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Modeling and CFD-simulation of woven textiles to determine permeability and retention properties

Rief S., Glatt E., Laourine E., Aibibu D., Cherif C., Wiegmann A.

Autex Research Journal

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2011

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Vol. 11, no. 3

78--83

EN

The previous paper (No. 2, Vol. 12-2011) [1] were analyzed the weave and construction parameters of high density woven fabric and their influence on the pore morphology, which directly effects the functional properties such as permeability and retention. The analysis encompassed physical and optical methods of testing. In this paper, newly developed methods, tools and programs will be presented for virtual imaging of the multi-filament woven fabric geometry with pore structure used to determine permeability and retention properties. Two methods are applied for the generation of virtual fabric. One method involves developing software that is able to model woven fabric in new condition from a series of realistic input parameters. In this step, deterministic and stochastic methods are combined to create the fabric’s geometry. The other method involves reconstruction/generation the 3D woven geometry from sequences of 2D cross section images. The results prove that the 3D pore morphology of high density multi-filament fabric can be illustrated in correlation of the woven construction parameters. The developed methods for modeling and the CFD simulation of woven fabric build an important basis for determining the mechanical flow properties such as permeability and retention characteristics of filters and barrier textiles. Additionally, the effects of mechanical loads on the fabric morphology and on the permeability values will be analyzed by applying uniaxial and biaxial tensile loads to the fabric. The tests provide the basis for a realistic prediction to the effects of the machine and construction parameters on the fabric properties and the resulting permeability and retention. These predictions can aid in analyzing the suitability of a fabric for a specific application.

2

Characterisation of barrier properties of woven fabrics for surgical protective textiles

Laourine E., Cherif C.

Autex Research Journal

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2011

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Vol. 11, no. 2

31--36

EN

The pore morphology of textile filter structures is important for numerous technical applications. It determines the functional properties of surgical textiles, such as the effective barrier function and wearing comfort. Surgical and protective textiles must fulfil both of these contradictory functions. To date, basic research has not been successful, either theoretically or experimentally, in describing the complex correlation between the 3D pore structure of woven textiles and their barrier properties while simultaneously remaining permeable. In an attempt to clarify this issue, high density multi-filament woven textiles were categorised according to their geometry, pore morphology, permeability and retention properties by virtual modelling of their 3D pore morphology. Differentiation was made between mesostructures (pores between the yarns) and microstructures (pores within the yarn itself). In this process it was possible to identify the influence of weaving parameters on the pore morphology and determine their resulting functional properties. Various new testing methods were developed and successfully implemented to characterise and evaluate the barrier properties. The experiments show that by selecting specific yarns and weave constructions, the permeability and woven structure can be positively influenced and adapted to fulfil a wide range of requirements. A major finding is that the permeability and retention properties of the weave can be independently controlled by choosing suitable machine parameters. Specifically, by varying the shed closing time a clear shift in the pore size distribution to smaller pore diameters can be achieved without altering the air permeability. A correlation between the construction and processing parameters and the 3D pore morphology of the woven textile was ascertained. The relation between the properties of a weave and the machine and construction parameters is extremely complex due to their interaction.

3

Calibration of a numerical model for masonry with application to experimental results

Churilov S., Dumova-Jovanoska E.

Architecture Civil Engineering Environment

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2008

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Vol. 1, no. 3

39-48

EN

A calibration of a numerical model for analysis of masonry walls with application to experimental results is presented in this paper. The experimental results used for calibration are derived from the research project "Optimization of shape of masonry units and technology of construction for earthquake resistant masonry buildings" conducted by Bosiljkov and Tomažević in 2005 for ZAG Ljubljana. This paper adopts micro-modelling strategy for analysis of masonry specimen by discrete element method and application of different nonlinear material models both for blocks and mortar. In order to determine the values and to calibrate the necessary material data for the used materials that were not obtained experimentally, several numerical investigations and simulations were performed. Numerical analysis of masonry walls was performed with the use of UDEC software. A comparison of numerical and experimental results as well as a comparison of the failure mechanisms is presented. With the assumed modelling strategy and numerical method, a satisfactory compliance with the experimental results regarding limit state and developed failure mechanisms is obtained. With the results from this research and literature survey several recommendations regarding material properties necessary for numerical analysis are provided in the end of this paper.

PL

W artykule przedstawiono opartą na wynikach badań kalibrację modelu numerycznego do analizy ścian murowych. Wyniki badań wykorzystywane do kalibracji pochodzą z projektu "Optymalizacja kształtu jednostek murowych oraz technologia budowy budynków murowych odpornych na trzęsienia ziemi" przeprowadzonych przez Bosiljkova i Tomaževića w 2005 roku dla ZAG Ljubljana. W artykule przyjęto strategię mikro modelowania do analizy próbki muru poprzez metodę elementu dyskretnego oraz zastosowanie różnych, nieliniowych modeli materiałowych zarówno dla bloczków, jak i zaprawy. W celu określenia wartości liczbowych oraz wykalibrowania koniecznych danych materiałowych dla zastosowanych materiałów, których nie uzyskano eksperymentalnie, przeprowadzono kilkanaście badań oraz symulacji numerycznych. Analiza numeryczna ścian murowych została wykonana przy użyciu programu UDEC. Zaprezentowano porównanie wyników analiz numerycznych z wynikami z badań, jak i mechanizmów zniszczenia. Przy założonej strategii modelowania oraz metodzie numerycznej uzyskano zadowalającą zgodność z wynikami z badań, co do stanu granicznego oraz rozbudowanych mechanizmów zniszczenia. Na podstawie wyników z tych badań oraz studiów literaturowych, na końcu artykułu przedstawiono kilka zaleceń dotyczących właściwości materiałowych koniecznych w analizach numerycznych.