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Composites And Carbon Fiber In The Dreamliner
Boeing's 787 Dreamliner
How Composites
And Carbon Fiber Are Used
by Todd Johnson
What is the average density
of the materials used in a modern airliner?
Whatever it is, the reduction
in average density has been huge since the Wright Brothers flew the first
practical airplane.
The drive to reduce weight in
airplanes is aggressive and continuous and accelerated by rapidly climbing fuel
prices.
This drive lowers specific
fuel costs, improves the range/payload equation and helps the environment.
Composites play a major part
in modern airplanes and the Boeing Dreamliner is no exception in maintaining
the decreasing weight trend.
Composites and Weight Reduction
The Douglas DC3 (dating back
to 1936) had a take-off weight of about 25,200 pounds with a passenger
complement of about 25.
With a maximum payload range
of 350 miles, that's about 3 pounds per passenger mile.
The Boeing Dreamliner has a
take-off weight of 550,000 pounds carrying 290 passengers. With a fully loaded
range of over 8,000 miles, that's roughly ¼ pound per passenger mile - 1100%
better!
Jet engines, better design,
weight saving technology such as fly by wire - all have contributed to the
quantum leap – but composites have had a huge part to play.
They are used in the
Dreamliner airframe, the engines, and many other components.
Use of Composites in the
Dreamliner Airframe
The Dreamliner has an
airframe comprising nearly 50% carbon fiber reinforced plastic and other
composites.
This approach offers weight
savings on average of 20 per cent compared to more conventional (and
outdated) aluminum designs.
Composites in the airframe
have maintenance advantages too.
A typically bonded repair may
require 24 or more hours of airplane downtime but Boeing has developed a new
line of maintenance repair capability that requires less than an hour to apply.
This speedy technique offers
the possibility for temporary repairs and a quick turnaround whereas such minor
damage might have grounded an aluminum airplane. That is an intriguing
perspective.
The fuselage is constructed
in tubular segments which are then joined together during final assembly.
The use of composites is said
to save 50,000 rivets per plane. Each rivet site would have required
maintenance checking as a potential failure location. And that's just rivets!
Composites in the Engines
The Dreamliner has GE
(GEnx-1B) and Rolls Royce (Trent 1000) engine options, and both use composites
extensively.
The nacelles (inlet and fan
cowls) are an obvious candidate for composites. However, composites are even
used in the fan blades of the GE engines.
The blade technology has
advanced tremendously since the days of the Rolls-Royce RB211. The early
technology bankrupted the company in 1971 when it's Hyfil carbon fiber fan
blades failed in bird strike tests.
General Electric has led the
way with titanium-tipped composite fan blade technology since 1995.
In the Dreamliner power
plant, composites are used for the first 5 stages of the 7 stage low-pressure
turbine.
More about Less Weight
What about some numbers? The
GE power plant's light weight fan containment case reduces aircraft weight by
1200 pounds (more than ½ ton). The case is reinforced with carbon fiber braid.
That is just the fan case
weight saving, and it is an important indicator of the strength/weight benefits
of composites.
This is because a fan case
has to contain all debris in case of a fan failure. If it will not contain the
debris then the engine cannot be certified for flight.
Weight saved in blade turbine
blades also saves weight in the required containment case and rotors. This
multiplies its saving and improving its power/weight ratio.
In total each Dreamliner
contains about 70,000 pounds (33 tons) of carbon fiber reinforced plastic - of
which about 45,000 (20 tons) pounds is carbon fiber.
Conclusion
The early design and
production problems of using composites in airplanes have now been overcome.
The Dreamliner is at the peak
of airplane fuel efficiency, minimized environmental impact and safety.
With reduced component
counts, lower levels of maintenance checking and greater airtime, the support
costs are significantly reduced for airline operators.
From fan blades to fuselage,
wings to washrooms, the Dreamliner's efficiency would be impossible without
advanced composites.
Todd Johnson
· Regional Sales Manager for Composites One, a distributor of composite
materials.
· B.S. in Business Management from University of Colorado Boulder's
Leeds School of Business
· Business Development Manager for Ebert Composites Corporation
Experience
Todd Johnson is a former writer for ThoughtCo,
who wrote about plastics and composite materials for 2-1/2 years between 2010
and 2013. He is a Regional Sales Manager at Composites One, a composite
materials distributor in San Diego, CA. Johnson provides support to the Greater
San Diego manufacturers of fiber reinforced and polymer products. He regularly
attends composite industry trade shows including JEC, ACMA, SME, and SAMPE. In
2008 he presented at the Global Pultrusion Conference in Baltimore, MD.
Previously, Todd spent six years as the Business Development Manager for Ebert
Composites Corporation.
Education
B.S., Business, Management, Marketing, and
Related Support Services - the University of Colorado-Boulder's Leeds School of
Business; attended Griffith University in Queensland, Australia.
Todd Johnson
ThoughtCo and Dotdash
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