U.S. patent number 3,571,901 [Application Number 04/833,009] was granted by the patent office on 1971-03-23 for method of fabricating a carbon-fiber reinforced composite article.
This patent grant is currently assigned to Union Carbide Corporation. Invention is credited to Raymond Vincent Sara.
United States Patent |
3,571,901 |
Sara |
March 23, 1971 |
METHOD OF FABRICATING A CARBON-FIBER REINFORCED COMPOSITE
ARTICLE
Abstract
Light weight composite refractory articles comprising a
plurality of metal or alloy coated carbon fibers bonded together by
an aluminum base matrix are provided. The coating metal or alloy
can be any material selected from the group consisting of silver,
silver-aluminum base alloys and mixtures thereof. The preferred
process for producing such composites comprises contacting silver
coated carbon fibers with an aluminum base material followed by hot
pressing the so-contacted fibers at the solidus temperature of the
aluminum base material to infiltrate aluminum around the
silver-coated fibers and then cooling the resultant article to a
completely solidified state. Such composite articles are
characterized by a high tensile strength coupled with a high
modulus of elasticity and are especially suited as materials of
construction for aerospace and hydrospace vehicles and systems.
Inventors: |
Sara; Raymond Vincent (North
Olmsted, OH) |
Assignee: |
Union Carbide Corporation (New
York, NY)
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Family
ID: |
25263180 |
Appl.
No.: |
04/833,009 |
Filed: |
June 13, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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727898 |
May 9, 1968 |
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Current U.S.
Class: |
29/419.1;
29/527.3; 29/527.5; 164/80; 164/91; 428/614; 416/230; 416/241R |
Current CPC
Class: |
C22C
49/14 (20130101); Y10T 428/12486 (20150115); Y10T
29/49801 (20150115); B64G 1/22 (20130101); Y10T
29/49984 (20150115); Y10T 29/49988 (20150115) |
Current International
Class: |
C22C
49/00 (20060101); C22C 49/14 (20060101); B64G
1/22 (20060101); B23p 017/00 () |
Field of
Search: |
;164/80,91,97
;29/182.2,182.5,419,527.3,527.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Metal-Ceramic Composite Structural Materials" L. N. Hjelm
S.A.M.P.E. Journal, Mov., 1965..
|
Primary Examiner: Campbell; John F.
Assistant Examiner: Reiley; D. C.
Parent Case Text
This application is a division of copending application Ser. No.
727,898, filed May 9, 1968.
Claims
I claim:
1. A method of producing a metal coated carbon fiber
aluminum-bonded composite article comprising:
a. contacting a plurality of silver coated carbon fibers with a
solidified aluminum base material;
b. heating the so-formed mass to the solidus temperature of the
aluminum base material and exerting a force thereon sufficient to
cause said aluminum base material to be infiltrated around said
silver coated fibers; and
c. cooling the resultant composite to a temperature at which said
aluminum base material completely solidifies to form an
aluminum-bonded silver-coated fiber composite article.
2. The method of claim 1 wherein said aluminum base material is an
alloy consisting essentially of 4.5 weight percent copper, 0.6
weight percent manganese, 1.5 weight percent magnesium with the
remainder being essentially aluminum.
3. A method of producing an aluminum-bonded silver-coated carbon
fiber composite article comprising:
a. forming an assembly comprising alternate layers of silver coated
carbon fibers and aluminum base foil, said fibers being positioned
thereon in a parallel manner;
b. placing the so-formed assembly in mold and heating it in an
inert atmosphere to a temperature approximately equal to the
solidus temperature of said aluminum base foil while exerting a
sufficient pressure on said assembly to cause said aluminum base
foil material to be infiltrated around said silver-coated carbon
fibers; and
c. cooling the resultant assembly to produce an aluminum-bonded
silver-coated carbon fiber composite.
4. The method of claim 3 wherein:
a. said aluminum base foil material consists essentially of 4.5
weight percent copper, 0.6 weight percent manganese, 1.5 weight
percent magnesium with the remainder being essentially aluminum;
and
b. said heating in step (b) is accomplished in a vacuum at a
temperature of about 550.degree. C.
5. The method of claim 1 wherein said aluminum-bonded silver-coated
carbon fiber composite article is heated to a temperature
sufficient to cause at least some said silver to alloy with at
least some of said aluminum to form at least a partial coating of a
silver-aluminum base alloy on said fibers.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high strength, high modulus
composite refractory articles composed of a plurality of carbon
fibers which are essentially coated with a thin layer of silver
and/or silver base alloys and bonded together by an aluminum base
matrix and to the process of producing the same.
2. Description of the Prior Art
In the space and missile industries, there has developed a need for
refractory materials of construction which exhibit exceptional
physical properties, for example, low density coupled with high
strength and stiffness. Attempts to produce such refractory
materials have centered around the fabrication of composite
articles.
One of the most promising materials available today for use in
composite form is carbon textiles since they possess excellent
refractory properties and are commercially available in all known
textile forms. Today, it is well known to form composites of carbon
textiles and resins.
Recently, efforts have been directed to forming composites of
carbon textiles and metals. The prime object of forming such
composites is to increase the strength of the metal matrix by the
inclusion therein of high strength carbon fibers.
Aluminum has been suggested as the matrix media for carbon
fiber-metal composites which are intended for use in aerospace
applications, in the main, due to its low density. However,
attempts heretofore to incorporate carbon fibers in an aluminum
matrix have met with little or no practical success due to the fact
that carbon, especially its graphic form, is not readily wetted by
molten aluminum.
The present invention overcomes the foregoing problem by employing
an intermediate coating or wetting agent which when applied to the
carbon fibers enables them to be readily bonded together by an
aluminum base matrix material.
SUMMARY
Broadly stated, the carbon fiber-aluminum composite article of the
invention comprises a plurality of carbon fibers each of which is
coated with either a thin layer of silver, a silver-aluminum base
alloy or mixtures thereof and bonded together, preferably in a
side-by-side or parallel manner, with an aluminum binder or matrix
material. Generally, this composite article may be provided by a
process which comprises coating carbon fibers with a thin but
essentially continuous film of silver, contacting the so-coated
fibers with a solidified aluminum base material, hot pressing the
so-produced assembly at the solidus temperature of the aluminum
base material to infiltrate it around the coated fibers and cooling
the resultant aluminum bonded carbon fibers to produce a composite
article. This article can then be formed into any desired shape by
known techniques which will readily suggest themselves to those
skilled in the art.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatical illustration of a portion of a carbon
fiber-aluminum composite article produced according to the
preferred teachings of the invention; and
FIG. 2 is a greatly magnified diagrammatical illustration of a
single fiber found in the composite of FIG. 1.
Referring now to the drawings in detail, FIG. 1 shows a portion of
a rectangular composite article 10 consisting of aligned graphite
fibers 12 (the silver coating and aluminum-silver zone thereon are
not shown) bonded together by an aluminum matrix 18. The graphite
fibers 12 are disposed in the aluminum matrix in a parallel manner
with their length dimension being perpendicular to the surface of
the drawing. FIG. 2 shows a single graphite fiber 12 taken from the
composite 10 of FIG. 1 having on its surface a coating of silver 14
and an aluminum-silver interface zone 16 between the silver coating
and the aluminum matrix 18.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
Carbon textiles in any form can be employed in the practice of the
instant invention. However, it is preferred to employ carbon fibers
in yarn or multifilament form. Carbon textiles are available
commercially and are generally produced by the techniques described
in U.S. Pat. Nos. 3,107,152 and 3,116,975, among others.
Silver can be deposited on the carbon fibers by a variety of
methods. The techniques available for accomplishing this include
electrodeposition from a conductive bath, reduction of salts to the
metal or sputtering. The exact deposition technique to be employed
is dictated by a number of factors. Sputtering can be used on
relatively complex shapes and results in a tenacious bond between
the thin silver coating and the carbon fiber substrate. Such a bond
is a highly desirable feature in carbon fiber-metal matrix
composites. Dipping of the carbon fibers into a silver containing
solution and chemically reducing the salt to the metal can also be
employed, however, with this technique it is difficult to
accurately control the thickness of the silver coating.
Electrodeposition of silver from a conductive bath is an ideal way
of coating carbon fibers with a thin film of silver and is the
preferred method since it results in a uniform, tenaciously bonded
metallic coating.
The following example illustrates in detail the preferred practice
of the instant invention.
A single ply graphite yarn composed of 720 monofilaments, each
characterized by an average modulus of elasticity of 33.5 .times.
10.sup.6 lb./in..sup.2 and an average tensile strength of 20
.times. 10.sup.4 lb./in..sup.2, was cut into a plurality of 4inch
lengths. These lengths of yarn were heated at 560.degree. C. for 30
seconds in a tube furnace which was open to the atmosphere. The
slightly oxidized fibers were immediately plated electrolytically
with silver by placing them in a strike solution for about 5 to 10
seconds and then into a conventional plating solution for about 5
to 10 seconds. The plating current employed was about 400 milliamps
for the strike solution and between about 600 to 800 milliamps for
the conventional plating solution. The make up of the strike and
conventional plating solution was as follows:
Strike Solution
Silver Cyanide (Ag CN) 6.5 g./1.
Potassium Cyanide (KCN) 68.0 g./1.
Regular Solution
Silver Cyanide (Ag CN) 41 g./1.
Potassium Cyanide (KCN) 40 g./1.
Potassium Hydroxide (KOH) 11 g./1.
Potassium Carbonate (K.sub.2CO.sub.3) 62 g./1.
The so-coated graphite fibers were cut into one-inch lengths and
then positioned in a parallel manner between alternate layers of
aluminum alloy foils measuring 0.003 inch .times. 0.125 inch
.times. 1.00 inch each. The aluminum alloy employed consisted of
4.5 weight percent copper, 0.6 weight manganese, 1.5 weight percent
magnesium with the remainder being essentially aluminum. Two single
plies of silver-coated yarn were used for each layer. The complete
array consisted of 22 layers of foil and 42, one-inch lengths of
silver-coated single ply yarn. This assembly was placed in a
graphite mold and hot pressed at 2,250 lb./in..sup.2 in vacuum at
approximately 550.degree. C. for one hour. The composite was
subsequently cooled in the mold to room temperature and then formed
into a 1/16" .times.1/8" .times. 1" specimen for physical property
measurements. This specimen evidenced an average tensile strength
of 44,100 lb./in..sup.2 and a Young's modulus of 13.0 .times.
10.sup.6 lb./in..sup.2.
The table below shows the improvement obtained by incorporating
silver coated graphite fibers in an aluminum base matrix material
by the technique of the instant invention. ##SPC1##
Composites produced by the technique of the instant invention are
extremely useful as materials of construction for subsonic and
supersonic aircraft, space system components and various propulsion
devices.
It will be appreciated by those skilled in the art that while the
preferred technique of the invention results in a composite article
which comprises silver-coated carbon fibers bonded together by an
aluminum base matrix, the silver coating on the carbon fibers may
be converted to a silver-aluminum base alloy by annealing the
composite during its fabrication or after it has been formed. The
only requirement being that the silver-aluminum base alloy not be
formed at a temperature in excess of the melting point of the
applied silver coating. Accordingly, it is clear that the instant
invention results in a unique type of composite comprising carbon
fiber which are coated with either silver, a silver-aluminum base
alloy or mixture thereof and bonded together by an aluminum base
matrix.
While the foregoing example concerns a composite having the fibers
positioned in a side-by-side relationship, it is readily apparent
to those skilled in the art that the carbon fibers may be randomly
orientated in the aluminum matrix if more isotropic physical
properties are desired without losing the benefits of the instant
invention. In addition, it is obvious that the thickness of the
silver can be varied as desired. All that is required is that it be
thick enough to prevent the aluminum matrix metal from coming into
contact with the reinforcing carbon fibers to such an extent that
there is essentially no bonding between the fibers and the matrix
metal. Likewise, it will be appreciated by those versed in the art
that although graphite fibers and fabrics are preferred in the
practice of the instant invention, nongraphitic carbon fibers and
fabrics may also be employed.
It should be noted here that while the invention can be
beneficially practiced by using pure aluminum as the matrix metal,
it is preferred to employ an aluminum base alloy which has an
incongruent melting temperature. Such alloys are well known in the
art and will not be discussed herein in detail.
In addition it should be noted that while it may be possible to
infiltrate the molten aluminum metal around the silver clad carbon
fibers without removing the silver therefrom, the preferred
practice of the invention involves infiltrating the matrix metal
around the filaments by heating the metal to a temperature at which
it begins to melt but below that at which it becomes completely
liquid, i.e., at its solidus temperature, and then forcing the
so-softened matrix metal around the individual filaments by the
means of an applied pressure. The amount of pressure to be applied
is not particularly critical and need only be sufficient to compact
the fibers and matrix material into an essentially nonporous
article.
The term carbon as used herein and in the appended claims is meant
to include both the nongraphitic and graphitic forms of carbon.
The foregoing example is presented for illustrative purposes only
and is not intended to unduly limit the reasonable scope of the
instant invention. The limitations of applicant's invention are
defined by the following claims.
* * * * *