Smart Materials

They are the materials which have the capability to respond to changes in their condition or the environment to which they are exposed, in a useful and usually repetitive manner. They are called by other names such as,

· Intelligent materials,

· Active materials and

· Adoptive materials.

The devises that are made using smart materials are called “Smart Devices”. Similarly the systems and structures that have incorporated smart materials are called “Smart Systems” and “Smart Structures”. In other words the complexity increases from smart materials to smart structures.

Stimulus Response System

A smart material or an active material gives an unique output for a well defined input. The input may be in the form of mechanical stress / strain, electrical / magnetic field or changes in temperature. Based on input and output, the smart materials are classified as follows.

1. Shape Memory Alloys (SMAs)

They are the smart materials which have the ability to return to some previously defined shape or size when subjected to appropriate thermal changes.

Eg.: Titanium-Nickel Alloys.

2. Magnetostrictive Materials

They are the smart materials which have the ability to undergo deformation when subjected to magnetic field.

Eg.: Terfenol-D, (Alloy of Iron and Terbium)

3. Piezoelectric Materials

These are the materials which have capability to produce a voltage when surface strain is introduced. Conversely, the material undergo deformation (stress) when an electric field is applied across it.

4. Electrorheological Fluids
They are the colloidal suspensions that undergo changes in viscosity when subjected to an electric field. Such fluids are highly sensitive and respond instantaneously to any change in the applied electric field.

Applications

1. Smart materials are used in aircrafts and spacecrafts to control vibrations and excessive deflections.

2. Smart concrete is used in smart structures. Smart concrete (a composite of carbon fibres and concrete) is capable of sensing minute structural cracks / flaws.

3. Smart materials have good potential to be used in health care markets. Active control drug delivery devices such as Insulin Pump is a possibility.
Smart materials have applications in the design of smart buildings and state of art vehicles. Smart materials are used for vibration control, noise mitigation, safety and performance.