Inherent Reinforcement

Outstanding properties exceptional strength and stiffness without reinforcements inherent flame resistance ... 

Flammability. PhenoHcs have inherently low flammabiHty and relatively low smoke generation. For this reason they are widely used in mass transit, tiinnel-building, and mining. Fiber glass-reinforced phenoHc composites are capable of attaining the 1990 U.S. Federal Aviation Administration (FAA) regulations for total heat release and peak heat release for aircraft interior facings (1,70). 

The mbber compound usually requires an inert inorganic filler and small particle sise carbon particle for reinforcement. The mbber polymers vary in inherent tensile strength from very high in the case of natural mbber to almost nonexistent for some synthetic polymers, eg, SBR. The fillers most commonly used for mbber compounds include carbon black, clay, calcium carbonate, siUca, talc (qv), and several other inorganic fillers. 

Thermosetting unsaturated polyester resins constitute the most common fiber-reinforced composite matrix today. According to the Committee on Resin Statistics of the Society of Plastics Industry (SPl), 454,000 t of unsaturated polyester were used in fiber-reinforced plastics in 1990. These materials are popular because of thek low price, ease of use, and excellent mechanical and chemical resistance properties. Over 227 t of phenoHc resins were used in fiber-reinforced plastics in 1990 (1 3). PhenoHc resins (qv) are used when thek inherent flame retardance, high temperature resistance, or low cost overcome the problems of processing difficulties and lower mechanical properties. 

Most processors of fiber-reinforced composites choose a phenol formaldehyde (phenoHc) resin because these resins are inherently fire retardant, are highly heat resistant, and are very low in cost. When exposed to flames they give off very Htde smoke and that smoke is of low immediate toxicity. PhenoHc resins (qv) are often not chosen, however, because the resole types have limited shelf stabiHty, both resole and novolac types release volatiles during their condensation cure, formaldehyde [50-00-0] emissions are possible during both handling and cure, and the polymers formed are brittle compared with other thermosetting resins. 

An inherent problem with all of the above moulding methods is that they must, by their nature, use short fibres (typically 0.2-0.4 mm long). As a result the full potential of the reinforcing fibres is not realised (see Section 2.8.5). In recent years therefore, there have been a number of developments in reinforced... 

For the third edition, I added sections or chapters on heat exchangers, furnaces, inherently safer design, and runaway reactions, and extended many other chapters. Although I have read many accident reports since the first edition appeared, most have merely reinforced the messages of the book, and I added only those incidents that tell us something new. 

Orientation of fibers relative to one another has a significant influence on the strength and other properties of fiber-reinforced composites. With respect to orientation three extremes are possible as shown in Fig. 5. Longitudinally aligned fibrous composites are inherently anisotropic, in that, maximum strength and reinforcement are... 

This calculation, which holds true for most metals, is generally applicable to TPs. However, the designer is to be familiar with the inherently nonlinear, anisotropic nature of most plastics, particularly the fiber-reinforced and liquid crystal plastics (Chapter 6). 

Unsaturated polyester resins based on maleic anhydride are widely used in coatings to manufacture boat hulls and truck caps and a variety of other uses where a smooth, weatherproof, hard-surfaced material is desired. Because these resin types are inherently brittle, hberglass is frequently added for reinforcement. Consumphon of unsaturated polyesters in the U.S. is well over a billion pounds per year, with about 50% going into construction and the marine industry. 

This is an extremely important area. Commercial polymers are very rarely prepared or used without additives and they often contain a combination of additives. These improve processability of the polymer, its durability, service life under adverse conditions (e.g., temperature, UV light and various chemical environments), strength (e.g., using reinforcing fillers), appearance (colorants), etc. A recent use of additives is to facilitate reprocessing or recycling or, alternatively, to promote decomposition (which is often difficult because the stability is inherent in the polymer s chemical structure). (The analysis of additives in polymers is the subject of Chapter 14.)... 

Added reinforcement is required to meet the criteria in (b) and (c) below when it is not inherent in the components of the branch connection. Sample problems illustrating the calculations for branch reinforcement are shown in Nonmandatory Appendix E. 

This article is an overview of the novel technology of self-reinforced LCPs with polyesters, poly(ethylene terephthalate) (PET) and poly(ethylene naphtha-late) (PEN) [10-13, 21, 23], LCP/polyester blends in a polyester matrix form in situ fibrils which improve the mechanical properties. LCPs have an inherently low melt viscosity, and provide LCP/polyester blends that effectively lower the melt viscosity during melt spinning [24], and fast injection-molding cycles. The miscibility between the LCP and polyesters can be controlled by the degree of transesterification [25] in the reactive extrusion step, and fibril formation in LCP-reinforced polyester fibers has been studied. 

ETFEs are inherently insensitive to moisture and UV. Stabilization is not needed. However, glass fibre reinforced grades can be altered by long outdoor exposures. 

Finally, metallic fibers find some limited applications as reinforcement in composites. They are generally not desirable due to their inherently high densities and because they present difficulties in coupling to the matrix. Nonetheless, tungsten fibers are used in metal-matrix composites, as are steel fibers in cement composites. There is increasing interest in shape memory alloy filaments, such as Ti-Ni (Nitanol) for use in piezoelectric composites. We will discuss shape-memory alloys and nonstructural composites in later chapters of the text. 

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