Plastics in Aerospace

Some of the applications of plastics in aerospace engineering are listed in Table 7.1. 

Epoxy resins, carbon fibre reinforced Aerospace applications - fuselages, helicopter blades 

20% glass fibre reinforced Aerospace applications 

30% glass fibre reinforced Aircraft and missile noses cones 

40% glass fibre reinforced Structural aerospace applications 

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The purpose of this subsection is to familiarize the reader with some of the basic characteristics and problems of composite laminate joints. The specific design of a joint is much too complex for an introductory textbook such as this. The published state-of-the-art of laminate joint design is summarized in the Structural Design Guide for Advanced Composite Applications [7-5] and Military Handbook 17A, Plastics for Aerospace Vehicles, Part 1, Reinforced Plastics [7-6]. Further developments can be found in the technical literature and revisions of the two preceding references. 

D. L. Schmidt, Ablative Polymers in Aerospace Technology, (G. F. D Alelio and J. A. Parker, eds.) Ablative Plastics, Marcel Dekker, Inc., New York (1971). 

Polyimide It is a high-cost heat and fire resistant plastic, capable of withstanding 500°F (260° C) for long periods and up to 900°F (482° C) for limited periods without oxidation. It is highly creep resistant with good low friction properties. It has a low coefficient of expansion and is difficult to process by conventional means. It is used for critical engineering parts in aerospace, automotive and electronics components subject to high heat, and in corrosive environments. 

Aromatic polyimides are most useful super engineering plastics which exhibit excellent thermal, electrical, and mechanical properties, and have been used widely in aerospace, electronics, and other industries over the past three decades [ 1 -4]. Aromatic polyimides are generally prepared through a two-step procedure by the ring-opening polyaddition of aromatic diamines to aromatic tet-racarboxylic dianhydrides in NMP (or DMAc) solution giving soluble polyamic acids, followed by thermal cyclodehydration (Eq. 1) [1-5]. 

Specialty polymers achieve very high performance and find limited but critical use in aerospace composites, in electronic industries, as membranes for gas and liquid separations, as fire-retardant textile fabrics for firefighters and race-car drivers, and for biomedical applications (as sutures and surgical implants). The most important class of specialty plastics is polyimides. Other specialty polymers include polyetherimide, poly(amide-imide), polybismaleimides, ionic polymers, polyphosphazenes, poly(aryl ether ketones), polyarylates and related aromatic polyesters, and ultrahigh-molecular-weight polyethylene (Fig. 14.9). 

Major polymer applications metal compressors in aerospace applications, pump housings, compressor valve plates, bushings, bearings, wear pads, piston rings and seals, gears, fasteners, plastic engine... 

This chapter will deal with the chemistry and applications of epoxies, phenolics, urethanes, and a variety of current vogue high-temperature polymers. Applications in fiber-reinforced plastics will be discussed in the individual sections on resin chemistry where appropriate. Separate sections will deal with adhesives and sealants. Adhesives are most important because, as early history demonstrates, they led the way to the application of resins in aerospace. A section is also included on silicone and polysulfide sealants. Although these materials are elastomers rather than resins, no discussion of aerospace polymers would be complete without some mention. Some major thermosetting polymers have been omitted from this review. Among these are the unsaturated polyesters, melamines, ureas, and the vinyl esters. Although these products do find their way into aerospace applications, the uses are so small that a detailed discussion is not warranted. 

In addition to the ISO 175 [39] standard for chemical degradation assessment for all plastics, the aerospace standard. EN 6063 [40] uses microscopic assessment of microcracks following immersion in the test environment. A particular test. EN 6030 [41], used in this industry is for the assessment of the effect of chemical paint stripper using the 45 tensile test for shear properties. 

Advanced polymer composites, which are high-performance materials consisting of a polymer matrix resin reinforced with fibers such as carbon, graphite, aramid, boron, or S-glass, have their market in aerospace. This is also expected to be the fastest growing sector of plastics sales, with growth projected at 22% a year. 

The editor takes the blame for the frequent use of the phrase reinforced plastics rather than the increasingly favoured, up-market term advanced composites , ffe recognizes that glass fibre reinforced composites are customarily excluded from the advanced composite category in aerospace circles, chiefly because of their relatively low modulus. But when their technical qualities as a whole are considered, including their durability in the broad sense, and when their cost effectiveness is also taken into account, reinforced plastics scarcely need rebadging. They are among the best materials in the world in the context of durability. 

Vertrel KCD-9547 is a proprietary azeotrope-like blend of Vertrel XF hydrofluorocarbon with trans-1,2-dichioro-ethylene and cyclopentane. It is ideally suited for use in vapor degreasing equipment to remove light oils, fingerprints, and particulate contaminants. Vertrel KCD-9547 is specially formulated to provide a high degree of compatibility with plastics, elastomers, and other nonferrous metals, such eis in aerospace parts. Vertrel KCD-9547 is nonflammable, has "zero" ozone depletion potential, and heis low global warming potential. It can replace CFC-113,1,1,1 -trichloroethane (1,1,1 -TCA), hydrochlorofluorocarbons (HCFC), and perfluorocarbons (RFC) in many applications. 

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