Smart Materials

INTRODUCTION

With the event of fabric science, many new, high-quality and cost-efficient materials have inherit use in various field of engineering. The materials became multifunctional and required the optimization of various characterization and properties. With the last evolution, the concept has been driving towards composite materials and recently, subsequent evolutionary step is being contemplated with the concept of smart materials.

WHAT ARE SMART MATERIALS?

Smart Materials are those materials that posses the power to vary their physical properties during a specific manner in response to its specific stimulus input. Here stimuli might be pressure, temperature, electric and magnetic fields, chemical and nuclear radiations too. These materials change their physical properties which might be shape, stiffness, viscosity, dumping etc. Materials achieve smartness which is usually programmed by material composition, special processing and modifying micro-structures and getting introduced to defects so on adapt to the varied levels of stimuli during a controlled fashion.

PROPERTIES OF SMART MATERIALS

Smart Materials have some nice properties such as sensing, actuating, controlling materials and devices. they can respond to various types of external stimulus, the ability to change their appearance and shape, Even some of them have property of shock absorbers, damage arrest and they can self-control, self-diagnostic, self-repair and self-healing themself too.

TYPES OF SMART MATERIALS

Piezo-Electric Materials.
Piezoelectric materials are quite common example of such materials where they produce a voltage when stress is applied. Since this effect also applies within the reverse manner, a voltage across the sample will produce stress within the sample. Suitably designed structures made up of these materials can therefore be made that bend, expand or contract when a voltage is applied. briefly these materials convert energy to electricity and vise-versa.Piezo elements are used in music for acoustic instruments. They are inserted in stringed instruments such as guitar, violin or Mandoline. The dynamic deformation/vibration of the cords is converted into a small alternating voltage.
Examples- silk, DNA, ZnO etc.

Shape Memory Alloys.
Shape Memory Alloys (SMA) or shape memory polymers, are materials which will hold different shapes at various temperatures. they will be deformed and returned to their original shape by heating. within the process, they generate an actuating force.Shape Memory Alloys are also used in Robotics like Muscle wire is NiTi alloy which can be stretched up to 8 % of its length and still recover. (at room temp 3 to 5 % stretch is possible) When a small current is passed through the wire it becomes much harder and returns to its original length with a reasonable force. A battery and switch are connected to muscle wire & a small weight stretches the muscle wire. The cycle of turning on and off the current has the effect of lifting and lowering of the weight.
Examples- copper-aluminium-nickel alloy, nickel-titanium alloy etc.

Magnetostrictive Materials.
These materials exhibit change in shape under the influence of magnetic flux and also exhibit change in their magnetization under the influence of mechanical stress. for straight forward to know , they modify their properties when exposed to magnetic flux .Magnetostrictive transducers - Convert magnetic energy in to mechanical energy.Vibration Speaker Technology using the highest power Smart Material . Install in seconds - peel and stick - no screws or mounting issues High quality sound without design compromise. No wires, no boxes, no grilles.Examples- cobalt, Terfenol-D etc.

Chromoactive Materials.
These materials change colour when subjected to a particular variation in stimuli. Even Some chromoactive materials are divided in few types depending upon stimuli like Photochromoic materials(change colour with change in Light), Thermochromic materials (change colour with change in Temperature) and Electrochromic materials(change colour with change in applied Electric field).
Examples- liquid displays etc.

Photoactive Materials.
These materials that interact with the sunshine electromagnetic field and modify either their own properties or those of the sector . In simple, it can have a reaction with sunlight and/or ultraviolet.There are several types: electroluminescents emit light when they are fed with electrical impulses, fluorescents reflect light with greater intensity and phosphorescents are able to emit light after the initial source has ceased.
Examples- crystal, solar cells etc.

CLASSIFICATION OF SMART MATERIALS.

Smart Materials are often classified into two types which are Active Smart Materials and Passive Smart Materials.

Active Smart Materials.
These materials possess the potential of modifying their geometric and material properties under the appliance of electrical , thermal or magnetic fields, thereby acquiring an inherent capacity to transduce energy.Piezoelectric materials, SMAs, ER fluids and magneto-strictive materials are considered to be the active smart materials.

Passive Smart Materials.
The materials, which aren't active, are called passive smart materials. Although smart, they lack the inherent capability to transduce energy.Fiber optic material may be a exemplar of a passive smart material. Such materials can act as sensors but not as actuators or transducers.

APPLICATION OF SMART MATERIALS

There are wide selection of applications which are utilized in Structural Health Monitoring, Self-Repair, within the Field of Defense and Space, In Nuclear Industries, In Structural Engineering, Biomedical Sectors. The scope of application of smart material includes solving engineering problems with unfeasible efficiency and provides a chance for creation of latest products that generate revenue. Important feature associated with smart materials and structures is that they encompass all fields of science and engineering. As far because the technical applications of smart materials cares , it involves composite materials embedded with fiber optics, actuators, sensors, Micro Electro Mechanical Systems (MEMSs), vibration control, sound control, shape control, product health or lifetime monitoring, cure monitoring, intelligent processing, active and passive controls, self-repair (healing), artificial organs, novel indicating devices, designed magnets, damping aeroelastic stability, reducing waste.