Fabric porosity

Fabric Construction for Water RepeUency. Fabric constmction, including twist, ply, and coarseness of yams, affects the performance of water repeUents. Waterproof films can more easUy be formed on close weaves than on open-weave fabrics. Hydrophobic finishes, which make individual fibers repeUent without altering fabric porosity, are generaUy appUed to fabrics whose pores are smaU (37). The relation of rainwear fabric constmction to the performance of repeUents has been reviewed (38). Some reports indicate that fabric roughness reduces repeUency (28,37). Mechanical action on fabrics, even after treatment, can reduce repeUency if the action increases fiber roughness or exposes fibers that have Utfle repeUent treatment. 

Graft wall (fabric) porosity (<30 days after graft placement)... 

The issues of initial Th and Pa are ones of accuracy, that is, how close the age determination is to the true age of the sample. A second concern, one that increases with the sample age, is the closed-system behavior of the U-Th-Pa decay chains. In general, older samples are more at risk because of the longer opportunity for diagenetic changes to have taken place. Speleothems with significant porosity are poorer candidates for closed-system behavior than are speleothems with dense fabrics. Fluid inclusions are a ubiquitous source of micron-scale fabric porosity but are generally isolated and thus do not translate to permeability with diagenetic implications. 

Fabrication. Porosity and surface roughness are important physical parameters for any useful scaffold. The scaffold can be classified into two basic forms either fibrous or foam-like. In order to form woven or non-woven meshes the scaffold must be amenable to spinning and this limits the number of materials that can be produced in this form. The most important fibre forming scaffold are the a-hydroxy acid based materials. Other fibre... 

Fabric porosity refers to the void fraction or the total void space within the volume of the prosthesis wall and serves as a useful measurement of the potential for in vivo tissue ingrowth. The porosity, P (%), of the graft is calculated using the following equation ... 

The interspacing and diameter/thickness of the yarn is often used to calculate what is termed the fabric s cover factor , meaning the actual area the solid part of the fabric covers when the fabric is laid on a surface. From a more practical sense, this is the fraction of a fabric surface area that comprises the fibres/filaments. Neglecting the very small interfibre interstices. Fig. 8.24 depicts the projected areas seen in this way for a plain-weave structure, which can be used to obtain a calculated estimate of the fabric porosity. 

Concerning a textile fabric s geometry, fabric thickness appears to have the most influence on thermal and hydroscopic behavior, explaining the majority of the phenomenon. This is because the increase in the thickness of fabric influences fabric porosity due to the corresponding increase of fabric volume, which is generally followed by an increase in the amount of air in the fabric interstices [4]. 

The ability of the layered textile substrate to contain the electrolyte in a confined region was also related to the fabric properties. These properties include type of material, fabric construction, yam density, and fabric porosity. 

The structure and properties of a nonwoven fabric are determined by, in addition to the properties of the constituent fibres and bonding materials, the stmctural architecture of fibres, bonding segment structure, and their distributions. The methods for the measurement of the key structural parameters of nonwoven fabrics discussed in this section include fabric thickness, mass per unit area, fabric density, fabric uniformity fabric porosity, pore size and pore size distribution, fibre orientation distribution, bonding segment structure, and their distributions. 

The nonwoven fabric mass per unit area and thickness usually vary in different locations in the fabric plane. The variation of either nonwoven thickness and/or fabric area weight determine the variation of local fabric packing density, local fabric porosity, and pore size distribution, and it thus influences the performance of nonwoven applications, such as the appearance, tensile properties, permeability, thermal insulation, sound insulation, filtration, liquid barrier and penetration, energy absorption, light opacity, and processability of nonwoven products. 

Porosity provides information on the overall pore volume of a porous material. Fabric porosity is defined as the ratio of the nonsolid volume (voids) to the total volume of nonwoven fabric, and the volume fraction of solid material is defined as the ratio of solid fibre materials to the total volume of fabric. While the fibre density is the weight of a given volume of the fibre solids only (ie, not containing other materials), the porosity can be calculated as follows by using the fabric bulk density and the fibre density ... 

The most important characteristics affecting quality of nanofibre membrane filters are fibre diameters (or fibre diameter distribution), nanofibre fabric porosity, and its homogeneity. Both the filtration efficiency of a nanofibre membrane and the pressure drop... 

Porosity. Fabric porosity also affects the thermal insulation characteristics of fabrics (Fan et al., 2000). Generally, a fabric with a highly porous structure can trap more air than one with a lower or nonporous structure. The air trapped inside the fabric increases its thermal insulation. 

Many nonwoven structures used for absorbent wound dressings exhibit anisotropic fluid transmission characteristics in the vertical and lateral directions of the fabric structure. The orientation of fibers within these materials is the main factor affecting anisotropic fluid transmission, and can be manipulated to design desirable transport properties by using appropriate fabric porosity, fiber diameter, and orientation distribution. 

The preform is a homogeneous, porous and isotropic medium. The fabric properties required for the flow model are permeability and porosity. Fabric porosity is not influenced by its composition hence the fabric is assumed to be homogeneous. Also the permeability of the fabric is experimentally evaluated using flow imaging technique which provides an average value considering composition and directional effects in the fabric. In case of anisotropic performs, permeability values in different directions can also be defined in the flow model at material property section. 

New material by name resin was created with specified density (1140 kg/m ) and viscosity (0.60 kg/m.s) along with the existing air (density 1.225 kg/cc, viscosity (1.7894e-5 kg/m.s). Multiphase VOF option was selected under the model option, air was defined as the primary phase and resin was set as secondary phase. Gravity (-9.81 m/s ) was activated in the operating conditions panel in the z direction, density of air (1.225 kg/cc) was specified under variable density parameter for better convergence of solution. Mixed mode (both for air and resin) boundary conditions for the inlet (pressure inlet, 0 pascal) and outlet (pressure outlet, -97325 pascals in z direction) were set. Mixed mode fabric permeability (viscous resistance, 1/m ) and fluid porosity (1-fabric porosity) were defined for the fabric. No slip boundary conditions were set (default) for the walls for both the phases. For resin phase, 1 was set under the volume fraction for inlet and 0 was set for back-flow volume fraction for outlet boundary conditions. 

A large family of fiber architectures is available for surgical implants (Fig. 2.3). The design and selection of these fiber architectures for tissue engineering can be carried out on the fiber and structural levels resulting in a wide range of dimensional scale, fiber tortuosity and fabric porosity as characterized by the fiber volume fraction-orientation map. ... 

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