Metal Foams: A Design Guide

222 Metal Foams: A Design Guide
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Figure 17.5 (a) Sound-absorbing lining on the underside of a highway
bridge; (b) the sound-absorbing elements are shaped like hemi-circular tubes
weathering, does not absorb water, and can be washed down to keep it clean.
The sound-absorbing structures have some shock-absorbing capacity, an attractive
appearance, and act as electromagnetic shields, limiting ignition and other
electromagnetic disturbances from passing vehicles, and shock waves caused
by tunnel sonic boom from ultra-high-speed trains.
17.4 Optical systems for space applications
ERG, the producers of the DUOCEL ® range of metal foams (see
Chapter 2, Section 2.5), exemplify successful applications of these materials
in aerospace. Ł This case study and the next two describe three of these.
Mirrors of all sorts play a key role in space technology. Whether the frequencies
are optical, infrared or microwave, precision, low mass and freedom from
long-term distortion are primary design constraints. Figure 17.6 shows the
basic structure of a DUOCEL-backed composite mirror used by both the Lockheed
Missile and Space Co. and the Hughes Aircraft Company Laser Systems
Division. The mirror face is stiffened by bonding it to a foam layer backed
by a stiff backing plate. The structure is light and very stiff; the all-metal
construction gives freedom from long-term distortion.
Optical (and other) systems for space application must retain their precision
despite extreme changes in levels of solar energy exposure. Figure 17.7
Ł Contact details: ERG Materials and Aerospace Corporation, 900 Stanford Ave, Oakland, CA
94608, USA. Phone: (510) 658-9785; Fax: (510) 658-7428.
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