From the standpoint of function, sandwich parts in naval aircraft can be divided into two broad classes: (1) radomes and (2) structural. The first class, radomes, is a reinforced plastic sandwich construction designed primarily to permit accurate and dependable functioning of the radar equipment. This type of construction was discussed in the preceding section under "Reinforced Plastics."

The second class, referred to as structural sandwich, normally has either metal or reinforced plastic facings on cores of aluminum or balsa wood. This material is found in a variety of places such as wing surfaces, decks, bulkheads, stabilizer surfaces, ailerons, trim tabs, access doors, and bomb bay doors. Figure 1-32 shows one type of sandwich construction using a honeycomb-like aluminum alloy core, sandwiched between aluminum alloy sheets, called "facings." The facings are bonded to the lightweight aluminum core with a suitable adhesive so as to develop a strength far greater than that of the components themselves when used alone.

Another type of structural sandwich construction consists of a low-density balsa wood core combined with high-strength aluminum alloy facings bonded to each side of the core. The grain in the balsa core runs perpendicular to the aluminum alloy facings, and the core and aluminum facings are firmly bonded together under controlled temperatures and pressures.

The facings in this type of construction carry the major bending loads, and the cores serve to support the facings and carry the shear loads. The outstanding characteristics of sandwich construction are strength, rigidity, lightness, and surface smoothness.

NOTE: Although the following References were current when this TRAMAN was published, their continued currency cannot be assured. Therefore, you need to be sure that you are studying the latest revision.

General Advanced Composite Repair Manual, Tech Order 1-1-690, Secretary of the Air Force, Washington, D.C., 1990.

Aircraft Radomes and Antenna Covers, NAVAIR 01-1A-22, Naval Air Systems Command Headquarters, Washington, D.C., 1990.

General Manual for Structural Repair, NAVAIR 01-1A-1, Commander, Naval Air Systems Command, Washington, D.C., 15 July 1969, Change 11, 15 August 1989.