Q2-27.
Radomes, wing tips, stabilizer tips, and an-
NONMETALLIC MATERIALS
tenna covers are made from what type of
In addition to metals, various types of plastic mate-
plastic?
rials are found in aircraft construction. Transparent
plastic is found in canopies, windshields, and other
METALLIC MATERIALS
transparent enclosures. Handle transparent plastic
LEARNING OBJECTIVE: Identify the
surfaces with care, because this material is relatively
soft and scratches easily. At approximately 225F,
properties of metallic materials used in aircraft
construction.
transparent plastic becomes soft and very pliable.
Metallurgists have been working for many years to
Reinforced plastic is made for use in the
improve metals for aircraft construction. Each metal
construction of radomes, wing tips, stabilizer tips,
has certain properties and characteristics that make it
antenna covers, and flight controls. Reinforced plastic
desirable for a particular application, but it may have
has a high strength-to-weight ratio and is resistant to
other qualities that are undesirable. For example, some
mildew and rot. Its ease of fabrication makes it equally
metals are hard, others comparatively soft; some are
suitable for other parts of the aircraft.
brittle, some tough; some can be formed and shaped
Reinforced plastic is a sandwich-type material. See
without fracture; and some are so heavy that weight
figure 2-25. It is made up of two outer facings and a
alone makes them unsuitable for aircraft use. The
center layer. The facings are made up of several layers
metallurgist's objectives are to improve the desirable
of glass cloth, bonded together with a liquid resin. The
qualities and tone down or eliminate the undesirable
core material (center layer) consists of a honeycomb
ones. This is done by alloying (combining) metals and
structure made of glass cloth. Reinforced plastic is
by various heat-treating processes.
fabricated into a variety of cell sizes.
You do not have to be a metallurgist to be a good
AM, but you should possess a knowledge and
High-performance aircraft require an extra high
understanding of the uses, strengths, limitations, and
strength-to-weight ratio material. Fabrication of
other characteristics of aircraft structural metals. Such
composite materials satisfies the special requirement.
knowledge and understanding is vital to properly
This construction method uses several layers of
construct and maintain any equipment, especially
bonding materials (graphite epoxy or boron epoxy).
airframes. In aircraft maintenance and repair, even a
These materials are mechanically fastened to
slight deviation from design specifications or the
conventional substructures. Another type of composite
substitution of inferior materials may result in the loss
construction consists of thin graphite epoxy skins
of both lives and equipment. The use of unsuitable
bonded to an aluminum honeycomb core.
materials can readily erase the finest craftsmanship.
Q2-24.
What is the most widely used metal in modern
The selection of the specific material for a specific
aircraft construction?
repair job demands familiarity with the most common
Q2-25.
What is the world's lightest structural metal?
properties of various metals.
Q2-26.
At what temperature does transparent plastic
PROPERTIES OF METALS
become soft and pliable?
This section is devoted primarily to the terms used
in describing various properties and characteristics of
metals in general. Your primary concerns in aircraft
maintenance are such general properties of metals and
their alloys as hardness, brittleness, malleability, ductil-
ity, elasticity, toughness, density, fusibility, conductiv-
ity, and contraction and expansion. You must know the
definition of the terms included here because they form
the basis for further discussion of aircraft metals.
Hardness
Hardness refers to the ability of a metal to resist
abrasion, penetration, cutting action, or permanent
Figure 2-25.--Reinforced plastic.
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