A SEMINAR REPORT ON

Smart Materials Concepts & Applications

Submitted in partial fulfillment of the requirements

for the award of degree of

BACHELOR OF TECHNOLOGY in

MECHANICAL ENGINEERING

Submitted by:

SAMSON T.

Roll No: 28, Reg No: 07 400 037

DEPARTMENT OF MECHANICAL ENGINEERING

COLLEGE OF ENGINEERING TRIVANDRUM

August 2010

A SEMINAR REPORT ON

Smart Materials Concepts & Applications

Submitted in partial fulfillment of the requirements

for the award of degree of

BACHELOR OF TECHNOLOGY in

MECHANICAL ENGINEERING

Submitted by:

SAMSON T.

Roll No: 28, Reg No: 07 400 037

DEPARTMENT OF MECHANICAL ENGINEERING

COLLEGE OF ENGINEERING TRIVANDRUM

August 2010

DEPARTMENT OF MECHANICAL ENGINEERING

COLLEGE OF ENGINEERING TRIVANDRUM

Certificate

Certified that seminar work entitled “Smart Materials Concepts &

Applications” is a bonafide work carried out in the seventh semester by “SAMSON T.

(07 400 037)” in partial fulfillment of the requirement for the award of Bachelor of

Technology in “MECHANICAL ENGINEERING” from University of Kerala during

academic year 2010 - 2011, who carried out the seminar work under the guidance and

no part of this work has been submitted earlier for the award of degree.

Dr. S. Anil Lal

Professor, Dept of Mech. Engg.

Prof. T. C. Rajan Dr. Baiju B

Asst., Professor, Dept of Mech. Engg. Asst. Professor, Dept of Mech. Engg.

HEAD OF DEPARTMENT

Prof. E. Abdul Rasheed Department of Mechanical Engineering

College of Engineering Thiruvananthapuram

ACKNOWLEDGEMENT

First of all I thank the almighty for providing me with the strength and

courage to present the seminar.

I avail this opportunity to express my sincere gratitude towards to Prof.

T. C. Rajan, Dr. Baiju B and Dr. S. Anil Lal of Department of Mechanical

Engineering for their inspiring assistance, encouragement and useful

guidance and to make my topic something of real value to me and my

colleagues.

I am thankful to Prof. E. Abdul Rasheed, Head of Department

Mechanical Engineering, Prof. Meerakumari, Head, PTDC for their kind co-

operation.

I am also indebted to all the teaching and non-teaching staff of the

Department of Mechanical Engineering for their cooperation and suggestions,

which is the spirit behind this report. Last but not the least, I express my

sincere gratitude from the depth of my heart to my parents, friends and all

well wishers for their kind support and encouragement in the successful

completion of my report work.

SAMSON T

V

ABSTRACT

`Smart' materials have the ability to perform both sensing and actuating

functions. Passively smart materials respond to external change in a useful

manner without assistance, while actively smart materials have a feedback loop

which allows them to both recognize the change and initiate an appropriate

response through an actuator circuit. One of the techniques used to impart

intelligence into materials is `Biomimetics', the imitation of biological functions

in engineering materials. Composite ferroelectrics fashioned after the lateral line

and swim bladders of fish are used to illustrate this idea. `Very smart' materials,

in addition to sensing and actuating, have the ability to `learn' by altering their

property coefficients in response to the environment. Field-induced changes in

the nonlinear properties of relaxor ferroelectrics and soft rubber are utilized to

construct tunable transducers. Integration of these different technologies into

compact, multifunction packages is the ultimate goal of research in the area of

smart materials

New 'smart' materials are being developed which can alter their properties

automatically in response to changes in the environment. Effects such as colour

changes can be produced from stimuli such as temperature. Other 'smart'

materials can adapt to their environments in a similar way to plants, with

actuators and sensors integrated into structural materials such as concrete and

steel, allowing the materials to monitor themselves. Designers are in a position to

identify needs and develop the best specifications for new materials. Truly

intelligent materials could be available in early 21st century, with technology for

manipulating molecular order in materials rapidly advancing.

TABLE OF CONTENTS ABSTRACT V LIST OF FIGURES VII 1.0 INTRODUCTION 1 2.0 CLASSIFICATION 3 3.0 PIEZOELECTRIC MATERIALS 4 4.0 ELECTROSTRICTIVE MATERIALS 5

5.0 MAGNETOSTRICTIVE MATERIAL 7 6.0 RHEOLOGICAL MATERIALS 9 7.0 THERMORESPONSIVE MATERIALS 11 8.0 ELECTROCHROMIC MATERIALS 13 9.0 APPLICATION 15 10.0 CONCLUSION 16 11.0 REFERENCE 17

LIST OF FIGURES

Fig 1 Piezoelectric Principle 4

Fig 2 Rheological Materials 9

Fig 3 Shape Memory Alloys 12

Fig 4 Electrochromic Materials 13

Fig 5 Electrochromic Materials 14

VII

1.0 INTRODUCTION

`Smart' materials have the ability to perform both sensing and actuating

functions. Passively smart materials respond to external change in a useful

manner without assistance, while actively smart materials have a feedback

loop which allows them to both recognize the change and initiate an

appropriate response through an actuator circuit. One of the techniques used

to impart intelligence into materials is `Biomimetics', the imitation of

biological functions in engineering materials. Composite ferroelectrics

fashioned after the lateral line and swim bladders of fish are used to illustrate

this idea. `Very smart' materials, in addition to sensing and actuating, have

the ability to `learn' by altering their property coefficients in response to the

environment. Field-induced changes in the nonlinear properties of relaxor

ferroelectrics and soft rubber are utilized to construct tunable transducers.

Integration of these different technologies into compact, multifunction

packages is the ultimate goal of research in the area of smart materials

Materials that have one or more properties that can be significantly

changed in a controlled fashion by external stimuli, such as

stress

temperature

electric or magnetic fields.

1

The main advantages of the smart materials are the following:

No moving parts

High reliability

Low power requirements, etc

High energy density (compared to pneumatic and hydraulic

actuators)

Excellent bandwidth

Classification of Smart Materials

Actuating Materials

o Electrorheological Fluids (ER Fluids)

o Shape Memory Alloys (SMA)

Sensing Materials

o Fiber Optic (F.O.) sensors

Dual-Purpose Materials (Actuating & Sensing)

o Magnetostrictive Materials

Piezoelectric Materials

2

2.0 CLASSIFICATION

Material Type

Shape memory alloys

Piezoelectric

Electrostrictive

Magnetostrictive materials

Fiber-optic sensor systems

Conductive polymers

Chromogenic materials and systems:

Thermo chromic

Electro chromic

Controllable fluids:

Electro rheological

Magneto rheological

Biomimetic polymers and gels

Fullerenes and carbon nanotubes

3

3.0 PIEZOELECTRIC MATERIALS Fig: 1 – Piezoelectric Principle

The piezoelectric effect describes the

relation between a mechanical stress and an

electrical voltage in solids.

It is reversbile: an applied mechanical stress

will generate a voltage and an applied

voltage will change the shape of the solid by

a small amount (up to a 4% change in

volume). In physics, the piezoelectric effect

can be described as the the link between electrostatics and mechanics.

History

The piezoelectric effect was discovered in 1880 by the Jacques and Pierre

Curie brothers. They found out that when a mechanical stress was applied on

crystals such as tourmaline, tourmaline, topaz, quartz, Rochelle salt and cane

sugar, electrical charges appeared, and this voltage was proportional to the

stress. First applications were piezoelectric ultrasonic transducers and soon

swinging quartz for standards of frequency (quartz clocks). An everyday life

application example is your car's airbag sensor. The material detects the

intensity of the shock and sends an electricla signal which triggers the airbag.

Piezoelectric materials

The piezoelectric effect occurs only in non conductive materials. Piezoelectric

materials can be divided in 2 main groups: crystals and cermaics. The most

well-known piezoelectric material is quartz (SiO2).

4

4.0 ELECTROSTRICTIVE MATERIALS

These materials can also change their dimensions on the application of

an electric field. Although the changes thus obtained are not linear in either

direction, these materials have widespread application in medical and

engineering fields.

Electrostriction is a property of all dielectric materials, and is caused by

the presence of randomly-aligned electrical domains within the material.

When an electric field is applied to the dielectric, the opposite sides of the

domains become differently charged and attract each other, reducing

material thickness in the direction of the applied field (and increasing

thickness in the orthogonal directions due to Poisson's ratio). The resulting

strain (ratio of deformation to the original dimension) is proportional to the

square of the polarization. Reversal of the electric field does not reverse the

direction of the deformation.

Electrostrictive materials, such as the ceramic PMN/PT/La

(0.9/0.1/1%), operating above Tmax with a DC bias field behave as a

piezoelectric ceramic material with C<is proportional to> symmetry. The

effective piezoelectric and electromechanical coupling coefficients are found

to be linear as a function of the DC bias field up to about 0.5MV/m, while the

elastic constant (at constant field) and the dielectric constant (at constant

stress) are found to have a quadratic dependence on the DC bias field. Above

0.5 MV/m the piezoelectric and the electromechanical coupling constants

begin to saturate due to higher 4th order electrostriction (S <is proportional

to> kE4, k negative) In essence these materials behave as tunable

piezoelectric materials with the piezoelectric coefficient being directly

proportional to the electrostrictive coefficient and the DC bias field (d3 =

2Q33EDC) up to saturation. The properties of DC biased resonators of this

5

material are derived from a nonlinear theory based on the Taylor's series

expansion of the thermodynamic potentials to 3rd and higher order terms in

field and stress. The resonance equations for the DC biased length

extensional (LE) resonator are presented and it is shown that DC biased

resonance techniques can be used to measure the electrostrictive and other

higher order coefficients at frequencies of interest to tbe ultrasonics

community. The experimental apparatus used to measure these properties

will be described and the limitations with regards to isolation of the

measurement signal and the DC bias signal will be discussed. We will show

that these materials, in conjunction with standard piezoelectric ceramics,

offer the transducer design engineer an extra degree of freedom and the

feasibility of unique transducer designs that will allow, for example, multiple

beam patterns from the same circular/linear array using an adjustable DC

bias profile on the array or tbe possible use of the field dependence of the

compliance to fabricate electrically active backing materials. In conclusion

we discuss how a better understanding of the macroscopic theory of

piezoelectric and electrostrictive materials can benefit the transducer

designer.

6

5.0 MAGNETOSTRICTIVE MATERIAL

These are quite similar to Electrostrictive materials, except for the fact

that they respond to magnetic fields. The most widely used Magnetostrictive

material is TERFENOL-D, which is made from the rarest of the rare earth

elements, i.e. Terbium. This material is highly non-linear and has the

capability to produce large strains.

Magnetostrictive (MS) technology and Magneto-Rheological Fluid

(MRF) technology are old “newcomers” coming to the market at high speed.

Various industries including the automotive industry are full of potential MS

and MRF applications. Magnetostrictive technology and Magneto-

Rheological Fluid technology have been successfully employed already in

various low and high volume applications. A structure based on MS might be

the next generation in design for products where power density, accuracy

and dynamic performance are the key features. Since the introduction of

active (MS) materials such as Terfenol-D, with stable characteristics over a

wide range of temperatures and high magnetoelastic properties, interest in

MS technology has been growing. Additionally, for products where there is a

need to control fluid motion by varying the viscosity, a structure based on

MRF might be an improvement in functionality and costs.

Two aspects of this technology, direct shear mode (used in brakes and

clutches) and valve mode (used in dampers) have been studied thoroughly

and several applications are already present on the market. Excellent

features like fast response, simple interface between electrical power input

and mechanical power output, and precise controllability make MRF

technology attractive for many applications.

7

Magnetostriction effects

Crystals of ferromagnetic materials change their shape when they are

placed in a magnetic field.. This phenomenon is called magnetostriction. It is

related to various other physical effects. Magnetostriction is, in general, a

reversible exchange of energy between the mechanical form and the

magnetic form. The ability to convert an amount of energy from one form

into another allows the use of magnetostrictive materials in actuator and

sensor applications.

8

6.0 RHEOLOGICAL MATERIALS

These fluids may find applications in brakes, shock absorbers and

dampers for vehicle seats. These can be fitted to buildings and bridges to

suppress the damaging effects, for example, high winds or earthquakes.

Fig. 2 Rheological Materials

Rheology is the study of the flow of matter: primarily in the liquid

state, but also as 'soft solids' or solids under conditions in which they

respond with plastic flow rather than deforming elastically in response to an

applied force. It applies to substances which have a complex molecular

structure, such as muds, sludges, suspensions, polymers and other glass

formers (e.g. silicates), as well as many foods and additives, bodily fluids (e.g.

blood) and other biological materials.

The flow of these substances cannot be characterized by a single value of

viscosity (at a fixed temperature). While the viscosity of liquids normally

9

varies with temperature, it is variations with other factors which are studied

in rheology. For example, ketchup can have its viscosity reduced by shaking

(or other forms of mechanical agitation) but water cannot. Since Sir Isaac

Newton originated the concept of viscosity, the study of variable viscosity

liquids is also often called Non-Newtonian fluid mechanics.

An electro-rheological fluid is a material in which a particulate

solid is suspended in an electrically non-conducting fluid such as oil. On

the application of an electric field, the viscosity and other material

properties undergo dramatic and significant changes. In this paper, the

particulate imbedded fluid is considered as a homogeneous continuum.

It is assumed that the Cauchy stress depends on the velocity gradient

and the electric field vector. A representation for the constitutive

equation is developed using standard methods of continuum mechanics.

The stress components are calculated for a shear flow in which the

electric field vector is normal to the velocity vector. The model predicts

(i) a viscosity which depends on the shear rate and electric field and

(ii) normal stresses due to the interaction between the shear flow and

the electric field. These expressions are used to study several

fundamental shear flows: the flow between parallel plates, Couette flow,

and flow in an eccentric rotating disc device. Detailed solutions are

presented when the shear response is that of a Bingham fluid whose

yield stress and viscosity depends on the electric field.

10

7.0 THERMORESPONSIVE MATERIALS

Thermoresponsive materials are sometimes also known as shape

memory alloys or shape memory polymers. These materials alter their shape

under the influence of the ambient temperature.

Magnetic Shape Memory Alloys

Like thermoresponsive materials that alter their shape under the

influence of the ambient temperature, magnetic shape memory alloys change

shape due to changes in magnetic fields.

Polychromic, Chromogenic or Halochromic Materials

Polychromic, chromogenic and halochromic materials all change

colour due to external influences. These external influences can be

alterations in pH, temperature, light or electricity. Materials that change

colour due to temperature are normally known as thermochromic materials

and those that alter due to light are photochromic materials.

Applications of Smart Nanomaterials

Smart nanomaterials are expected to make their presence strongly felt

in areas like:

Healthcare, with smart materials that respond to injuries by delivering

drugs and antibiotics or by hardening to produce a cast on a broken

limb.

Implants and prostheses made from materials that modify surfaces and

biofunctionality to increase biocompatibility

Energy generation and conservation with highly efficient batteries and

energy generating materials.

Security and Terrorism Defence with smart materials that can detect

11

toxins and either render them neutral, warn people nearby or protect

them from it.

Smart textiles that can change colour, such as camouflage materials

that change colour and pattern depending upon the appearance of the

surrounding environment. These materials may even project an image

of what is behind the person in order to render them invisible.

Surveillance using “Smartdust” and “Smartdust Motes” that are

nanosized machines housing a range of sensors and wireless

communication devices. Individually they can float undetected in a

room with other dust particles. By combining the information gathered

from hundreds, thousands or millions of these tiny specs can give a full

report on what is occurring with the area including sound and images.

Fig. 3 Shape Memory Alloys

12

8.0 ELECTROCHROMIC MATERIALS

Electrochromism is the phenomenon displayed by some materials of

reversibly changing color when a burst of charge is applied. Various types of

materials and structures can be used to construct electrochromic devices,

depending on the specific applications.

One good example of an electrochromic material is polyaniline which

can be formed either by the electrochemical or chemical oxidation of aniline.

If an electrode is immersed in hydrochloric acid which contains a small

concentration of aniline, then a film of polyaniline can be grown on the

electrode. Depending on the oxidation state, polyaniline can either be pale

yellow or dark green/black. Other electrochromic materials that have found

technological application include the viologens and polyoxotungstates. Other

electrochromic materials include tungsten oxide (WO3), which is the main

chemical used in the production of electrochromic windows or smart glass.

Polymer-based solutions have recently been developed by John Reynolds

and colleagues at the University of Florida. These promise to provide flexible

and cheap electrochromics in a variety of colours, going all the way up to

black.

Fig. 4 Electrochromic Materials

As the color change is persistent

and energy need only be applied to

effect a change, electrochromic

materials are used to control the

amount of light and heat allowed to pass

through windows ("smart windows"),

and has also been applied in the

automobile industry to automatically

tint rear-view mirrors in various lighting

13

conditions. Viologen is used in conjunction with titanium dioxide (TiO2) in

the creation of small digital displays. It is hoped that these will replace liquid

crystal displays as the viologen, which is typically dark blue, has a high

contrast compared to the bright white of the titania, thereby providing the

display high visibility.

ICE 3 high speed trains use electrochromatic glass panels between the

passenger compartment and the driver's cabin. The standard mode is

clear/lucent and can be switched by the driver to frosted/translucent mainly

to keep passengers off "unwanted sights" for example in case of (human)

obstacles.

Fig. 10 Electrochromic

Materials

14

9.0 APPLICATION

Fast response valves High power density hydraulic pumps

Active bearings for reduction of machinery noise

Footwear

Sports equipment

Precision machining

Vibration and acoustic sensors

Dampers, etc.

Healthcare, with smart materials that respond to injuries by delivering

drugs and antibiotics or by hardening to produce a cast on a broken

limb.

Energy generation and conservation with highly efficient batteries and

energy generating materials.

Security and Terrorism Defence with smart materials that can detect

toxins and either render them neutral, warn people nearby or protect

them from it.

Smart textiles that can change colour, such as camouflage materials

that change colour and pattern depending upon the appearance of the

surrounding environment. These materials may even project an image

of what is behind the person in order to render them invisible.

Surveillance using “Smartdust” and “Smartdust Motes” that are

nanosized machines housing a range of sensors and wireless

communication devices. Individually they can float undetected in a

room with other dust particles. By combining the information gathered

from hundreds, thousands or millions of these tiny specs can give a full

report on what is occurring with the area including sound and images.

15

10.0 CONCLUSION

Optical-fibre crack-monitoring sensors are capable of detecting crack-

width up to 5µm. The technologies using smart materials are useful for both

existing and emerging technologies.

Smart Materials described here need further research to evolve the

design guidelines of systems.

The technologies using smart materials are useful for both new and

existing constructions. Of the many emerging technologies available the few

described here need further research to evolve the design guidelines of

systems. Codes, standards and practices are of crucial importance for the

further development.

Piezoelectrics and magnetostrictives are most effective for high

frequency control applications. Piezoelectrics for applications were size of the

element is of concern. Magnetostrictives are good when size is of no concern.

Shape memory alloys are very effective for low frequency vibration or shape

control. Electrorheological fluids are still being explored. Sandwich beams

are generally the only structural application

Fiber optic sensors are very effective in all application

16

11.0 REFERENCE

→ Erin B. Murphy, Fred Wudl, “The world of smart healable materials”, Review

Article Progress in Polymer Science, Volume 35, Issues 1-2, January-February

2010, Pages 223-251

→ Frank Stajano a,*, Neil Hoult b,1, Ian Wassell a, Peter Bennett b, Campbell

Middleton b, Kenichi Soga b, Smart bridges, smart tunnels: Transforming wireless

sensor networks from research prototypes into robust engineering infrastructure,

Technical report, Federal Highway Administration, Turner- Fairbank Highway

Research Center, January 2008.

→ Giola B. Santoni, Lingyu Yu, Buli Xu, Victor Giurgiutiu, “Lamb Wave-Mode Tuning

of Piezoelectric Wafer Active Sensors for Structural Health Monitoring”,

Transactions of the ASME Vol. 129, DECEMBER 2007, PP. 752-762.

→ Victor Giurgiutiu, Andrei Zagrai, JingJing Bao, “Embedded Active Sensors for In-

Situ Structural Health Monitoring of Thin-Wall Structures”, Journal of Pressure

Vessel Technology, AUGUST 2002, Vol. 124, pp. 293-302.

→ K F Hale, “An optical-fibre fatigue crack-detection and monitoring system”, Smart

Mater. Struct. 1 (1992) 156-161.

17