Fibrous Network Materials

It has been shown that the anisotropy depends on the orientation of the diagonals of indentation relative to the axial direction 14). At least two well defined hardness values for draw ratios A. > 8 emerge. One value (maximum) can be derived from the indentation diagonal parallel to the fibre axis. The second one (minimum) is deduced from the diagonal perpendicular to it. The former value is, in fact, not a physical measure of hardness but responds to an instant elastic recovery of the fibrous network in the draw direction. The latter value defines the plastic component of the oriented material. 

In a simple model for this case, which, as in the 3-D case, ignores fiber straightening and anisotropy of the fibrous network, a plane stress version of Eqn. (35) can be developed. As such, it can only be used for plane stress states. Consider the x-y plane to be that in which the fibers are woven or the whiskers are lying. The strain rates in this plane are taken to be homogeneous throughout the composite material and crzz, axz and ayz are taken to be zero. The resulting law is... 

Similar descriptions apply to animal tissues, except that the cellular materials can themselves be fibrous (as in muscle) within a fibrous network of connecting collagen. This complexity is far greater than is found in engineering materials for which the mathematical understanding of composite materials has been developed. Worse, biological materials deform by large amounts (more than 1%) and are nonlinear, both... 

The nucleus (Figure 2.15) consists of nucleoplasm surrounded by a nuclear envelope. The nucleoplasm is a material rich in DNA in which proteins called lamins form a fibrous network that provides structural support. A prominent feature of the nucleoplasm is a network of chromatin fibers composed of DNA and DNA packaging proteins known as the histones. The DNA is believed to be attached to the lamins. The nuclear envelope is composed of two membranes that fuse at structures called nuclear pores. The outer nuclear membrane is continuous with the rough endoplasmic reticulum. The nuclear pores (Figure 2.16) are relatively... 

Fibrous networks with permanent interconnections will effectively entrap and immobilize liquid in the meshes, and possess both the elastic properties of ideal solids and the viscosity properties of Newtonian liquids. Consequently, self-supporting supramolecular materials will be obtained [8-10,15-21]. til contrast, systems consisting of nonpermanent/or transient interconnecting (or entangled) fibers or needles can only form weak and viscous paste at low concentrations [6,7]. 

The strategy of this approach is to construct 3D permanent interconnecting nanocrystal fibrous networks from a system consisting of separate crystal needles using a tailor-made micro/nanostructure (Fig. 10a), and to engineer the materials with required micro/nanostructure (Fig. 10b), based on the CMB mechanism. 

Briefly, paper is made from a very dilute aqueous suspension of anionically charged cellulosic fibres which, after water removal, fam a fibrous network, i.e., a paper sheet. In many cases, filler particles such as ground or precipitated calcium carbonate or clay are added to the fibre suspension to enhance the optical performance or printability of the paper. Also, a variety of other components are added to improve specific properties of the paper sheet (e.g., wet and dry strength agents) or to facilitate the paper production process (e.g., retention aids to minimize the loss of fines and filler material to the process water, dewatering aids or defoaming chemicals). The majority of these chemical additives are polymers. 

A small-molecule gel (SMG) is a typical class of supramolecular materials. An SMG forms when a hot solution of a smaU-molecular gelator is cooled to a certain temperature, namely gelation temperature T. The gelator molecules, at a concentration in excess of the equilibrium concentration at Tg, self-organize into a three dimensional (3D) fibrous network. 

Soft materials display combined solid and liquid properties, the so-caUed rheological properties. Correspondingly, the structures are normally compHcated. This can be because soft materials consist of certain network structures. In many cases, these are fibrous network stmctures, ranging from nanoscale to microscopic scales. Therefore, the understanding on the formation of fibrous networks is the key to fabricate and engineer materials of this type. 

The book covers subjects related to important soft functional materials that have fibrous network structures. The materials include small-molecule physical... 

Industrial Applications Characterizing soft material interfaces understanding fibrous network structures in nanodevice preparation functionalizing/ encapsulatiing particles by initiated chemical vapor deposition (iCVD) functional polymer coatings high refractive index coatings papers ... 

You should be familiar with GORE-TEX. It s a fabric that s used in outdoor clothing— rain jackets and boots and other garments designed to keep out the weather. The material itself is made up of a fibrous network containing very small holes, as shown in Figure 14.2. These... 

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