Dry Fabrics Research Articles

High sensitivity measurements of thermal properties of textile fabrics

A new testing apparatus is proposed to measure the thermal properties of fabrics made from polymeric materials. The calibration of the apparatus and the data acquisition procedure are considered in detail in order to measure thermal conductivity, resistance, absorption and diffusivity constants of the tested fabric samples. Differences between dry and wet fabrics have been carefully detected and analyzed. We have developed a new measurement protocol, the ThermoTex protocol, which agrees with the UNI EN 31092 standard and entails accurate quantification of the experimental errors according to a standard statistical analysis, thus allowing a rigorous investigation of the physical behavior of the phenomena involved. As a consequence, our equipment exhibits great potential for optimizing the thermal comfort of fabrics, according to the market demand, thanks to the possible development of a predictive phenomenological theory of the effects involved.

Enhancements to Modeling Dry Fabrics for Impact Analysis

The focus of this paper is on improving the modeling of dry fabric-based systems widely used in propulsion engine containment systems. Simulations of fabrics under impact using finite elements (FEs) provide valuable insight into the mechanics of fabric behavior and its energy absorption characteristics. In this model, the fabric is treated as an equivalent continuum model composed of thin shell elements. The fabric is made of simple weave Kevlar49, whose behavior is characterized using uniaxial quasi-static and high-strain rate tension tests, picture frame tests, and friction tests. The methodology is general enough to be used with any dry fabric. Test results are used to determine the parameters used in the constitutive and FE models. The constitutive model is programmed as a user-defined material model. Details and results from FE simulations of a suite of 26 high-velocity ballistic test results are presented. Results show that the developed model provides very reasonable predictive capabilities.

An elaboration on the shear characterization of dry woven fabrics using trellising tests

AbstractMaterial characterization of woven fabric composites in dry form is one of the most crucial steps prior to the design and optimization of composite manufacturing processes. High stiffness of yarns under axial tension and low stiffness under in‐plane shear makes the latter the dominant deformation mode during draping of woven fabrics. Bias‐extension (BE) and shear frame (SF) tests are two widely used experimental setups for the characterization of woven fabrics under the shear (also called trellising) mode. This article outlines two general approaches for the characterization and normalization of data collected from the above standard tests. The first approach is based on the total energy absorbed by the fabric specimen along with the total work induced by the external force on the moving head of the tensile test machine. The second approach uses a variational formulation along with the principle of virtual work. Using both approaches, it is shown how, in the BE test, an auxiliary specimen with a different aspect ratio can be used to cope with the problem of nonuniform deformation (formation of three different shear regions) in the specimens. To illustrate the application of both methods, they are applied to predict in‐plane shear stiffness of a glass/PP plain weave under SF and BE tests. It is suggested that the shear stress can be used as a normalized parameter to compare data from different trellising tests. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

OS0301 メソスケールモデルによるドライファブリックの成形シミュレーション

OS0301 メソスケールモデルによるドライファブリックの成形シミュレーション

Dyeing of cotton fabric with a reactive disperse dye in supercritical carbon dioxide

A novel method was developed for the dyeing of cotton fabric with a vinylsulfone reactive disperse dye in supercritical carbon dioxide by carrying out dye adsorption (or uptake) and a catalytic fixation reaction with a phase transfer catalyst—Triethylene diamine (TEDA) in separated baths, respectively. The results show that the dye adsorption or uptake in supercritical carbon dioxide dyeing bath significantly depended on system temperature and pressure, as well as an appropriate experiment time; significant improvements of dye fixation efficiency and color strength on wet and dry cotton fabrics after a Soxhlet extraction were achieved by employing the catalyst of TEDA under various conditions. The fastness data indicate that acceptable rub and staining fastness rated at 4–5 was obtained for the dyed cotton samples involving a catalytic fixation step, except that a fading fastness should be further improved.

Friction Measurement on Dry Fabric for Forming Simulation of Composite Reinforcement

Forming processes are highly influenced by all the interface conditions between the tooling and the workpieces. For thermo-mechanical processes like hot forging or cutting processes friction is widely studied for a long time but for composite parts, it is not the case because the problem is not so crucial: forming forces are generally weak enough to allow the part be realized with any forming device; surface quality is not highly affected by the friction conditions; for pre-impregnated fabrics, the viscous or even fluid matrix acts like a lubricant and avoids defects due to sticking between fibre reinforcement and metallic tools. Nevertheless, friction seems to have an important role when precise simulations are expected. Up to now, few studies have been focussed on friction during composite forming processes. The aim of the present study is to make a contribution on that topic for an experimental point of view using an high precision device able to measure small friction forces. The relative fibre orientations can be monitored in order to explore the whole range of geometrical configurations. The final goal is to develop an efficient tool for finite element simulations of dry and pre-impregnated fibre fabrics accounting for the main specificity of fabrics, that is to say their strong anisotropy.

Analyze of the Contact Behaviour between Two Layers of Dry Glass Plain Weave Fabric

The market demand for thicker complex shaped structural composite parts is increasing. Processes of the Liquid Composite Moulding (LCM) family, such as Resin Transfer Moulding (RTM) are considered to manufacture such parts. The first stage of the RTM process concerns the preforming of the part. During the preforming of multi-layered reinforcements, friction between the plies occurs and needs to be characterize and then to be taken into account for the forming simulation. An experimental device designed to analyze the ply/ply, ply/tool and yarn/yarn frictions has been built. Tests carried out on a glass plain weave highlight specific contact behaviour for dry reinforcement fabric in comparison to non-technical textiles. This behaviour exhibits a substantial variation of the contact tangential loads which is directly related to shocks between the yarns. It demonstrated that period and amplitude of the friction response is directly related to the relative positioning of the samples but also to fabric meso-strucrure. In addition, the sample relative orientation has a significant influence on the friction response. The meso-architecture is responsible for the high variations of the friction coefficient as a function of the ply orientations for different fabrics. In addition, the friction response appears to be very sensitive to tests parameters like the relative positioning, orientation of the samples and the cycling. A honing effect classically observed in dry fabric testing has also been pointed out through cyclic experiments. It can be attributed to both fibre material abrasion and fibre reorganisation inside the yarn.

Computational Analysis of Low Velocity Impact Response of Composite Panels

The present work deals with the finite element modelling of low velocity impact response of different types of composite panels for body armour application. The response of these composites panels including bonded, unbonded and partially bonded laminates has been simulated using non-linear finite element package LS-DYNA. 2D shell elements in LS-DYNA have been used to represent both resin bonded glass fabric targets and dry woven glass fabric panels. The hemispherical shaped projectile is being modelled with 3D solid elements. The results of the numerical analysis showed that the value of contact force for the fully bonded composites panels was significantly higher than that observed for the panels consisting of dry woven glass fabric. However, the corresponding displacement was substantially lower. The similar simulation of the partially bonded composite panels has shown a reduction of both the contact force and the displacement. In addition, it has been shown that the partially bonded composite panels are capable of absorbing higher levels of energy than the rigid panels.

Design and Potentiality of an Apparatus for Measuring Yarn/Yarn and Fabric/Fabric Friction

The market demand for thicker complex shaped structural composite parts is increasing. Processes of the Liquid Composite Moulding (LCM) family, such as Resin Transfer Moulding (RTM) are considered to manufacture such parts. The first stage of the RTM process consists in the preforming of the part. During the pre-forming of multilayered reinforcements, frictions between the plies occur and need to be taken into account for the forming simulation. An experimental device designed to analyse the ply/ply and ply/tool frictions has been set up. The different set up steps of the device are described. First results are presented, which show the ply/ply friction behaviour for a glass plain weave fabric. A specific contact behaviour has been observed for dry reinforcement fabric in comparison to non-technical textiles. A honing effect classically observed in dry fabric testing has also been pointed out through cyclic experiments. It can be attributed to both fibre material abrasion and fibre reorganisation inside the yarn.

The effect of meso-level uncertainties on the mechanical response of woven fabric composites under axial loading

First, a finite element unit cell model of a glass fibre plain weave has been developed via an implicit subroutine. Because of the complex behaviour of fibrous yarns, a user-defined constitutive model needed to be defined. Material properties of yarns in the dry fabric are extracted by fitting the numerical model to experimental data under the uni-axial and bi-axial extension modes. Subsequently, two sets of geometrical and material-related meso-level uncertainty factors are studied using two-level factorial designs. Through the obtained half-normal probability plots, as well as the main and interaction factor effects, the most significant parameters are identified and discussed.

The Beat

The Beat

Multi-Scale Ballistic Impact Simulation of Dry Woven Fabric with Elastic Crimped Fibers

A material model has been developed to realistically simulate the behavior of loose woven fabrics with elastic crimped fibers subject to varying loading conditions such as in-plane and transverse loading. It is based upon a multi-scale micromechanical approach that includes the architecture of the fabric and the phenomenon of fiber reorientation, with fiber simplified as one dimensional elastic members with a single failure criterion. The material model is implemented as a user-defined subroutine in the explicit, non-linear dynamic finite element code LSDYNA. Results of fabric test simulations run in LSDYNA using this material model agree well with experimental results, demonstrating the material model s capability to accurately simulate ballistic impact of woven fabrics.

Mechanical characterization of flocked fabric for automobile seat cover

In this study, the tensile and tearing properties of substrate, substrate with adhesive and flocked fabric were studied with developed regression model which explains the relationships between fabric forms and tensile and tearing strength of the flocked fabrics. Warp and weft tensile strengths of wet flocked fabric are generally higher than the warp and weft tensile strengths of dry flocked fabric due to the high wet properties of cotton yarn. Weft tensile elongation of the flocked fabric is generally higher than warp tensile elongation due to the higher crimp ratio of the flocked fabric in the weft direction. Warp and weft tearing strengths of wet form substrate with adhesive and flocked fabric are higher than those of dry forms of substrate with adhesive and flocked fabric. One of the reasons could be the decrease of inter-yarn frictional forces due to the lubrication effect of the wet form of acrylic adhesive in substrate with adhesive fabric. Generally, tearing strength of flocked fabric is low compared with substrate. It was concluded that the regression model used in this study could be viable and reliable tools and flocked fabric could be considered as an alternative seat cover material to use in automotive industry.

The Utility of Polyester and Cotton as Swabbing Substrates for the Removal of Cellular Material from Surfaces*

Various types of cotton and polyester fabrics were tested to ascertain the optimal physical and chemical characteristics of fabrics needed for the removal of cellular material from surfaces. DNA quantitation values obtained on dried saliva stains showed no difference between cotton and polyester across all constructions and solvent conditions. Fabrics used dry and with water yielded higher quantitation values than those used with isopropanol. Quantitation values were also higher for wovens and nonwovens than knits across all solvent conditions. Low thread count fabrics used with water yielded higher quantitation values, but no correlation between thread count and quantitation values was observed with dry fabrics. A low thread count woven fabric, however, outperformed other tested fabrics when swabbing object surfaces in a highly used room. Full DNA profiles from fingerprints on glass surfaces were obtained with low thread count woven and nonwoven fabrics but not with the knit fabric tested.

Permeability of AR-glass fibers roving embedded in cementitious matrix

The Textile Reinforced Concrete (TRC) are developed and employed in some serious applications recently. Nevertheless, the utilization of High-Performance fibers to bear load at TRC is relatively low in comparison to dry textile due to incomplete penetration of cementitious matrix into bundle of fibers. The main attempt of this paper is addressing a simple model to evaluate the quantity of penetration of cementitious matrix into bundle of fiber by means of the geometry of the bundle of fibers and distribution of cement particle size. For this purpose, an ideal geometry for bundle of fiber is contemplated. Then on the basis of certain cement particle size distribution geometrical limitation for penetration of cement within bundle of fibers has been discussed. Accordingly, the influence of geometrical parameters of the fiber bundle namely, fibers diameters, packing density and titer of bundle on penetration is considered analytically. For experimental work an AR-glass tow is surrounded by knitting pillar stitch to reinforce the concrete. To change geometry of bundle of fibers, different knitting tension and stitch length are used during production of samples. Then, the prepared samples are embedded in fine grained concrete. The yarn pull-out test has been carried out to reveal the efficiency of fibers in concrete. Partial penetration of cement is demonstrated by model and verified by experimental work due to the geometric restriction of bundle of fibers.

Evaluation of Poisson’s ratio of textiles from mesoscopic models

The magnitudes of Poisson’s ratios can attain some peculiar values for woven fabrics, in contrast to conventional engineering materials, leading to unusual stress–strain relationships. A mesoscopic discrete model of dry fabric has been presently developed at the scale of the armor, accounting for the yarn–yarn interactions at the yarns crossing points. From a mechanical viewpoint, yarns are modeled as elastic straight bar elements representing stretching springs connected at frictionless hinges by rotational springs. The motion of each node along the yarn is described by a lateral displacement and a local rotation. The reaction force exerted by the transverse yarns at the contact points is calculated from Timoshenko theory, and the work of the reaction forces is incorporated into the structure potential energy. The equilibrium shape of textile structures submitted to external loading is identified as configurations achieving the minimum of the potential energy; a genetic search algorithm has been implemented for the determination of the global minimum of the total potential energy. The transverse behavior of plain weave fabric is evaluated in terms of the Poisson’s ratio, based on virtual simulations at the mesoscopic scale of analysis. Poisson’s ratio first increases towards a maximum due to the rapid shrinkage of the sample in the transverse direction, and decreases thereafter when the crimp changes are exhausted, with yarn extension as the main deformation mechanism. The influence of the mechanical properties of both warp and weft on Poisson’s coefficient is assessed. Scaling laws of the equivalent elastic properties of plain weave versus characteristic geometrical parameters (as the pick spacing) of the plain weave armor are determined. The predictions of the mesoscopic models provide a guideline for the design of woven fabrics.

TG studies of synergism between red phosphorus (RP)–calcium chloride used in flame-retardancy for a cotton fabric favorable to green chemistry

The combined effect between calcium chloride and red phosphorus (RP) on the flame-retardancy of a cotton fabric (woven construction massing 152 g/m2) has been studied in this work. The laundered bone-dried massed samples were impregnated with suitable concentrations of individual aqueous red phosphorus suspensions and/or calcium chloride solutions and some bunches were impregnated with appropriate admixed solutions of the both chemicals. An acceptable synergistic effect was then experienced by using an admixed bath containing 0.20 F red phosphorus and 0.20 M calcium chloride for impartation of flame-retardancy to a cotton fabric. By using a vertical flame spread test the optimum mass of the mixture needed to donate flame-retardancy was obtained to be about 5.88 g anhydrous additives per 100 g dry fabric. Thermogravimetry (TG/DTG) results concerning untreated and treated cotton fabrics at the optimum addition were obtained and their curves were compared and commented, fortifying the flame spread tests outcomes. It can be deduced that the applied treatment functioned as a catalyst at the combustion’s temperature of the polymeric substrate and, thermosensibilized the combustion process. This synergism is in favor of green chemistry as well as the economical and industrial view points.

Study of Mechanical and Thermomechanical Properties of Jute/Epoxy Composite Laminate

This article presents the development and the characterization of composite material (laminate) containing natural jute fiber reinforcement. Thermal characterization of jute fiber reinforcement shows the influence of the temperature on the mechanical behavior of fiber. At 180°C the jute fabric loses 50% of its mechanical characteristics. The laminate obtained by a process known as infusion is polymerized at a temperature lower than that which affects the mechanical properties of dry fabric. The digital image correlation carried out on laminated jute/epoxy (warp and weft direction) under tensile test shows the presence of a considerable gradient of deformation. This gradient is explained by the variability related to the local voluminal change of jute fibers of one place to the other and the nature of the weaving of the jute fiber. The three-point bending tests show a significant dispersion of rupture stress. The thermomechanical tests carried out on samples in the two principal directions, show that the thermal coefficient of expansion in warp direction is 48% larger compared to the weft direction. The thermogravimetric test shows that this laminate absorbs up to 4% water mass after 8 h in a climatic chamber with 70% moisture content.

Experimental analysis of the contact between layers of dry fabrics

A better apprehension of the behaviour of the interface between sheets of woven reinforcement during the forming of dry fabrics is necessary for a better optimization of the LCM processes. Even if numerical studies are carried out to simulate multi-layer forming, the contact between the layers is very roughly modelled using an approximate friction coefficient. To knowledge, only few preliminary results can be found concerning the contact fabric/fabric. In order to understand and characterize the contact between layers of different fabrics, a specific friction device has been designed in our lab. This machine was designed with the aim of carrying out tests as well on fabric/ fabric, fabric/metal but also fibre/fibre friction. After a short presentation of the device, results concerning steel/steel friction will be presented in order to validate the device. Then first results obtained about fabric/fabric contact will be given, in order to point out the contacts mechanism involved.

Development of Fabric Constitutive Behavior for Use in Modeling Engine Fan Blade-Out Events

The development of a robust and reliable material model for fabrics used to prevent fan blade-out events in propulsion engines has significant importance in the design of fan-containment systems. Currently, Kevlar is the only fabric approved by the Federal Aviation Administration to be used in fan-containment systems. However, very little work has been done in building a mechanistic-based material behavior model, especially one that can be used to quantify the behavior of Kevlar when subjected to high-velocity projectiles. Experi- mental static and high strain rate tensile tests have been conducted at Arizona State University to obtain the material properties of Kevlar fabric. In this paper we discuss the development and verification of a constitutive model for dry fabrics for use in an explicit finite-element program. Results from laboratory tests such as tension tests including high-strain rate tests, picture frame shear tests, and friction tests yield most of the material properties needed to define a constitutive model. The material model is incorporated in the LS-DYNA commercial program as a user-defined subroutine. The validation of the model is carried out by numerically simulating actual ballistic tests conducted at NASA-GRC and fan blade out tests conducted at Honeywell Aerospace Propulsion Engines.