Aerospace application

This property, measured for proprietary cyanate esters (Hercules HX-1562, 1565, 1939-3 and 954-2 resins)/P75 graphite combination and cyanate ester-epoxy blend/graphite combination, showed their superiority over the industrial standards based on tetraglycidyl epoxy/graphite systems [197]. Mechanical properties also confirmed that they are suited for dimensionally stable structures. Advanced composite structures capable of withstanding exposure to tern- 

In 2003 Piccard and Borschberg from the Ecole Polytechnique Federate de Lausanne (EPFL) initiated construction of the Solar Impulse - a fixed-wing aircraft that will circle the world on solar power.i i The prototype. Solar Impulse HB-SIA, successfully passed all the tests. The advanced polymers used in its construction are listed in Table 3.4. i 

Aramid fiber PARA (LCP) Polyester coated F ultruded, rowing 

Butyl rubber MR Sheet, strip, tubing, extrusions, moldings 

Chloroprene Chloroprene Nylon cloth Gaskets, seals. 

Epoxy cresol Novolac ECN For high temperature composite 

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Today, carbon fibers are still mainly of interest as reinforcement in composite materials [7] where high strength and stiffness, combined with low weight, are required. For example, the world-wide consumption of carbon fibers in 1993 was 7,300 t (compared with a production capacity of 13,000 t) of which 36 % was used in aerospace applications, 43 % in sports materials, with the remaining 21 % being used in other industries. This consumption appears to have increased rapidly (at 15 % per year since the early 1980s), at about the same rate as production, accompanied by a marked decrease in fiber cost (especially for high modulus fibers). 

Allbericci, P, Aerospace applications. In Kinlock, A.J. (Ed.), Durability of Structural Adhesives. Applied Science Publishers, London, 1983, Ch. 8. 

National Materials Advisory Board, National Research Council, Structural Adhesives with Emphasis on Aerospace Applications. Marcel Dekker, Inc., New York, 1976. 

Standard shapes for composite stiffeners are not likely to occur for most aerospace applications. There, the value and function of the structure warrant optimizing the stiffener design. In contrast, for more everyday applications such as scaffolding, stairways, and walkways in chemical plants, competitive pressures lead to a situation where compromises in stiffener efficiency are readily accepted (overdesign) in order to achieve lower cost than would be associated with optimum design. 

More than two decades have passed since the first edition of this book appeared in 1975. During that time, composite materials have progressed from almost an engineering curiosity to a widely used material in aerospace applications, as well as many other applications in everyday life. Accordingly, the contents of the first edition, although in most respects timeless fundamental mechanical behavior and mechanics analyses, must be expanded and updated. 

Fiber-reinforced plastics have been widely accepted as materials for structural and nonstructural applications in recent years. The main reasons for interest in FRPs for structural applications are their high specific modulus and strength of the reinforcing fibers. Glass, carbon, Kevlar, and boron fibers are commonly used for reinforcement. However, these are very expensive and, therefore, their use is limited to aerospace applications. 

King, Fowler, Lyon Light-weight Alloys for Aerospace Applications 11, Proc. TMS Meeting, New Orleans, USA, Feb 17-21, 1991, pp. 423-437... 

As a light, strong metal, beryllium holds considerable promise as a useful engineering material, but because of an inherent directional brittleness, a really significant commercial use, e.g. in the aircraft industry, has not proved possible. It has been used to a limited extent in aerospace applications, and it was employed as heat shields for the Project Mercury space capsule. It has also found use in precision guidance systems when fairly pure environmental conditions can be assured. 

Polyetheretherketone PEEK is a high-temperature, crystalline engineering TP used for high performance applications such as wire and cable for aerospace applications, military hardware, oil wells and nuclear plants. It holds up well under continuous 450°F (323° C) temperatures with up to 600°F (316° C) limited use. Fire resistance rating is UL 94 V-0 it resists abrasion and long-term mechanical loads. 

The high-temperature glassy or crystalline transitions of the linear aromatic and heterocyclic polymers were an important drawback for die structural aerospace applications, which need a good flow for the adhesive or composite formulations. 

Isothermal Infiltration. Several infiltration procedures have been developed, which are shown schematically in Fig. 5.15.P3] In isothermal infiltration (5.15a), the gases surround the porous substrate and enter by diffusion. The concentration of reactants is higher toward the outside of the porous substrate, and deposition occurs preferentially in the outer portions forming a skin which impedes further infiltration. It is often necessary to interrupt the process and remove the skin by machining so that the interior of the substrate may be densified. In spite of this limitation, isothermal infiltration is used widely because it lends itself well to simultaneous processing of a great number of parts in large furnaces. It is used for the fabrication of carbon-carbon composites for aircraft brakes and silicon carbide composites for aerospace applications (see Ch. 19). 

Corrosion resistant and oxidation resistant coatings for rocket engines and other aerospace applications. 

To this date, the fabrication of structural ceramic composites has been limited to prototypes mostly in high-cost, high-performance aerospace applications such as missile guidance fins, hypersonic fuselage skins, inner flaps, and rocket nozzles. 

Polymers containing no secondary or tertiary C-H or are aromatic (PEEK or Kevlar ) or perfluorpolymers (PTFE) are generally resistant to oxidation and require no anti-oxidant additives. However, the high temperature necessary for curing or fabrication of high performance polymers (especially for aerospace applications) can cause oxidation. For this reason, these materials are often prepared and fabricated under a nitrogen atmosphere. 

Bevenot X., Trouillet A., Veillas C. et.al., Hydrogen leak detection using an optical fibre sensor for aerospace applications, Sensors Actuators B 2000 67 57-67. 

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