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smart materials

Civil engineering materials used in advanced construction materials

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smart materials

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  1. INTRODUCTION TO SMART MATERIALS & RECYCLING OF MATERIALS.

  2. infrastructure Need of the modern society

  3. The commonly used materials for construction are cement, concrete, sand, bricks etc. Until relatively recent times, most periods of technological development have been linked to changes in the use of materials (eg the stone, bronze and iron ages). And that the fusion between designer materials and the power of information storage and processing has led to a new family of engineered materials and structures.

  4. WHAT ARE SMART MATERIALS? Smart materials can be expressed as materials respond to environmental stimuli. Environmental stimuli can be in the form of temperature,moisture,pH,electric and magnetic fields.

  5. SMART MATERIALS Smart materials are materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, temperature, moisture, pH, electric or magnetic fields

  6. EXAMPLES: • Photochromatic materials are smart materials that change colour in response to light. • Certain shape memory alloys and polymers change/recover their shape in response to heat. • Some electro and magneto-rheological fluids change viscosity to electric and magnetic stimuli.

  7. Smart concrete

  8. Magneto-rheological liquids used to damp bridges to reduce earthquake effects. Cable stayed bridge

  9. magneto-rheological liquids • A grey blob oozes down the side of a laboratory beaker. • It's heading for the table, but before it gets there a low hum fills the air. • Someone just switched on an electromagnet. • The goop stiffens, quivers, then carries on oozing only after the hum subsides. • Is it alive? • No, just magnetized.

  10. The nervous systems of future robots might use MR fluids to move joints and limbs in lifelike fashion An MR washing machine. Magnetic dampers inside the machine will decrease noise and vibration--and save energy.

  11. There are a number of types of smart material, some of which are already common. Some examples are as following: • Piezoelectric • Shape memory alloys and shape memory polymers. • Magnetic shape memory • pH-sensitive polymers • Temperature-responsive polymers • Halochromic • Chromogenic systems • Non-Newtonian fluid

  12. PIEZOELECTRIC • Piezoelectric materials are materials that produce a voltage when stress is applied. • This effect is reversible - • PIEZOELECTRICITY- • Suitably designed structures made from these materials can therefore be made that bend, expand or contract when a voltage is applied.

  13. THE CONVERSE PIEZOELECTRIC EFFECT

  14. SHEAR MOTION

  15. Applications of Piezoelectric materials - • production and detection of sound • generation of high voltages • electronic frequency generation • microbalances, and ultra fine focusing of optical assemblies • basis of a number of scientific instrumental techniques with atomic resolution, the scanning probe microscopies such as STM, AFM, MTA, SNOM etc, as well as more mundane uses including acting as the ignition source for cigarette lighters.

  16. SENSOR : • The principle of operation of a piezoelectric sensor is that a physical dimension, transformed into a force, acts on two opposing faces of the sensing element. Depending on the design of a sensor, different "modes" to load the piezoelectric element can be used: longitudinal, transversal and shear.

  17. Experimental apparatus for a Piezoelectric Sensor

  18. Piezoelectric sensor

  19. TEMPERATURE-RESPONSIVE POLYMER • A temperature-responsive polymer is a polymer which undergoes a physical change when external thermal stimuli are presented. • The ability to undergo such changes under easily controlled conditions makes this class of polymers fall into the category of "smart materials".

  20. After numerous investigations of poly(N-isopropylacrylamide) (poly-NIPAAm), there was a sparked interest in the applications of this and many other stimuli-responsive polymers.

  21. poly(N-isopropylacrylamide)(poly-NIPAAm),

  22. There has been extensive research in the applications of intelligent polymers for use as , • stationary phases, • extraction compounds, • surface modifiers, • drug delivery, • and gene delivery.

  23. CHROMISM • In chemistry, chromism is a process that induces a reversible change in the colors of compounds. • In most cases, chromism is based on a change in the electron states of molecules, especially the π- or d-electron state, so this phenomenon is induced by various external stimuli which can alter the electron density of substances.

  24. CHROMISM CRYSTALS

  25. Chromism is classified by what kind of stimuli are used. The major kinds of chromism are as follows. • thermochromism is chromism that is induced by heat, • electrochromism is induced by the gain and loss of electrons. • solvatochromism depends on the polarity of the solvent. • Ionochromism - color change caused by ions. • Halochromism - color change caused by a change in pH. • Tribochromism - color change caused by mechanicalfriction.

  26. Photochromismis induced by light irradiation. • This phenomenon is based on the isomerization between two different molecular structures. • Spiro forms of lactones and oxazines are frequently used as leuco dyes, frequently displaying chromism - reversible change between their colorless and color form. • spiro compound – Lactone-

  27. Photochromic Lens • Light sensitive sunglasses that darkens when exposed to bright sunlight.

  28. HALOCHROMISM • A halochromic material is a material which changes colour when pH changes occur. • Halochromicsubstances are suited for use in environments where pH changes occur frequently, or places where changes in pH are extreme.

  29. Application- • detect alterations in the acidity of substances, like detection of corrosion in metals. • may be used as indicators to determine the pH of solutions of unknown pH.The colour obtained is compared with the colour obtained when the indicator is mixed with solutions of known pH. The pH of the unknown solution can then be estimated. • Disadvantages of this method – • include its dependency on the colour sensitivity of the human eye, and that unknown solutions that are already coloured cannot be used.

  30. SHAPE MEMORY ALLOY (SMA) • A shape memory alloy (SMA, also known as a smart alloy, memory metal, or muscle wire) is an alloy that "remembers" its shape, and can be returned to that shape after being deformed, by applying heat to the alloy. • Shape memory alloys have numerous applications in the medical and aerospace industries

  31. How Shape Memory Alloys Work Molecular Rearrangement Phase changes.

  32. A solid state phase change is similar in that a molecular rearrangement is occurring, but the molecules remain closely packed so that the substance remains a solid. • In most shape memory alloys, a temperature change of only about 10°C is necessary to initiate this phase change.

  33. The two phases, which occur in shape memory alloys, are Martensite, and Austenite.

  34. Martensite, is the relatively soft and easily deformed. The molecular structure in this phase is twinned. Austenite, the stronger phase of shape memory alloys, occurs at higher temperatures. The shape of the Austenite structure is cubic.

  35. PH-SENSITIVE POLYMERS • pH sensitive polymers are materials which will respond to the changes in the pH of the surrounding medium by varying their dimensions. • Exhibited due to the presence of certain functional groups in the polymer chain.

  36. There are two kinds of ph sensitive materials: one which have acidic group (-COOH, -SO3H) and swell in basic pH, and others which have basic groups (-NH2) and swell in acidic pH. Polyacrylic acid is an example of the former and Chitosan is an example of the latter. The mechanism of response is same for both, just the stimuli vary.

  37. NON-NEWTONIAN FLUID • A non-Newtonian fluid is a fluid whose flow properties are not described by a single constant value of viscosity. • Many polymer solutions and molten polymers are non-Newtonian fluids • Eg. ketchup, starch ,paint, blood and shampoo. • The relation between shear stress & strain rate • Linearity. • Can define the coefficient of viscosity (time dependents)

  38. Common exampleof a non-newtonian • An inexpensive, non-toxic example of a non-Newtonian fluid is a suspension of corn starch (corn flour) in water, sometimes called oobleck • The application of force — for example by stabbing the surface with a finger, or rapidly inverting the container holding it — leads to the fluid behaving like a solid rather than a liquid. This is the "shear thickening" property of this non-Newtonian fluid.

  39. More gentle treatment, such as slowly inserting a spoon, will leave it in its liquid state. Trying to jerk the spoon back out again.

  40. A person moving quickly and applying sufficient force with his feet can literally walk across such a liquid.

  41. A shear thinning fluid is paint • one wants the paint to flow readily off the brush when it is being applied to the surface being painted, but not to drip excessively.

  42. Applicationsof Smart Materials Piezo transducers –damage detection. Smart material tags In aircrafts & spacecrafts In the design of smart building –for vibration control , noise migration, safety and performance.

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