Smart Materials

04-12-17
Smart Materials
Mehrshad Mehrpouya
Department of Mechanical and Aerospace Engineering
Sapienza University of Rome

2Graduate School / presentatie secretaresse overleg TBM
https://www.linkedin.com/in/mehrpouya/
https://www.slideshare.net/MehrshadMehrpouya
The Course Outlines:
Introduction of Smart Materials.
Shape memory materials and their applications.
Piezoelectric Materials and their applications.
Chromogenic systems including
Thermochromic, Photochromic, and
Electrochromic materials.
Smart polymers including SMP, PH sensitive,
etc.
Application of finite element modeling for the
design of smart products.

Course Overview
•In this course we will study the fundamental conceptsIn this course we will study the fundamental concepts
behindbehind different typesdifferent types of smart materials.of smart materials.
•We will emphasize our discussion aroundWe will emphasize our discussion around currentcurrent
applicationapplication of smart materials in the different fields.of smart materials in the different fields.
•We will also discuss the possibleWe will also discuss the possible design of variousdesign of various
engineering applicationsengineering applications by this materials.by this materials.

Types of Materials
- Metals- Metals
- Ceramics- Ceramics
- Polymers- Polymers
- Composites- Composites
- Semiconductors- Semiconductors
- Electronic / Optical- Electronic / Optical
- Glass- Glass
- Wood- Wood

What is “active material”?
Donald J. Leo definition in Smart Material Systems book;
A material that exhibits useful coupling between multiple physical
domains. A domain (mechanical) is any physical quantity defined with 2
state variables (stress and strain).
Active
Material
Mechanical
Energy
Electrical
Energy
Example of Electromechanical Coupling

What are smart materials?
• Smart materials are materials that have
one or more properties.
• They can be significantly altered in a
controlled fashion by external stimuli, such
as stress, temperature, moisture, pH,
electric or magnetic fields.

What are the examples?
 Piezoelectric materials
 Shape memory alloys
 Magnetorheological
 PH sensitive polymers
 Chromogenic systems
 Thermochromic materials
 Photochromic materials
 Electrochromic

What are Piezoelectric materials?
 The word originates from the greek word
“piezein”, which means “to press”.
Discovered in 1880 by Pierre Curie in
quartz crystals
 The molecular structure of piezoelectric
materials produces a coupling between
the mechanical stress and the
electric field.
 Piezoelectrics are materials that can
create electricity when subjected to a
mechanical stress.
 They will also work in reverse,
generating a strain by the application of
an electric field.

The Application of Piezoelectric Materials
A lighter is a good example of how piezoelectric
materials are used in a usual application.

• Charging pads under the cross
walk collect energy from the
vibrations.
• Energy generated by that
piezoelectric panels can charge
to lithium icon batteries.

How does a shoe fitted with
a piezocell work?

As long as there is physical activity, piezoelectricity
could generate power.

Shape Memory Materials
Shape memory alloys (SMAs) and shape memory polymers (SMPs)
are thermo-responsive materials where deformation can be induced
and recovered through temperature changes.

Timeline of Memory Metals
1932 - A. Ölander discovers the pseudoelastic properties of Au-Cd alloy.
1949 - Memory effect of Au-Cd reported by Kurdjumov & Kandros.
1967 – At Naval Ordance Laboratory, Beuhler discovers shape memory effect in Nickel-Titanium
alloy, Nitinol, which proved to be a major breakthrough in the field of shape memory alloys.
1970-1980 – First reports of nickel-titanium implants being used in medical applications.
Mid-1990s – Memory metals start to become widespread in medicine and soon move to other
applications.
Number of publication per year

Shape Memory Alloys
• SMAs can be actuated by stress,
temperature or presence of a magnetic
field.
• They become deformed once heated above
the transformation temperature, but
regain their shape as they cool.
• One of the most common alloys is a
combination of nickel-titanium or
Nitinol.

Shape memory wires
 This shortening can be used to
control a robotic hand.
 When a small electrical current
passes through the wire it
becomes smart.
 The functionality of SMAs is really
depends on its composite, he
percentage of Nickel and
Titanium elements.

SMAsSMAs
SuperelasticSuperelastic
(SE)(SE)
Shape MemoryShape Memory
Effect (SME)Effect (SME)

Transformation Temperature (TT)
Mf Ms As Af
AusteniteMartensite
TEMPERATURE
Mf
Ms As Af
AusteniteMartensite
TEMPERATURE
(twinned)
(twinned)
Mf=Martensitic Finish
Ms=Martensitic Start
As=Austenitic Start
Af=Austenitic Finish

Superelastic behavior (SE)
Stress-Strain Diagram

Superelastic behavior (SE)
SMAs deformed above a critical
temperature show a large reversible
elastic deformation (recoverable
strains up to 10%. much exceeding
the elasticity) as a result of stress-
induced martensitic transformation.
SMA Actuators
Frames for eyeglasses
Cardiovascular Stents
Antennas for cellular phones

Shape Memory Effect (SME)
Stress-Strain-Temperature Diagram

Shape Memory Effect (SME)
Shape memory effect defines as the recovery
of the apparently permanent deformation
during martensitic transformation in a
stress-free situation.
 Orthodontic archwires
 Engines
 Actuators for smart systems
 Couplings

Existing and potential SMA applications
in the medical/biomedical domain

in the automotive domain

in the aerospace domain

Companies that sell Nitinol material or
products based on Nitinol are:
Materials
Dynalloy, Inc. http://www.dynalloy.com/
Memry http://www.memry.com/
Raychem http://www.raychem.com/
Fort Wayne Metals http://fwmetals.com
Applications
AMF http://www.nitifrance.com/
Intrinsic Devices http://www.intrinsicdevices.com/
Shape Memory App http://www.sma-inc.com/
Actuator Solutions http:// www.actuatorsolutions.de

Magnetorheological
Magnetorheological fluid (MR fluid) is a type of smart material that has the ability to
change state when placed in a magnetic field.
These fluids are composed of iron-like particles.
In their normal state they are fluid.
When placed in a magnetic field the particles are attracted to each other and join up
to form a solid.

MAGNETO-RHEOLOGICAL (MR) DAMPER
Magnetorheological

PH sensitive polymers
• pH sensitive or pH responsive polymers are materials which will
respond to the changes in the pH of the surrounding medium by varying
their dimensions.
• This behavior is exhibited due to the presence of certain functional
groups in the polymer chain.
• Such materials increase its size (swell) or collapse depending on the
pH of their environment.

PH sensitive polymers
The sensor is prepared by entrapping within a polymer matrix a pH
sensitive dye that responds, through visible colour changes (see the
Figure) to spoilage volatile compounds that contribute to a quantity
known as Total Volatile Basic Nitrogen (TVB-N).

Chromogenic systems
• Chromogenic systems change colour in response to electrical, optical
or thermal changes.
• Thermochromic materials change in colour depending on their
temperature.
• Photochromic materials, which change colour in response to light - for
example, light sensitive sunglasses that darken when exposed to bright
sunlight.
• These include electrochromic materials, which change their colour or
opacity on the application of a voltage (e.g. liquid crystal displays).

Thermochromic Materials
 They have a reaction to the
temperature.
 Tiny capsules in thermochromic
ink contain liquid crystals.
 As the temperature changes
these crystals move.
 The reorientation of the crystals
causes a change in colour at a
specific temperature.

Thermochromic materials
• Colour-changing
thermochromic pigments are now
routinely made as inks for paper
and fabrics – and incorporated
into injection moulded plastics.
• A new type of phosphorescent
pigment, capable of emitting light
for up to 10 hours, has opened
up entirely new design
opportunities for instrumentation,
low-level lighting systems etc.

Photochromic materials
This causes them to undergo a reversible change of colour when exposed to a
certain amount of light.
 Photochromic lenses become
dark when they are exposed to
UV radiation.
 Once the UV radiation is
removed, the lenses gradually
return to their normal state.
 They can be made of either
glass or plastic.

Electrochromic
•Electrochromism is the
phenomenon displayed by some
materials of reversibly changing
colour by using bursts of charge to
cause electrochemical redox
reactions in electrochromic
materials.
•Various types of materials and
structures can be used to
construct electrochromic
devices, depending on the specific
applications.

Electrochromic
• Flip a switch and an
electrochromic window can
change from clear to fully
darkened or any level of tint in-
between.
• The windows operate on a very
low voltage (one to three volts)
and only use energy to change
their condition, not to maintain
any particular state.
Boeing 787

Thank you forThank you for
your attentionyour attention
Boeing 787

Smart Materials

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