Figure 2: Materials used to manufacture Boeing 787 Dreamliner
man first took to the air. Composite materials
contributed a major part in weight reduction.
Nowadays there are three main types of composite
materials widely used in aerospace: carbon fibre,
fibre glass and aramid-reinforced epoxy. There
are others, such as boron-reinforced composite
(itself a composite formed on a tungsten core).
Composite materials are versatile, used for both
structural applications and components in all
aircraft and spacecraft, from hot air gondolas and
gliders, to passenger airliners and war planes.
Depending on mechanical proper ties,
composite materials are used in different areas of
an aircraft and its components. Carbon fibre, for
example, has a unique fatigue behaviour and can
be somewhat brittle, as Rolls Royce discovered
in the 1960s when the innovative RB11 jet
engine with carbon fibre compressor blades
failed catastrophically due to bird strikes. In an
experimental programme, Boeing successfully
applied about 1,500 composite parts to replace
metal components in their helicopter production.
The application of composite-based components
in place of metal as part of the maintenance
cycle is growing rapidly in commercial and leisure
aviation. Overall though, carbon fibre is still
the most widely used component of composite
materials in the aerospace industry.
The competitive nature of the aircraft
manufacturing business ensures that every
possibility to reduce operating costs is explored
and exploited, especially when there is need for
new materials. New materials can be defined as
those which have yet to be applied in ‘as-designed’
application in aviation. Some of these materials,
particularly Metal Matrix composites (MMC) and
Ceramic Matrix composites (CMC) have had some
in-flight testing and are approaching military use
but have yet to gain wide ranging acceptance by
Original Equipment Manufacturers (OEMs) for
various reasons. Other developments include
Carbon Nanotube Technology, Shape Memory
Metals (SSMs) and experiments with different
core materials.
Pre-impregnated or prepreg materials
are reinforced materials that have been pre-
impregnated with either thermoplastic or
thermoset resin, hence their name prepreg. Resin
impregnation process precisely controls the fibre
to liquid thermoset resin. Excess resin is removed
from the reinforcement and the resin undergoes
partial curing, changing from liquid to the solid
state. This known as the “B-stage”. Prepreg in
B-stage requires refrigerated storage conditions.
The autoclave curing process is then activated by
heat and pressure application.
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