In His Name

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In His Name

• Sharif University of Technology
• Civil Engineering Department
• Presented by
• Hatef Monajemi

Nov 2005
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COPOSITE MATERIALS

• A combination of two or more materials
  (reinforcement, matrix or resin, filler, etc),
  differing in form or composition on a
  macro-scale. The constituents retain their
  identities, i.e.., they do not merge into each
  other, although they act in concert. Normally,
  the components can be physically identified and
  exhibit an interface between each other.

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BRIEF HISTORY

• The use of combination of materials to
  compensate for shortcoming of one or to
  capitalize on the advantages of another has a
  long history. Human have been using composite
  materials for thousands of years . Some of old
  and contemporary composite materials are
• Mud/Straw bricks
• Concrete
• fiberglass

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Mud/Straw Bricks

• A cake of dried mud is easy to break by
  bending, which puts a tension force on one edge,
  but makes a good strong wall, where all the
  forces are compressive. On the contrary, a piece
  of straw has a lot of strength when you try to
  stretch it but almost none when you crumple it
  up. But if you embed pieces of straw in a block
  of mud and let it dry hard, the resulting mud
  brick resists both squeezing and tearing and
  makes an excellent building material.

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Concrete

• another well-known composite is concrete. Here
  aggregate (sand and gravel) is bound together by
  cement. concrete has good strength under
  compression and it can be made stronger under
  tension by adding metal rods to the composite (so
  creating reinforced concrete).

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Fiberglass

• Fiberglass developed in the late 1940s, was
  the first modern composite and is still the most
  common.

Flight simulator
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COMPOSITES MARKETS

• TRANSPORTATION
• CONSTRUCTION
• MARINE
• CORROSION-RESISTANT
• CONSUMER
• ELECTRICAL/ELECTRONIC
• APPLIANCES/BUSINESS
• AIRCRAFT/DEFENSE

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U.S. COMPOSITES SHIPMENTS - 1996 MARKET
SHARE SEMI-ANNUAL STATISTICAL REPORT - AUGUST
26, 1996
Aircraft/Aerospace 0.7
Transportation 30.6
Construction 20
Other- 3.4
Consumer Products - 6
Marine - 11.6
Electrical/ Electronic - 10
Appliance/Business Equipment - 5.3
Corrosion-Resistant Equipment - 12.4
Includes reinforced thermoset and
thermoplastic resin composites, reinforcements
and fillers.
SOURCE SPI Composites Institute
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CLASSIFICATION OF COMPOSITE MATERIALS ACCORDING
TO THEIR MATRIX PHASE

• Polymer matrix composites
• Metal matrix composites
• Ceramic matrix composites

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FIBER REINFORCED POLYMER (FRP)

• A polymeric matrix that is reinforced with
  fibers, embeded in it.

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FRP COMPOSITE INGREDIENTS

• Resin
• Resin Holds the constituents together,
  Protects the fibers, distributes the load evenly
  among fibers, transfers stress beteen fibers,
  separates the fibers and in a nutshell it affects
  the physical properties of the end product.
• Fiber
• Fiber serves as the reinforcement and
  provides primary strength and stiffness in one
  direction.
• Fillers and Additives
• Fillers and Additives are used as process or
  performance aids to impart special properties to
  the end product.

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DIFFERENT POLYMER MATRICES

• Thermosetting
• a thermosetting polymer is a polymer that is
  substantially infusible and insolvable after
  being cured.
• Example epoxies, polyesters, phenolics
• Thermoplastic
• a thermoplastic is a polymer that can be
  repeatedly softened by heating and hardened by
  cooling.
• Example polyamide, polyethylene ,
  polysulfone

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Stress-strain behavior of different polymer
matrices
Thermoplastic polymers
Thermosetting polymers
Notice to the range of ultimate strains of
different polymers
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DIFFERENT FIBERS

• Natural fibers
• they were formerly used for economy but now
  are generally replaced by man-made fibers
  (synthetics) with both better properties and
  lower costs.
• Example sisal , jute
• Synthetic organic fibers
• they offer low densities and high strengths
  but (with exception of Kevlar) low stiffnesses
  and their range of Application is limited because
  of their low stiffness.
• Example nylon ,polyester, aramids (Kevlar)
• Synthetic inorganic fibers
• they are most commonly used fibers and the
  use of glass is more than others because of its
  lower cost .
• Example glass, boron, carbon, aluminum
  oxide , silicon carbide

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Stress-strain behavior of common-place fibers in
civil engineering applications
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Comparison of FRPs and Steel

• Unlike steel that yeilds FRPs behave linearly
  elastic to failure
• Both Carbon and Glass FRPs are much stronger than
  steel
• The ultimate strains of FRPs are less than steel

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FRACTURE OF UNIDERECTIONAL FRP UNDER TENSION

• considering the effect of fibers orientation
  on the strength of a composite material made up
  of a continuous aligned fibers embedded in a
  matrix, it should be recognized that there are 3
  possible modes of failure...
• 1-tensile fracture of fibers
• 2-shear faliure of matrix
• 3-tensile failure of matrix
• or matrix/fiber interface

Tensile fracture of fibers
shear faliure of matrix
tensile failure of matrix
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THE STRENGTH OF FRPS IN COMPRESSION
The strength of a fiber reinforced polymer in
compression is considerably lower than tension,
the long thin fibres buckle easily under a
compressive load.
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localized buckling test for E-glass
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ADVANTAGES OF FRPS

• Non-corrosive
• Anisotropic
• High strength to weight ratio
• Excellent fatigue characteristic (particularly
  carbon fibers)
• Electromagnetic neutrality
• High tensile strength
• Rapid and easy installation (which can lower
  construction costs and down time)

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DISADVANTAGES OF FRPS

• Low strain at failure
• Extremely low lateral load due to the relatively
  poor mechanical properties of the matrix
• Excesive creep and relaxation in some cases
  (particularly for Aramid FRPs)
• The potential for ultra-violet (UV) degradation
  of polymer matrices in external applications
• Expansion due to moisture absorption
  (particularly for Aramid FRPs)
• Rapid and severe loss of bond, strength and
  stiffness at elevated temperatures

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COMPOSITE IN CIVIL ENGINEERING

• Civil Engineers are known to test the
  limits of building structures, by going higher,
  longer or lighter. On the other hand Civil
  Engineers are by definition very conservative.
  These two professional characteristics come
  together when Civil Engineers are exploring the
  exciting opportunities offered by the high-tech
  Engineering materials available to them today.
  The challenges to reduce weight, increase spans,
  build higher or slender constructions
  automatically mean they must look at new
  engineering materials in their daring designs.
• If the advantages that Composites offer
  are combined with the physical limits of Civil
  Engineering an interesting development can occur.
  Composites are more often a part of the material
  forming and basis for Civil Engineering projects.
• Civil Engineering today faces challenges
  that require building reinforced structures that
  can overcome natural disasters like earthquakes
  and hurricanes. This requires the creative use of
  Composite materials in existing structures and
  structural systems.
• FRPs can be used in different structures.
  now a days FRPs have become an alternative to
  steel reinforcements for concrete structures to
  make them more earthquake resistant.
• It is expected that Composite Engineering
  will make more and successful inroads into Civil
  Engineering and will play a more and vital role
  in pushing the future of the building and
  construction process to the limits.

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Examples
Placement of H-Deck sections on FRP stringers
for Laurel Lick Bridge.
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BORJALARAB-DUBAI
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WICKWIRE RUN BRIDGE