The document discusses smart structures that integrate sensors and actuators to interact with their environment in adaptive ways. It describes various smart materials, such as piezoelectric and shape memory alloys, that respond to environmental stimuli and the importance of material properties, like crystal structure, for their functions. Additionally, it highlights the potential applications of these technologies in improving material efficiency and the development of intelligent structures with learning capabilities.

2. Smart structure incorporates
sensors and actuators into the material of
the structure in such a way that enables
the structure to sense its environment and
then respond appropriately in a pre-
programmed manner.

6. Data Acquisition (tactile sensing): the aim of
this component is to collect the required raw
data needed for an appropriate sensing and
monitoring of the structure.
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SENSOR
ACTUATOR
Electric Field 5mV

7. Data Transmission (sensory nerves): the
purpose of this part is to forward the raw data to
the local and/or central command and control
units.

8. Command and Control Unit (brain): the role
of this unit is to manage and control the whole
system by analyzing the data, reaching the
appropriate conclusion, and determining the
actions required.
LOAD 50
Electric Field 5mV
CONTROL UNIT
5mV
means
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Recover
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APPLY 10mV

9. Data Instructions (motor nerves): the
function of this part is to transmit the
decisions and the associated instructions back
to the members of the structure.

10. Action Devices (muscles): the purpose of this
part is to take action by triggering the controlling
devices/ units.
CONTROL UNIT
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Electric Field 10mV
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CMPENSATING 50

11. Smart materials are materials that respond to
environmental stimuli, such as temperature,
moisture, pH, or electric and magnetic fields.

12. o Piezoelectric
o Electrostrictive
o Magnetostrictive
o Shape Memory Alloys (SMA)
o Optical Fibres.
o Electro/Magneto -rheological

13. They produce an electricThey produce an electric
field when exposed to afield when exposed to a
change in dimensionchange in dimension
caused by an imposedcaused by an imposed
mechanical forcemechanical force
(piezoelectric or generator(piezoelectric or generator
effect). Conversely, aneffect). Conversely, an
applied electric field willapplied electric field will
produce a mechanicalproduce a mechanical
stressstress

17. A material must be formed as a single crystal to be
truly piezoelectric

18. Ceramics have a multi-crystalline structure
made up of large numbers of randomly orientated
crystal grains. The random orientation of the grains
results in a net cancellation of the piezoelectric
effect. The ceramic must be polarized to align a
majority of the individual grains' effects.

19. Piezoelectric ceramic
materials are not
piezoelectric until the
random ferroelectric
domains are aligned. This
alignment is accomplished
through a process known
as poling. Poling consists
of inducing a DC voltage
across the material. The
ferroelectric domains align
to the induced field
resulting in a net
piezoelectric effect

22. Actuator Stroke Amplification
Rod
Cusp
Piezo-Bender Flap Hinge Axis

23. Electrostrictive. This material has the same
properties as piezoelectric material, but the
mechanical change is proportional to the square of
the electric field. This characteristic will always
produce displacements in the same direction.
PMN (lead magnesium niobate).

24. Magnetostrictive. When subjected to a
magnetic field, and vice versa (direct and converse
effects), this material will undergo an induced
mechanical strain. Consequently, it can be used as
sensors and/or actuators. (Example: Terfenol-D.)

25. N
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N
S
N
S
S
N
N
S

27. ULTRASONIC TERFENOL-D DEVICE

29. Shape Memory Alloys. When subjected to a
thermal field, this material will undergo phase
transformations which will produce shape
changes. It deforms to its ‘martensitic’ condition
with low temperature, and regains its original
shape in its ‘austenite’ condition when heated
(high temperature). (Example: Nitinol TiNi.)

30. Nitinol is an alloy based on Ni and Ti. It exhibits the
shape-memory effect (SME). Above a certain
temperature it exists in a phase called ‘austenite’, and
makes a transition to ‘martensite’ on cooling through
that temperature. It can be deformed severely when in
the martensitic phase, and yet it recovers its shape on
heating to the austenitic phase. In other words, it
behaves as if it has a memory of the shape it had while
in the austenitic phase. This effect finds two types of
uses in smart structures.

31. Either the shape-recovery tendency is used for
achieving large-throw actuation; or, if the material is
prevented from recovering its shape, a strong internal
stress is generated which changes the effective
stiffness of the medium, thus finding uses in
vibration-control applications. A large number of
applications exist for shape-memory alloys (SMAs)
like Nitinol. An example of an actively smart structure
in this context is the folding-box type protective
shroud. On being heated by solar energy in outer
space, the SMA actuator converts itself from a stowed
to a fully deployed (unfolded) shape, thus providing
protection to the satellite from being hit by the debris
of earlier or abandoned satellite parts.

34. Electro- and magneto-
rheological fluids that
change viscosity in
response to electric or
magnetic field.

36. Optical Fibres. Fibres that use intensity,
phase, frequency or polarization of modulation to
measure strain, temperature, electrical/magnetic
fields, pressure and other measurable quantities.
They are excellent sensors.
They are highly compatible with composites
(because both are fibres).

38. Today, the most promising technologies for lifetime efficiency and
improved reliability include the use of smart materials and structures.
Understanding and controlling the composition and microstructure of
any new materials are the ultimate objectives of research in this field,
and is crucial to the production of good smart materials. The insights
gained by gathering data on the behaviour of a material’s crystal inner
structure as it heats and cools, deforms and changes, will speed the
development of new materials for use in different applications.
Structural ceramics, superconducting wires and nanostructural
materials are good examples of the complex materials that will
fashion nanotechnology. New or advanced materials to reduce weight,
eliminate sound, reflect more light, dampen vibration and handle
more heat will lead to smart structures and systems which will
definitively enhance our quality of life.

39. Intelligent structures are smart
structures that have the added capability of
learning and adapting rather than simply
responding in a pre-programmed manner. This
learning and adapting is usually accomplished
by the inclusion of an artificial neural network
(ANN) into the smart structure.