TM 1-1500-204-23-11
a. Carbon. Carbon and graphite ibers are made
d. Quartz. Quartz iber is similar to iberglass but
from organic materials. The two major types of carbon
is far less "visible" to radar, a property known as
are pitch based or those derived from synthetic iber
transmissibility. Because of this, the primary use of
precursors. The ibers are manufactured by heating
quartz is the construction of radomes. Quartz is
these precursor ilaments in a controlled atmosphere
also used for high temperature applications in the
to drive off hydrogen and other non-carbon atoms.
neighborhood of 700 F. These ibers are clear but
Depending on processing, the strength and stiffness
appear white and may be dyed any color during
of the ibers can be modiied. Carbon ibers and
production. Quartz ibers are available in any fabric
graphite ibers differ in the temperature at which the
form listed in paragraph 4-3.
ibers are made and heat treated, and the amount
of residual carbon left behind. Carbon ibers typically
e. Boron One of the stiffest and strongest rein-
are heated to about 2400 F and are 93 to 95%
forcing ibers is boron. The boron iber is 0.005 inch
carbon, while graphite ibers are heated to between
in diameter. It is made by chemical vapor deposition
3450 to 5450 F and are more than 99% carbon.
of elemental boron onto a cleaned 0.0005 inch diam-
This results in different properties for each mate-
eter tungsten ilament. The boron iber has a high
rial. Due to these different properties, carbon ibers
bending stiffness and cannot be bent around an object
are not necessarily interchangeable, similar to differ-
any smaller than the diameter of a dime. Due to this
ences between 2024-T3 and a 7075-T6 aluminum
relatively high bending stiffness, boron ibers cannot
alloys. While they re both aerospace grade aluminum
be woven into cloth or used for complex contoured
alloys, they have very different strength and stiffness
parts. Boron s high tensile and compressive strength
properties and are not generally considered inter-
plus its lack of galvanic corrosion potential makes the
changeable. The most desirable property for high
iber very popular for repairs to cracked metallic struc-
performance structures is the stiffness to weight ratio.
tures. Boron is only available as pre-impregnated,
Fiber bundles (tows) are identiied by the number of
unidirectional tape.
ibers in the bundle by thousands. For example, 12
K tow contains 12,000 ibers. Carbon is available
f. Polyethylene. This iber is sold under the trade-
in any fabric form listed in paragraph 4-3. Carbon
mark Spectra or Dyneema. The ibers are the
ibers are always dark gray or black in color. They
same as those found in plastic milk containers but
are moderately lexible. Carbon ibers have a high
are processed to align the molecular structure. The
potential for causing galvanic corrosion when used
material is used in composite armor. Polyethylene is
with metallic fasteners and structures.
naturally clear but appears white and may be dyed
any color during production. These ibers are avail-
b. Aramid. Kevlar is DuPont s trademark name
able in any fabric form listed in paragraph 4-3. To
for aramid ibers. This type of iber is produced
make polyethylene ibers bondable, they are usually
from two liquid chemicals using a complex process
corona treated. The treatment strips electrons to cre-
resulting in spun ilaments. Aramid is an organic iber
ate more chemically bondable sites.
that is 43 percent lighter than and twice as strong in
tension as glass. One of the outstanding properties
4-3. FIBER FORMS. Most composite materials are
of aramid is toughness; therefore, it is often used
available in two basic forms: unidirectional materials
for ballistic protection and body armor. Aramid ibers
or woven fabrics.
are generally weak in compression and dificult to
cut due to fuzzing. Bundles of aramid ibers are not
a. Fabrics. Most fabrics are classiied by their
designated by the number of ibers but by the weight.
areal weight, usually in ounces per square yard or
The weight term (denier) is deined as the weight in
grams per square meter. The areal weight is based on
grams of 9000 meters of ilament. Aramid ibers are
the iber, tow size and weave density measured in tows
available in any fabric form listed in paragraph 4-3.
per inch or centimeter. Repair fabrics will be speciied
Aramid is naturally yellow in color and darkens when
not only by the iber type, tow size and weave style,
exposed to ultraviolet (UV) radiation with degraded
but also the areal weight. Differences in areal weight
properties.
affect the structural performance composite. Two
fabrics with the same iber, tow size and weave style
c. Fiberglass. Fiberglass is made from glass mar-
are not necessarily interchangeable due to differences
bles melted and spun or extruded through tiny holes
in areal weight. Additionally, a single ply of fabric has
into ibers. Glass is an inorganic material that will not
strength in not just one, but two directions (See igure
burn and will not support combustion. These ibers
4-5). This is due to the simple fact that weaving is
normally appear white and any color may be added
the interlacing of yarns, or tows in a distinct pattern,
during manufacture. Glass ibers are very lexible
usually at 90 to each other. The fabric s integrity
and may be woven, draped or formed to almost any
is maintained by the mechanical interlocking of the
contour. The most common types of iberglass are
yarns. Drape (the ability of a fabric to conform to a
S-glass and E-glass.
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