Friction core-spun yarns for electrical properties of woven fabrics

This paper reports a study to develop a spinning method of open-end friction core-spun yarn (OFCY) and its conductive fabric for shielding the electrostatic discharge and electromagnetic applications. To facilitate weaving of stainless steel (SW) and to reduce the material cost, initially OFCY yarn was made from SW core and polyester (PET) and stainless steel staple (SS) fibers, produced by a DREF III open-end friction spinning method. The core-spun yarns were woven into a variety of woven structures, which are made from semi-automatic loom, successfully. The conductive fabrics could be suitable for shielding home electronic and electrical appliances, cellular phones, and digital devices from electromagnetic fields. The variations of EMSE, and ESD of the woven fabric structure, and blend ratio of stainless steel yarns are also described. It has been shown that the EMSE and ESD attenuation of the woven fabric can be tailored in a number of ways including fabric structure, density, and the amount of conductive filler material.     

Comparative study of the electrical and structural properties of woven fabrics

The application of woven fabrics as the substrate materials for electronic products causes the need to examine their electrical properties at various external effects. This paper presents the results of electrical properties of the fabrics of cotton, cotton/polyethyleneterephtalate (PET) and PET. Dielectric loss factor and dielectric permeability were analyzed in a wide range of temperatures and frequencies. Relaxation peak which appears in this measuring region was identified as the secondary β-relaxation. At different frequencies the dielectric permeability has been analyzed at a different relative humidity at room temperature. At the higher values of relative humidity with the increase of frequency leads to greater reduction of the dielectric permeability and this is more prominent in the samples of cotton and cotton/PET blend. The dc volume resistivity has been investigated in the function of relative humidity at room temperature and interpreted by the raw composition and the structural properties. On the basis of the obtained results, it was concluded that on the electrical properties of cotton/PET blend, cotton has greater impact i.e. the component with the higher dielectric permeability value and smaller dc volume resistivity value.     

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.     

Tailoring the properties of leno woven fabrics by varying the structure

Abstract

This study focused on the development of woven structures based on leno weave with tailored performance properties. To achieve this objective, pure leno and hybrid leno weaves were used to produce woven fabrics. In hybrid weaves, leno weave was combined with 1/1 plain, 3/1 twill, and 2/2 matt weaves, and 12 samples were produced with three different weft thread densities. The multifilament polyester yarn was used as warp and weft material. The characterization of physical and mechanical properties showed that comparable tensile properties were achieved by leno and hybrid weave fabrics, but the hybrid structures offered lower resistance to puncture as compared to pure leno fabrics. A multi-response optimization technique was used to determine the best sample under a particular set of conditions.     

Low velocity impact properties of intra-ply hybrid composites based on basalt and nylon woven fabrics

In this paper, the low velocity impact behavior of homogenous and hybrid composite laminates reinforced by basalt–nylon intra-ply fabrics was experimentally investigated. Epoxy resin was used as matrix material. The purpose of using this hybrid composite is to combine the good mechanical properties of basalt fiber with the excellent impact resistant of nylon fiber. Five different types of woven fabrics were used as reinforcement with different volume percentages of nylon (0%, 25%, 33.3%, 50% and 100%). The effect of nylon/basalt fiber content on maximum force, maximum deflection, residual deflection, total absorbed energy, elastic energy, size and type of damage were studied at several low velocity impact nominal energy levels (16, 30 and 40 J). The results indicate that impact performance of these composites is significantly affected by the nylon/basalt fiber content. The visual inspection and ultrasonic C-scan of the impact damaged specimens reveals that content of nylon/basalt fiber controls the type and size of damage.     

Investigation on mechanical properties of woven alovera/sisal/kenaf fibres and their hybrid composites

The go-green concept results in multipoint focus towards materials made from nature; easily decomposable and recyclable polymeric materials and their composites along with natural fibres ignited the manufacturing sectors to go for higher altitudes in engineering industries. This is due to the health hazard and environmental problems faced in manufacturing and disposal of synthetic fibres. This study was undertaken to analyse the suitability of new natural fibre as an alternative reinforcement for composite materials. In this paper, tensile, flexural and impact test is made for the woven alovera and kenaf (AK), sisal and kenaf (SK), alovera, sisal and kenaf fibre hybrid epoxy composites (ASK). The composite laminates are made through a hand-layup process. The surface analysis is studied through scanning electron microscopy. From the investigation the SK hybrid composite shows good tensile property, AK hybrid composite shows better flexural property and the best impact strength is observed for ASK hybrid composite. The natural fibres slowly replace the synthetic fibres from its environmental impact, marching towards a revolution in engineering materials.     

Complex permittivity and microwave absorbing properties of SiC fiber woven fabrics

A comparative investigation of electric conductivity, complex permittivity, and microwave absorbing properties of KD-1 and Nicalon-202 fibers in the form of fabrics within the range of 8.2–12.4 GHz (X band) has been carried out. The electric conductivity value of KD-1 filaments is two orders larger than Nicalon-202. Both the values of real part (ε′) and imaginary part (ε″) of KD-1 fabrics are larger than their counterparts of Nicalon-202 especially the imaginary part, which is in agreement with larger DC conductivity (σ_d). The surface morphology and chemical component were characterized by SEM, EDS, Raman spectroscopy and XRD, which shows that both the KD-1 and Nicalon-202 SiC fibers are rich in carbon, while there is rich carbon layer on the surface of the former and the degree of order in the free carbon phase is higher compared with the latter. In addition, the amount of amorphous Si–C–O phase of KD-1 fibers is higher while the SiC crystal is smaller than Nicalon-202. The free carbon on the surface of KD-1 fibers can establish electric conductivity network. The larger ε″ and ε′ of KD-1 fabrics are believed to be mainly caused by conductive network established by rich carbon outer layer and relaxation polarization enhanced by more Si–C–O phase. The reflection loss of KD-1 and Nicalon-202 fabrics is −3.5 to 0.7 and −5.1 to −4.3 dB, calculated according to tested complex permittivity.     

预定型机织物剪切变形实验研究

在改进像框实验的基础上,对斜纹和缎纹预定型碳纤维织物的剪切性能进行了实验观察。研究发现,预定型机织物的剪切机制与织物剪切相似。根据实验结果,从定型剂的浓度和织物结构分析了预定型织物的剪切性能。随着定型剂浓度提高,织物的折皱角越大,织物剪切性能越差;与预定型斜纹织物相比,预定型缎纹织物相对较容易成型,剪切载荷较小。利用立式显微镜观察剪切过程中纱线宽度的变化,拟合得到了宽度变化方程,建立预定型机织物的折皱角模型,预测结果与实验结果误差在2°内,证明了该模型的有效性。     

Effect of statistical yarn tensile strength on the probabilistic impact response of woven fabrics

The probabilistic impact response of flexible woven fabrics can be described through the V₀–V₁₀₀ or probabilistic velocity response (PVR) curve which describes the probability of fabric penetration as a function of projectile impact velocity. One source of variability that affects the probabilistic nature of fabric impact performance is the statistical distribution of yarn tensile strengths. In this paper the effects of the statistical yarn strength distribution characteristics on the probabilistic fabric impact response are computationally studied using five different strength distributions with differing mean strengths and distribution widths. Corresponding fabric PVR curves are generated for each strength distribution using a probabilistic computational framework that involves randomly mapping yarn strengths onto the individual woven yarns of a fabric finite element model and then running a series of impact simulations for the case of a four-sided clamped fabric impacted at the center by a spherical projectile.     

Shear deformation and micromechanics of woven fabrics

This paper includes an experimental study and a mathematical analysis of the shear deformation of woven fabrics by using picture-frame type shear testing. Four types of weaves were tested and compared: a loose plain weave, a tight plain weave, a twill and a satin weave. The locking shear angle was determined both in picture-frame tests and manual shear tests. The experimental data presented for each fabric include curves of shear load–shear stress as a function of either the shear angle or the shear rate, and measured locking shear angles. The shear deformation data were analysed by following elasticity principles and taking into account the effects of fibre inextensibility. A microstructural analysis was carried out in all four fabrics to investigate the shear locking on the basis of a geometrical approach and the maximum packing fibre fraction.     

预浸机织织物二维剪切性能模型

利用安装在拉伸试验机上的像框剪切装置, 研究了平纹预浸碳纤维机织织物的剪切行为。研究发现,预浸碳纤维织物的剪切行为与织物的分阶段剪切行为类似。根据实验结果, 分两个不同剪切阶段建立了预浸碳纤维织物的二维剪切性能模型。在剪切初始阶段, 利用扭力弹簧来模拟纱线交叉点之间的剪切摩擦, 通过实验确定了扭力弹簧扭转刚度系数。在剪切第二阶段, 给出了载荷与剪切角之间的关系模型。试验结果表明, 利用扭力弹簧可以很好地模拟剪切初始阶段的剪切摩擦。      

Referenceless segmentation of flaws in woven fabrics

The automatic segmentation of flaws in woven fabrics is achieved by applying Fourier analysis to the image of the sample under inspection, without considering any reference image. No prior information about the fabric structure or the defect is required. The algorithm is based on the structural feature extraction of the weave repeat from the Fourier transform of the sample image. These features are used to define a set of multiresolution bandpass filters, adapted to the fabric structure, that operate in the Fourier domain. Inverse Fourier transformation, binarization, and merging of the information obtained at different scales lead to the output image that contains flaws segmented from the fabric background. The whole process is fully automatic and can be implemented either optically or electronically. Experimental results are presented and discussed for a variety of fabrics and defects.     

Mechanical properties of hybrid fabrics in pultruded cement composites

This work concerns the tensile properties of cement-based hybrid composites manufactured as: (i) sandwich composites that combine different layers of single fabric types; and (ii) hybrid composites, made from several yarn types within the same fabric. Hybrid combinations of low-modulus fabrics of polyethylene (PE) or polypropylene (PP) and high-modulus AR glass or aramid fabrics were prepared by the pultrusion process and tested in tension. Influence of pultrusion direction on the results was one of the parameters studied. It was found that hybrid composites made from PE and AR glass sustain strains better than 100% AR glass composites, and are stronger than a single PE fabric composite. A hybrid fabric composites made with combination of high strength–high cost aramid and low stiffness–low cost PP yarns performed better than a single aramid fabric composite relative to their reinforcing volume contents. Results show that making hybrid composites is an attractive option for cement-based elements. The performance of hybrid fabric composites is also influenced by the arrangement of fabric layers in the laminates. Composites with brittle and relatively strong fabrics (glass) at the mid-section and ductile fabrics (PE) near the surfaces of the composite performed better in tension than composites with the opposite arrangement.     

Basalt woven fiber reinforced vinylester composites: Flexural and electrical properties

A preliminary comparative study of basalt and E-glass woven fabric reinforced composites was performed. The fabrics were characterized by the same weave pattern and the laminates tested by the same fiber volume fraction. Results of the flexural and interlaminar characterization are reported. Basalt fiber composites showed higher flexural modulus and apparent interlaminar shear strength (ILSS) in comparison with E-glass ones but also a lower flexural strength and similar electrical properties. With this fiber volume fraction, scanning electron microscopy (SEM) analysis of the fractured surfaces enabled a better understanding both of the failure modes involved and of points of concern. Nevertheless, the results of this study seem promising in view of a full exploitation of basalt fibers as reinforcement in polymer matrix composites (PMCs).     

Mathematical modelling of capillary micro-flow through woven fabrics

The present work considers the capillary flow of Newtonian fluids along a single fibre yarn and through a plain-woven fabric. In the first case, one-dimensional Darcy's flow is considered through the micro-pores of the fibre yarns. In the second case, two-dimensional in-plane network infiltration is considered through the micro-pores of the network of fibre yarns in the fabric. In both cases predictions include the infiltration length as a function of time, the apparent permeability and the capillary pressure. The latter case also includes the number of unsaturated transverse yarns and the degree of saturation. All predictions are compared to experimental measurements and the agreement is very good.     

Interlaminar fracture properties of weft-knitted/woven fabric interply hybrid composite materials

An experimental study has been undertaken to characterize the delamination behavior and tensile properties of interply hybrid laminated composites reinforced by interlock weft-knitted and woven glass fiber preform fabrics. The hybrid composites, comprising the alternate layers of interlock and uniweave fabrics, were compared to interlock knitted (only) and uniweave (only) composites with respect to delamination and tensile performances. Mode-I double cantilever beam and mode-II end-notched flexure tests were carried out to assess the interlaminar fracture toughness using aluminum-strip stiffened specimens. The mode-I and mode-II interlaminar fracture toughness values, G _IC and G _IIC, for the hybrid composite were about three and two times higher than that for the uniweave composite, respectively. The tensile strength and modulus of the hybrid composite were 315 MPa and 12.8 GPa in the wale direction, respectively, demonstrating that the strength and modulus were found to be slightly lower than those of the uniweave composite, and significantly improved in comparison with the interlock knitted composites.     

Hybrid composites based on aramid and basalt woven fabrics: Impact damage modes and residual flexural properties

The low-velocity impact behaviour of hybrid laminates reinforced with woven aramid and basalt fabrics and manufactured by resin transfer moulding was studied. Specimens with different stacking sequences were tested at three different energies, namely 5, 12.5 and 25 J. Residual post-impact properties of the different configurations of aramid/basalt hybrid laminates were characterized by quasi static four point bending tests. Post-impact flexural tests have been monitored using acoustic emission in order to get further information on failure mechanisms. Results indicate that hybrid laminates with intercalated configuration (alternating sequence of basalt and aramid fabrics) have better impact energy absorption capability and enhanced damage tolerance with respect to the all-aramid laminates, while basalt and hybrid laminates with sandwich-like configuration (seven basalt fabric layers at the centre of the laminate as core and three aramid fabric layers for each side of the composite as skins) present the most favourable flexural behaviour.     

On the mechanical response of woven para-aramid protection fabrics

The initial condition of the structure of the fabric's knitting form, before applying a load, is closely correlated with the performance of the fabric under loading. The present study focuses on the mechanical response of para-aramid protection fabrics under tensile loading and suggests a knitting angle as a considerable factor for the behavior of the fabric. A global and a local method are applied to monitor the effect of this angle on the fabric's performance and deformation mechanism. The experimental results indicate that this angle affects both the fracture propagation mode and the fracture toughness. A failure onset detection mode, based on this angle, is also suggested, followed by a calculation of the further feasible deformation of a permanently deformed zone until the next failure.