3. A]Classify and explain different types of Smart Materials.
Answer:
SMART MATERIALS :
Smart Materials are being developed since last decade in the laboratories all around the world. These are materials which are capable of generating controllable response to the environment. As actuators, they can produce controllable force to modify the response of a system. As sensors, the same material could be used to monitor the response of the system. Smart materials are being traditionally used in aerospace applications since last decade. Using smart actuators one can modify the flexible modes of a system such that the control effort would not interfere with the vibrating frequencies of the structure. Active vibration controllers are developed for Helicopters and Large space structures using this principle. Tailoring the gamut of smart materials towards diverse applications is still a major challenge to the researchers and engineers involved in these fields.
- Piezoelectric materials :
Piezoelectric materials are very common example of such materials where they produce a voltage when stress is applied. Since this effect also applies in the reverse manner, a voltage across the sample will produce stress within the sample. Suitably designed structures made from these materials can therefore be made that bend, expand or contract when a voltage is applied. They can also be used in optical tracking devices, magnetic heads, dot-matrix printers, computer keyboards, high frequency stereo speakers, accelerometers, micro-phones, pressure sensors, transducers and igniters for gas grills.
2. Shape Memory Alloys (SMA):
Shape memory polymers, are materials that can hold different shapes at various temperatures. They can be deformed and returned to their original shape by heating. In the process, they generate an actuating force. Shape memory alloy, such as nitinol, an alloy of nickel and titanium, which has a corrosion resistance similar to stainless steel, making it particularly useful for biomechanical applications. Such types of materials can be used in coffee-pot thermostat, super elastic spectacle frames, stents for veins, whereas shape memory polymer has the ability to regain its original shape when heated. These are generally used in biodegradable surgical sutures that will automatically tighten to the correct tension and also in self-repairing car bodies that will recover shape on gentle heating after a dent.