U.S. patent application number 09/733566 was filed with the patent office on 2002-08-15 for continuous metal matrix composite consolidation.
Invention is credited to Gordon, Brian Louis, Joseph, Brian E., Witzqall, James Frederick.
Application Number | 20020108932 09/733566 |
Document ID | / |
Family ID | 24948164 |
Filed Date | 2002-08-15 |
United States Patent
Application |
20020108932 |
Kind Code |
A1 |
Gordon, Brian Louis ; et
al. |
August 15, 2002 |
Continuous metal matrix composite consolidation
Abstract
A method for the fabrication of large metal matrix composite
structures comprising the continuous brazing of aluminum matrix
braze-clad tape using an infrared laser to melt the braze clad on
the tape while applying pressure to the tape and simultaneously
contacting it with previously applied tape layers on a rotating
mandrel. The apparatus utilized to accomplish this fabrication
process may include a variety of pre and post-contact heaters and
preferably includes instruments for the continuous monitoring and
control of the process.
Inventors: |
Gordon, Brian Louis;
(Wheeling, WV) ; Joseph, Brian E.; (Wheeling,
WV) ; Witzqall, James Frederick; (Wheeling,
WV) |
Correspondence
Address: |
AUZVILLE JACKSON, JR.
8652 RIO GRANDE ROAD
RICHMOND
VA
23229
US
|
Family ID: |
24948164 |
Appl. No.: |
09/733566 |
Filed: |
December 8, 2000 |
Current U.S.
Class: |
219/121.6 ;
219/121.85 |
Current CPC
Class: |
B23K 35/282 20130101;
B23K 35/002 20130101; Y10T 428/30 20150115; Y10T 428/24942
20150115; B22F 2999/00 20130101; B23K 35/262 20130101; C22C 49/06
20130101; B32B 15/01 20130101; C22C 18/02 20130101; B23K 35/286
20130101; Y10T 428/12625 20150115; B23K 1/0056 20130101; Y10S
428/92 20130101; B22F 12/00 20210101; B32B 15/017 20130101; B23K
26/0846 20130101; C22C 21/02 20130101; C22C 13/00 20130101; C22C
47/06 20130101; B22F 2998/00 20130101; B23K 2103/10 20180801; B22F
10/10 20210101; B22F 10/20 20210101; B23K 35/0238 20130101; C22C
47/14 20130101; Y02P 10/25 20151101; C22C 18/04 20130101; B32B
15/016 20130101; B22F 3/005 20130101; B22F 2999/00 20130101; B22F
10/20 20210101; B22F 2203/03 20130101; B22F 2999/00 20130101; B22F
3/26 20130101; B22F 10/20 20210101; B22F 2999/00 20130101; B22F
3/005 20130101; B22F 2202/01 20130101; B22F 2998/00 20130101; C22C
47/20 20130101; B22F 2202/11 20130101; B22F 2202/01 20130101; B22F
2998/00 20130101; C22C 47/068 20130101; B22F 2999/00 20130101; B22F
10/20 20210101; B22F 2203/03 20130101; B22F 2999/00 20130101; B22F
3/26 20130101; B22F 10/20 20210101 |
Class at
Publication: |
219/121.6 ;
219/121.85 |
International
Class: |
B23K 026/20 |
Claims
What is claimed is:
1. A method for the fabrication of structural members of metal
matrix composites comprising: A) providing a rotating mandrel
having a surface addressed by a linearly traversing compaction
wheel; B) angularly feeding an metal matrix prepeg tape having a
braze coating on at least one surface of said tape at the point of
contact between said mandrel surface and said compaction wheel so
as to define a V-shaped junction, said braze coating addressing
said mandrel surface as said prepeg tape is angularly fed; C)
impacting said braze coating with a beam of infrared radiation at
said junction to melt said braze coating in said junction; and D)
simultaneously with the impacting of said beam of infrared
radiation in said junction, rotating said mandrel so as to take up
said prepeg tape as said melted braze coating cools and solidifies
and pressing said compaction roll against said prepeg tape so as to
cause consolidation of said prepeg tape with previously applied
layers of said prepeg tape on said mandrel surface.
2. The method of claim 1 wherein said prepeg tape comprises a
matrix of aluminum or an alloy of aluminum encompassing ceramic
fibers.
3. The method of claim 2 wherein said ceramic fibers comprise
aluminum oxide.
4. The method of claim 1 wherein said infrared radiation is
produced by a stacked multi-bar infrared laser.
5. The method of claim 4 wherein said stacked multi-bar infrared
laser includes optical lenses that shape the infrared radiation
into a pattern that matches the cross sectional dimensions of said
prepeg tape.
6. The method of claim 1 wherein said mandrel is collapsible so as
to permit removal of multiple layers of applied prepeg tape
therefrom when fabrication is complete.
7. The method of claim 1 wherein said mandrel surface and said
compaction wheel both comprise the same or different ceramic
materials.
8. The method of claim 1 wherein said prepeg tape is preheated with
infrared reflector lamps prior to entering said junction.
9. The method of claim 1 including the further step of providing an
optical pyrometer that views said melted braze coating in said
junction and provides temperature feedback information for
controlling the power of said infrared radiation or the speed of
rotation of said mandrel.
10. The method of claim 1 further including the application of
vibratory energy to said prepeg tape prior to entry into said
junction at a frequency of between about 1000 and 25000 vibrations
per minute.
11. The method of claim 1 wherein said prepeg tape comprises a
matrix of 1100 aluminum alloy or pure aluminum having aluminum
oxide fibers embedded therein, said braze coating is selected from
the group consisting of 96.5 Sn/3.5 Ag, 70 Sn/30 Zn, 84 Zn/11 Al/5
Cu and 88 Al/12 Si, the temperature of said braze coating in said
junction ranges from about 375.degree. F. to about 1200.degree. F.,
said infrared radiation is provided by an infrared laser operating
at a power level of from about 100 to about 450 watts and said
prepeg tape is fed at a rate of between about 0.65 and about 1.5
inches/sec.
12. The method of claim 11 wherein said prepeg tape is about 0.5
inches wide and about 0.15 inches thick.
13. The method of claim 1 further including the introduction of an
inert gas into said V-shaped junction.
14. An apparatus for the fabrication of structural members of metal
matrix composites comprising: A) a rotating mandrel having a
peripheral surface; B) a carriage mechanism; C) a compaction wheel
attached to said carriage mechanism so as to permit controlled
lateral traverse of said compaction wheel across said peripheral
surface; D) a metal matrix composite prepeg tape feeding mechanism
that supplies metal matrix tape having a braze coating applied
thereto on the surface of said tape that addresses said peripheral
surface to a junction between said peripheral surface and said
compaction wheel, said junction defining a V-shape between said
metal matrix tape and said peripheral surface as it enters said
junction; and E) a laser generating an infrared beam that impacts
said braze coating in said junction causing it to fuse as said
metal matrix tape passes under said compaction wheel.
15. The apparatus of claim 14 wherein said prepeg tape comprises a
matrix of aluminum or an aluminum alloy encompassing ceramic
fibers.
16. The apparatus of claim 15 said laser comprises a stacked
multi-bar infrared laser.
17. The apparatus of claim 16 wherein said stacked multi-bar
infrared laser includes optical lenses that shape the infrared beam
into a pattern that matches the cross sectional dimensions of said
prepeg tape.
18. The apparatus of claim 14 wherein said mandrel is collapsible
so as to permit removal of multiple layers of applied prepeg tape
therefrom when fabrication is complete.
19. The apparatus of claim 14 wherein said peripheral surface and
said compaction wheel both comprise the same or different ceramic
materials.
20. The apparatus of claim 14 further including preheaters that
heat said prepeg tape prior to entering said junction.
21. The apparatus of claim 20 wherein said preheaters comprise
infrared reflector lamps.
22. The apparatus of claim 14 further including an optical
pyrometer that addresses said junction and views said braze coating
in said junction and provides temperature feedback information for
controlling the power of said laser or the rotation speed of said
mandrel.
23. The apparatus of claim 14 further including a mechanism for
inducing vibratory energy to said prepeg tape prior to entry into
said junction at a frequency of between about 1000 and 25000
vibrations per minute.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to methods and apparatus for
the continuous consolidation of metal matrix composite materials
and more particularly to methods and apparatus for the
consolidation of aluminum matrix, ceramic fiber reinforced metal
matrix composites in prepeg tape form.
BACKGROUND OF THE INVENTION
[0002] The advantageous properties of metal matrix composites,
especially aluminum matrix composites that incorporate ceramic
reinforcing fibers are well known and recognized in the art and
include high specific strength, high specific stiffness,
maintenance of properties at extremes of high and low temperature
and their resistance or lack of outgassing in a vacuum which is a
major shortcoming of many competitive materials. These properties
are of particular importance in aviation and space vehicle and
structural applications. In fact, it has been estimated that the
use of aluminum matrix composites of this type in, for example,
launch vehicles could reduce their weight by as much as 30%, thus
increasing their available payload by alike amount.
[0003] What is inhibiting the use of such materials in launch and
similar vehicles, is a cost effective manufacturing method for the
production of large structures from these materials. The provision
of such a method would permit such applications for these materials
and provide all of the accompanying attendant benefits to such
use.
OBJECTS OF THE INVENTION
[0004] It is therefore an object of the present invention to
provide a method for the manufacturing of large structural members
from aluminum metal matrix composites (AMCs).
[0005] It is another object of the present invention to provide
cost effective such a manufacturing method.
[0006] It is yet another object of the present invention to provide
apparatus for the implementation of such a manufacturing
method.
SUMMARY OF THE INVENTION
[0007] According to the present invention, there is provided a
method for the fabrication of large AMC structures comprising the
continuous brazing of aluminum matrix braze-clad tape using an
infrared laser to melt the braze clad on the tape while applying
pressure to the tape and simultaneously contacting it with
previously applied tape layers on a rotating mandrel. The apparatus
utilized to accomplish this fabrication process may include a
variety of pre and post-contact heaters and preferably includes
instruments for the continuous monitoring and control of the
process.
DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic perspective view of apparatus suitable
for the manufacture of AMC structures in accordance with the
process of the present invention.
[0009] FIG. 2 is a schematic depiction of the area of contact
between the mandrel surface, and the incoming prepeg tape at the
point of application of infrared laser radiatiion in accordance
with the process of the present invention.
DETAILED DESCRIPTION
[0010] The present invention provides a method for the cost
effective fabrication/manufacture of large structural members of
aluminum metal matrix composites. The feedstock for the process is
a metal matrix composite (MMC), specifically an aluminum matrix
composite (AMC), in prepeg tape form comprised of alumina
(Al.sub.2O.sub.3) fibers in an aluminum/ aluminum alloy matrix. The
prepeg tape is coated with a "brazing" alloy, i.e. an aluminum
alloy having a lower melting point than the aluminum matrix of the
prepeg tape, prior to application in the process of the present
invention. Fabrication is accomplished by applying the braze
material coated prepeg tape to a rotating mandrel with the
application of pressure while simultaneously melting the braze
coating at the junction between the prepeg tape and the mandrel
surface using a laser, preferably an infrared or diode laser that
provides very limited and very localized heating and melting of the
braze coat. The laser beam of infrared radiation preferably has a
rectangular cross section to enhance heating efficiency in the area
of the junction. As will be seen from the detailed description that
follows, a variety of pre and post-contact heaters and process
control devices are preferably used to control and monitor the
process. The braze-coated feedstock just described can be
prefabricated at a remote location and provided in coil form, or,
as described hereinafter, can be prepared just prior to fabrication
by coating the AMC prepeg with the braze coat in line just prior to
exposure to the laser radiation and application to the mandrel.
[0011] While any number of techniques such as spraying (thermal,
arc, plasma, etc.), surface alloying, etc. can be used to apply the
lower melting braze coating to the prepeg tape, in the case where
the braze coating is applied in line with the consolidation
operation, the prepeg tape is guided through a pot of molten
brazing, i.e. lower melting, metal, extracted from the pot of metal
through a coating thickness control device such as a die or air
knife, and then through a cooling chamber to solidify the coating.
Preferably, the pot of molten metal is equipped with an ultrasonic
pulse inducing element comprising a power supply, a transducer and
a probe to facilitate coating of the matrix of the prepeg tape with
the braze coating. When used, the ultrasonic probe is inserted into
the pot of lower melting molten metal it produces a cavitation
field that results in pressure waves that reduce the contact angle
and improve the wetting of the lower melting material to the
prepeg. The cooling chamber can be highly sophisticated, but can be
as simple a metal tube through which is flowed a chilled gas such
as nitrogen and through which the braze coated prepeg travels on
exit from the coating pot and the thickness control device.
[0012] Referring now to FIG. 1, the consolidation apparatus 10 of
the present invention, comprises a rotating mandrel 12 supported on
legs 14 (or any other suitable support system), a laser 16 that
directs a beam of infrared radiation 18 to the junction 20 between
braze coated prepeg tape 22 and surface 24, a carriage unit 26 that
supports and imparts lateral traversing motion to compaction wheel
28, pre-heaters 30 and post heater(s) 32. According to a preferred
embodiment of the present invention, an optical pyrometer 33 can be
used to monitor the temperature at junction 20 and the signal
therefrom used to control either the mandrel rotation an/or
carriage unit traverse speeds or the intensity of laser 16, to
thereby control the temperature of the molten braze coating 36 (see
FIG. 2) that occurs at junction 20.
[0013] Referring now to FIG. 2 that schematically depicts a side
view of consolidation apparatus 10 and shows the relative positions
of laser 16, infrared radiation beam 18, compaction wheel 28,
mandrel 12 and incoming braze-coated prepeg tape 22 at junction 20,
it is readily observed that at junction 20, there exists a "front"
of molten metal 34 that comprises the molten or liquid form of
braze coating 36 on prepeg tape 22. Front 34 is produced by the
localized heating induced by the impact of infrared raditation beam
18 upon the surface of braze coating 36. It must be noted, that
although not specifically depicted in FIG. 2, surface 24 of mandrel
12 includes at least one wrap of previously applied prepeg tape 22
to which incoming feedstock prepeg tape 22 is adhered as braze
coating 36 melts due to the localized and controlled heating action
of infrared radiation beam 18, and subsequently cools as it is
removed from the area of front 34 due to rotation of mandrel 12 in
the direction shown by arrow 38 thereby building serial overlying
layers of AMC joined to each other by alternating layers of braze
material 36. Simultaneously with the creation of front 34 and the
movement of prepeg tape 22 in the direction indicated by arrow 38,
compaction wheel 28 pushes prepeg tape 22, and consequently
associated melted braze coating 36, into intimate contact with
surface 24 on mandrel 12 causing prepeg tape 22 to adhere firmly
thereto. The specific conditions under which such fabrication can
occur are described in greater detail hereinafter.
[0014] Consolidation apparatus 10 fundamentally comprises a 2-axis
filament winder of the type used in the fabrication of polymer
matrix composites. According to a preferred embodiment, mandrel 12
can be up to 48 inches long and up to about 36 inches in diameter.
Of course, larger dimensioned devices can be used in those cases
where larger structural members are being fabricated. The
rotational movement of mandrel 12 and the linear traverse of
compaction wheel 28 on carriage unit 26 are controlled and
coordinated by means of "Pattern Master" software or the like that
are supplied with the filament winder unit, or custom deigned and
implemented if a specific non-standard wrap pattern is required or
desired.
[0015] Laser 16 preferably comprises a stacked multi-bar infrared
laser. An array of optical lenses 39 are used to shape infrared
radiation beam 18 into a rectangular pattern that matches the
cross-sectional dimension of prepeg tape 22. According to a
preferred embodiment of the invention, laser 16 is powered by a DC
power supply capable of delivering 75 amps to the preferred stacked
multi-bar diode laser 16. Laser 16 in this configuration is
designed to operate in a continuous wave mode at a power of up to
500 watts. Water cooling of the laser head is required to maintain
the life of the diodes and is conventionally accomplished by means
of a water-to-air chiller unit (not shown). Multi-bar diode lasers
of this type are commercially available from Opto Power
Corporation, 3321 E. Global Loop, Tucson, Ariz. 85706.
[0016] Mandrel 12 must, of course be collapsible or otherwise
removable once the finished structure is completed by completion of
the wrapping operation. Similarly, surface 24 of mandrel 12 should
be of a material that will resist adhesion to melted and cooled
braze coating 36 and simultaneously minimize conductive heat loss
from the parts during fabrication to provide better and more
accurate process control, although in the latter case, alternative
process controls may be used to minimize the effects of the
material on surface 24 on the brazing process. In one embodiment of
the present invention, a suitable ceramic tube fabricated from
shale and fire clay was cut into three segments and attached to a
chuck arrangement to allow for expansion and contraction. In this
case, the amount of material removed during the cutting operation
was minimized to prevent surface 24 from being out of round.
[0017] As shown in FIG. 1, immediately after junction 20 prepeg
tape 22 is contacted on its reverse side 40 by compacting wheel 28
to accomplish consolidation. As with surface 24 of mandrel 12,
compacting wheel is preferably fabricated from a ceramic material
to minimize conductive heat loss from junction 20 during
consolidation. A highly preferred material for compaction wheel 28
is zirconium phosphate which exhibits these and other suitable
properties. Of course, suitable alternative process controls can
make the selection of materials for compaction wheel 28 less
critical. Compaction wheel 28 is arranged to ride at top dead
center of mandrel 12 and is guided in its movement by carriage
assembly 26. Compaction wheel 28 in addition to providing
compressive energy for consolidation also has a second important
function, in that it provides a V-shaped cavity at junction 20
thereby reducing reflective losses by trapping some of the infrared
radiation of beam 18 and creating a "multiple bounce" situation
where most of the incoming radiation is used for heating and less
of such radiation is lost due to reflection from the various
surfaces at junction 20.
[0018] Preheat lamps 30, and where used post heat lamp(s) 32
preferably comprise reflector lamps as line sources of infrared
energy to preheat or post heat prepeg tape 22 prior to or after
exit from junction 20. Preheat lamps 30 preferably heat prepeg tape
22 to a temperature of about 500.degree. F. in order to reduce the
heating load on laser 16. As will be obvious to the skilled
artisan, such preheating may not be required if a higher powered
laser is used. Post heating lamp(s) 32 are similarly configured,
and if and where applied can be used to control the cool down of
prepeg tape 22 as it exits junction 20 to reduce the thermal
stresses that may be induced by the brazing process.
[0019] According to an alternative preferred embodiment of the
present invention, a rotary ball vibrator 42 that induces vibration
in the range of from about 1000 to about 25000 vibrations per
minute is added to consolidation apparatus 10 to provide a more
thorough mixing of molten braze alloy front 34 at junction 20.
Rotary ball vibrator 42 is attached to a metal rod 44 that contacts
prepeg tape 22 just before it enters junction 20. The presence of
rotary ball vibrator 42 causes prepeg tape 22 to vibrate at the
same frequency as vibrator 42 which in turn induces oscillations in
front 34 at junction 20. Thus, these oscillations occur in junction
20 as prepeg tape 22 is addressed by compaction wheel 28.
[0020] According to yet another alternative preferred embodiment of
the present invention, a flow of inert gas is applied over the
heated area at junction 20 to minimize the formation of oxides in
front 34 during brazing. Free flowing argon, nitrogen or the like
inert gas directed to the area of junction 20 appears to provide
such benefit.
[0021] Optical pyrometer 33 may be included to provide temperature
feedback information to the control circuits of laser 16 thereby
assuring that the appropriate amount of heat is being applied at
junction 20 to achieve satisfactory melting of braze coating 36 and
consolidation as described above.
[0022] Finally, at least in process development and refinement
situations, it can be desirable to include a video camera (not
shown) to closely monitor the area of junction 20 to obtain the
appropriate operating parameters for a specific given prepeg tape
22 and braze coating 34 composition.
[0023] In practice, the method of the present invention is carried
out using the above-described apparatus 10 by first wrapping an
initial turn of a suitable prepeg tape of, for example, pure
aluminum, 1100 alloy aluminum or any other suitable aluminum,
titanium, magnesium etc. metallic matrix containing a ceramic
reinforcing material, for example, Nextel 610.TM. aluminum oxide
1500 denier fibers commercially available from the 3M Corporation,
Minneapolis, Minn. According to a specifically preferred embodiment
of the present invention the prepeg tape, whatever its composition,
is about 0.5 inches wide, 0.015 inches thick with a rectangular
cross section about mandrel 12. Prepeg tape 22 is provided as a
coil on a payoff for continuous feeding. Consolidation apparatus 10
is then activated. Mandrel 12 begins to turn, laser 16 is focused
on junction 20 and prepeg 22 is fed into junction 20 for
consolidation by compacting wheel 28. The specific process
conditions are largely a matter of choice as dictated by the
materials being consolidated (the AMC matrix alloy and the braze
coating composition), the power of laser 16, the rotational speed
of mandrel 12 etc. However, in the case of fabrication of the
above-described prepeg tape bearing braze coatings of the types
referred to in the examples below, melting temperatures in the
range of from about 375 to about 1200.degree. F. produced by a
suitable laser operating at between about 100 and about 450 watts
and prepeg tape feed rates on the order of between about 0.65 and
1.50 inches/sec. have been found useful and appropriate.
EXAMPLES
[0024] The following examples when considered in conjunction with
the foregoing detailed description will serve to better illustrate
the successful practice of the present invention.
Examples 1-4
[0025] Prepeg tapes comprising Nextel 610.TM. fibers in pure
aluminum were consolidated as described hereinabove using the
following braze coatings and under the following tabularly
presented operating conditions:
1 Braze Braze Coating Temperature Laser Power Tape Feed Rate 1)
96.5 Sn/3.5 Ag 430-500.degree. F. 426 Watts 0.70 inches/sec. 2) 70
Sn/30 Zn 389-707.degree. F. 110 Watts 1.06 inches/sec. 3) 84 Zn/11
Al/5 Cu 715-845.degree. F. 268 Watts 0.87 inches/sec. 4) 88 Al/12
Si 1070-1220.degree. F. 373 Watts 1.27 inches/sec.
[0026] Under each of the foregoing conditions, satisfactory
consolidated round structural shapes of the prepeg material
indicated were fabricated.
[0027] As the invention has been described, it will be apparent to
the skilled artisan that the same may be varied in many ways
without departing from the spirit and scope of the invention. Any
and all such modifications are intended to be included within the
scope of the appended claims.
* * * * *