Page 205 - Aeronautical Engineer Data Book

164 Aeronautical Engineer’s Data Book
loads with their own internal structure. Small,
low speed aircraft have straight, almost rectan­
gular, wings. For these wings, the main load is
in the bending of the wing as it transmits load
to the fuselage, and this bending load is carried
primarily by the spars, which act as the main
structural members of the wing assembly. Ribs
are used to give aerodynamic shape to the wing
profile.

10.2 Materials of construction
The main structural materials of construction
used in aircraft manufacture are based on
steel, aluminium, titanium and composites.
Modern composites such as carbon fibre are in
increasing use as their mechanical and temper­
ature properties improve. Tables 10.3 and 10.4
show indicative information on the properties
of some materials used. Advanced composites
can match the properties of alloys of
aluminium and titanium but are approxi­
mately half their weight. Composite material
specifications and performance data are
manufacturer specific, and are highly variable
depending on the method of formation and
lamination. Composite components in
themselves are costly to manufacture but
overall savings are generally feasible because
they can be made in complex shapes and
sections (i.e. there are fewer components
needing welding, rivets etc.). Some aircraft
now have entire parts of their primary struc­
ture made of carbon fibre composite. Stainless
steel is used for some smaller and engine
components. Table 10.5 gives basic data on
constituents and properties.

10.2.1 Corrosion
It is important to minimize corrosion in
aeronautical structures and engines. Galvanic
corrosion occurs when dissimilar metals are in
contact in a conducting medium. Table 10.6
shows the relative potentials of pure metals.