Wyniki wyszukiwania - Biblioteka Nauki

1

Drape study on textiles for concrete applications

100%

Eckers V. , Janetzko S. , Gries T.

Autex Research Journal

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2012

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tom Vol. 12, no. 2

50--54

EN

Textile reinforced concrete (TRC) is an eco-friendly material with a high freedom in design. As soon as complex curved parts are to be designed, the question of the drapability of the reinforcing materials arises. Different process parameters can be modified in the production of the reinforcing textiles which strongly influence the handling and the draping behaviour. To be able to choose a textile structure in the design stage which fulfils the requirements concerning drapability, a new test method was developed. This article describes this test method and shows results of a test series on different textile structures, including a brief discussion of the results. Finally, a transfer to a sample geometry is shown.

2

Optimisation of the warp yarn tension on a warp knitting machine

100%

Pohlen V. , Schnabel A. , Neumann F. , Gries T.

Autex Research Journal

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2012

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tom Vol. 12, no. 2

29--33

EN

Investigations (calculations) based on a warp yarn tension analysis on a warp knitting machine with multiaxial weft yarn insertion allow prospective reduced yarn tension differences in technical warp knits. From this a future opportunity is provided to substitute the subjective warp let-off adjustment by a model of tension control. The outcome of this is a higher reproducibility with associated increasing process reliability and rising product quality.

3

Kinematic model for yarn movement in turbulent air flows

100%

Jungbecker P. , Seide G. , Gries T.

Autex Research Journal

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2008

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tom Vol. 8, no. 4

94--99

EN

In the textile industry a tool is needed that can predict fibre and yarn movement in turbulent air streams. The Institut für Textiltechnik of RWTH Aachen University (ITA) has developed a yarn model that can be used to study the movement of single fibres and yarns in turbulent air flows. The kinematic model is described in this article. Special attention is paid to the aerodynamic forces that determine the flight path of fibres and yarns. The coefficient of drag tangential to the fibre axis ct was studied thoroughly using computational fluid dynamics (CFD). It is shown that the diameter has a strong influence on the wall shear stress. Neglecting this effect for thin fibres can lead to errors in the coefficient of drag of a factor of 500. The turbulence intensity also has an important influence on the boundary layer development, which also determines the coefficient of drag. The assumptions made for the yarn model were tested in an experiment in which yarn flight paths were detected with a high-speed video camera. The comparison to the simulation results confirms the usability of the yarn model.

4

A quick, reliable, and economic method for evaluating the properties of rotor-spun yarn

88%

Das D. , Ishtiaque S. M. , Mac T. , Veit D. , Gries T.

Autex Research Journal

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2004

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tom Vol. 4, no. 3

123--128

EN

An attempt has been made to evaluate the primary and secondary properties of blended rotor-spun yarn both quickly and reliably from only a small sample of fibre. The concept of the quickspin system of yarn production is partially utilised in this research work. The natural and synthetic fibres are blended in a 50/50 ratio according to five different methods on an Uster Micro Dust and Trash Analyser 3 (MDTA 3), and the best blending method is evaluated with the help of a suitable image analysis technique. Furthermore, the reliability of rotor-spun yarns produced from MDTA 3 slivers with conventionally produced rotor-spun yarns from card and draw-frame slivers has been checked in terms of their properties.

5

Improving the mechanical properties of braided shape memory polymer stents by heat setting

75%

Schreiber F. , Schuster P. , Borinski M. , Vogt F. , Blindt R. , Gries T.

Autex Research Journal

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2010

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tom Vol. 10, no. 3

73--76

EN

The aging population is one of the biggest challenges of the 21st century and so is the subsequent increase in patients with cardiovascular diseases. The state-of-the-art treatment for cardiovascular stenosis is an angioplasty in combination with stenting of the affected artery. Stents can be either laser cut out of a tube or an interwoven such as a braided structure. Furthermore, there are two groups of stents regarding their expansion behaviours: balloon expandable and self-expandable. Within this paper, a new approach to braiding stent-like structures out of a novel shape memory polymer fibre will be discussed. Furthermore, the heat treatment of the stent structure will be investigated to improve its characteristics such as radial stiffness.

6

Textile composite materials for small intestine replacement

75%

Deichmann T. , Michaelis I. , Junge K. , Tur M. , Michaeli W. , Gries T.

Autex Research Journal

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2009

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tom Vol. 9, no. 4

105--108

EN

Down to the present day there are no sufficient techniques for a small intestine replacement, mostly because of the high standards for such implants. An indication for the need of novel operation techniques is the small patient survival rate of just 80 % for isolated small intestine transplantation and 62 % for combined liver-small intestine transplantation. The five year survival rates of the patients are merely 42 %. In order to overcome these limitations the authors are developing a partly resorbable textile-foam-composite for small intestine replacement The novel implant consists of a non resorbable textile PVDF mesh which is foamed with a micro porous, resorbable, and drug loaded polymer. The resorbable polymer serves on the one hand as initial sealing, therefore no intestine substance and bacteria can leak out into surrounding tissue, on the other hand it needs to be micro porous in order to ensure cell ingrowth. For the macro porous textile mesh warp knitting technology is used. The warp knitted tubular structure remains inside the body as a long term implant and provides mechanical support to ingrowing cells. In order to evaluate biomechanical properties of the warp knitted tubular PVDF meshes to compare them to the mechanical characteristics of small intestine tissue, tensile tests were conducted. Results of tensile tests on warp knitted structures with three different loop densities of 8, 12, and 16 loops per cm were compared to tensile tests on native small intestine tissue probes. The recorded curves of small intestine and warp knitted structures showed similar characteristics. The two characteristic Young Modules as well as the curve progression of the warp knitted structure with 12 loops per cm showed good accordance to the values of the native small intestine. Morphological analysis of the textile structures by digital image processing showed adequate pore size and porosity of the textile mesh.