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Many users relate additive manufacturing (AM) directly with fast and high-quality prototyping and manufacturing. Nevertheless, already within the different printing techniques there are significant...

In this study, an algebraic model and its experimental verification was carried out to investigate the effect of moisture content on the heat loss that takes place due to conduction of sock fabrics. The results show that increasing moisture content in the studied socks caused a significant increase in their conductive heat loss. Plain knitted socks with different fiber composition were wetted to a saturated level, and then their moisture content was reduced stepwise. When achieving the required moisture content, the socks samples were characterized by the Alambeta testing instrument for heat transfer. Three different existing modified mathematical models for the thermal conductivity of wet fabrics were used for predicting thermal resistance of socks under wet conditions. The results from both ways are in very good agreement for all the socks at a 95% confidence level. In the above-mentioned models, the prediction of thermal resistance presents newly a combined effect of the real filling coefficient and thermal conductivity of the so-called “wet” polymers instead of dry polymers. With these modifications, the used models predicted the thermal resistance at different moisture levels. Predicted thermal resistance is converted into heat transfer (due to conduction) with a significantly high coefficient of correlation.

In the research project presented in this paper, the effects of welding width, pressure force, power, and speed of ultrasonic welding parameters on hydrostatic pressure resistance were examined. A flexible and lightweight PVC-coated hybrid textile material with uniform thickness was used for weather protection purposes. Three main welding parameters at three different levels were selected based on the preliminary test results involving welding widths of 6 and 12 mm. A lapped type of seam was applied for ultrasonic welding and conventional joining techniques. A conventionally sewn zigzag seam was produced using three main factors at two different levels according to the application area. To avoid seam permeability, the conventional seam was sealed with tape by means of hot-air tape welding and subsequently investigated regarding its hydrostatic pressure resistance. The hydrostatic pressure resistance value of the conventional seam was then compared with ultrasonic weld seams of 6 and 12 mm welding width, and its parametric influence on the quality of the seam was analyzed. The result shows that the ultrasonic weld seam with a 12 mm welding width provided a higher hydrostatic pressure resistance than the 6 mm welding width and the conventionally sewn seam. Statistical analyses were also carried out to prove the significant effect of welding process parameters on hydrostatic pressure resistance, whereby the obtained results were statistically significant. A suitable nonlinear numerical model was also developed to predict the hydrostatic pressure resistance.

Because of the decisive role of tow orientation in braided fabric on the mechanical performance of composite, having an accurate tow orientation prediction method for each specific mandrel shape is a cornerstone for applying circular braiding technology. This work presents a numerical method to predict the tow orientation on an irregular, constant cross-section mandrel. In this numerical method, the cross-section of the mandrel is approximated by a series of line segments, and then the surface meshes of the mandrel are generated in STL format. A set of kinematic equations, which was deduced from the simultaneous motion relationship between the translation of the take-up device and the rotation of the spools, was used to calculate the sequence of the deposition points located on the edges of surface mesh for the approximated tow orientation. Braiding experiments for various process parameters were conducted on a mandrel with a specially designed cross-section manufactured using a three-dimensional printer and the angle of the braiding tow was measured. The influence of translation speed, shape of cross-section and convergence region length on braiding angle were analysed via a comparison of the simulation results and the experimental data. Two types of variation of the braiding angles in the braided fabric and its influence factors are also discussed in detail. It was shown that the numerical method, which can rapidly predict the braiding angle for an irregular, constant cross-section mandrel, is beneficial for optimizing the process parameters for hollow composite component manufacture.

This paper presents latest development of a modelling algorithms and simulation results, related to 3D braiding machines with individually driven switches and horn gears. The early developed 3D braiding machines and the current software from the braiding producer covers only rectangular sets of horn gears. Based on complete emulation of the braiding process with the carrier motion, a generalized method for the simulation of any configuration of horn gears with different sizes was developed and reported earlier by the author. In this work, an extension of the algorithms with individually controlled switches is presented. These switches allow production of profiles for textiles reinforced composites with complex cross section, changing during the production. The machine emulation can be coupled with FEM based braiding process simulation and the complete product can be virtually produced and analyzed.

High X-ray absorption and, therefore, excellent X-ray protection properties are related to heavy chemical elements. Therefore, a composite fiber for X-ray protection applications was developed consisting of an organic cellulose part and an inorganic part. Whereas the preceding part provides the common properties connected to fibers and the latter part ensures the X-ray protection effect. The treatment of this composite fiber along the whole textile chain is presented and the possible usage as a common textile fiber in spinning and knitting processes is impressively demonstrated. Textile properties such as air permeability and abrasion stability are successfully tested. Furthermore, the microscopic structure is characterized by means of optical and scanning electron microscopy. The X-ray protective properties are determined by transmission experiments. The realization of a textile product is shown by production of a glove, where protective properties are impressively shown by 3D X-ray tomography. A...

This paper deals with performance properties related to human thermo-physiological comfort of three-layer textile systems used for the production of outerwear for cold protection. The transfer of heat and fluids through the compound single layers (woven and non-woven) is investigated and compared to the heat and mass transfer of the systems for clothing. Six characteristics are measured for both single layers and systems of layers: thermal resistance, air permeability, water vapor resistance, relative water vapor permeability, the accumulative one-way transport index and overall moisture management capacity. For each of the characteristics, regression analysis is applied to prove or reject the proposed mathematical dependencies between the transfer abilities of the single layers and the respective systems. The results obtained showed that the fluid transfer abilities of the single layers applied in clothing for cold protection strongly affect the fluid transfer ability of the system of layers, while the heat transfer of the system is dominated by the heat transfer ability of the thermo-insulating layer. The proposed approach for assessment of the transfer processes through a system of layers for the production of outerwear for cold protection could be successfully applied in the design of other textile and clothing items, produced by using systems of different textile layers.

This paper presents an experimental investigation regarding the influence of the thermal and chemical treatment over the strength of one type industrially used basalt fibers. The fibers are heated at 160℃, 320℃, 480℃, 640℃, or 800℃ using a muffle furnace for 32, 64, 128, or 256 min. In the second series, the fibers are treated with 10% to 30% H2SO4, HCl and NaOH aqueous solutions for 48 h. The strength of the fibers is tested after the different treatments and is found to be decreased even after moderate heating temperatures. The fibers are as well investigated by scanning electron microscopy and energy-dispersive spectroscopy. By energy-dispersive spectroscopic method, the surface composition of the fiber is determined and significant changes in composition are observed even after treatment at 160℃. Obviously the change in surface composition is related to the change in the strength. A possible explanation can be the decomposition of the sizing on the fiber surface.

This paper presents a comprehensive experimental study, conducted on a series of woven and non-woven fabric samples from different materials (cotton, polyester, and polyamide) and 14 three-layer systems of textile materials, used for production of outerwear clothing for protection from cold. Heat and mass transfer properties, related to the thermophysiological comfort of the outerwear clothing, namely conductive thermal resistance, water vapor resistance, relative water vapor permeability, air permeability, accumulative one-way transport of liquids, and overall moisture management capacity, were determined for the system of layers and the compound single layers. The transfer properties of the single layers were presented as a function of their thickness, mass per unit area, and areal porosity. The transfer properties of the system of layers were presented as a function of the thickness, mass per unit area, and bulk density of the systems. Regression analysis was applied to derive regression equations. The results obtained allowed assessment of the existence and trend of the influence, as well as evaluation of the strength of the dependences.

This chapter represent applications of the topologically generated geometries of textile structures as initial geometry for FEM computations, performed by the author or his students. Reported are examples of knitted structures with HyperWorks and LS-Dyna and braided structures with Impact-FEM and VTMS. Examples of homogenisation of textile reinforced composites are reported using Voxelisation or using the method of inclusions within TexComp.

The cloths and other ready to use products are normally represented as 2D objects. For thier modelling are used shell or plate elements, which elastic behaviour has to be identified bevore the modelling. The yarn level is seldom modelled until now for the ready structures, but with the increasing computational power this will become possible. This chapter presents a method of the structural cells, as topological units of the yarn level structure. Some direct applications in the area of spacer fabrucs and tubular fabrics are demonstrated. Issues of the modelling of cutting of fabrics are discoussed.

Common textile materials as cotton or polyester do not possess reliable X-ray absorption properties. This is due to their morphology and chemical composition in particular. Common fibers are built up from organic polymers containing mainly the elements carbon, hydrogen, oxygen and nitrogen. These “light” elements only have low X-ray absorption coefficients. In contrast, inorganic materials composed of “heavy” elements with high atomic numbers, e.g. barium or bismuth, exhibit X-ray absorption coefficients higher by up to two orders of magnitude. To obtain a flexible yarn with high X-ray absorption properties both these materials, the organic polymer and the inorganic X-ray absorber, are combined to an inorganic/organic composite fiber material. Hence, as the organic component cellulose from modified Lyocell-process is used as carrier fiber and blended with inorganic absorber particles of low toxicity and high absorption coefficients, as bariumsulphate, bariumtitanate or bismuthoxide. A content of inorganic absorber particles equally distributed in the whole fiber of up to 20% is achieved. The composite fibers are produced as staple or filament fibers and processed to multifilament or staple fiber yarns. The staple fiber yarns are rotor-spinned to increase the comfort of the subsequent textile material. Several woven fabrics, considering multilayer structure and different warp/weft density, are developed. The energy dependent X-ray shielding properties are determined in dependence on the different yarn compositions, yarn types and structural parameters of the woven fabrics. As a result, a production process of textile materials with comfortable and dedicated X-ray absorption properties is established. It offers a promising opportunity for manufacturing of specialized textiles, working clothes or uniforms applicable for medicine, air craft and security personal, mining as well as for innovative composite materials.

Triaxial braided reinforcements are extensively used as main constituent materials in various biomedical and composite applications. The material parameters, and the choice of process parameters during the braiding process, have a significant influence on the geometrical and mechanical properties of these reinforcements. In this study, the manufacturing on a braiding loom of triaxial braids with a large range of braiding angle is presented. On these samples geometrical properties, as bias yarn length, crimp, linear mass, are experimentally identified in function of the braiding angle. From uniaxial tests, the specific tensile behavior of these braided fabrics is characterized. These results are compared with analytical models described in the literature. Associated to this experimental approach, the geometry of these triaxial braids is numerically modeled thanks to TexMind Braider software dedicated for three-dimensional creation of braided structures. Comparison between characteristics experimentally identified and computed is analyzed.

3D spacer fabrics are a type of sandwich structure consisting of two separate multifilament fabric outer layers linked together with a layer of spacer monofilaments . They have been widely used as energy absorbing materials and composite reinforcement. The microstructure features and compression behavior of a typical spacer fabric were investigated experimentally and numerically in this study. Eight unit cells with 64 spacer monofilaments were reconstructed from scanning of the fabric via Micro X-ray computed tomography (μCT). The geometric variations of the reconstructed spacer monofilaments were analyzed quantitatively. It was found that spacer monofilaments in different unit cells are different in length, curvature and torsion. A series of FE models based on different numbers and combinations of the identified unit cells were created. The FE simulation results showed that the geometric variations of spacer monofilaments have strong influence on the compression behavior, and the model with shorter length, lower curvature and torsion of spacer monofilaments has higher compression resistance. The compression resistance in the densification stage of the fabric increases with increasing the number of spacer monofilaments adopted due to more evident interactions among spacer yarns. This study provides an in-depth understanding on the compression behavior of spacer fabric.

International audience; In the production of body armor panels, multilayer aramid fabrics are normally used. A main problem of these panels is the high weight and consequential lower comfort for the wearer. In a recent survey it was shown that most officers in the United States would prefer an improved comfort and also reduced weight in their ballistic vests. To reduce layers with a concomitance of the same safety standards, the panel has to be improved. One solution is to reduce the slippage of the yarns during the penetration of the knife and with this to increase the absorbed impact energy. The tests showed that the placement of a layer of wool fabric on the top of the aramid panel changes the penetration behavior. The main goal of this work is the investigation of the influence of the woven wool structure over the penetration of aramid panels. For this investigation, the stab resistance of five aramid fabrics with different properties and patterns combined with one layer of wool on the top and bottom of the panel has been tested and compared against pure aramid panels, according to the VPAM test instruction “Stab- and Impact Protection”. In addition, an optical evaluation of the stab tests has been done using a high-speed camera. Also, the stab recess in the aramid layers was evaluated optically, using a digital microscope. The experimental results confirm that wool can increase the stab resistance of body armor panels, but results are dependent on the properties and pattern of the aramid fabrics, too.

Woven belts and tapes are used in wide area of technical applications and as reinforcement for composites. Contrary to the art design of the woven fabrics, where the colour and pattern appearance is more important than the mechanical parameters, in the technical products the strength, stiffness, compressibility and other mechanical properties have the importance.

This work presents an investigation about the bending rigidity of double braided ropes. The braid structure is subjected to bending condition by fixing one end and leaving the other end to hang freely and bend under its own weight to a set deflection limit and its length is measured. The length and deflection are then used to calculate the bending stiffness and bending moment using the beam deflection equation. The bending behavior of single braided and double braided tubular ropes is also studied and compared. Highest bending rigidity was obtained with double braided tubular ropes compared to single braided tubular ropes. It is observed that, braided structures are very weak under transverse loading, their strength are improved when more structural layers are braided together. High braiding angle of braid structures is observed to improve bending stiffness and bending moment.

In this study, the mechanical behavior of double braided tubular ropes under tensile loads is studied experimentally and analytically. The outer braid is referred as the braid cover and the inner braid is considered as an elastic tubular braid core. A predictive model of the mechanical response of the braids based on the constituent monofilament (yarn) properties and braid geometry based on known research works was used. The model has accounted for the changes in the braid geometry, including braid angle and diameter. Both braid angle and diameter are found to be critical design parameters. Image analysis is employed to experimentally characterize the structural parameters of the braids and their deformation. The structures are tested in tension and their stress–strain response is recorded. The experimental results have been compared to the theoretical stress–strain curves of braid cover-core structures and the results have been observed to agree well between them, though the theoretical model underestimates the Young’s modulus of the braid cover-core structure.

Mathematical model for calculation of the stress-strain behavior of the wound package is presented. It uses the split of the body of cylindrical layers with finite thickness under assumption for orthotropic, linear elastic behavior of the single layers. The numerical results demonstrate, that in certain cases the windings and layers lose their tension forces, where the winding package loses its stability. Wound structures are widely used in the textile production for storing (depositing) and transporting of textile yarns during the production of textiles. Each package usually consists of only one yarn, which is wound over the cylindrical or conical tube. The wound structure is stable because of the light tension in the yarn. The stability of the structure depends on a large number of processes and material parameters. These parameters and their interactions are still not investigated completely [1]. Well known are stability conditions for piece of yarn over certain surface, based on the static friction coefficient and the geodesic angle of the surface. These conditions do not describe completely the stability of the whole package. In some cases, the inner or outer layers of the bobbin are being deformed significantly and the package is no more usable. In order to analyze and predictthe conditions, where the package loses its stability, the stress-strain behavior of wound packageshas to be investigated. There are works in some particular fields, for instance for the cases of filament winding and warp beams winding [2], [3], [4], [5] etc., as well as for fabric rolls [6]. Here we use the same mathematical model to obtain the stress-strain distribution, but the winding layers are represented as orthotropic (not isotropic, as in many in earlier works) material. The higher orthotropy causes numerical problems. They are avoid by using analytical solution with software MAPLE.