Organic Reinforcing Fibers

As the organic plastic or its residual char are removed by the ablative aspects of the hyper-environment, the reinforcing fibers or particle fillers are left exposed and unsup-... 

The fabricator has a variety of alternatives to choose from regarding the kind, form, amount of reinforcement to use, and the process vs. requirements (Table 8-28). With the many different types and forms (organics, inorganics, fibers, flakes, and more) available, practically any performance requirement can be met and molded into any shape. Possible shapes range from very small to extremely large, and from simple to extremely complex. 

The organofunctional portion bonds with the resin in the adhesive or the organic medium, and the silane portion bonds to the inorganic or substrate surface. Silane coupling agents are commonly used between the adhesive and the adherend, between resin matrix and reinforcing fibers in composites, and between resin matrix and mineral fillers in compounds. The resulting interface provides... 

Strong graphite fibers are made by pyrolysis, at 1500°C or above, of oriented organic polymer fibers (e.g., those of polyacrylonitrile, polyacrylate esters, or cellulose). When incorporated into plastics the reinforced materials are light and very strong. Other forms of graphite such as foams, foils, or whiskers can also be made. 

The matrix resins for foamed composites include rigid pol)ruretha-nes, unsaturated polyesters, vinyl esters, and their hybrid resins, such as, unsaturated polyester-urethane hybrid resins and vinyl ester-urethane hybrid resins. The reinforcing fibers include glass fibers, carbon fibers, and organic fibers such as polyamide fiber (Kevlar, DuPont), polyamide-... 

As the organic polymer or its residual char are removed by the ablative aspects of the hyper-environment, the reinforcing fibers or particle fillers are left exposed and unsupported. If vitreous in composition, they undergo melting. The resultant molten material covers the surface as liquid droplets, irregular globules, or a thin film. Continued addition of heat to the surface causes the melt to be vaporized. A fraction of the melt may be splattered by internal pressure forces, or sloughed away when acted upon by external pressure and shear forces of the dynamic environment. 

Fillers are particulate, organic or, for the most part, inorganic substances in solid form. Their incompatibility with the basic material (matrix) results in a multiphase system, the compatibility of which can, however, be increased by means of coupling additives (coatings) - similarly to the process with reinforcing fibers leading, at the least, to bridge formation. 

When an applications engineer thinks of typical reinforcing fibers for plastics the first thing that comes to mind will be glass fibers. In the actual history of this technology, however, the use of organic fibers began several decades earlier with the use of natural cellulose fibers to reinforce phenolic resins (Fig. 37). 

Whereas natural fibers, mainly in the form of short fibers and fabric chips, have foimd application above all in the curable phenoplast and aminoplast molding compounds, it was more than anything else the development of the polyesters and epoxy resins that made it necessary to develop new kinds of reinforcing fibers to optimize the properties of these products as well. Modem, high-strength, synthetic organic fibers are the results of these efforts [112]. 

Reinforced (fiber glass) polyester is a common building material, that yields to PVC. It is useful in partitions, prefabricated sheets, pipelines, furniture and coatings. This unsaturated polyester is also an organic cement in flooring or adhesives. 

G Roncato, R Federowsky. Process and Device for Producing a Yam or Ribbon Formed from Reinforcement Fibers and a Thermoplastic Organic Material. U.S. Patent 5011523, April 30, 1991. 

G Roncato, R Fedorowsky, P Boissonnat, D Loubinoux. Apparatus for Manufacturing a Composite Strand Formed of Reinforcing Fibers and of Organic Thermoplastic Material. U.S. Patent 5316561, May 31, 1994. 

This right ahout-face embarrassed me and forced me to devote myself to the investigation of various classes of materials unfamiliar to me, including metals (Al, etc.), ceramics, carbonaceous materials, reinforcing fibers for fiber-reinforced resin (super-drawn polyethylene fibers, etc.), organic polymers, and so on. I also tried to develop piezoelectric loudspeakers using poly(vinylidene fluoride) (PVDF). 

Primary business activities are based on the applications of structural composites as the business product. Secondary business activities serve the needs of the primary industries, often as suppliers of raw materials. A third level of business activity involves providing basic and specialized training for the use of structural composites in specific applications and markets. As an example, the primary industry might be an aircraft manufecturer or a construction engineering firm, the secondary industry could then be a cement suppher or a resin and reinforcement fiber manufacturer, and the tertiary industry could be an organization that provides training in the use of advanced composite materials for aircraft maintenance workers or in the use of concrete and paving blends. In a very real sense, the opportunity for an individual s success in this field is as limitless as the opportunities for new developments and applications of the materials. 

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