Session A7
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Disclaimer — This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University
of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on
publicly available information and may not provide complete analyses of all relevant data. If this paper is used for any purpose
other than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at the
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ENVIRONMENTAL BENEFITS OF CERAMIC MATRIX COMPOSITES IN JET
ENGINES
Brandt Miao, [email protected], Mena 1pm, Brendan Marani, [email protected], Vidic 2pm
Abstract—Most mainstream transportation methods involve
the burning of fuel to power an engine which in turn releases
harmful emissions into the atmosphere. With environmental
consciousness being such a high priority issue, a devotion to
developing more fuel-efficient engines has grown in recent
years. One such result emerging from these efforts involves
material usage within aircraft engines. The implementation of
ceramic matrix composites (CMCs) into jet engines of aircraft
provides a multitude of benefits, and drastically increases
engine efficiency. The enormous turbines, compressors, and
shrouds of most current jet engines are constructed from
nickel based superalloys. CMCs, in this case silicon carbide
fibers reinforced in a silicon carbide matrix, aim to replace
these superalloys by offering substantially better thermal
capabilities and much lighter weights. Manufacturing these
CMC parts has proven to be the biggest challenge in their
implementation; however, mass production methods
involving numerous heat treatments are becoming more
viable. As this process continues to improve, an increasing
amount of jet engines will be able to use these lighter, more
durable parts. A jet engine running with CMC components
has shown to yield fuel savings of up to 15% when compared
to an engine of traditional nickel based superalloys. This fuel
reduction not only saves companies money, but it lessens the
harsh carbon footprint of air travel, making CMCs both
economic and environmentally sustainable. Aircraft are
currently responsible for around 11% of the carbon dioxide
emissions released in the United States, and it is estimated
that these values will triple by mid-century. The immediate
benefits of CMC usage in aircraft engines are apparent, but
analyzing the less obvious results is just as necessary. The
production of CMCs does produce waste as a byproduct,
however this is an upfront downside that can be outweighed
by the continuous fuel savings. Recycling is another concern
that needs to be addressed. Currently, options for reusing
CMCs are slim, but future research may be able to change
this. The introduction of CMCs into the aircraft industry is a
promising step towards a cleaner future.
Key Words —Aircraft Emission, Ceramic Matrix Composites,
Engine Efficiency, Jet Engine, Silicon Carbide
University of Pittsburgh Swanson School of Engineering 1
3.31.2017
AN INTRODUCTION TO CMCS AND
ENGINE EFFICIECY
Environmental awareness is an ever-increasing topic in
the world of transportation due to heavy use of combustion
engines. These engines burn fuel and in return release high
amounts of carbon and nitrogen oxide emissions. For aircraft,
the lighter the plane, the less fuel that needs to be consumed
during flight. One such way that engineers have been able to
achieve this is through the usage of lighter materials.
Recently, ceramic matrix composites have been a promising
material to replace the nickel based superalloys used in the
turbofan engines of commercial airliners due to their extreme
light weight and thermal capabilities. CMCs are, however,
nothing new to this world. Automotive applications of CMCs
were first studied in the 1990s, and in the 2000s they were
implemented in high performance sports cars [1]. The
manufacturing process of these CMC brake discs and clutches
however were extremely limited to only top-tier performance
cars due to the impractically high production costs.
Fortunately, this is no longer the case. Advancements in liquid
silicon infiltration processes have reduced both the time and
cost of mass producing CMCs [2]. This process involves
surrounding ceramic fibers with carbon, and submerging
them into liquid silicon to allow the carbon and silicon to react
and form the ceramic matrix. The emergence of this material
as a much more viable alternative allows the benefits
associated with it to be more easily reaped at a commercial
level.
COMPREHENDING THE WORKINGS OF A
JET ENGINE
Almost all commercial aircraft utilize turbofan jet
engines. The main components of this engine include an
intake fan, a high-pressure compressor and turbine, a lowpressure compressor and turbine, and a combustion chamber,
as seen in Figure 1.
Brandt Miao
Brendan Marani
concrete. Crystalline ceramics, such as the silicon carbide
(SiC) used in the CMCs of aircraft engines, are known for
having exceptional hardness, but also being brittle. Therefore,
by combining a SiC matrix with a reinforcing fiber, the
resulting CMC will inherit the hardness of the ceramic matrix,
while the fibers will stop brittle fractures. Different types of
CMCs are referenced as “fiber/matrix”, so carbon (C) fibers
in a silicon carbide matrix is given shorthand as “C/SiC”.
Physical Properties
The majority of current jet engines utilize nickel based
superalloys specifically designed to withstand high
temperatures. Large amounts of research and development
have been put towards optimizing nickel based superalloys
for aircraft engines, but the material in and of itself has
limiting factors. CMCs have been a candidate material to
replace these nickel based superalloys for some decades now,
but are just now becoming commercially available. Previous
production methods required up to ten cycles of treatment to
create the appropriate matrix, whereas current processes only
require one [2]. The additional cycles originally made for a
time-inefficient process, as well as a costly one due to the
need for additional materials. The resurgence of CMCs aims
to finally replace the use of nickel based superalloys. Many
different types of CMCs exist, each with their own unique
properties. Silicon carbide ceramics have proven to be the
most effective for use of both the fiber and matrix of CMCs
in jet engines. These SiC/SiC CMCs yield two major benefits
over the traditionally used nickel superalloys: significantly
better operating temperatures, and a weight reduction of
around 33%.
The specific strength of a material is a measure of force
per unit area at failure. Comparing specific strength values of
materials at a given temperature is an effective way to assess
the thermal capabilities of the materials. Figure 2 shows a
graph of various types of CMCs and other materials, most
notably nickel based superalloys, and their specific strength
as a function of temperature.
FIGURE 1 [3]
Depiction of the components of a turbofan jet engine
Surrounding the turbines are large stationary shrouds, which
encase the turbines and help better direct air flow. These
components of the engine which experience the greatest
exposure to extreme temperatures are referred to as the core.
As air flows into the high and low pressure compressors, it is
compressed to the necessary temperature and pressure needed
for combustion, which occurs in the combustion chamber.
Combustion further raises the temperature and pressure of the
air as it moves on to flow through the turbines, powering their
respective compressors. The significant difference in
temperature and pressure of the exhaust air provides thrust to
power the aircraft. Air that does not flow through the
compressors goes through the bypass ducts, represented by
the pink colored channels above and below the core in Figure
1. The bypass ducts narrow as they near the rear of the engine,
causing the air to achieve a high exhaust velocity. This
process is similar to how a balloon produces a propulsion
force when the neck is let open and air is allowed to flow out
freely. In a jet engine, this process creates additional thrust
force in conjunction with the thrust from the core. The
primary components of interest at this point in CMC
production include those of the engine’s core.
CMCS: UNDERSTANDING TECHNICAL
ASPECTS
Composition
Composites are constructed from multiple different
materials with different properties. The composite will retain
many of the characteristics of its parent materials, often
resulting in a more favorable material. A common example of
a composite material is reinforced concrete. Concrete on its
own retains its shape well, but will break easily when
stretched. To account for this weakness, steel bars are
implemented into the concrete to increase its tensile strength.
Here, the steel bars are acting as the fibers of the composite,
while the concrete is the matrix which surrounds the fibers.
Ceramic matrix composites are a group of composite
materials with a similar overall structure to reinforced
FIGURE 2 [4]
Graphical representation of the specific strengths of
various materials at different temperatures
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This data comes from Professor Nitin P. Padture, the head of
Brown University’s Advanced Ceramics and Nanomaterials
Laboratory. The graph shows that C/SiC CMCs seem to offer
better overall specific strength; however, they suffer one
critical drawback. Professor Padture notes that while C/SiC
CMCs have a higher specific strength, they are not as durable
as SiC/SiC CMCs. SiC/SiC CMCs therefore, have a much
more elongated lifespan, and are a better option for
commercial jet engines since they will require less
maintenance. In terms of jet engines, a SiC/SiC CMC built
engine is capable of operating at up to 400°F (204°C) hotter
than one of nickel based superalloys [5]. As a result of this,
air that was previously needed to cool down the inferior nickel
based superalloys and prevent component failure can be
redirected to the bypass ducts. With more air flowing through
the bypass ducts, more non-combustion related thrust can be
produced.
A current jet engine is not composed entirely of nickel
based superalloys, so it is important to note how much they
contribute to the overall weight of the engine. The Mineral,
Metals, and Materials Society (TMS) estimates that nickel
superalloys are responsible for about 50% of the weight of a
jet engine [6]. While the actual numeric weight of a jet engine
varies tremendously with different models, in total one third
of the weight of the engine can be shed off, equating to
hundreds of pounds, even the lightest models. Significant
weight reduction requires less lift force to keep the aircraft
suspended in air during flight. This lift force is directly related
to the thrust force, meaning that less thrust from the engine
would be required for aircraft operation. However, the
development and optimization of spinning CMC components
yield benefits even farther than just this. Citing the definition
of rotational inertia and the rotational application of Newton’s
second law of motion allow this to be proved through physics.
Rotational inertia can be defined generally by I = Cmr2, where
I is the object’s rotational inertia, C is a shape-dependent
constant, m is the objects mass, and r is the radius of the
object. Rotationally, Newton’s second law states that T = Iα,
where T is the net torque on the object, I is once again the
object’s rotational inertia, and α is the object’s angular
acceleration. Combining these effectively provides an
equation which shows that torque varies directly with mass.
In other words, CMC parts of less mass will require less
torque provided by the airflow to achieve the same angular
acceleration as their nickel based superalloy counterparts. The
excess air can therefore be redirected to the bypass ducts for
further compression and thrust in a similar manner as the
excess cooling air from improved thermal performance can.
This effectively increases the percentage of engine thrust
produced through non-combustion related sources.
and impregnating them with a carbon-rich resin. This creates
a tape of fibers, which is shaped to the necessary dimensions
with a mold. A heat treatment is applied to the molded tape to
set the geometry of the part. A burnout process called
pyrolysis is then carried out to bake out unwanted compounds
as a waste byproduct, resulting in a porous carbon matrix
surrounding the fibers. The pores in the matrix are filled with
molten silicon, which reacts with the carbon in the matrix to
create the SiC matrix [2]. The fabrication of CMCs with this
method is referred to as liquid silicon infiltration (LSI). The
LSI production method produces a material that is incredibly
dense in the sense that it has an extremely low porosity and
level of impurity, allowing the resulting CMC to be incredibly
resistant to corrosion.
FIGURE 3 [2]
Visual outline of the LSI process
In most cases combining two brittle ceramic materials
also yields a brittle material. This is where the initial
proprietary coating of the fibers comes into play. The United
States Department of Energy’s Oak Ridge National
Laboratory has revealed that the bond-altering coating applied
to the SiC fibers at the beginning of production changes the
way in which the fibers and the matrix interact [5]. This
chemical alteration allows the SiC fibers to act less brittle, and
are able to carry the load on the material. As a result, the
SiC/SiC CMC obtains a new dimension of strength, and
becomes a valuable material in jet engine production.
The LSI production method has offered a much cheaper
and faster way to produce CMCs than other methods. Plans to
set CMCs into mass production have already started and show
no signs of stopping soon. Currently, the NGS Advanced
Fibers Company in Japan has the only plant dedicated to SiC
ceramic fiber production, but GE Aviation is in the process of
building two plants in Alabama to accommodate for the
expected tenfold increase in demand of CMCs within the next
decade [7]. One plant will be dedicated to producing SiC
ceramic fibers similar to the NGS plant in Japan, and the other
will be used to transform these fibers into the CMC material
using liquid silicon infiltration. GE Aviation’s new plants will
be built specifically to manufacture engine parts, as the engine
is the most suitable use of CMCs due to high temperatures.
Mass Production
In aircraft jet engines, both the fiber and the matrix are
made from SiC ceramics. The production process of SiC/SiC
CMCs begins by adding a bond-altering coating to SiC fibers,
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combustor liners [5]. While all these parts are static and do
not move during operation, the goal of large aviation
corporations is to reach a point where spinning components
such as turbines and compressors can also be optimized for
CMC production. Rotating engine parts benefit even more
from weight reduction than stationary ones, because not only
do they reduce the aircraft’s overall weight, the individual
part’s rotational inertia is reduced. Since these parts will be
spinning, the lighter weight means they will turn easier,
allowing them to compress air more efficiently. CFM
International’s promising start with turbine shrouds is a step
in the right direction for large-scale implementation of CMCs
in jet engines. Reaching the level of use planned for the GE9X
and beyond could mean massive improvements in terms of
engine efficiency.
Corporal Pioneer: GE Aviation
A joint venture between GE Aviation and Safran
Aircraft Engines known as CFM International is the producer
of the world’s most successful commercial aircraft engine, the
CFM56. With over 22,000 installed engines delivered, the
CFM56 is being used in almost twice as many aircraft than
the next most popular engine [8]. CFM’s newest engine, the
LEAP, aims to replace the CFM56. The LEAP engine
introduces the use of a large ceramic matrix composite turbine
shroud. While using only one CMC part may sound
lackluster, its effects are easily observed. CFM International
reports and guarantees the LEAP engine to have fuel savings
of at least 15% over the CFM56, which uses no CMC parts
[5]. Inspecting the prices of these engines, however, reveals
one of the more negative sides of the LEAP engine. At a list
price of $13.9 million, the LEAP exceeds the price of the
CFM56 by $3.9M [9]. This should not be surprising however,
as it is often the case to have to pay a premium for fuel
efficiency. For example, a car might come in two trim levels;
standard and hybrid. The hybrid model will tend to be more
expensive upfront, but the real savings are observed in the
long-run with reduced fuel costs. This same idea can be
applied to the LEAP and CFM56 engines. The United States
Aviation Research Group notes that a typical flight in a
CFM56-powered Boeing 737-800 costs $3,326 in fuel per
hour of flight [10]. Considering the use of two engines per
737-800 and the LEAP engine’s 15% fuel savings, this
translates to $2,827 an hour, meaning it takes 15,631 hours of
flight to pay off the premium of the two LEAP engines per
aircraft. This is a relatively trivial feat, considering that the
Massachusetts Institute of Technology’s Airline Data Project
reports that the average 737-800 will surpass this amount
within about 4 years of a 20+ year long life expectancy [11].
The primary goal of a company is to provide a good or
service and make a profit from it. Looking beyond the initial
four years of use proves why these CMC engines are such an
economically sustainable investment for companies. After
offsetting the initial cost, every four years a single 737-800
aircraft out of a company’s fleet will save $2.45M each year
in fuel costs. Factoring in fleets of up to one hundred 737800s and around sixteen more years of operation, the savings
reach well into billions of dollars. By saving companies such
large amounts of money, CMCs are allowing airline
companies to contribute to economic sustainability. With the
saved money, companies are able to provide a better good or
service, which is then more desired by customers. As a
company’s customer base grows as a result of this, they incur
even more profit, and the cycle repeats itself. Both parties are
satisfied and the process is self-perpetuating, and therefore
sustainable.
The capabilities of ceramic matrix composites in jet
engines are not defined simply by the LEAP engine alone. GE
Aviation has plans to produce the GE9X engine in 2019,
which will consist of five total CMC components including a
shroud similar to the LEAP engine, and multiple nozzles and
EXAMINING ENVIRONMENTAL IMPACT
Understanding Aircraft Emissions
Efficiencies through productivity and cost are not the
only benefits CMC parts have to offer. Another dimension of
the problem engulfing our world now is protecting the
environment while retaining the brute power of technology.
Currently, airplane emissions are a sizeable portion of what is
tearing down the atmosphere. A report from the Center of
Biological Diversity states that with aircraft usage continuing
on the path it is now, 43 gigatons (43 trillion kilograms) of
carbon dioxide are to be let off into the atmosphere,
destroying ecosystems and the barrier that protects earth from
cancerous UV rays. The United States itself released 200
billion kilograms of carbon dioxide in 2014 [12]. Carbon
dioxide is one of the abundant greenhouse gases in the
atmosphere. While greenhouse gases are important in keeping
the Earth at a sustainably warm temperature, too many of
them causes the phenomenon of global warming [13]. Carbon
dioxide emissions also make oceans and bodies of water more
acidic, disturbing the water’s pH balance and killing aquatic
life. Aircraft pollution contains a dangerous compound called
nitrous oxide in addition to carbon dioxide [14]. Nitrous oxide
right now is the third strongest greenhouse gas in countries
like the United Kingdom. It does not have a major impact on
the local ecosystems; however, it does a great deal of damage
to the Earth’s atmosphere. At this point, global aircraft
emissions are growing to be equivalent to the emissions
produced by an entire country’s worth of air pollution, from
cars to factories. While automotive emissions unsurprisingly
exceed them, aircraft emissions, if counted as the total
emissions released by a single country, would rank seventh
highest in the world, only slightly behind countries like
Germany and ahead of countries like Sweden [12]. Aircraft
emissions themselves have tripled in quantity over the last
couple of years, and right now it seems there is no decrease in
their destructive power. While the amount of emissions given
off by aircraft has always been a great deal, they are growing
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at alarmingly fast rates, and action must be taken in order to
avoid the harmful effects.
Recycling CMCs
A distinct issue with CMCs is the difficulty in recycling
them. While recycling the composites would not happen for
a number of years due to their survivability and lesser need
for corrosion treatment and other maintenance, the process
must still be considered. When an aircraft is at the end of its
lifespan, multiple waste management and environmental
legislations, such as the EU-directive for End-of-Life
Vehicles, agree that all engineering materials should be
recyclable and sustainable in some way [16]. As with most
other materials in existence, to remain powerful and practical,
they must be sustainable in some way, whether it be in
recycling old materials into new ones or converting old
materials into energy. In the long term, almost all materials
are limited. CMCs themselves are recyclable, but the process
is costly and the remnants that are obtained from recycling are
small in comparison to the quantity that is being initially
recycled. Composites are not as easy to recycle as regular
metals because with composites, homogeneous particles must
be liberated in order to separate the CMC into its raw
materials [16]. The fiber or matrix itself hinders the process
as well because of the types of reinforcement that holds the
material together. Recycling techniques exist that can take the
composites and turn them completely into energy using
combustion. While these processes are very good at
producing energy, the ultimate goal in recycling these
composites is getting material back for future use. The market
itself for recycling CMCs is bare to say the least, because as
seen, there is very little room for profit. The recycled parts
that are created in recycling plants turn out to cost more than
their newly created counterparts and are of a lesser quality
than the newly created CMCs [16]. This brings up the
question for many companies to consider whether it is worth
it to look environmentally sensitive to settle the qualms of
people preaching for environmental change and pay out, or
simply pay for newly created, high quality material.
Multiple legislations from the EU-directive for End-ofLife Vehicles and other types of waste management are
allowing for increased demand in this field, however broad
commercialization for the recycling market is still far off [16].
One specific organization that set out to help push this process
along is the Aircraft Fleet Recycling Association (AFRA)
[17]. Comprised of Boeing and multiple other aerospace
companies, AFRA set an objective to state that retired aircraft
are not to be simply disposed of; rather they should be
recycled and be put to further use for the company. They have
conducted research that pushes towards finding processes that
can reinvigorate the used, old materials and give the created
recycled materials the same properties that their virgin
counterparts may have. AFRA does not only this, but it makes
sure that the processes that happen are carried out in the
proper manner. They conduct strict audits that make sure that
all removal and recycling processes are held to high standard
and are safe. This action helps keep all the recycling processes
Linking CMCs to Emissions
There are many different ways to address this problem
in an aircraft. One such way is to use a different form of
energy other than the primary environmental threat: fossil
fuels. Other options available include solar and electric
energy. However, while being implemented in cars and
various other automobiles, transferring the technology from
ground travel to air travel is a far-off prospect and has rarely
been put into action. Safety issues must be considered first.
Ceramic matrix composites are a way for aviation companies
and manufacturers to approach this environmental issue,
while also improving the aircraft itself and its cost. As
specified previously, CMC parts in an airplane engine have
enhanced features, like heat resistance and lower weight. Both
of these properties help improve the impact on the
environment, and reduce emissions. The lower weight of
CMCs allows for a lighter aircraft in general. This means that
the engine itself does not need to produce as much lift,
reducing the amount of fuel that must be used and therefore
reducing the amount of carbon dioxide emissions that are put
into the atmosphere. The other big jump in efficiency, heat
resistance, has a similar effect. An increase in heat resistance
allows the engine to operate at higher yet still safe
temperatures before the heat causes the engine to fail. The
hotter the engine can be, it can produce greater levels of lift
and thrust. This allows for the engine to take in less fuel and
provide the same amount of power required to fly the aircraft
to its destination. With less fuel expenditure comes less need
to burn the fuel itself creating less production of harmful
carbon dioxide and nitrous oxide gases.
Adverse Effects
While this technology does benefit the environment
from its ability to decrease the amount of carbon dioxide and
other harmful gases from entering the atmosphere, it does
have downsides that cannot be ignored. While the efficiency
of production has increased in terms of how long it takes to
produce a substantial amount of CMCs, it does not make the
process any more environmentally friendly than it was in the
first place. The process itself requires large quantities of
energy and leaves behind waste. During the processing and
creation of the ceramic matrix composites, residual material
and other gases may be given off depending on the process
used. This means more waste and potentially toxic chemicals
going off to various landfills. One such example is from the
process previously mentioned, liquid silicon infiltration [2].
One of the big disadvantages of this method is that after the
process is completed, there is residual silicon left over in the
matrix of fibers. This silicon must be washed and cleaned
thoroughly, and that residual waste must be disposed of.
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from going unnoticed, or passed at below proficient
standards.
Ceramic matrix composites should be used for their
superior efficiency and weight reduction, not for their
recycling capability. As this material is partly experimental at
the moment, extensive research into strong forms of recycling
has not been fully accomplished yet. However, simply
because ceramic matrix composites cannot be recycled well
right now does not mean that they are not beneficial to the
environment in the long run. As more research and
development is put towards developing superior recycling
methods, the usage of CMCs becomes increasingly more
sustainable.
produces 30% less nitrous oxide gases then the average large
aircraft engine, 10% less fuel burn rate than the widely used
GE90 engine, and a 5% better fuel consumption rate versus
any twin-aisle engine available [18]. This engine is projected
to come in 2019. In the future, more engines will be created
with an increasing number of CMC parts. The GE9X already
produces astounding results in its environmental capacity,
reducing exhaust emissions by one third. As CMC parts are
optimized and added to jet engines, continually increasing
benefits can be yielded. A problem that needs to be addressed
in the future is manufacturing cost. Production capabilities
have already grown a great deal from what they were 20 years
ago, and in our age of technology everything is being
produced at high rates. As more companies see the advantage
in this, the industry for CMCs will become more competitive,
driving companies to want to lower their production price.
With enhanced efficiency and power, CMC engines will save
money for companies, through less fuel and less required
maintenance. When these parts are worn through, enhanced
recycling techniques will be used, possibly discovered from
organizations like AFRA, so that these CMC parts can be
repurposed at the same or greater efficiency that their virgin
counterparts can produce. The future holds a promising
position for ceramic matrix composites in the power of jet
engines. With environmentally sound power and efficiency
constantly being pushed to new heights, ceramic matrix
composites will lead the aircraft industry into a new age of
strength.
Weighing the Benefits
While these are distinct issues that need to be treated in
the future for maximum adaption to the environment, the
current state of power and efficiency of ceramic matrix
composites overturn these disadvantages in many cases. In
this sense, ceramic matrix composites are a bit like solar
panels, a form of renewable energy. When creating the solar
panels, multiple toxic gases are given off into the atmosphere.
Regardless, solar energy is still considered eco-friendly
because in the long term, solar panels prevent a lot more gases
from being spilled into the atmosphere, opposed to coal and
fossil fuel burning. In the creation of ceramic matrix
composites, multiple gases and other chemical runoff may
occur, but the efficiency that these CMC parts provide for
airplane engines pushes a positive environmental impact in
the long run. In this scenario, CMCs can be considered
superior to solar panels, because the silicon runoff and
leftovers that occur when creating ceramic matrix composites
can be recycled, as they can easily be restored into usable
silicon. More proficient engines created with CMCs reduces
the amount of gases including carbon dioxide and nitrous
oxide by up to 30% when compared to competitors in the
commercial market [18]. The amount of exhaust an engine
produces per flight is much more harmful than the waste that
comes out of creating the singular parts. Not to mention these
flights stack on top of each other, and within a few years, the
aircraft is not only easily breaking even, but it will have far
exceeded its initial environmental drawbacks.
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THE FUTURE OF CMCS IN AIRCRAFT
Right now, the most advanced CMC engine, the LEAP
engine, is fitted with only one CMC part. This single
component is part of what separates the LEAP engine from its
standard nickel based superalloy counterpart by an efficiency
advantage of 15% [5]. Currently, GE is creating the next
generation engine, the GE9X, and it yields many impressive
figures [18]. The GE9X, which is produced using five
separate ceramic matrix composite parts, is the quietest
engine ever created, has the lowest emissions from a GE
engine, and has the best rate of fuel consumption. This
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ACKNOWLEDGMENTS
We would like to thank our writing instructor Rachel
McTernan for continually providing us with feedback on our
progress. We would also like to thank Dr. Budny and the
University of Pittsburgh Swanson School of Engineering for
allowing us the opportunity to write this paper, giving us
experience on the topic and exposure to feedback from
professional engineers. Additionally, thanks to our Co-Chair
Colleen Hilla for meeting with us and reviewing the various
sections and areas of our paper and how we could improve
upon them.
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