Smart Materials & Structures

Instructor: Mira Mitra Department of Aerospace Engineering

IIT Bombay 2013-2014

Textbooks 2. Smart Materials and Structures, M. V. Gandhi and B. D. Thompson, Springer, 1992 1. Smart Structures, Analysis and Design, A. V. Srinivasan and D. M. McFarland, Cambridge University Press, 2000 3. Smart Structures: Physical behavior, mathematical modeling and applications, P. Gaudenzi, Wiley, 2009 4. Dynamics of Smart Structures, R. Vepa, Wiley, 2010 5. Engineering Analysis of Smart Material Systems, D. J. Leo, Wiley, 2007

Smart ? Dictionary meaning: brisk, spirited, mentally alert, bright, knowledgeable, shrewd, Witty, clever, stylish

Smart Systems?

The term has been adapted by the engineering community over last two decades

Type 1 Has extraordinary/advanced ability to perform their designed function. The Attributes of smartness here include abilities to self-diagnose, repair, recover, report and learn. Ability to sense a variable like temperature, pressure, light, strain etc. Diagnose the nature and extent of any problem Initiate an appropriate action to address the identified problem Store the process in memory and learn Examples: Automatic doors, photo-chromatic glasses, smart band-aid, acoustic emission, embedded optical fibre (light emits from the broken end), self-healing tires, smart fabric

Smart Band-aids

Diagnoses Danger Before Infection Takes Hold Imagine placing an adhesive bandage on a cut and having the bandage tell you immediately that dangerous bacteria have gotten into the wound and that you need to seek a doctor's help. Researchers at the University of Rochester have taken the first major step toward a bandage that will change color depending on what kind of bacteria may be present in a wound. It can give an instant diagnosis as to whether the wound may require special care or what kind of antibiotics may work best in treating it. The bandage is part of the Center for Future Health's "smart medical home"-a series of devices working in conjunction in the home to monitor a family's health.

Smart-fabric

adapts to changing temperatures by opening when warm or shutting tight if cold

Platelet TechnologyTM

• Brinker Technology Platelet TechnologyTM

• discrete particles released into pressurised pipe flow

• when particles encounter modified flow at a leak, fluid forces entrain them into the leak and hold them against the pipe wall

• seals and marks the position of the leak for subsequent detection.

(All figures courtesy of Brinker Technology)

The 'Smart' drill machine measures motor speed, drilling distance, motor torque and leg thrust to determine the geological structure of the drilled medium.

Smart Drill, Rambor mining technology

Bose Aviation Headset

• Contain a sensor and cancelling circuit (inverse of incoming sound, still able to hear 95% of speech range)

• Developed for the Rutan/Yeager Voyager flight around the world (both would have been deaf without it)

• Coveted by pilots

• Cost about $1,000

Type 2 Systems with multi-functionality Examples: De-icing coating, mosquito repellent fabric, fluorescent structures

Made of soft, washable fabric, woven with optical and electrical fibres into it, the ‘Smart shirt’ monitors the wearer’s heart rate, body temperature, respiration and a host of other vital functions. The information can be relayed wirelessly to doctors or personal trainers. Future applications include shirts for parental use to monitor babies and for military use to provide a trapped soldier’s exact location and give support units exact information about wounds.

Waterproof clothing

• Goretex®

• discovered in 1969 by Bob Gore

• ~ 14 x 1012 micropores per m².

• each pore is about 700x larger than a water vapour molecule

• water drop is 20,000x larger than a pore

Biomimetics: Lotus effect

• most efficient self-cleaning plant

• mimicked in paints and other surface coatings

• pipe cleaning in oil refineries (Norway)

• Lotus effect self-cleaning surfaces

• surface of leaf water droplet on leaf

Smart Structures Earlier A smart structure is defined as structures possessing capability to sense, measure, process, diagnose and learn. These processes either help in improved delivery of the intended function/performance or help in maintaining structural integrity

Current The above definition also includes structures with advance multi-functionalities

The subject of smart structure is interdisciplinary including material science, mechanics, Electronics, data processing, bio-mechanics. etc

Examples of Smart Structures Aircraft: Monitoring at key locations on the aircraft the state of strains To warn the pilot of any impending development and propagation of Cracks, wings that alter shape with respect to air speed and pressure To increase performance and fuel efficiency

Spacecraft: Pointing of large antennas maintained through an elaborate networks of sensors and actuators

Buildings: Buildings designed to resist earthquake damage

Bridges: Remote monitoring of strain, deflection and vibration characteristics in order to warn of impending failures

Examples of Smart Structures

Ships: Hulls and propulsion systems that detect noise, remove turbulence and prevent detection

Machinery:

Tool chatter suppression, rotor critical speed control

Pipelines: Monitoring of leakage and damage to underground pipes for water, oil and gas

Medical devices: Blood sugar sensors, micrometer capsules that unclog arteries. Filters that expand After insertion into a vessel to trap blood clots.

Smart Structures

Most Common Definition

A structure with abilities to sense, diagnose, actuate, learn (some or all) in order to perform the designed function or maintain structural integrity

A Broader Definition (??)

Also include structures with advanced multi-functionalities in many cases the design is bio-mimetic Examples: de-icing /anti-drag coating, Earthquake resistant design

Scope of the course

Some of Common Applications of Smart Structures

Shape Control

Vibration Control

Structural Health Monitoring

Self-Healing Composites

Shape Control

Boeing & Airbus are carrying out research to develop movable winglet using SMA to make more effective drag reduction This is in contrast to present day fixed wingtips/winglets rise up sharply at an angle

Morphing Wing in UAV (Shape Control)

The major difference to the traditional discrete morphed wing design that uses flaps and ailerons with excessive complexity and weight penalty is that we're using smart materials such as shape memory alloys

Vibration Control

Active vibration control of prototype of space truss using piezoelectric actuators (European Space Agency)

Vibration Control of Bridge Tendon

Vibration Control Using Smart Hydraulic Actuator

Schematic of Vibration Control

Structure

Controller

Input/actuation Output/response

Sensing

Excitation

Active Control

Structure

Input/actuation Output/response

Sensing

Excitation

Passive Control

Structural Health Monitoring

Mississippi Bridge Collapse in 2007

Structural Health Monitoring

A Wireless Sensor Network for Structural Health Monitoring (SHM) is designed, implemented, deployed and tested on the 4200ft long main span and the south tower of the Golden Gate Bridge.

(Accelerometer Board)

Battery (4 X 6V Lantern Battery)

Bi-directional Path Antenna

Schematic of SHM

Structure

Diagnostic unit, signal processing, Feature extraction

Designed Input through Smart actuators

Output/response from sensor

Excitation

Self-Healing Composites

A microencapsulated healing agent is embedded in a structural composite matrix containing a catalyst capable of polymerizing the healing agent. a, Cracks form in the matrix wherever damage occurs; b, the crack ruptures the microcapsules, releasing the healing agent into the crack plane through capillary action; c, the healing agent contacts the catalyst, triggering polymerization that bonds the crack faces closed