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Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
COMPOSITE
MATERIALS
Asst. Prof. Dr. Ayşe KALEMTAŞ
Office Hours: Tuesday, 16:30-17:30
[email protected], [email protected]
Phone: +90 – 252 211 19 17
Metallurgical and Materials Engineering Department
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
ISSUES TO ADDRESS
Reinforcement Materials
Reinforcement-Matrix Interactions
Composite material design
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Reinforcements
Function is to reinforce the primary phase
Imbedded phase is most commonly one of the following shapes:
Fibers
Particles
Flakes
In addition, the secondary phase can take the form of an infiltrated
phase in a skeletal or porous matrix
Example: a powder metallurgy part infiltrated with polymer
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing 2/e”
Possible physical shapes of imbedded phases in composite materials:
(a) fiber, (b) particle, and (c) flake
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
FIBERS
Filaments of reinforcing material, usually circular in
cross-section
Diameters range from less than 0.0025 mm to about 0.13 mm,
depending on material
Filaments provide greatest opportunity for strength
enhancement of composites
The filament form of most materials is significantly stronger
than the bulk form
As diameter is reduced, the material becomes oriented in the
fiber axis direction and probability of defects in the structure
decreases significantly
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Continuous versus Discontinuous Fibers
Continuous fibers - very long; in theory, they offer a
continuous path by which a load can be carried by the
composite part
Discontinuous fibers (chopped sections of continuous
fibers) - short lengths (L/D = roughly 100)
Important type of discontinuous fiber are whiskers - hair-
like single crystals with diameters down to about 0.001 mm
(0.00004 in.) with very high strength
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Particles and Flakes
A second common shape of imbedded phase is
particulate, ranging in size from microscopic to
macroscopic
Flakes are basically two-dimensional particles - small flat
platelets
The distribution of particles in the composite matrix is
random, and therefore strength and other properties of the
composite material are usually isotropic.
Strengthening mechanism depends on particle size
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fiber Orientation
The fibers may be oriented randomly within the material, but it is
possible to arrange for them to be oriented preferentially in the
direction expected to have the highest stresses. Such a material
is said to be anisotropic (different properties in different
directions), and control of anisotropy is an important means of
optimising the material for specific applications.
At a microscopic level, the properties of these composite are
determined by the orientation and distribution of the fibers, as
well as by the properties of the fiber and matrix materials. These
topic known as composite micromechanics is concerned with
developing estimates of the overall material properties from
these parameters.
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fiber Orientation
One-dimensional reinforcement, in which maximum strength and stiffness are obtained
in the direction of the fiber
Planar reinforcement, in some cases in the form of a two-dimensional woven fabric
Random or three-dimensional in which the composite material tends to possess
isotropic properties
Fiber orientation in composite materials: (a) one-dimensional, continuous fibers;
(b) planar, continuous fibers in the form of a woven fabric; and (c) random, discontinuous fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
A three dimensional weave is also possible
This could be found when fabrics are knitted or weaved together
Fiber Orientation
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
The properties of fiber composites can be tailored to meet different loading requirements
By using combinations of different fiber orientation quasi-isotropic materials may be produced
Figure. (a) shows a unidirectional arrangement
(b) shows a quasi-isotropic arrangement
Fiber Orientation
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Strongest, but
anisotropic Weaker, but
isotropic
Fiber Orientation
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Maximum strength is
obtained when long fibers
are oriented parallel to
the applied load
The effect of fiber
orientation and strength
can be seen in the plot
Fiber Orientation
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
FIBERS
COMMERCIALLY AVAILABLE FORMS OF
REINFORCEMENT
Filament: a single thread like fiber
Roving: a bundle of filaments wound to form a large
strand
Chopped strand mat: assembled from chopped
filaments bound with a binder
Continuous filament random mat: assembled from
continuous filaments bound with a binder
Many varieties of woven fabrics: woven from rovings
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fiber Materials
Materials for Fibers
Metals – Steel
Polymers – Kevlar
Ceramics – SiC and Al2O3
Carbon – High elastic modulus
Boron – Very high elastic modulus
Glass – Most widely used filament
The most important commercial use of fibers is in polymer composites
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
FIBERS
COMMERCIALLY AVAILABLE FORMS OF
REINFORCEMENT
Close up of a roving Roving Filaments
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
FIBERS
COMMERCIALLY AVAILABLE FORMS OF
REINFORCEMENT
Random mat and woven fabric (glass fibers)
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
FIBERS
COMMERCIALLY AVAILABLE FORMS OF
REINFORCEMENT
Carbon fiber woven fabric
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
FIBERS
NANO FIBERS
Comparison - human hair, pollen grain, nanofibers Nanofibers (PA6) - 5000x magnified
http://www.elmarco.com/gallery/nanofibers/
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Specific strength versus
specific modulus for
different types of fibers
FIBER PROPERTIES
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Glass Fibers
Fiberglass refers to a group of products made from individual glass fibers
combined into a variety of forms.
Glass fibers can be divided into two major groups according to their
geometry: continuous fibers used in yarns and textiles, and the
discontinuous (short) fibers used as batts, blankets, or boards for insulation
and filtration.
Fiberglass can be formed into yarn much like wool or cotton, and woven into
fabric which is sometimes used for draperies. Fiberglass textiles are
commonly used as a reinforcement material for molded and laminated
plastics. Fiberglass wool, a thick, fluffy material made from discontinuous
fibers, is used for thermal insulation and sound absorption. It is commonly
found in ship and submarine bulkheads and hulls; automobile
engine compartments and body panel liners; in furnaces and air conditioning
units; acoustical wall and ceiling panels; and architectural partitions.
http://www.madehow.com/Volume-2/Fiberglass.html#ixzz3GRPTTRFE
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Glass Fibers
The basic raw materials for fiberglass products are a variety
of natural minerals and manufactured chemicals. The major
ingredients are silica sand, limestone, and soda ash. Other
ingredients may include calcined alumina, borax, feldspar,
nepheline syenite, magnesite, and kaolin clay, among
others.
Silica sand is used as the glass former, and soda ash and
limestone help primarily to lower the melting temperature.
Other ingredients are used to improve certain properties,
such as borax for chemical resistance. Waste glass, also
called cullet, is also used as a raw material.
http://www.madehow.com/Volume-2/Fiberglass.html#ixzz3GRPTTRFE
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Glass Fibers
– Tensile strength
– Chemical resistance
– Moisture resistance
– Thermal properties
– Electrical properties
There are four main types of glass used in fiberglass:
– A–glass
– C–glass
– E–glass
– S–glass
Fiberglass properties vary somewhat according to the type of glass used.
However, glass in general has several well–known properties that contribute to
its great usefulness as a reinforcing agent:
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Due to the relatively inexpensive cost glass fibers are the most commonly used reinforcement
There are a variety of types of glass, they are all compounds of silica with a variety of metallic oxides
Designation Property or Characteristic Composition, %
E, electrical low electrical conductivity
55 SiO2, 11 Al2O3, 6 B2O3,
18 CaO, 5 MgO
S, strength high strength 65 SiO2, 25 Al2O3, 10 MgO
C, chemical high chemical durability
65 SiO2, 4 Al2O3, 6 B2O3,
14 CaO, 3 MgO, 9 K2O
M, modulus high stiffness
A, alkali high alkali or soda lime glass
D, dielectric low dielectric constant
The most commonly used glass is E-glass due to its low cost
Glass Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Most widely used fiber
Uses: piping, tanks, boats, sporting goods
Advantages
Low cost
Corrosion resistance
Low cost relative to other composites:
Disadvantages
Relatively low strength
High elongation
Moderate strength and weight
Types:
E-Glass - electrical, cheaper
S-Glass - high strength
Glass Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Glass fibers produced by spinning liquid glass directly to
fine fibers. Just as in the Griffith experiments, the strength
is based on small diameter.
Modulus ranges from 70- 90 GPa.
Strength ranges from 1.7-5 GPa
Breaking strain from 2 to 5%
Density ~ 2.5 gm/cm3.
“E glass” (electrical, borosilicate glass) is the cheapest
and most common. “R glass” and “S glass” is more
expensive but more corrosion resistant, for example and
higher strength.
Glass Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Carbon fibers have gained a lot of popularity in the last
two decades due to the price reduction
“Carbon fiber composites are five times stronger than
1020 steel yet five times lighter. In comparison to 6061
aluminum, carbon fiber composites are seven times
stronger and two times stiffer yet still 1.5 times lighter”
Initially used exclusively by the aerospace industry they
are becoming more and more common in fields such as
automotive, civil infrastructure, and paper production
Carbon Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Carbon Fibers
http://www.utsi.edu/research/carbonfiber/cf.htm
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Carbon Fibers
http://www.utsi.edu/research/carbonfiber/cf.htm
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
2nd most widely used fiber
Examples
aerospace, sporting goods
Advantages
high stiffness and strength
low density
intermediate cost
Properties:
Standard modulus: 207-240 GPa
Intermediate modulus: 240-340 GPa
High modulus: 340-960 GPa
Diameter: 5-8 microns, smaller than human hair
Fibers grouped into tows or yarns of 2-12k fibers
Carbon Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Modulus ranges from 200-750 GPa (cf. Steel-210)
Strength ranges from 2-6 GPa
Breaking strain ranges from 0.2 - 2 %
Density ranges from 1.76- 2.15 g/cm3
Highest cost compared to glass or aramid, but greatest
range of properties.
Internal structure consists of radially-aligned graphite
platelets, which leads to some anisotropy in properties in
the fibers. Both thermal and electrical conductivity are
generally good (but then insulation required where metals
might be in contact for carbon-fiber composite).
Carbon Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Types of carbon fiber
vary in strength with processing
Trade-off between strength and modulus
Intermediate modulus
PAN (Polyacrylonitrile)
fiber precursor heated and stretched to align
structure and remove non-carbon material
High modulus
made from petroleum pitch precursor at lower cost
much lower strength
Carbon Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Carbon Fiber Production
Carbon fiber is currently produced in relatively limited quantities mostly
via two manufacturing processes:
Based on pitch (coal tar and petroleum products)
Based on Polyacrylonitrile (PAN)
Current global capacity for pitch-based carbon fiber is estimated at
about 3,500 metric tons per year.
Global use for PAN-based carbon fiber is increasing rapidly, and total
production capacity currently does not meet the demand.
PAN-based carbon fiber is more expensive to produce, hence, limiting
its use to high end applications, (used primarily by aerospace and
sporting equipment industries)
Carbon Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Carbon Fiber Properties
Pitch and PAN carbon fibers have properties that suit different
applications.
The most common carbon-fiber type is PAN, primarily for structural
reinforcement because of its high tensile strength.
Mesophase pitch fibers, on the other hand, offer designers a different
profile. They are easily customized to meet specific applications. They
often have a higher modulus, or stiffness than conventional PAN
fibers, are intrinsically more pure electrochemically, and have higher
ionic intercalation.
Mesophase Pitch fibers also possess higher thermal and electrical
conductivity, and different friction properties.
Carbon Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Global demand for high-strength, light-weight and durable
fiber is growing; typical applications in:
Portable power
Rechargeable batteries and fuel cell electrodes
Fiber reinforced plastics, FRP
Energy production; windmill blades
Building and construction materials: concrete and
asphalt reinforcements, soil erosion barriers
Electronics, composite materials for automotives &
general transportation,
Specialty and niche markets.
Carbon Fibers
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fibers – Others
Boron
High stiffness, very high cost
Large diameter - 200 microns
Good compressive strength
Polyethylene - trade name: Spectra fiber
Textile industry
High strength
Extremely light weight
Low range of temperature usage
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Ceramic Fibers (and matrices)
Very high temperature applications (e.g.
engine components)
Silicon carbide fiber - in whisker form.
Ceramic matrix so temperature resistance is
not compromised
Infrequent use
Fibers – Others
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fiber Material Properties
Steel: density (Fe) = 7.87 cm3; TS=0.380 GPa; Modulus=207 GPa
Al: density=2.71 g/cm3; TS=0.035 GPa; Modulus=69 GPa
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fibers-Aramid
-Aramid fibers are also becoming
more and more common
-They have the highest level of
specific strength of all the
common fibers
-They are commonly used when
a degree of impact resistance is
required such as in ballistic
armour
-The most common type of
aramid is Kevlar http://armorus.en.made-in-
china.com/product/weEnpAcbaUYC/China-Covert-
Aramid-Bulletproof-Vest-Body-Armor-TAT-FJ-2-.html
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fibers-Aramid
Kevlar and Aramid Fibers (Opaque Armor)
Only the highest grade, waterproof Kevlar and aramid fibers are used.
These fibers offer superior blast, fragmentation, explosive and small arms
ballistic protection. All materials are tested in an independent laboratory
and are custom fabricated according to TAC specifications.
http://www.texasarmoring.com/armored_vehicle_bulletproofing_materials.html
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
FIBER PROPERTIES
COMPARATIVE COST OF FIBER REINFORCEMENT
Fiber Cost ($/lb)
Boron 320
Silicon Carbide 100
Carbon 30
Alumina 30
Kevlar 20
E-Glass 3
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fiber Reinforced Composites
CHARACTERISTICS OF FIBER REINFORCED
COMPOSITES
As can be seen
from this plot, the
strength of the
composite
increases as the
fiber length
increases (this is a
chopped E-glass-
epoxy composite)
Composite Materials Asst. Prof. Dr. Ayşe KALEMTAŞ
Fiber Reinforced Composites
Some commonly used fibers for polymer matrix
composites:
Glass fibers
Carbon fibers
Aramid fibers
Some commonly used fibers for metal matrix
composites:
Boron fibers
Carbon fibers
Oxide ceramic and non-oxide ceramic fibers