Arrays of fibers

A variation on the exact soiutions is the so-caiied seif-consistent modei that is explained in simpiest engineering terms by Whitney and Riiey [3-12]. Their modei has a singie hollow fiber embedded in a concentric cylinder of matrix material as in Figure 3-26. That is, only one inclusion is considered. The volume fraction of the inclusion in the composite cylinder is the same as that of the entire body of fibers in the composite material. Such an assumption is not entirely valid because the matrix material might tend to coat the fibers imperfectiy and hence ieave voids. Note that there is no association of this model with any particular array of fibers. Also recognize the similarity between this model and the concentric-cylinder model of Hashin and Rosen [3-8]. Other more complex self-consistent models include those by Hill [3-13] and Hermans [3-14] which are discussed by Chamis and Sendeckyj [3-5]. Whitney extended his model to transversely isotropic fibers [3-15] and to twisted fibers [3-16]. 

Applications. Boron fibers are used as unidirectional reinforcement for epoxy composites in the form of preimpregnated tape. The material is used extensively, mostly in fixed and rotary wing military aircrafts for horizontal and vertical stabilizers, mdders, longerons, wing doublers, and rotors. They are also used in sporting goods. Another application is as reinforcement for metal matrix composites, in the form of an array of fibers pressed between metal foils, the metal being aluminum in most applications. 

Ceramic matrix composites are produced by one of several methods. Short fibers and whiskers can be mixed with a ceramic powder before the body is sintered. Long fibers and yams can be impregiated with a slurry of ceramic particles and, after drying, be sintered. Metals (e.g., aluminum, magnesium, and titanium) are frequently used as matrixes for ceramic composites as well. Ceramic metal-matrix composites are fabricated by infiltrating arrays of fibers with molten metal so that a chemical reaction between the fiber and the metal can take place in a thin layer surrounding the fiber. 

Ozone decomposition in airplanes Selective catalytic reduction of NOx Arrays of corrugated plates Arrays of fibers Gauzes Ag Methanol -> formaldehyde Pt/Rh NO production from ammonia HCN production from methane Foams Catalytic membranes reactors... 

Ershoff (14, 16) tested the effects of a vast array of fibers on toxicity of 5 sodium cyclamate. In male rats the most complete protection was afforded by 10 gum Karaya, 10 blond psyllium seed or husk, 20 alfalfa meal and 20 carrot root powder. The most effective substance in female rats was alfalfa meal fed as 15 or 20 of the diet (Table IV). 

The potential for further extensive development in ceramic-fiber composites is thus dependent upon the production of a wide array of fiber compositions as a significant existing problem is of property mismatch between the fiber and matrix. It has, therefore, been emphasized that the challenge is to either obtain new fibers with improved thermoxidative stability in comparison to the limited number currently available, or to suitably modify existing fiber materials. 

It is important to realize that mechanical properties can also be critical in non-structural applications. For example, in the design of the thermal protection system of the space shuttle, highly porous, fibrous silica tiles are used. The microstructure of these materials, shown in Fig. 1.1, consists of a bonded array of fibers, usually based on silica glass. Clearly, the prime reason for using these materials was their low thermal conductivity but the resistance to thermal and structural stresses was a key item in the final design. In some non-structural applications, mechanical properties can be important in determining the lifetime... 

Depth filters consist of an array of fibers oriented randomly, and the filters retain particles inside the filter material. Depth filters are constructed of materials such as cotton, fiberglass, sintered metals, and diatomaceous earth. Insoluble or colloidal particles are removed from the fluid by attraction and capture or adsorption to the filter matrix. Particles of 0.01 pm can be retained by these filters. Frequently, materials of various stages are combined in one filter, where the feed comes into contact with the matrix initially more open. Depth filters are operated in perpendicular mode [6]. 

Arrays of whiskers, but no microparts Arrays of fibers, but no microparts Single fibers, simple/ complex microparts Single fibers, simple/ complex microparts... 

Current attitudes regarding composite materials (14-16) emphasize the relationship of structural performance to the properties of a ply. A "ply is a thin sheet of material consisting of an oriented array of fibers embedded in a continuous matrix material (Fig. 6). These pli are stacked one upon other, in a defined sequence and orientation, and bonded together yielding a laminate with tailored prop es. The properties of the laminate are related to the properties of the ply by the specification... 

When we implement different holograms, according to n values, in the SLM and an incident light wavelength is illuminating the pixels, different diffracted angles are obtained by placing an array of fibers at the output, in the focal plane, a A-router is implemented. 

A wide array of fiber tows (each of which consists of hundreds of filaments) are used for composite tape manufacturing. The diameter of filaments are usually in a range from 6 to 8 pm for carbon fibers (CF) and from 10 to 17 xm for glass fibers (GF). Also, aramid fiber (AF) tows or other polymeric fibers in this range of diameters are available. The... 

In the model (51), a spunbonded web (henceforth referred to as layer ) is represented by an array of fiber strands connected on a two-dimensional x-y lattice. 

There are, in general, five assumptions underlying all the mechanistic interface theoretical studies, namely (1) elastic constituent material behavior, (2) zero thickness for the interface, (3) perfect bond, (4) identical constituent bulk and in situ properties, and (5) a regular or repeating array of fibers. It is known that actual composites violate most, if not all, of these assumptions. However, the theoretical predictions still are an invaluable tool in identifying important local geometry and material variables, and in obtaining quantitative estimates of the stress state at the interface. ... 

A theoretical model was developed to simulate the consolidation by compression molding, both in isothermal and non-isothermal conditions. - The model assumes a towpreg lamina as an array of fibers with attached particles (Figure 5a). The stacking of a number of these laminae together with different possible arrangements leads to a preform (Figure 5b). 

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