Page 343 - AWSAR 2.0

of human body, it is a structure made up of structural components like organs, bones, and tissues. If the human body fails it means its organs, bones, tissues fail to perform their task. Similarly, the mechanical or civil structures fail because their structural components break down under some loading condition. Coming back to the question how to tell that a structure is failed or going to fail is by monitoring the health of the structural components used for building it. Technically it is called Structural Health Monitoring (SHM).
The next query that comes to mind is how to monitor huge structural components? Structures can be classified into two categories mobile and immobile. Mobile structures, like aeroplanes, and ships, can be moved for monitoring to the place where monitoring instruments are kept. But while monitoring the services provided by the structure has to be suspended. Another task is to build the scaffoldings
and other fixtures to properly
hold the components in place
while monitoring. The immobile
structures like buildings and
bridges cannot be moved so
the monitoring instruments
have to be brought near the
structure. To give an example of
structural health monitoring the
railway tracks are continuously
scrutinised before the train
moves on them. Actually, the
train engine (wagon) carries
an instrument that uses the
technique used by bats while
flying to make their path or to
communicate and is called the
Sound Navigation and Ranging
(SONAR). The instrument sends ultrasound waves through the rails, if there is a crack in the track the ultrasound waves get reflected back and the instrument catches them. Now
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comparing the time of sending and receiving the signal the distance of the crack is estimated and accidents are avoided. But this is one of the techniques, which cannot be used for every structure. This motivates to develop a compact monitoring instrument, which can be used while the structure is functional and can monitor easily any structural components.
The current research deals with the development of such SHM device. The device will be a small patch of a smart composite material. Before getting into the details of the device let’s first take an overlook on composite materials and incorporating smartness into it. Composite materials are non-conventional materials or engineered materials. By engineered materials it is meant that these materials are developed using the conventional materials which are used in daily lives abundantly. Composite materials as the name suggest are the mixture of two
materials to utilize their best characteristic. One of the examples of composite material is the Fiber Reinforced Polymer Composite (FRPC). In FRPC fibers of particular materials are hold together using a polymer.
All of us have broken a stick into two if we bend it, but the same stick if we pull along its length is difficult to break. The same kind of behaviour is observed in the fibers of many materials, that is, they are strong in one direction and week in other. To take the advantage of the high strength of fibers in one direction, the number of fibers is arranged in a particular
direction where the strength is required and a molten polymer (resin) generally called as matrix is poured to hold all the fibers in place. Matrix alone has a very low strength but has
To take the analogy of human body, it is a structure made up of structural components like organs, bones, and tissues. If the human body fails it means its organs, bones, tissues fail to perform their task. Similarly, the mechanical or civil structures fail because their structural components break down under some loading condition.