Cutting Edge Technologies (1984) / Chapter Skim
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Introduction
Introduction
Pages 79-85
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From page 79... ...
also are emerging as major structural materials. The new Lear Fan Turboprop, for example, makes extensive use of carbon-fiber-reinforced epoxy to save 40 percent of the weight of a similar structure in aluminum.
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From page 80... ...
The easily removed plastic panels simplify body repair and reduce corrosion.3 Progress has also been made with inorganic materials. Portland cement has been the most extensively used and cheapest material of construction for more than 100 years, but unless it is reinforced with steel it can be used only in compression because of its poor tensile properties, a consequence of the presence of pores that act as crack nuclei.4 However, by controlling ingredient particle size, adding surface-active agents to improve the rheology of the paste and polymers to fill in the pores, and working the mixture to remove entrapped gas bubbles, a MacroDefect-Free (MDF)
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From page 81... ...
It consists of 0.2-micrometer M-thick platelets of 99 percent pure CaCO3, interleaved with thin layers of protein. Its tensile strength also is about that for a conventional aluminum alloy, and it is as tough as Plexiglas.4 Inorganic glasses have been with us for millennia, but metallic glasses are a relatively recent arrival, and they represent one of an increasing group of materials whose useful and different properties are a conse
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From page 82... ...
RS aluminum alloy components are now entering service, e.g., on Boeing 757 aircraft, providing improved strength-to-weight ratios and MgZn2 particles Grain boundary CO2AIg particles FIGURE 3 Structure of rapidly solidified cobalt-containing aluminum alloy. CO2A19 particles are small in size and well distributed throughout matrix and grain boundary.7
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From page 83... ...
This improvement is thought to be caused in part by the CO2Alg particles acting as hydrogen recombination catalysts, reducing the likelihood of hydrogen atoms entering the aluminum alloy and causing embrittlement.7 Other developments include treatments to change the chemical composition or structure of the surface of a solid to improve its mechanical properties or durability. With wear and corrosion costing U.S.
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From page 84... ...
Likewise, it has been found that the wear resistance of a diesel fuel injection pump can be increased a hundredfold via yttrium implantation.8 Chemical treatments that alter the structure of oxide films also are proving useful. Such films can be made porous and then filled with Teflon, graphite, or MoS2 to produce hard, corrosion-resistant, and lubricious surfaces.
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From page 85... ...
. The adsorbed molecules of this and similar organic substances inhibit the transformation of the strong oxide whiskers in humid, salt-containing environments into weak, stress-raising, hydroxide platelets.~° The result is a severalfold increase in bond life.
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