Advanced Materials

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Advanced Materials

• Human Powered Aircraft Group

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Advanced Materials

• Advanced materials are used in aircraft design
  to
• -Reduce weight
• -Improve strength
• -Design morphing wings
• -Create self-healing structures

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Examples of Advanced Materials

• Memory Polymers
• Composites
• Biocomposites
• Thermoplastics
• Alloys

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Memory Polymers Veriflex and Veritex

• Veriflex is a shape memory polymer resin which
  modifies its shape in response to temperature
  changes.
• Veritex is a dynamic composite that utilizes
  Veriflex resin as its matrix. When heated,
  Veritex is pliable and maintains shape as it
  cools, regaining structural stiffness. Once
  reheated it returns to its original shape and can
  be remolded without degrading.
• Future polymers may respond to light, electric
  fields and magnetic fields.

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Composites

• Composites are a combination of two or more
  organic or inorganic components one of which
  serves as a matrix holding the materials together
  and then other of which serves as reinforcement
  in the form of fibers
• Composites are lightweight and strong but they
  are complex to manufacture, expensive and hard to
  inspect for flaws

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Thermoplastics

• Thermoplastics are a new type of materials that
  is replacing thermosets such as epoxy,
  bismaleimide, or polyimide, as the matrix for
  composites
• Thermoplastics are easier to produce and are much
  more durable and tougher than thermosets

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Biocomposites

• Biocomposites combine plant fibers with resins to
  create natural based composite materials.
• High tensile plant fibers including, kenaf,
  industrial hemp, and flax, can be combined with
  traditional resins to create an alternative to
  traditionally steel or fiberglass applications.
• Some advantages over traditional composites
• Reduced weight
• Increased flexibility
• Greater moldability
• Less expensive
• Sound insulation
• Renewable resource
• Self-healing properties

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Alloys

• Benefits of Alloys
• Decreased weight
• Durable
• Easy to manufacture and repair

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Application to Morphing Wings

• Stronger, shape memory and self-healing polymers
  are applicable to the design of morphing wings
• Lockheeds 14ft remote-control aircraft makes use
  of Veriflex and Veritex polymers to change shape
  and ensure a streamline profile as the wings
  morph.
• Nextgen Aeronautics tested a wing that's
  structure of aluminum lattices expanded and
  compressed consequently stretching and shrinking
  the wings silicone-rubber skin and causing the
  wing tips to move forward and back, and changing
  the wing span and chord.

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• Future development of Personal Air Vehicles
  (PAV), calls for safer, easy to fly planes.
• Self-healing (often biocomposite) materials can
  be utilized to reduce maintenance.
• An Aeronautic Vehicle Integrated Health
  Management System is looking into self-healing
  materials that will fill cracks in the structure
  by breaking capsules and releasing adhesive.

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Aeronautical Integrated Vehicle Health Monitoring
System (IVHM)

• Detection of damaging events
• Characterization of the damage
• Prioritization of the seriousness of the damage
• Identification of the cause of the damage
• Formulation of the response
• Execution of the response

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What is IVHM?

• Intelligent sensing system
• Detects and measures quantities and uses this
  information to make forward looking decisions
• Uses thousands and perhaps millions of different
  sensors used to measure different quantities
  (stress, strain, temperature, acoustics, etc)

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How Does IVHM work?

• Separates structures (skin, ribs, components,
  etc...) into a series of cells
• Each cell is equipped with a group of sensors
• The sensors communicate with neighboring cells as
  well as a central computer.

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Types of Sensors

• Fiber Optic
• Piezoelectric
• Infrared imaging

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Fiber Optic Sensors

• Can measure strain, temperature and pressure
• Specifically they can measure bond line
  integrity, acoustic emissions, and corrosion
• Uses Bragg grating to measure changes in light
  signal
• A change in stress moves the Bragg grating
  producing a shift in the reflected wavelength
• Fiber Optics are brittle so they must be embedded
  into materials, this is very expensive and
  complicates manufacturing and repair practices.

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Piezoelectric Materials

• Convert mechanical input into an electrical
  signal (sensor) or convert and electrical pulse
  into a mechanical action (actuator)
• Can detect energies caused by impact events or
  defect generation (cracks, delamination)
• Arrays of sensors allow a pinpoint determination
  of the damage location
• Sensors have been able to detect cracks 0.005
  inches in length of six inches
• Will be embedded or surface mounted. Less
  expensive option

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Infrared Imaging

• Detects heat signatures in order to detect leaks,
  cracks, debonding, corrosion, poor electrical
  wiring and contacts, and to assess overall
  thermal profiles of components.
• Most often used to detect defects or damage in
  the propulsion system.
• Widely used, inexpensive

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Joint Strike Fighter

• Airframe Structures
• Engine
• Electronics
• Mission Systems
• Components
• Hydraulics
• Drive Shafts
• Fuel system
• Electrical system

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Summary of IVHM

• Rapidly growing field dependant on the
  improvement and development of sensing
  technologies.
• It will enable less reliance on statistical based
  scheduled maintenance and moves towards a
  condition based maintenance which will greatly
  reduce ownership costs

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References

• http//showcase.netins.net/web/creativecomposites/
  Biocomposites.html, Creative Composites, Ltd., 19
  September 2006
• http//www.crgrp.net/veriflex.htm, CRG
  Industries, LLC., 19 September 2006
• Flying off the Drawing Board, Jeff Wise,
  Popular Mechanics, volume 183 no. 7, July 2006
• http//www.crgindustries.com/veritex.htm, CRG
  Industries, LLC, 19 September 2006
• http//www.centennialofflight.gov/essay/Evolution_
  of_Technology/composites/Tech40.htm, U.S.
  Centennial of Flight Commission, 23 September
  2006
• http//ammtiac.alionscience.com/pdf/2004MaterialEA
  SE27.pdfsearch22Vehicle20Integrated20Health2
  0Monitoring20System22, The AMPTIAC Quarterly,
  Volume 8, Number 3, Sensors and Sensing
  Technologies for Integrated Vehicle Health
  Monitoring Systems