Marcin Barburski

Picture Frame Test of Woven Composite Reinforcements with a Full-Field Strain Registration:

Results of picture frame shear tests with optical registration of the strain fields are presented for glass (plain and twill, three types) and glass/PP woven (plain and twill) fabric reinforcements for composite materials. Four problems were investigated. (1) How does the shear diagram vary with differences in test conditions? The major factor is the sample pretension, which is influenced by its gripping, removing/preserving yarns near the grips and “conditioning” in the shear cycles. (2) Does the shear of the fabric differ from the pure shear prescribed by the frame? The differences are normally negligible. (3) How large are the variations of the local fabric shear? The scatter of the local fabric shear does not exceed 2°. (4) How is shear of the fabric translated into deformations of the yarns on the micro-scale? Different stages of the fabric deformation are identified: rotation of the yarns followed by their lateral compression.

Carbon composites based on multiaxial multiply stitched preforms. Part 2. KES-F characterisation of the deformability of the preforms at low loads

Deformability of multiaxial multiply stitched carbon preforms is studied at low loads using the Kawabata evaluation system. Results of the test in tension, shear, compression, bending and friction are reported. Both bi- and quadriaxial fabrics demonstrated a fairly uniform behaviour. The general features of deformability are formulated and generic values of parameters for evaluation purposes are proposed.

Analysis of the mechanical properties of conveyor belts on the three main stages of production

Conveyors belts are used wherever it is necessary to transport materials quickly and promptly. They are made of fabric-rubber core (carcass) and rubber covers. The carcass may consist of several spacers made of synthetic polyamide–polyester fabrics impregnated with a solution of latex that provides an intermediate layer to prevent delamination of the vulcanized composite. The main goal of this research work is to analyse the mechanical properties of conveyor belts during three main stages of production: raw fabric, fabric impregnated with latex, and conveyor belt. For this purpose, nine fabrics of different weaves with a width of 1 m were produced with polyester warp and polyamide weft threads. The fabrics were coated with latex and then vulcanized. Subsequently, the structural parameters and the mechanical properties of each product were measured at each of the three stages of conveyor belt production. This article presents the effect of fabric structure on the mechanical properties of the products of these three production stages. Results show that differences in the mechanical properties of products at different stages of conveyor belt production depend on number of intersections of yarns in woven fabrics. In addition, significant differences were observed in the mechanical properties depending on the applied weaves.

Analysis of the pipe conveyor belt pressure on the rollers on its circuit

Conveyor belts are widely used in almost all industries, agriculture and construction. They are made of fabric and rubber carcass and rubber covers. Pipe conveyor belts are a relatively new technology in comparison to the conventional conveyor belts, as they offer many advantages and additional features. However, one of the main problems concerning pipe conveyor belts and appearing at the close of the belt is the collapse of the edges inward. This causes gaping of the belt, which may result in a loss of material being carried. The main purpose of the performed study was to develop a new woven structure which would restrict the undesirable effect of collapsing the edges of the pipe conveyor belt inward. To achieve the main objective, it was pre-determined, how the weave influences the piping of the belt. Nine fabrics of different weaves were made with polyester warp and polyamide weft. New position was built as part of the research to measure the pressure of piped belt on a set of rollers located on its circuit. Analysis of the results allowed development of the new woven structure with a variable rigidity on the belt width. In one woven fabric three different weaves were used symmetrically to its longitudinal axis. The study of the newly designed belt showed that it has better closing properties and that the effect of collapsing the edges inward was eliminated.

Experimental characterization of steel fibre knitted fabrics deformability

Extremely fine steel fibres (12 μm diameter) are spun into yarns and then knitted into fabric, which is used, among other applications, as a mould cover in forming of automotive glass. High requirements of the glass quality (absence of dioptric distortions) ask for a perfect evenness of the mould cover surface, which depends on the local distortions of the fabric, created during tensioning of the fabric over the mould. These distortions can be predicted using nonlinear finite element draping simulation, providing that the material laws describing the fabric resistance to deformation are known. This article describes an experimental procedure for derivation of such laws using biaxial tension, shear, and compression tests. Test results for a typical steel fibre knitted fabric are presented together with an example of the draping simulation.

Experimental Study of Steel and Glass Knitted Fabrics Thickness under Pre-Strain and Shear

In this paper the compression behaviour after different pre-strain and different shear angle of steel and glass fibre knitted fabrics will be analysed. These types of materials are used during the production of automotive windshields and other glasses in a car. The production of a windshield involves a step whereby the glass is deformed to the desired shape by using a mould. It is important that during this forming step the glass is not damaged and that the optical quality of the glass falls within the specifications of the customer. A knitted steel fibre fabric covers the mould. Since this fabric comes in direct contact with the glass, it is a key factor that determines the quality of the formed windshield. Variation of the fabric thickness can affect the optical quality of the glass. Thus far fabric very often manufacturers operate on the basis of empirical trial and error results to design their products. The challenge of the present work is to establish an experimental procedure for identification of the material laws for knitted fabrics deformation resistance. The paper describes an experimental procedure for derivation of the fabric thickness dependence on its deformation, using biaxial tension, shear and compression tests. The compression tests are performed on an Instron mechanical testing machine. During the test, a load cell (1 kN) pushes down with a constant speed of 1 mm/min onto the sample, compressing it. The load cell is attached to a cylinder which has a diameter of 70mm. The knitted fabrics was tested in the relaxed state and after pre-tension on the biaxial tester with pre-strains of 5x5%, 10x10%, 15%x15%, 0x10%, 10x0%, 0x20%, 20x0% and they was also tested after different shear angle (5°, 10°, 15°, 25°). Difference of thickness of fabrics after pres-strain is till 90 µm and for 25°shear angle is about 30 µm. Acknowledgements The work was funded by the grant 631/MOB/2011 of the Polish Ministry of Science and High Education, with the support from K.U.Leuven and N.V. Bekaert S.A.

Influence of oxidation on steel fiber yarn and knitted fabric properties

Fine steel fibers are spun into yarns and then knitted into fabric, which is used, among other applications, as a high resistance separation material in forming of automotive glass. In press bending, the glass sheet is first heated to temperature of about 650℃ and subsequently vacuum pressed on a mold covered by steel fiber knitted fabric. This high temperature changes the surface of fibers by oxidation, which influences mechanical properties of yarn and fabrics. The paper investigates interrelation between change of yarn and fabric properties caused by oxidation. Higher tensile resistance of the oxidized fabric corresponds to higher bending stiffness and higher friction of the oxidized yarn. The change of the fabric biaxial tension behavior influences the optical quality of the formed glass.

Steel fibre knitted fabric for automotive glass forming: Variations of the fabric thickness on the mould and glass optical quality

Extremely fine steel fibres (12 µm diameter) are spun into yarns and then knitted into fabric, which is used, among other applications, as a mould cover in the formation of automotive glass. High requirements of the glass quality (absence of dioptric distortions) ask for a perfect evenness of the mould cover surface, which depends on the local distortions of the fabric created during tensioning of the fabric over the mould. In this paper, compression behaviour of steel knitted fabrics combined with the fabric deformation in biaxial tension and shear is studied. Interaction of the fabric with the formed glass depends on the local changes of the fabric compression behaviour due to local fabric deformations on the mould. The deformation of the fabric is further linked to quality of the glass using quantitative optical distortion system based on moiré patterns to measure glass dioptric distortions.

Internal Structure of the Sheared Textile Composite Reinforcement: Analysis Using X-Ray Tomography

X-ray micro computed tomography (Micro-CT) is a non-destructive technique that can provide information on the internal structure of materials. The purpose of micro-CT is to assess the presence of defects as well as characterizing internal structures and potential damage present in the produced part. Simple shear is an interesting deformation mechanism for woven fabric draping. The internal structure change of the carbon fibre twill fabric after shear deformation is chosen as a subject of this paper. Parameters of the mesoscopic internal structure of the woven fabric like cross section, shape, area, and middle line coordinates can be obtained from micro-CT images through image processing procedures. Details of the image data processing for sheared fabric cross sections are discussed. This paper illustrates the possibilities of micro-focus computer tomography in materials research, namely for defining geometrical properties of textile. Image processing is also used for the recognition of fibre direction in the yarns. Described methodology can be applied for determining structure of a fabric, and the results can be used for further micromechanical modelling. Identification of the fibres orientation is important for estimation of the mechanical properties of composites and can be achieved with image processing techniques.

Influence of designs of weaves on acoustic attenuation of fabrics

The results of acoustics tests of different structure woven fabrics are presented. The researches were performed in the aeroacoustic anechoic chamber. Ten fabrics were tested (four of them with honeycomb 3D design) to check their acoustic properties. The tests were conducted inside lower and medium acoustical frequency zones. The presented studies showed that all fabrics with honeycomb weaves had much less attenuation than other fabrics, mostly due to less dense structures at higher thicknesses and more open internal structures. Having analyzed the obtained results, some comments are shown and possibilities of using such woven structures are proposed.