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use composite materials extensively in the 20-25% weight percent range.
Figure 4. Cutaway view of the Eurofighter Typhoon structure.
The composites applications trend over the years in US and European combat aircraft is
summarized in Figure 5. As shown in the figure, the composite fraction of the structural weight
for fighter and attack aircraft seems to be leveling off at 30 percent. The payoff in combat aircraft
is in performance in the form of reduced weight, increased payload and speed. Based on the
prevalent applications seen by composites in combat aircraft, this limit is an indicator of lack of
confidence in composite applications in highly 3-D loaded fuselage and wing substructures such
as the main spars, and bulkheads e.g. the wing and landing gear attach bulkheads. Manufacturing
and structural demonstration of innovative concepts in these areas is the next step if the 30
percent barrier is to be broken. Affordability is also a concern since costs associated with aircraft
specific structural concept development, production implementation and recurring fabrication of
complex composite parts with built in metal fittings and trunnions can exceed the $/lb saved
ceiling for an aircraft. Therefore, cost reduction strategies for heavily loaded substructure need to
be developed.
(SM1) 1-5
0
10
20
30
40
50
60
70
80
90
1965 1970 1975 1980 1985 1990 1995 2000 2005
Business Jets
Commercial
Bombers & Transports
Fighters
Rotors
Advanced Composites Content
(% of Structural Weight)
F-14 F-15 F-16
F-18C/D
B-1B
A310
AV-8B
AVTEK
400 BEECH
STARSHIP
A320
C-17
777
F-22
F-18E/F
RAH-66 V-22
F-111
Year
Figure 5. Composite Application Trend in US and European Combat Aircraft
Another feature to note in Figure 5 is the weight fraction of composites in the B-2, which seems
to have broken the 30 percent barrier. This in spite of being a heavy lift class of aircraft where, as
will be shown later, the limiting composites percent weight is even lower than for fighter/attack
category of combat aircraft. Figure 6 illustrates the extent of carbon fiber and glass fiber
composites usage on the B-2 that results in the high weight fraction. For the B-2, stealth or
minimizing the radar cross-section was the primary driver and as such carbon fiber composites
were extensively used in the primary structure to offset the weight penalty from radar absorbing
materials applied to the exterior. Due to the lower density of composites compared to metals, the
volume fraction of the airframe that is composite is considerable and may exceed 60 percent. Of
special note in the case of the B-2 is that stealth performance requirements dictate significantly
increased usage of composites.
(SM1) 1-6
Aft / Center
Fixed Wing Assembly
Trailing
Edge
GLAS
Inboard Elevon
Mid Elevon
Outboard Elevon
Split Rudder
Outboard Wing
Assembly
Intermediate
Wing Assembly
Crew Station
Assembly
Nose Landing
Gear
Main Landing
Gear
Wing
Tips
Leading
Edge
Fiberglass / Epoxy
Fiberglass / Polyimide
Graphite / Epoxy
Graphite / Polyimide
Aluminum
Titanium
Figure 6. Application of Composites in the B-2 Bomber
Transport Aircraft
Operating efficiency and economy with passenger comfort are paramount in commercial
transport aircraft. Reduced airframe weight pays off in fuel economy and, therefore, reduces
Direct Operating Costs (DOC) for the operators. Several NASA Research and Development
Programs (e.g. Advanced Composites for Energy Efficiency) have demonstrated the DOC
savings potential of carbon fiber polymer matrix composites. In addition, NASA programs have
recognized the need to reduce associated manufacturing costs so that the increased initial
acquisition costs do not offset the DOC savings attained with composite structures. NASA’s
Advanced Composites Technology program developed prototype composite wing and fuselage
structures for commercial transports using integrated design and manufacturing concepts that
would lower the costs of such structures.
The first significant application of composites in commercial transports, however, was in Europe
in 1983 when Dasa Airbus introduced an all composite rudder for the A300 and A310, followed
in 1985 by a much more complex vertical tail fin. The metal vertical tail had about 2,000 parts
excluding fasteners, whereas, the composite vertical had less than 100 parts. As a consequence,
the composite vertical was not only lighter but also lower cost than the metal vertical because of
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