Material selection for unmanned aerial vehicle

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 34-40 © IAEME
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 5, Issue 8, August (2014), pp. 34-40
© IAEME: www.iaeme.com/IJMET.asp
Journal Impact Factor (2014): 7.5377 (Calculated by GISI)
www.jifactor.com
34

IJMET
© I A E M E
MATERIAL SELECTION FOR UNMANNED AERIAL VEHICLE
AKSHAY BALACHANDRAN1, DIVYESH KARELIA2, Dr. JAYARAMULU CHALLA3
1,2UG Students, Department of Production Engineering,
3Professor, Department of Production Engineering,
Fr. Conceicao Rodrigues College of Engineering, FrAgnel Ashram, Bandstand, Bandra (W),
Mumbai, Maharashtra, India, Pin Code: 400 050
ABSTRACT
This paper explains and details about a brief study and comparison of the various available
engineering and structural materials which is the key requirement for the optimum functioning of
Unmanned Aerial Vehicles (UAVs) known as drone and referred to as Remotely Piloted Aircraft
(RPA) of 'Advanced class' of this competition. The major requirements that these materials on UAVs
with respect to physical and mechanical properties must fulfill are: resistance to buckling, high
ultimate tensile strength, less inflammable, high strength to weight ratio, low thermal gradient,
resistance to noise and vibration, resistance against deteriorative fuels and chemicals, low corrosion
and oxidation, ease of shape ability, fastening and joining, high fatigue and endurance limit. In order
to fulfill these requirements, our system comprised of these engineering materials: carbon fiber, fiber
plastic, Balsa, Thermocol, rubber, Aluminium alloy, alloy steel, thin plywood. The system performed
well and stood true on all its expectations. There are off-the-shelf materials available for their
respective tasks but they lack on one parameter or other.Additionally, their cost is prohibitive at
times. The material selection, explained in this paper, is comprehensive, inexpensive and rugged and
can be implemented on any kind of UAV vehicle.
Keywords: Aero, High Strength to Weight Ratio, Balsa, Carbon Fiber, Fiber Plastics.
I. INTRODUCTION
SAE International is a global association of more than 138,000 engineers and related
technical experts in the aerospace, automotive and commercial-vehicle industries. SAE
International's core competencies are life-long learning and voluntary consensus standards
development. To nurture and encourage talent in the field of aviation, SAE International conducts

‘Aero Design Series’ competition annually in the USA. The competition involves student teams from
all over the world designing and fabricating UAVs. Depending on the design and event objectives,
there are three classes in this competition: Micro, Regular and Advanced Class.
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The objective of the Advanced Class, of the 2013 edition of SAE Aero Design Series, was to
design the most efficient aircraft capable of accurately dropping a three pound (3 lb) humanitarian
aid package from a minimum of 100ft off the ground. Though the class was mostly focused on
mission success, students were needed to perform trade studies to optimize empty weight and
anticipate repair build-up weight while meeting several aircraft design requirements.
The Advanced Class also involved an array oftasks to be accomplished to win high flight
points, primary of which was dropping a three pound (3 lb) humanitarian aid package from a
minimum of 100ft off the ground. The objectives were:
1. Team must be able to provide high strength and stability to the UAV at high altitudes and
speeds.
2. Team must be able to resist and balance the forces acting dynamically on the body of the UAV.
3. Team should be able to select the right materials at the right place with the right properties.
Figure 1: Stress analysis
An important requirement of the UAV was that it should have a high precision and accuracy
during flight. For this it was necessary to have high strength to weight ratio, the key requirement.
The design should be aerodynamic for which material used should be easily formable or shapeable.
A Rigid frame for containing the engine and other major functional features and provide rigidity in
motion.Part specific functions. For example: wings, fuselage, landing gear, etc. The entire body
should weigh less so as to minimise the fuel consumption.
Furthermore, it’s evident from the design objectives that a sturdy and rugged design was a
necessity so as to build a stable, stiff and strong body which could assist the pilot on the base station
for precise cargo expulsion. This summarizes the DAS requirements for Advanced class event of
‘SAE Aero Design Series 2013’ and to satisfy the same, this paper proposes a comprehensive study
of engineering materials suitable for UAV:

Parameters Balsa Wood Carbon Fiber Rohacell
Weight 5 5 5
2 4.5 5
Availability 5 5 1
Cost 4 4 0.5
Machinability 5 4 3
Total 21 22.5 14.5
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II. MATERIAL SELECTION

Figure 2: Material study
Strength to weight
ratio
1. Wood (Balsa)
A light weight and strong material, but splinters and requires a lot of maintenance and less
durability. It is stronger for its weight than any other material except for certain alloy steels.Timber is
readily worked by hand, using simple tools and is therefore far cheaper to use than metal. Timber
from deciduous trees is said to be 'hardwood'. It can be seen, therefore, that the term 'softwood'
and 'hardwood' apply to the family or type of tree and do not necessarily indicate the density of the
wood. That is why balsa, the lightest and most fragile of woods, is classed as a hardwood. BALSA,
although very soft and low in strength properties, is a hardwood, which grows in CentralAmerica. It
is the lightest timber in general use and is pinkish white to pale brown in colour. Dueto its porosity,
if it is badly stored or inadequately protected in use, it very readily deteriorates ifexposed to
moisture. Its principal uses in aircraft construction are the making of fairings, filletsand light, low
density contour blocks.
2. Carbon fiber
Carbon fiber (also commonly called graphite) has special properties making it ideal for
applications ranging from aerospace to automobiles. When combined with resin to form a
composite, it produces parts that are extremely light and rigid. Carbon parts are lighter and stronger
than their metal counterparts. For that reason, carbon fiber is being used extensively in the aerospace
industry. High-end vehicles are incorporating carbon to make one piece vehicle frames. Perhaps the
biggest user of carbon fiber is the aircraft industry, both commercial and military. Here are the
biggest users of carbon fiber. Carbon fibre is awesome. It's light, incredibly strong and you can make
almost anything out of it, including planes like the fancy new 787 Dreamliner. What it's not great at,
though, is taking lightning strikes, and apparently planes get hit by lightning all the time. Scarily,
carbon fibre is literally shredded by the strike.Carbon fiber construction offers exceptional strength
and stiffness at a lower density than traditional metal materials. The high temperature epoxy resins
with which the fibers are cured are highly resistant to water, fuel, anti-freeze, and solvents which
might cause wear or deterioration and they can be protected from ultraviolet radiation using the same
paint finishes used on metal airplane components.
3. Thermocol (Polystyrene)
Polystyrene (PS) is a synthetic aromatic polymer made from the monomer styrene, a liquid
petrochemical.It is a very inexpensive resin per unit weight. It is a rather poor barrier to oxygen and
water vapor and has a relatively low melting point.[4] Polystyrene is one of the most widely used
plastics, the scale of its production being several billion kilograms per year.Expanded polystyrene
(EPS) is a rigid and tough, closed-cell foam. It is usually white and made of pre-expanded
polystyrene beads.Due to its technical properties such as low weight, rigidity, and formability, EPS
can be used in a wide range of different applications.

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4. Rubber (For landing gear)

For aircraft, the landing gear supports the craft when it is not flying, allowing it to take off,
land and usually to taxi without damage. Wheels are typically used but skids, skis, floats or a
combination of these and other elements can be deployed depending both on the surface and on
whether the craft only operates vertically (VTOL) or is able to taxi along the surface.
Aircraft tires are designed to withstand extremely heavy loads for short durations. The
number of tires required for aircraft increases with the weight of the plane (because the weight of the
airplane has to be distributed better). Aircraft tire tread patterns are designed to facilitate stability in
high crosswind conditions, to channel water away to prevent hydroplaning, and for braking
effect.Aircraft tires are usually inflated with nitrogen or helium to minimize expansion and
contraction from extreme changes in ambient temperature and pressure experienced during flight.
Dry nitrogen expands at the same rate as other dry atmospheric gases, but common compressed air
sources may contain moisture, which increases the expansion rate with temperature.The use of an
inert gas for tire inflation will eliminate the possibility of a tire explosion.
5. Aluminium Alloys
Alloys composed mostly of aluminium have been very important in aerospace manufacturing
since the introduction of metal skinned aircraft. Aluminium-magnesium alloys are both lighter than
other aluminium alloys and much less flammable than alloys that contain a very high percentage of
magnesium.
The following aluminium alloys are commonly used in aircraft and other aerospace structures.
7068 aluminium
7075 aluminium
6061 aluminium
6063 aluminium
2024 aluminium
5052 aluminium
The addition of scandium to aluminium creates nanoscale Al3Sc precipitates which limit the
excessive grain growth that occurs in the heat-affected zone of welded aluminium components. This
has two beneficial effects: the precipitated Al3Sc forms smaller crystals than are formed in other
aluminium alloys and the width of precipitate-free zones that normally exist at the grain boundaries
of age-hardenable aluminium alloys is reduced. However, titanium alloys, which are stronger but
heavier, are cheaper and much more widely used. The main application of metallic scandium by
weight is in aluminium-scandium alloys for minor aerospace industry components. These alloys
contain between 0.1% and 0.5% (by weight) of scandium. The advantages of aluminium alloys (2219
etc.) also include their high performance under cryogen temperatures in contact with liquid oxygen,
hydrogen, and helium. The so-called cryogen reinforcement happens in these alloys, i.e. the strength
and flexibility increase parallel to the decreasing temperature. They are used for manufacturing
various components of spaceship equipment: brackets, fixtures, chassis, covers and casing for many
tools and devices.
6. Steel
To facilitate the discussion of steels, some familiaritywith their nomenclature is desirable. A
numericalindex, sponsored by the Society of Automotive Engineers (SAE) and the American Iron
and Steel Institute(AISI), is used to identify the chemical compositionsof the structural steels.The
various nickel steels are produced by combiningnickel with carbon steel. Steels containing from3 to
3.75 percent nickel are commonly used. The corrosion resistant steel mostoften used in aircraft

construction is known as 18-8 steel because of its content of 18 percent chromiumand 8 percent
nickel. Stainless steel can be used for almost any part ofan aircraft. Some of its common applications
are in thefabrication of exhaust collectors, stacks and manifolds,structural and machined parts,
springs, castings, tierods, and control cables.Molybdenum in small percentages is used in
combinationwith chromium to form chrome-molybdenumsteel, which has various uses in aircraft.A
series of chrome-molybdenum steel most used in aircraftconstruction is that series containing 0.25 to
0.55percent carbon, 0.15 to 0.25 percent molybdenum, and 0.50 to 1.10 percent chromium. These
steels, when suitablyheat treated, are deep hardening, easily machined,readily welded by either gas
or electric methods, andare especially adapted to high temperature service
38
7. Titanium Alloys

Due to their high tensile strength to density ratio,high corrosion resistance,fatigue resistance,
high crack resistance, and ability to withstand moderately high temperatures without creeping,
titanium alloys are used in aircraft, armor plating, naval ships, spacecraft, and missiles. For these
applications titanium alloyed with aluminium, zirconium, nickel, vanadium, and other elements is
used for a variety of components including critical structural parts, fire walls, landing gear, exhaust
ducts (helicopters), and hydraulic systems. In engine applications, titanium is used for rotors,
compressor blades, hydraulic system components, and nacelles
8. Aircraft Plywood
High-strength plywood also known as aircraft plywood, is made from mahogany and/or
birch, and uses adhesives with increased resistance to heat and humidity.Structural aircraft-grade
plywood is more commonly manufactured from African mahogany or American birch veneers that
are bonded together in a hot press over hardwood cores of basswood or poplar. Basswood is another
type of aviation-grade plywood that is lighter and more flexible than mahogany and birch plywood
but has slightly lessstructural strength. All aviation-grade plywood is manufactured to specifications
outlined in MIL-P-607, which calls for shear testing after immersion in boiling water for three hours
to verify the adhesive qualities between the plies and meets specifications.
9. Carbon fiber reinforced plastic (CFRP)
There has been a push for innovation in the aviation industry. Since the early 1900's,
aluminum has been the primary material used in aircraft construction, and accounts for anywhere
between 65 and 75 percent of the total weight of a passenger aircraft. Recently, a new material has
made its way to the aviation scene. This strong and lightweight material is known as carbon fiber.
With the release of the Boeing 787, which is about 50 percent advanced composites, namely carbon
fiber, discussion has ensued around the changes it will bring in the aviation industry. This new
technology is said to allow for greater fuel efficiency, lower maintenance, longer flights, and an
overall lighter aircraft.Although the initial cost of the mainly carbon fiber plane is greater than a
mainly aluminum plane, in time, the cost will be lower because of the fuel efficiency and lower
maintenance costs. This technology is revolutionary to the aviation industry, especially because of
the energy saving properties. Energy continues to be an issue in today's world, and the use of carbon
fiber will impact energy consumption drastically. A change from aluminum to advanced composites
opens the aviation industry to great changes.Relative to its size, this material is very strong in its
fibrous state, and it is made even stronger after being woven together with several other strands. A
study done by Vaupell Northwest Molding and Tooling and SABIC Innovative Plastics shows that
carbon fiber has a tensile strength of about 38.3 pounds per square inch while aluminum, depending
on the type, has a tensile strength roughly between 27 and 33.1 pounds per square inch. A stronger
material will increase the longevity of the aircraft because it is not as prone to damage. This proves
its ability to have lower maintenance costs. An aluminum plane with corrosion must be taken out of

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp.
service and completely repaired. Avoiding corrosion with carbon fiber removes that repair cost and
time. It is arguable that repairing carbon fiber takes long periods of time
have to mold and cure. However, this is not the case. In Boeing's article about the new 787 aircraft,
they state that it has been designed from the start with the capability to be repaired in exactly the
same manner that airlines would repair an airplane today
aircraft can be repaired in the exact same way that a traditional aluminum plane would be
repaired.Carbon fiber is stronger than aluminum, but it is also proven to be lighter tha
the same study by Vaupell and SABIC, these two companies observed that carbon fiber provides
approximately 50% lower specific gravity (SG) than aircraft
specific gravities plays a large role in the overall
the plane is now carbon fiber instead of aluminum.

Figure 3

CONCLUSION AND FUTURE SCOPE
The complete Material Selection

!
from conforming to the design requirements of ‘SAE Aero Design Series’, it is a fully functional unit
which can be placed on any UAV. It proves to be a
requirements of the UAV. The future scope
options with different twist angles in terms of
parameters such as remaining fuel and
velocity the material can withstand
REFERENCES
[1] About SAE AERO International,
[2] SAE Aero 2013 rules.pdf, http://students.sae.org/cds/aerodesign/rules/rules.pdf
[3] OS Engines, http://www.osengines.com/
[4] Internal Combustion engines,
[5] Vladimir N. Orlov@ and FL Stephen Berry
Institute, The University of Chicago,
June 1993), http://berrygroup.uchicago.edu/papers/329.pdf
[6] Muffler effects, http://onlinelibrary.wiley.com/doi/10.1029/96GL03338/
[7] Propeller analysis, Estimating R/
Nicolai, Technical Fellow, Lockheed Martin Aeronautical Company.
[8] Flying quality analysis of three surface aircraft,
http://icas.org/ICAS_ARCHIVE/ICAS2002/PAPERS/521.PDF

34-40 © IAEME
39
because plastic composites
es - with bolted repairs”. This means that the
aircraft-grade aluminum. The difference in
weight of an aircraft especially when 50 percent of
3: Material analysis
for a UAV have been designed and implemented. Apart
V. tool necessary for assisting the flight and mission
from here is to explore suitable material and sizing
wing area. Additionally, measurement of critical
airspeed can also be undertake to check the density and
https://www.sae.org/about/.
com/.
www.asmeconferences.org/ICEF2014/.
Department of Chemistv and the James Franck
(Received 17 March 1993; accepted for publication 17
pdf.
abstract
C Model Aerodynamics And Performance
PDF.

– 6340(Print),
than aluminum. In
pdf.
abstract.
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Material selection for unmanned aerial vehicle

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