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International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 440
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-04-8 | © 2012 Bonfring
Abstract--- Materials have a strong relationship with aerospace industry, as it always determines the weight,
strenght, efficiency, cost and difficulty of maintainance of an aircraft. Therefore, the discovery of new material
usually makes a break through in performance of an aircraft. Especially the findings of smart material, makes an
innovation in aircraft because it can provide a special function or property . Accordingly, the smart materials
receive a great attention inorder to improve the performance of aircraft.
Keywords--- Smart Wing, Aircraft Tyres, Helicopter Blades
I. INTRODUCTION
MART materials or designed materials are materials that have one or more properties that can be significantly
changed in a controlled fashion by external stimuli such as stress, temperature, moisture, pH, electric or
magnetic fields. There are number of types of smart materials some of which are already common. Some examples
are piezoelectric material, shape memory alloys, chromogenic systems etc. Studying of the smart materials is a key
to make the innovation of aerospace industry. The reason is the conventional automatic system has several
limitations comparing to the smat system. Therefore,studying smart material is necessary for improving aircraft‟s
performance.
II. WHAT ARE SMART MATERIALS?
Smart materials are the materials that have the property that can be significantly changed in a controlled fashion
by external stimuli, such as, stress, temperature, moisture, pH, electric or magnetic fields. Science and technology
have made amazing developments in the design of electronics and machinery using standard materials, which do not
have particularly special properties (i.e. steel, aluminum, gold). Imagine the range of possibilities, which exist for
special materials that have properties scientists can manipulate. Some such materials have the ability to change
shape or size simply by adding a little bit of heat, or to change from a liquid to a solid almost instantly when near a
magnet; these materials are called smart materials.
Figure 1
Jincy Philip, Student, Sathyabama University, Chennai. E-mail: jahovayera@gmail.com
Litty John, Student, Sathyabama University, Chennai. E-mail: johnlitty@rocketmail.com
PAPER ID: MEP36
Impact of Smart Materials in Aero Industry
Jincy Philip and Litty John
S
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 441
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-04-8 | © 2012 Bonfring
2.1. Different Types of Smart Materials
Piezo Electric Material: which produces voltage when stress is produced.
Shape Memory Alloys: which large deformation can be induced and recovered through temperature changes
or stress changes.
Thermo Electric Material: are used to build devices that convert temperature differences into electricity and
vice-versa.
Photomechanical Material: change shape under exposure to light.
III. PIEZO ELECTRIC MATERIAL
The classic definition of piezoelectricity is the generation of electricity polarization in a material due to the
mechanical stress. It is called as direct effect. The piezoelectric material has a converse effect that a mechanical
deformation will happen if an electrical charge or signal is applied. Accordingly, it can be a sensor to detect the
mechanical stress by direct effect. Alternatively, a significant increase of size due to the electrical charge can be an
actuator. Piezoelectric materials have two unique properties which are inter related.
Figure2
When a Piezo electric material is deformed it produces electricity in small but measurable. Alternately, when an
electrical is deformed, it gives off a electrical discharge current is passed through a piezoelectric material it
experiences a significant increase in size (up to a 4% change in volume) (as shown in the figure2). The property that
can be altered influences what types of applications the smart material can be used for.
3.1. Properties of Piezo Electric Material
Among different types of smart material, piezoelectric material is widely used because of the fast
electromechanical response, wide bandwidth, high generative force and relatively low power requirements. There
are two main types of piezoelectric materials that are applied as smart materials, which are piezoelectric ceramic and
polymer. The piezoelectric material has a converse effect that a mechanical deformation will happen if an electrical
charge or signal is applied. Accordingly, it can be a sensor to detect the mechanical stress by direct effect.
Alternatively, a significant increase of size due to the electric charge can be actuator.
3.2. Theorem Of Piezo Electric Material
Basically, piezoelectric material is a transducer between electricity and mechanical stress.[1]
.The Piezo electrical
material has this effect because of its crystalline structure. For the crystal, each molecule has a polarization; it means
one end is more negatively charged while the other end is more positively charged, and it is called dipole.
Furthermore, it directly affects how the atoms make up the molecule and how the molecules are shaped.
Therefore, the basic concept of piezoelectricity is to change the orientation of polarization of the molecules.
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 442
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-04-8 | © 2012 Bonfring
Figure 3
IV. ROLE OF PEIZO ELECTRIC MATERIAL IN AERO INDUSTRY
Aerospace manufacturers face extreme pressure to lower costs, while increasing performance and satisfying
stringent safety standards. Producers in the commercial airline, defense and space exploration sectors continually
seek new materials that are reliable and robust, and meet the needs of highly specialized applications.. The two
important Piezo electric materials are piezoelectric ceramic and polymer.
Advanced ceramics, such as Alumina, Silicon Nitride and Aluminum Nitride are currently being used to
manufacture critical aerospace components, because they have several advantageous physical properties. These
inorganic, non-metallic materials retain dimensional stability through a range of high temperatures and exhibit very
high mechanical strength. They also demonstrate excellent chemical resistance and stiffness-to-weight ratio, thereby
providing manufacturers with the ability to design Components that offer optimal performance in their intended
application.
4.1. Instrumentation and Control System
Electro ceramic materials (piezoelectric and dielectric) are used in aerospace transducers and sensors such as
accelerometers (for measurement of vibration), gyroscopes (for measurement of the acceleration and pitch of
aircraft, missiles and satellites) and level sensors (e.g. fuel tanks). One of the most successful commercial aircrafts in
recent times, the Boeing 777, uses Piezo ceramic material [6]
within the 60 ultrasonic fuel tank probes located on
each aircraft. The ultrasonic transducers are installed at a variety of locations in each fuel tank. A pulsed electric
field is applied to the Piezo ceramic material, which then responds by oscillating. The resulting sound waves are
reflected off the surface of the fuel and picked up by the Piezo-electric ceramic transducer. A digital signal processor
interprets the „time of flight‟ measurement of the sound waves in order to continually indicate the amount of fuel
present. Similar ultrasonic fuel probes are also used in fighter aircraft and other level sensing applications because of
their ability to provide highly accurate readings, regardless of the orientation of the aircraft.
4.2. Seals and Thermocouples
Advanced ceramics are also ideally suited for aerospace [7]
applications that provide a physical interface between
different components, due to their ability to withstand the high temperatures, vibration and mechanical shock
typically found in aircraft engines and other high stress locations. Ceramics are commonly found in seals for gas
turbine engines, fuel line assembly, and thermocouples. Where ceramic/metal assemblies are required, joining the
two materials generally involves metalizing the ceramic surface and then brazing the components together.
4.3. Aero Engine Component Repair
Research into the development of advanced brazing materials for aero engine component repair has also led to
the development of brazing materials ideal for the repair of gas turbine engine components. One example is the use
of pre-sintered performs (PSP) for high temperature brazes repair applications. With turbine temperatures reaching
up to 1300ºC (2350ºF) and the presence of hot corrosive gases, components experience considerable erosion and
wear.
The pre-sintered performs consist of a blend of super alloy and low melting point braze and are customized to fit
the shape of the component and then tack-welded into place and brazed. The ability to provide a range of near net
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 443
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-04-8 | © 2012 Bonfring
thicknesses can eliminate the need for most post-braze machining and extend the life of engine components by up to
300 percent, making it a more reliable and cost effective method than traditional welding which requires post-braze
machining or grinding.
4.4. Ion Propulsion
Ion propulsion technology, which uses electricity to charge heavy gas atoms that accelerate from the spacecraft
at high velocity and push it forwards, traditionally incorporated quartz discharge vessels. Quartz has now been
replaced by Alumina because of the need for a material with the same dielectric properties but with higher structural
stability. Alumina is easier to fabricate and offers good thermal shock resistance, ensuring that the chamber can
withstand the extremes of temperature that occur during plasma ignition. It is also lighter, which reduces the costs
associated with each launch.
4.5. Aerodynamic Feature
In term of shape changing, it means the changing of aerodynamic feature. Conventionally, the aircrafts‟ control
surface is still controlled indirectly and lack of flexibility. However, the piezoelectric actuator can perform an
innovative mechanism of control system; it greatly increases the performance and maneuverability due to flexible,
efficient and thin actuator.
4.6. Vibration Control
Regarding vibration, it is an unwanted effect in aircraft because it can contribute to stress concentration, material
fatigue, shortening service life, efficiency reduction and noise. Obviously, these problems influence the safety and maintenance
cost sharply. Besides, the noise problem is always considered, especially the passengers‟ aircraft, as the noise is a great
annoyance.
Figure 4
Therefore, the engineers always want to minimize the vibration. Conventionally, it is difficult to provide a
precise active damping which produces a vibration with anti-resonance frequency. By the piezoelectric material, it
can be used as sensor and actuator at the same time, so it has a fast enough response to produce the anti resonance
vibration [8]
(Fig4). Furthermore, it is flexible, small and thin to be applied in many parts of aircraft.
4.7. Cabin Interior Noise
The noise of aircraft is a significant annoyance to the passengers. Conventionally, the passive damping device is
used which is just capable of high frequency vibration. However, the interior noise from vibration of fuselage and
engine is low frequency hence the passive damping device cannot perform a satisfied noise reduction. Accordingly,
an active damping device is needed and the piezoelectric material is suitable choice.
Basically, this noise reduction system is called Active Structural Acoustic Control (ASAC). In this system, the
piezoceramic patch actuators are used with passive vibration insulations to optimize the capabilities (Manner HP &
Wierach P). The Bombardier Dash-8 turbo prop aircraft was used as the test model and the result is satisfied (Figure
5). There was a reduction more than 20dB at the blade passage frequency of 61Hz.
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 444
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-04-8 | © 2012 Bonfring
Figure 5
4.8. Ceramic Heat Shields and Windscreens
Ceramic fibers are used as heat shields for fire protection and thermal insulation in aircraft and space shuttles
because they resist heat, are lightweight and do not corrode. Other significant characteristics include high melting
temperatures, resiliency, tensile strength and a chemical inertness. In addition, aircraft windshields are heated by a
transparent, electric-conducting ceramic coating embedded in the glass to keep them clear from fog and ice.
4.9. Smart Materials to Design a Smart Wing
A conventional aircraft wing uses hydraulics and an electronic motor to move the flaps into their proper positions
for ascent and descent, so it is very heavy and noisy. By replacing those with these „smart materials‟ [2]
that we can
manipulate through applied heat using electrical current. When electricity is applied, it heat the spring on the bottom
that will contract and pull the flap down. So it eliminated the need for a hydraulic and motor system within the
aircraft‟s wing, because the current would be provided by a power supply already located within the aircraft. Many
structures are available for this (fig6).
Figure 6
4.10. Use of Piezoelectric Material in Aircraft Tyres
Piezoelectric materials like Quartz are used for producing electricity [4]
. Piezoelectric cell are mounded at the
places where mechanical strain is produced. These piezoelectric cells can be mounted inside the tyres of aircraft
(figure7) to generate electricity and used in most efficient way. During takeoff and landing of aircraft the pressure
exerted on the Quartz plates are considered. The pressure exerted is far below the sustainability of plates. Hence can
be used for production of electricity.
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 445
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-04-8 | © 2012 Bonfring
Figure 7
4.11. Energy Saving Helicopter Blades
Helicopters can Perform some incredible aerobatic feats. But they are also noisy, shaky and expensive to run.
Figure 8
Researches‟ are developing helicopter blades featuring shape-shifting smart materials that could lead to a
smoother, quieter more fuel efficient ride. The blades used are piezoelectric actuators [11]
mechanical devices
incorporating a material that change a shape when subjected to an electrical field.
As a helicopter blade passes to air, smart materials attached in blade (see fig8) leaves behind a wake, and as the
blade behind it passes through that wake it experiences a periodic vibration. Having blade actuation [6]
allows you to
put a periodic motion into the blade flaps with a right amplitude, phase and frequency to cancel out that vibration.
V. FUTURE OF SMART MATERIALS
The enabling advantages of Smart materials utilization often outweigh the challenges, and because of this, the
future of this field is promising. As more applications across all industry sectors are designed and put into use. The
Smart materials market will continue to grow and the cost of the material will continue to fall. At the same time the
quality of material produced will increase.
Considering the variety of research and development currently being performed in the area of smart materials, it
is clear that new application will continue to be developed and that this field will grow. The overall growth in the
utilization of Smart materials will provide designers with more options, and those in the aero industry should
continue to take advantage of the unique engineering solutions provided by Smart materials.
VI. CONCLUSION
In the studying of smart materials, their properties in response to external condition such as temperature, stress,
electrical charge, magnetic field, are understood and these unique properties receive a great attention from airspace
industry. The reason is that properties can be applied to different parts in the aircraft to improve the overall
performance. For eg. By using the smart material actuator, its performance is much more efficient than the
conventional system since the electricity is directly conversed to actuation, number of parts is greatly reduced and
transmitting speed of electricity is much higher. Moreover, an innovative research is experiencing to make the
adaptive wing or control surfaces which can greatly increase the maneuverability. In addition smart material is
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 446
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-04-8 | © 2012 Bonfring
usually light in weight and can be made in the compact size. At the same time, cost can be reduced and maintenance
can be minimized by using vibration control smart material. By using piezoelectric material in helicopter blade we
can reduce the noise that‟s created during the flight. Therefore the smart materials represent the innovation of
aerospace industry and they are believed to be widely used in the future.
REFERENCES
[1] Zhong Lin Wang & Z.C.Kang, “Function and Smart Materials Structural Evolution& Structural Analysis”,
1998.
[2] Yousefi-koma, A & Zimick, Application of smart structures to aircraft for the performance enhancement,
Canadian Aeronautics and space journal, volume 49,no4,2003.
[3] Hartal, Dj&Lanonds, Journal of aerospace engineering, 2007, volume221, issue4, p535-552.
[4] Joshi, Application of Magnetic Smart Materials, 1999.
[5] Hariz, smart materials, structures and integrated system, SPIE-the international society of optical engineering,
1999.
[6] Le-letty, claeyreren f, Amplified Piezo Electric ceramic Actuation for Aero Space Application, Cedrat
Technologies, SA.
[7] Joshi, C & Bent, Application of Magnetic Smart Materials to Aerospace Motion Control. 1999.
[8] Giyrgiutiu, Recent advances in smart-material rotor control actuation, University of South Carolina. V 2000.
[9] The piezoelectric effect, Radio Education and Research Center 2007.
[10] Joshi, C, Bent, B, Drury, M, Preble, J & Nguyen, „High Force‟, Precision Positioning Using Magnetic Smart
Materials. 19.
[11] Newton, David V, Main, John A, Garcia, Ephraim, Massengill, Lloyd; “Piezoelectric actuation systems:
optimization of driving electronics”, Proc. SPIE Vol. 2717, p. 259-266.
[12] C.Nam, Yakima, Application of smart materials for aircraft maneuver enhancement, volume4701,pp 226-236.