity of Fabrics by Using Fractal Method

In this article, a fractal effective thermal conductivity model for woven fabrics with multiple layers is developed. Structural models of yarn and plain woven fabric are derived based on the fractal characteristics of macro-pores (gap or channel) between the yarns and micro-pores inside the yarns. The fractal effective thermal conductivity model can be expressed as a function of the pore structure (fractal dimension) and architectural parameters of the woven fabric. Good agreement is found between the fractal model and the thermal conductivity measurements in the general porosity ranges. It is expected that the model will be helpful in the evaluation of thermal comfort for woven fabric in the whole range of porosity.