U.S. patent application number 09/966946 was filed with the patent office on 2002-07-11 for ceramic oxide pre-forms, metal matrix composites, and methods for making the same.
Invention is credited to Davis, Sarah J., Holloway, Scott R., Satzer, William J. JR., Skildum, John D., Visser, Larry R., Waite, Ernest R..
Application Number | 20020088599 09/966946 |
Document ID | / |
Family ID | 22888109 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020088599 |
Kind Code |
A1 |
Davis, Sarah J. ; et
al. |
July 11, 2002 |
Ceramic oxide pre-forms, metal matrix composites, and methods for
making the same
Abstract
Ceramic oxide pre-forms comprising substantially continuous,
ceramic oxide fibers, and methods for making the same. The ceramic
oxide pre-forms are useful, for example, as in making metal matrix
composites reinforced with substantially continuous, ceramic oxide
fibers.
Inventors: |
Davis, Sarah J.; (Harvest,
AL) ; Holloway, Scott R.; (North St. Paul, MN)
; Satzer, William J. JR.; (Eagan, MN) ; Skildum,
John D.; (North Oaks, MN) ; Visser, Larry R.;
(Oakdale, MN) ; Waite, Ernest R.; (River Falls,
WI) |
Correspondence
Address: |
Office of Intellectual Property Counsel
3M Innovative Properties Company
PO Box 33427
St. Paul
MN
55133-3427
US
|
Family ID: |
22888109 |
Appl. No.: |
09/966946 |
Filed: |
September 27, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60236092 |
Sep 28, 2000 |
|
|
|
Current U.S.
Class: |
164/97 ;
164/98 |
Current CPC
Class: |
F16D 55/00 20130101;
F16D 2055/0016 20130101; F16D 55/22 20130101; F16D 2200/006
20130101; F16D 2250/0015 20130101; F16D 2250/0007 20130101; B22D
19/14 20130101; F16D 2200/0039 20130101; F16D 2200/003
20130101 |
Class at
Publication: |
164/97 ;
164/98 |
International
Class: |
B22D 019/14; B22D
019/02 |
Claims
What is claimed is:
1. A porous ceramic oxide pre-form comprising porous, sintered
ceramic oxide material and substantially continuous ceramic oxide
fibers having lengths of at least 5 cm, the porous, sintered
ceramic oxide material securing the substantially continuous
ceramic oxide fibers in place, wherein the porous, sintered ceramic
oxide material extends along at least a portion of the length of
the substantially continuous ceramic oxide fibers, wherein the
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned.
2. The ceramic oxide pre-form according to claim 1 wherein the
substantially continuous ceramic oxide fibers have lengths of at
least 10 cm.
3. The ceramic oxide pre-form according to claim 1 wherein the
porous, sintered ceramic oxide material is comprised of alpha
alumina.
4. The ceramic oxide pre-form according to claim 3 wherein at least
a portion of the substantially continuous ceramic oxide fibers is
in the form of tows.
5. The ceramic oxide pre-form according to claim 3 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, and wherein
at least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
6. The ceramic oxide pre-form according to claim 1 wherein the
substantially continuous ceramic oxide fibers have a first Young's
modulus and the ceramic oxide material has a second Young's
modulus, and wherein the first Young's modulus is greater than the
second Young's modulus.
7. The ceramic oxide pre-form according to claim 6 wherein at least
a portion of the substantially continuous ceramic oxide fibers is
in the form of tows.
8. The ceramic oxide pre-form according to claim 6 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, and wherein
at least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
9. The ceramic oxide pre-form according to claim 1 comprising at
least two groupings of the substantially continuous ceramic oxide
fibers spaced apart with the porous, sintered ceramic oxide
material between the groupings of substantially continuous ceramic
oxide fibers.
10. The ceramic oxide pre-form according to claim 9 wherein at
least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
11. The ceramic oxide pre-form according to claim 9 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, and wherein
at least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
12. The ceramic oxide pre-form according to claim 1 comprising at
least two groupings of the substantially continuous ceramic oxide
fibers spaced apart with the porous, sintered ceramic oxide
material between the groupings of substantially continuous ceramic
oxide fibers, wherein at least two of the groupings having a
rectangular cross-section.
13. The ceramic oxide pre-form according to claim 1 wherein the
ceramic oxide pre-form is elongated and has a rectangular
cross-section perpendicular to the length of the substantially
continuous ceramic oxide fibers.
14. The ceramic oxide pre-form according to claim 1 wherein the
ceramic oxide pre-form is elongated and has substantially constant
cross-sectional area.
15. The ceramic oxide pre-form according to claim 1 wherein the
substantially continuous ceramic oxide fibers are encapsulated
within the porous, sintered ceramic oxide material.
16. The ceramic oxide pre-form according to claim 1 wherein at
least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
17. The ceramic oxide pre-form according to claim 1 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, and wherein
at least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
18. A method for making a porous ceramic oxide, the method
comprising: positioning at least one elongated fiber insert in a
cavity, the fiber insert comprising substantially continuous
ceramic oxide fibers having lengths of at least 5 cm, wherein the
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned; introducing a slurry into the cavity such
that a pre-determined portion of the elongated fiber insert is
coated with the slurry, the slurry comprising liquid medium and
discontinuous ceramic oxide fibers dispersed therein; removing at
least a sufficient amount of the liquid medium to cause the
discontinuous fibers to consolidate and secure the fiber insert to
provide an article comprising the elongated fiber insert and the
discontinuous fibers, wherein the consolidation of the
discontinuous fibers extends along at least a portion of the length
of the fiber insert; drying the consolidated article to provide a
green ceramic oxide pre-form comprising the elongated fiber insert
and the discontinuous fibers, wherein at least one consolidation of
the discontinuous fibers secures the fiber insert in place, and
wherein the consolidation of the discontinuous fibers extends along
at least a portion of the length of the fiber insert; and heating
the green ceramic oxide pre-form to at least one temperature
sufficient to provide a porous ceramic oxide pre-form comprising
porous, sintered ceramic oxide material securing the substantially
continuous ceramic oxide fibers in place, wherein the porous,
sintered ceramic oxide material extends along at least a portion of
the length of the substantially continuous fibers, and wherein the
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned.
19. The method according to claim 18 wherein the substantially
continuous ceramic oxide fibers have lengths of at least 10 cm.
20. The method according to claim 18 wherein at least a portion of
the discontinuous fibers comprise alpha alumina discontinuous
fibers.
21. The method according to claim 18 wherein the substantially
continuous, longitudinally aligned, ceramic oxide fibers are
encapsulated within the green ceramic oxide material.
22. The method according to claim 18 wherein the fiber insert
further comprises fugitive binder material bonding at least a
portion of the substantially continuous, longitudinally aligned,
ceramic oxide fibers together.
23. The method according to claim 22 wherein the fugitive binder
material is selected from the group consisting of wax, polyvinyl
alcohol, polyvinyl pyrrolidone, epoxy resin, and combinations
thereof.
24. The method according to claim 18 wherein at least a portion of
the substantially continuous ceramic oxide fibers is in the form of
tows.
25. The method according to claim 24 wherein the porous, sintered
ceramic oxide material has an open porosity of at least 85% by
volume and secures the substantially continuous, longitudinally
aligned, ceramic oxide fibers in place.
26. The method according to claim 18 wherein the porous, sintered
ceramic oxide material has an open porosity of at least 85% by
volume and secures the substantially continuous, longitudinally
aligned, ceramic oxide fibers in place.
27. A porous ceramic oxide pre-form comprising: a first porous,
sintered ceramic article including an aperture for receiving a
porous ceramic oxide; and a second ceramic article positioned in
the aperture, the second ceramic article comprising porous,
sintered ceramic oxide material and substantially continuous
ceramic oxide fibers having lengths of at least 5 cm, the porous,
sintered ceramic oxide material securing substantially continuous
ceramic oxide fibers in place, wherein the porous, sintered ceramic
oxide material extends along at least a portion of the length of
the substantially continuous fibers, and wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned.
28. The ceramic oxide pre-form according to claim 27 wherein the
substantially continuous ceramic oxide fibers have lengths of at
least 10 cm.
29. The ceramic oxide pre-form according to claim 27 wherein the
porous, sintered ceramic oxide material of the second ceramic
article is comprised of alpha alumina.
30. The porous ceramic oxide pre-form of claim 29 wherein at least
a portion of the substantially continuous ceramic oxide fibers is
in the form of tows.
31. The porous ceramic oxide pre-form of claim 29 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place.
32. The porous ceramic oxide pre-form of claim 29 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, and wherein
at least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
33. The ceramic oxide pre-form according to claim 27 wherein the
substantially continuous, longitudinally aligned, ceramic oxide
fibers have a first Young's modulus and the ceramic oxide material
of the second ceramic article has a second Young's modulus, wherein
the first Young's modulus is greater than the second Young's
modulus, and wherein the first porous, sintered ceramic article
comprises ceramic oxide material having a third Young's modulus,
and wherein the second Young's modulus is greater than the third
Young's modulus.
34. The porous ceramic oxide pre-form of claim 33 wherein at least
a portion of the substantially continuous ceramic oxide fibers is
in the form of tows.
35. The porous ceramic oxide pre-form of claim 33 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place.
36. The porous ceramic oxide pre-form of claim 33 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, and wherein
at least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
37. The porous ceramic oxide pre-form of claim 27 wherein at least
a portion of the substantially continuous ceramic oxide fibers is
in the form of tows.
38. The porous ceramic oxide pre-form of claim 27 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place.
39. The porous ceramic oxide pre-form of claim 27 wherein the
porous, sintered ceramic oxide material has an open porosity of at
least 85% by volume and secures the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, and wherein
at least a portion of the substantially continuous ceramic oxide
fibers is in the form of tows.
40. A method for making a porous, sintered ceramic oxide pre-form
for an article comprising metal matrix material, the method
comprising: designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers having
lengths of at least 5 cm, wherein the metal matrix composite
material to comprise at least one ceramic oxide pre-form comprising
ceramic oxide material extends along at least a portion of the
length of the substantially continuous, longitudinally aligned,
ceramic oxide fibers, and wherein the substantially continuous,
longitudinally aligned, ceramic oxide fibers have a first Young's
modulus and the ceramic oxide material has a second Young's
modulus, and wherein the first Young's modulus is greater than the
second Young's modulus; and preparing, based on the resulting
design, a porous, sintered ceramic oxide pre-form comprising the
ceramic oxide material securing the substantially continuous,
ceramic oxide fibers in place, wherein the ceramic oxide material
extends along at least a portion of the length of the substantially
continuous ceramic oxide fibers, and wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned.
41. The method according to claim 40 wherein the porous, sintered
ceramic oxide material has an open porosity of at least 85% by
volume and secures the substantially continuous, longitudinally
aligned, ceramic oxide fibers in place.
42. The method according to claim 41 wherein the porous, sintered
ceramic oxide material of the second ceramic article is comprised
of alpha alumina.
43. The method according to claim 41 wherein the metal matrix is
one of aluminum or an alloy thereof.
44. The method according to claim 40 wherein the substantially
continuous ceramic oxide fibers have lengths of at least 10 cm.
45. The method according to claim 40 wherein the porous, sintered
ceramic oxide material of the second ceramic article is comprised
of alpha alumina.
46. The method according to claim 40 wherein at least a portion of
the substantially continuous ceramic oxide fibers is in the form of
tows.
47. The method according to claim 46 wherein the metal matrix is
one of aluminum or an alloy thereof.
48. The method according to claim 46 wherein the porous, sintered
ceramic oxide material has an open porosity of at least 85% by
volume and secures the substantially continuous, longitudinally
aligned, ceramic oxide fibers in place.
49. The method according to claim 48 wherein the porous, sintered
ceramic oxide material of the second ceramic article is comprised
of alpha alumina.
50. The method according to claim 48 wherein the metal matrix is
one of aluminum or an alloy thereof.
51. The method according to claim 40 wherein the porous, sintered
ceramic oxide material of the second ceramic article is comprised
of alpha alumina.
52. The method according to claim 40 wherein the metal matrix is
one of aluminum or an alloy thereof.
53. A method for making a porous, sintered ceramic oxide pre-form
for an article comprising metal matrix material, the method
comprising: designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers having
lengths of at least 5 cm; preparing, based on the resulting design,
an elongated pre-form comprising the substantially continuous,
longitudinally aligned, ceramic oxide fibers and binder material
bonding fibers together; preparing a green ceramic oxide pre-form
comprising green ceramic oxide material extending along at least a
portion of the length of the elongated pre-form; and heating the
green ceramic oxide pre-form to provide a porous, sintered ceramic
oxide pre-form comprising ceramic oxide material securing the
substantially continuous, longitudinally aligned, ceramic oxide
fibers in place, wherein the ceramic oxide material extends along
at least a portion of the length of the substantially continuous
ceramic oxide fibers, and wherein the substantially continuous
ceramic oxide fibers are essentially longitudinally aligned.
54. The method according to claim 53 wherein the substantially
continuous ceramic oxide fibers having lengths of at least 10
cm.
55. The method according to claim 53 wherein the porous, sintered
ceramic oxide material is comprised of alpha alumina.
56. The method according to claim 55 wherein at least a portion of
the substantially continuous ceramic oxide fibers is in the form of
tows.
57. The method according to claim 53 wherein at least a portion of
the substantially continuous ceramic oxide fibers is in the form of
tows.
58. The method according to claim 57 wherein the porous, sintered
ceramic oxide material has an open porosity of at least 85% by
volume and secures the substantially continuous, longitudinally
aligned, ceramic oxide fibers in place.
59. The method according to claim 58 wherein the porous, sintered
ceramic oxide material is comprised of alpha alumina.
60. The method according to claim 53 wherein the metal matrix is at
least one of aluminum or an alloy thereof.
61. The method according to claim 53 wherein the porous, sintered
ceramic oxide material has an open porosity of at least 85% by
volume and secures the substantially continuous, longitudinally
aligned, ceramic oxide fibers in place.
62. The method according to claim 61 wherein the porous, sintered
ceramic oxide material is comprised of alpha alumina.
63. A met al matrix composite article comprising a porous ceramic
oxide and metal matrix material, wherein the ceramic oxide pre-form
comprises substantially continuous ceramic oxide fibers having
lengths of at least 5 cm, and a porous, sintered ceramic oxide
material extending along at least a portion of the length of the
substantially continuous ceramic oxide fibers, wherein the
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned, and wherein the porous ceramic oxide
material is infiltrated with at least a portion of the metal matrix
material extending into the porous, sintered ceramic oxide
material.
64. The metal matrix composite article according to claim 63
wherein the substantially continuous ceramic oxide fibers have
lengths of at least 10 cm.
65. The metal matrix composite article according to claim 63
wherein the porous, sintered ceramic oxide material is comprised of
alpha alumina.
66. The metal matrix composite article according to claim 63
wherein the metal matrix material is aluminum or an alloy
thereof.
67. The metal matrix composite article according to claim 63
comprising at least two groupings of the substantially continuous
ceramic oxide fibers spaced apart with the porous, sintered ceramic
oxide material between the groupings of substantially continuous
ceramic oxide fibers.
68. The metal matrix composite article according to claim 63
comprising at least two groupings of the substantially continuous
ceramic oxide fibers spaced apart with the porous, sintered ceramic
oxide material between the groupings of substantially continuous
ceramic oxide fibers, wherein at least two of the groupings having
a rectangular cross-section.
69. The metal matrix composite article according to claim 63
wherein the ceramic oxide pre-form is elongated and has a
rectangular cross-section perpendicular to the length of the
substantially continuous fibers.
70. The metal matrix composite article according to claim 63
wherein the ceramic oxide pre-form is elongated and has
substantially constant cross-sectional area.
71. The metal matrix composite article according to claim 63
wherein the substantially continuous ceramic oxide fibers are
encapsulated within the porous, sintered ceramic oxide
material.
72. The metal matrix composite article according to claim 63
wherein the metal matrix material is aluminum or an alloy
thereof.
73. The metal matrix composite article according to claim 63
wherein the article is a brake caliper.
74. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 73 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
75. The metal matrix composite article according to claim 63
wherein at least a portion of the substantially continuous ceramic
oxide fibers is in the form of tows.
76. The metal matrix composite article according to claim 75
wherein the porous, sintered ceramic oxide material is comprised of
alpha alumina.
77. The metal matrix composite article according to claim 75
comprising at least two groupings of the substantially continuous
ceramic oxide fibers spaced apart with the porous, sintered ceramic
oxide material between the groupings of substantially continuous
ceramic oxide fibers.
78. The metal matrix composite article according to claim 75
wherein the metal matrix material is aluminum or an alloy
thereof.
79. The metal matrix composite article according to claim 75
wherein the article is a brake caliper.
80. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 79 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
81. The metal matrix composite article according to claim 63
wherein the porous, sintered ceramic oxide material has an open
porosity of at least 85% by volume and secures the substantially
continuous, longitudinally aligned, ceramic oxide fibers in
place.
82. The metal matrix composite article according to claim 81
wherein the porous, sintered ceramic oxide material is comprised of
alpha alumina.
83. The metal matrix composite article according to claim 81
comprising at least two groupings of the substantially continuous
ceramic oxide fibers spaced apart with the porous, sintered ceramic
oxide material between the groupings of substantially continuous
ceramic oxide fibers.
84. The metal matrix composite article according to claim 81
wherein the metal matrix material is aluminum or an alloy
thereof.
85. The metal matrix composite article according to claim 81
wherein the article is a brake caliper.
86. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 85 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
87. The metal matrix composite article according to claim 63
wherein the porous, sintered ceramic oxide material has an open
porosity of at least 85% by volume and secures the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
and wherein at least a portion of the substantially continuous
ceramic oxide fibers is in the form of tows.
88. The metal matrix composite article according to claim 87
wherein the porous, sintered ceramic oxide material is comprised of
alpha alumina.
89. The metal matrix composite article according to claim 87
comprising at least two groupings of the substantially continuous
ceramic oxide fibers spaced apart with the porous, sintered ceramic
oxide material between the groupings of substantially continuous
ceramic oxide fibers.
90. The metal matrix composite article according to claim 87
wherein the metal matrix material is aluminum or an alloy
thereof.
91. The metal matrix composite article according to claim 88
wherein the article is a brake caliper.
92. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 91 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
93. A metal matrix composite article comprising a porous ceramic
oxide and metal matrix material, wherein the ceramic oxide pre-form
comprises: a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and a second ceramic
article positioned in the aperture, the second ceramic article
comprising porous, sintered ceramic oxide material and
substantially continuous ceramic oxide fibers having lengths of at
least 5 cm, the porous, sintered ceramic oxide material securing
the substantially continuous ceramic oxide fibers in place, wherein
the porous, sintered ceramic oxide material extends along at least
a portion of the length of the substantially continuous fibers, and
wherein the substantially continuous ceramic oxide fibers are
essentially longitudinally aligned; and wherein the porous,
sintered ceramic oxide material is infiltrated with at least a
portion of the metal matrix material.
94. The metal matrix composite article according to claim 93
wherein the substantially continuous ceramic oxide fibers have
lengths of at least 10 cm.
95. The metal matrix composite article according to claim 93
wherein the porous, sintered ceramic oxide material of the second
ceramic article is comprised of alpha alumina.
96. The metal matrix composite article according to claim 93
wherein the article is a brake caliper.
97. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 96 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
98. The metal matrix composite article according to claim 93
wherein at least a portion of the substantially continuous ceramic
oxide fibers is in the form of tows.
99. The metal matrix composite article according to claim 93
wherein the porous, sintered ceramic oxide material of the second
ceramic article is comprised of alpha alumina.
100. The metal matrix composite article according to claim 93
wherein the article is a brake caliper.
101. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 100 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
102. The metal matrix composite article according to claim 93
wherein the porous, sintered ceramic oxide material has an open
porosity of at least 85% by volume and secures the substantially
continuous, longitudinally aligned, ceramic oxide fibers in
place.
103. The metal matrix composite article according to claim 102
wherein the porous, sintered ceramic oxide material of the second
ceramic article is comprised of alpha alumina.
104. The metal matrix composite article according to claim 102
wherein the article is a brake caliper.
105. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 104 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
106. The metal matrix composite article according to claim 93
wherein the porous, sintered ceramic oxide material has an open
porosity of at least 85% No by volume and secures the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
and wherein at least a portion of the substantially continuous
ceramic oxide fibers is in the form of tows.
107. The metal matrix composite article according to claim 106
wherein the porous, sintered ceramic oxide material of the second
ceramic article is comprised of alpha alumina.
108. The metal matrix composite article according to claim 106
wherein the article is a brake caliper.
109. A disc brake for a motor vehicle comprising a rotor; inner and
outer brake pads disposed on opposite sides of the rotor and
movable into braking engagement therewith; a piston for urging the
inner brake pad against the rotor; and the brake caliper according
to claim 108 comprising a body member having a cylinder positioned
on one side of the rotor and containing the piston, an arm member
positioned on the other side of the rotor and supporting the outer
brake pad, and a bridge extending between the body member and the
arm member across the plane of the rotor.
Description
[0001] This application claims priority to U.S. Provisional Patent
Application No. 60/236,092, filed Sep. 28, 2000, the disclosure of
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention pertains to ceramic oxide pre-forms
comprising substantially continuous, ceramic oxide fibers, and
metal matrix composites reinforced with ceramic oxide
pre-forms.
BACKGROUND OF THE INVENTION
[0003] The reinforcement of metal matrices with ceramics is known
in the art (see, e.g., U.S. Pat. Nos. 4,705,093 (Ogino), 4,852,630
(Hamajima et al.), 4,932,099 (Corwin et al.), 5,199,481 (Corwin et
al.), 5,234,080 (Pantale) and 5,394,930 (Kennerknecht), and Great
Britain Pat. Doc. Nos. 2,182,970 A and B, published May 28, 1987
and Sep. 14, 1988, respectively). Examples of ceramic materials
used for reinforcement include particles, discontinuous fibers
(including whiskers) and continuous fibers, as well as ceramic
pre-forms.
[0004] Typically, ceramic material is incorporated into a metal,
thereby creating a metal matrix composite s (MMC) to improve the
mechanical properties of an article made of the metal. For example,
conventional brake calipers for motorized vehicles (e.g., cars and
trucks) are typically made of cast iron. To reduce the overall
weight of the vehicle, as well as in particular unsprung weight
such as brake calipers, there is a desire to use lighter weight
parts and/or materials. One technique for aiding in the design of
MMCs, including placement of the ceramic oxide material and
minimizing the amount of ceramic oxide material needed for the
particular application, is finite element analysis.
[0005] A brake caliper made of cast aluminum would be about 50
percent by weight lighter than the same (i.e., the same size and
configuration) caliper made of cast iron. The mechanical properties
of cast aluminum and cast iron are not the same (e.g., the Young's
modulus of cast iron is about 100-170 GPa, while for cast aluminum
it is about 70-75 GPa; the yield strength of cast iron is 200-500
MPa, while for cast aluminum it is 150-170 MPa). Hence, a brake
caliper made from cast aluminum has significantly lower mechanical
properties such as bending stiffness and yield strength than the
cast iron caliper. Typically, the mechanical properties of such an
aluminum brake caliper are unacceptably low as compared to a cast
iron brake caliper having the same size and shape. A brake caliper
made of an aluminum metal matrix composite material (e.g., aluminum
reinforced with ceramic fibers) that had the same configuration and
at least the same (or better) mechanical properties, such as
bending stiffness and yield strength, as a cast iron brake caliper
is desirable.
[0006] One consideration for some MMC articles is the need for
post-formation machining (e.g., adding holes or threads, or
otherwise cutting away material to provide a desired shape) or
other processing (e.g., welding two MMC articles together to make a
complex shaped part). Conventional MMCs typically contain enough
ceramic reinforcement material to make machining or welding
impractical or even impossible. Hence, it is desirable to produce
"net-shaped" articles that require little, if any, postformation
machining or processing. Techniques for making "net-shaped"
articles are known in the art (see, e.g., U.S. Pat. Nos. 5,234,045
(Cisko) and 5,887,684 (Doll et al.)). In addition, or
alternatively, to the extent feasible, the ceramic reinforcement
may be reduced or not placed in areas will it interfere with
machining or other processing such as welding.
[0007] Another consideration in designing and making MMCs is the
cost of the ceramic reinforcement material. The mechanical
properties of continuous polycrystalline alpha-alumina fibers such
as that marketed by the 3M Company, St. Paul, Minn., under the
trade designation "NEXTEL 610", are high compared to low density
metals such as aluminum. In addition, the cost of ceramic oxide
materials such as the polycrystalline alpha-alumina fibers, is
substantially more than metals such as aluminum. Hence, it is
desirable to minimize the amount of ceramic oxide material used,
and to optimize the placement of the ceramic oxide materials in
order to maximize the properties imparted by the ceramic oxide
materials.
[0008] Further, it is desirable to provide the ceramic
reinforcement material in a package or form, such as a porous
ceramic pre-form, that can be relatively easily used to make a
metal matrix composite article therefrom.
SUMMARY OF THE INVENTION
[0009] In one aspect, the present invention provides porous ceramic
oxide (e.g., calcined or sintered) pre-forms comprising
substantially continuous ceramic oxide (i.e., glass, crystalline
ceramic, and combinations thereof) fibers. In another aspect, the
present invention provides metal matrix composite articles
comprising at least one porous ceramic oxide pre-form (including
porous ceramic oxide pre-forms according to the present invention)
comprising substantially continuous ceramic oxide fibers.
[0010] Typically, the substantially continuous ceramic oxide fibers
have lengths of at least 5 cm (frequently at least 10 cm, 15 cm, 20
cm, 25 cm, or more). In some embodiments of the present invention,
the substantially continuous ceramic oxide fibers are in the form
of tows (i.e., the tows are comprised of the substantially
continuous ceramic oxide fibers). Typically, the substantially
continuous ceramic oxide fibers comprising the tow have lengths of
at least 5 cm (frequently at least 10 cm, 15 cm, 20 cm, 25 cm, or
more), although their lengths may also be less 5 cm.
[0011] Preferably, the porous ceramic oxide pre-form, which extends
along at least a portion of the length of the substantially
continuous ceramic oxide fibers, comprises porous ceramic oxide
material securing the ceramic oxide fibers in place. In another
aspect, the ceramic oxide fibers can include, or even consist
essentially of, substantially continuous, longitudinally aligned,
ceramic oxide fibers, wherein "longitudinally aligned" refers to
the generally parallel alignment of the fibers relative to the
length of the fibers. Optionally, the fibers are encapsulated
within the porous ceramic oxide material.
[0012] In some embodiments according to the present invention, the
substantially continuous ceramic oxide fibers have a first Young's
modulus and ceramic oxide material comprising the ceramic perform
has a second Young's modulus, wherein the first Young's modulus is
greater than the second Young's modulus.
[0013] In some embodiments according to the present invention, a
porous ceramic oxide pre-form comprises:
[0014] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0015] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material and substantially continuous ceramic oxide fibers having
lengths of at least 5 cm, the porous, sintered ceramic oxide
material securing substantially continuous ceramic oxide fibers in
place, wherein the porous, sintered ceramic oxide material extends
along at least a portion of the length of the substantially
continuous fibers, wherein the substantially continuous ceramic
oxide fibers are essentially longitudinally aligned, wherein the
substantially continuous, longitudinally aligned, alpha alumina
fibers have a first Young's modulus and the ceramic oxide material
of the second ceramic article has a second Young's modulus, wherein
the first Young's modulus is greater than the second Young's
modulus, wherein the first porous ceramic article comprises ceramic
oxide material having a third Young's modulus, and wherein the
second Young's modulus is greater than the third Young's
modulus.
[0016] In one aspect, the present invention provides a green
ceramic oxide pre-form comprising green ceramic oxide material
securing ceramic oxide fibers in place, wherein the green ceramic
oxide material extends along at least a portion of the length of
the fibers, wherein the ceramic oxide fibers consist essentially of
substantially continuous, longitudinally aligned, ceramic oxide
fibers. Optionally, the fibers are encapsulated within the green
ceramic oxide material.
[0017] In another aspect, the present invention provides a porous
ceramic oxide pre-form comprising porous ceramic oxide material
securing ceramic oxide fibers in place, wherein the porous ceramic
oxide material extends along at least a portion of the length of
the fibers, wherein the ceramic oxide fibers consist essentially of
substantially continuous, longitudinally aligned, ceramic oxide
fibers. Optionally, the fibers are encapsulated within the porous
ceramic oxide material.
[0018] In another aspect, embodiments of the present invention
include, for example, a ceramic porous comprising porous ceramic
oxide material having an open porosity (as measured in the Example,
below), in increasing order of preference, of at least 20%
(typically in the range of 20% to 95%, more typically in the range
from 25% to 95%, preferably, at least 50%, more preferably, in the
range from 50% to 90%, even more preferably, at least 85%, and most
preferably, in the range from 85% to 95%) by volume, securing
substantially continuous, longitudinally aligned, ceramic oxide
fibers in place, wherein the porous ceramic oxide material extends
along at least a portion of the length of the fibers. Optionally,
the fibers are encapsulated within the porous ceramic oxide
material.
[0019] In another aspect, the present invention provides a method
for making a porous ceramic oxide pre-form, the method
comprising:
[0020] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous,
longitudinally aligned, ceramic oxide fibers;
[0021] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers (including whiskers) dispersed therein;
[0022] removing a sufficient amount of the liquid medium to cause
the discontinuous fibers to consolidate and secure the fiber insert
to provide an article comprising the elongated fiber insert and the
discontinuous fibers (including whiskers), wherein the
consolidation of discontinuous fibers extends along at least a
portion of the length of the fiber insert;
[0023] drying the consolidated article to provide a green ceramic
oxide pre-form comprising the elongated fiber insert and the
discontinuous ceramic oxide fibers, wherein at least one
consolidation of the discontinuous fibers secures the fiber insert
in place, wherein the consolidation of discontinuous fibers extends
along at least a portion of the length of the fiber insert; and
[0024] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous ceramic oxide material securing the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
wherein the porous ceramic oxide material extends along at least a
portion of the length of the fibers.
[0025] In another aspect, the present invention provides a method
for making a porous ceramic oxide pre-form, the method
comprising:
[0026] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous,
longitudinally aligned, ceramic oxide fibers;
[0027] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers (including whiskers) dispersed therein;
[0028] removing a sufficient amount of the liquid medium to cause
the discontinuous fibers to consolidate and secure the fiber insert
to provide an article comprising the elongated fiber insert and the
discontinuous fibers, wherein the consolidation of the
discontinuous fibers extends along at least a portion of the length
of the fiber insert; and
[0029] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous ceramic oxide material securing the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
wherein the porous ceramic oxide material extends along at least a
portion of the length of the fibers.
[0030] In another aspect, the present invention provides a method
for making a green ceramic oxide pre-form, the method
comprising:
[0031] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous,
longitudinally aligned, ceramic oxide fibers;
[0032] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers (including whiskers) dispersed therein;
[0033] removing a sufficient amount of the liquid medium to cause
the discontinuous fibers to consolidate and secure the fiber insert
to provide an article comprising the elongated fiber insert and the
discontinuous fibers, wherein the consolidation of the
discontinuous fibers extends along at least a portion of the length
of the fiber insert; and
[0034] drying the consolidated article to provide a green ceramic
oxide pre-form comprising the elongated fiber insert and the
discontinuous fibers, wherein at least one consolidation of the
discontinuous fibers secures the fiber insert in place, wherein the
consolidation of discontinuous fibers extends along at least a
portion of the length of the fiber insert.
[0035] In another aspect, the present invention provides a method
for making a green ceramic oxide pre-form, the method
comprising:
[0036] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous,
longitudinally aligned, ceramic oxide fibers;
[0037] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers (including whiskers) dispersed therein;
and
[0038] removing a sufficient amount of the liquid medium to cause
the discontinuous fibers to consolidate and secure the fiber insert
to provide an article comprising the elongated fiber insert and the
discontinuous fibers, wherein the consolidation of the
discontinuous fibers extends along at least a portion of the length
of the fiber insert.
[0039] In one embodiment, the present invention provides a porous
ceramic oxide pre-form comprising porous, sintered ceramic oxide
material and substantially continuous ceramic oxide fibers having
lengths of at least 5 cm, the porous, sintered ceramic oxide
material securing the substantially continuous ceramic oxide fibers
in place, wherein the porous, sintered ceramic oxide material
extends along at least a portion of the length of the substantially
continuous ceramic oxide fibers, wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned.
[0040] In another embodiment, the present invention provides a
porous ceramic oxide pre-form comprising porous, sintered ceramic
oxide material securing tows comprised of substantially continuous
ceramic oxide fibers in place, wherein the porous, sintered ceramic
oxide material extends along at least a portion of the length of
the substantially continuous ceramic oxide fibers, and wherein the
tows of substantially continuous ceramic oxide fibers are
essentially longitudinally aligned.
[0041] In another embodiment, the present invention provides a
porous ceramic oxide pre-form comprising porous, sintered ceramic
oxide material and substantially continuous, longitudinally
aligned, ceramic oxide fibers having lengths of at least 5 cm, the
porous, sintered ceramic oxide material having an open porosity of
at least 85% by volume and securing the substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, wherein the
porous, sintered ceramic oxide material extends along at least a
portion of the length of the substantially continuous,
longitudinally aligned, ceramic oxide fibers.
[0042] In another embodiment, the present invention provides a
porous ceramic oxide pre-form comprising porous, sintered ceramic
oxide material having an open porosity of at least 85% by volume
securing tows comprised of substantially continuous, longitudinally
aligned, ceramic oxide fibers in place, wherein the porous,
sintered ceramic oxide material extends along at least a portion of
the length of the tows of substantially continuous, longitudinally
aligned, ceramic oxide fibers.
[0043] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0044] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous ceramic oxide
fibers having lengths of at least 5 cm, wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned;
[0045] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0046] removing at least a sufficient amount of the liquid medium
to cause the discontinuous fibers to consolidate and secure the
fiber insert to provide an article comprising the elongated fiber
insert and the discontinuous fibers, wherein the consolidation of
the discontinuous fibers extends along at least a portion of the
length of the fiber insert;
[0047] drying the consolidated article to provide a green ceramic
oxide pre-form comprising the elongated fiber insert and the
discontinuous fibers, wherein at least one consolidation of the
discontinuous fibers secures the fiber insert in place, and wherein
the consolidation of the discontinuous fibers extends along at
least a portion of the length of the fiber insert; and
[0048] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material securing the
substantially continuous ceramic oxide fibers in place, wherein the
porous, sintered ceramic oxide material extends along at least a
portion of the length of the substantially continuous fibers, and
wherein the substantially continuous ceramic oxide fibers are
essentially longitudinally aligned.
[0049] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0050] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising tows comprised of substantially
continuous ceramic oxide fibers, wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned;
[0051] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0052] removing at least a sufficient amount of the liquid medium
to cause the discontinuous fibers to consolidate and secure the
fiber insert to provide an article comprising the elongated fiber
insert and the discontinuous fibers, wherein the consolidation of
the discontinuous fibers extends along at least a portion of the
length of the fiber insert;
[0053] drying the consolidated article to provide a green ceramic
oxide pre-form comprising the elongated fiber insert and the
discontinuous fibers, wherein at least one consolidation of the
discontinuous fibers secures the fiber insert in place, and wherein
the consolidation of the discontinuous fibers extends along at
least a portion of the length of the fiber insert; and
[0054] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material securing the
substantially continuous ceramic oxide fibers in place, wherein the
porous, sintered ceramic oxide material extends along at least a
portion of the length of the substantially continuous fibers, and
wherein the tows of substantially continuous ceramic oxide fibers
are essentially longitudinally aligned.
[0055] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0056] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous ceramic oxide
fibers having lengths of at least 5 cm, wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned;
[0057] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0058] removing a sufficient amount of the liquid medium from the
slurry to cause the discontinuous fibers to consolidate and secure
the fiber insert to provide an article comprising the elongated
fiber insert and the discontinuous fibers, wherein the
consolidation of discontinuous fibers extends along at least a
portion of the length of the fiber insert; and
[0059] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material securing the
substantially continuous ceramic oxide fibers in place, wherein the
porous, sintered ceramic oxide material extends along at least a
portion of the length of the substantially continuous fibers, and
wherein the substantially continuous ceramic oxide fibers are
essentially longitudinally aligned.
[0060] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0061] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising tows comprised of substantially
continuous ceramic oxide fibers, wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned;
[0062] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0063] removing a sufficient amount of the liquid medium from the
slurry to cause the discontinuous fibers to consolidate and secure
the fiber insert to provide an article comprising the elongated
fiber insert and the discontinuous fibers, wherein the
consolidation of discontinuous fibers extends along at least a
portion of the length of the fiber insert; and
[0064] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material securing the
substantially continuous ceramic oxide fibers in place, wherein the
porous, sintered ceramic oxide material extends along at least a
portion of the length of the substantially continuous fibers, and
wherein the tows of substantially continuous ceramic oxide fibers
are essentially longitudinally aligned.
[0065] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0066] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous,
longitudinally aligned, ceramic oxide fibers having lengths of at
least 5 cm;
[0067] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0068] removing at least a sufficient amount of the liquid medium
to cause the discontinuous fibers to consolidate and secure the
fiber insert to provide an article comprising the elongated fiber
insert and the discontinuous fibers, wherein the consolidation of
the discontinuous fibers extends along at least a portion of the
length of the fiber insert;
[0069] drying the consolidated article to provide a green ceramic
oxide pre-form comprising the elongated fiber insert and the
discontinuous fibers, wherein at least one consolidation of the
discontinuous fibers secures the fiber insert in place, and wherein
the consolidation of the discontinuous fibers extends along at
least a portion of the length of the fiber insert; and
[0070] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material having an open
porosity of at least 85% by volume securing the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
wherein the porous, sintered ceramic oxide material extends along
at least a portion of the length of the substantially continuous,
longitudinally aligned, ceramic oxide fibers.
[0071] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0072] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising tows comprised of substantially
continuous, longitudinally aligned, ceramic oxide fibers;
[0073] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0074] removing at least a sufficient amount of the liquid medium
to cause the discontinuous fibers to consolidate and secure the
fiber insert to provide an article comprising the elongated fiber
insert and the discontinuous fibers, wherein the consolidation of
the discontinuous fibers extends along at least a portion of the
length of the fiber insert;
[0075] drying the consolidated article to provide a green ceramic
oxide pre-form comprising the elongated fiber insert and the
discontinuous fibers, wherein at least one consolidation of the
discontinuous fibers secures the fiber insert in place, and wherein
the consolidation of the discontinuous fibers extends along at
least a portion of the length of the fiber insert; and
[0076] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material having an open
porosity of at least 85% by volume securing the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
wherein the porous, sintered ceramic oxide material extends along
at least a portion of the length of the substantially continuous,
longitudinally aligned, ceramic oxide fibers.
[0077] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0078] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising substantially continuous,
longitudinally aligned, ceramic oxide fibers having lengths of at
least 5 cm;
[0079] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0080] removing a sufficient amount of the liquid medium from the
slurry to cause the discontinuous fibers to consolidate and secure
the fiber insert to provide an article comprising the elongated
fiber insert and the discontinuous fibers, wherein the
discontinuous fibers consolidate to secure the fiber insert in
place, and wherein the consolidation of discontinuous fibers
extends along at least a portion of the length of the fiber insert;
and
[0081] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material having an open
porosity of at least 85% by volume securing the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
wherein the porous, sintered ceramic oxide material extends along
at least a portion of the length of the substantially continuous,
longitudinally aligned, ceramic oxide fibers.
[0082] In another embodiment, the present invention provides a
method for making a porous ceramic oxide, the method
comprising:
[0083] positioning at least one elongated fiber insert in a cavity,
the fiber insert comprising tows comprised of substantially
continuous, longitudinally aligned, ceramic oxide fibers;
[0084] introducing a slurry into the cavity such that a
pre-determined portion of the elongated fiber insert is coated with
the slurry, the slurry comprising liquid medium and discontinuous
ceramic oxide fibers dispersed therein;
[0085] removing a sufficient amount of the liquid medium from the
slurry to cause the discontinuous fibers to consolidate and secure
the fiber insert to provide an article comprising the elongated
fiber insert and the discontinuous fibers, wherein the
consolidation of discontinuous fibers extends along at least a
portion of the length of the fiber insert; and
[0086] heating the green ceramic oxide pre-form to at least one
temperature sufficient to provide a porous ceramic oxide pre-form
comprising porous, sintered ceramic oxide material having an open
porosity of at least 85% by volume securing the substantially
continuous, longitudinally aligned, ceramic oxide fibers in place,
wherein the porous, sintered ceramic oxide material extends along
at least a portion of the length of the substantially continuous,
longitudinally aligned, ceramic oxide fibers.
[0087] In another embodiment, the present invention provides a
porous ceramic oxide pre-form comprising:
[0088] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0089] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material and substantially continuous ceramic oxide fibers having
lengths of at least 5 cm, the porous, sintered ceramic oxide
material securing substantially continuous ceramic oxide fibers in
place, wherein the porous, sintered ceramic oxide material extends
along at least a portion of the length of the substantially
continuous fibers, and wherein the substantially continuous ceramic
oxide fibers are essentially longitudinally aligned.
[0090] In another embodiment, the present invention provides a
porous ceramic oxide pre-form comprising:
[0091] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0092] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material securing tows comprised of substantially continuous
ceramic oxide fibers in place, wherein the porous, sintered ceramic
oxide material extends along at least a portion of the length of
the substantially continuous fibers, wherein the tows of
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned.
[0093] In another embodiment, the present invention provides a
porous ceramic oxide pre-form comprising:
[0094] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0095] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material and substantially continuous ceramic oxide fibers having
lengths of at least 5 cm, the porous, sintered ceramic oxide
material having an open porosity of at least 85% by volume securing
the substantially continuous, longitudinally aligned, ceramic oxide
fibers in place, wherein the porous, sintered ceramic oxide
material extends along at least a portion of the length of the
substantially continuous, longitudinally aligned, ceramic oxide
fibers.
[0096] In another embodiment, the present invention provides a
porous ceramic oxide pre-form comprising:
[0097] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0098] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material having an open porosity of at least 85% by volume securing
tows comprised of substantially continuous, longitudinally aligned,
ceramic oxide fibers in place, wherein the porous, sintered ceramic
oxide material extends along at least a portion of the length of
the substantially continuous, longitudinally aligned, ceramic oxide
fibers.
[0099] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0100] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers having
lengths of at least 5 cm, wherein the metal matrix composite
material to comprise at least one ceramic oxide pre-form comprising
ceramic oxide material extends along at least a portion of the
length of the substantially continuous, longitudinally aligned,
ceramic oxide fibers, and wherein the substantially continuous,
longitudinally aligned, ceramic oxide fibers have a first Young's
modulus and the ceramic oxide material has a second Young's
modulus, and wherein the first Young's modulus is greater than the
second Young's modulus; and
[0101] preparing, based on the resulting design, a porous, sintered
ceramic oxide pre-form comprising the ceramic oxide material
securing the substantially continuous, ceramic oxide fibers in
place, wherein the ceramic oxide material extends along at least a
portion of the length of the substantially continuous ceramic oxide
fibers, and wherein the substantially continuous ceramic oxide
fibers are essentially longitudinally aligned.
[0102] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0103] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers having
lengths of at least about 5 cm, wherein the metal matrix composite
material to comprise at least one ceramic oxide pre-form comprising
ceramic oxide material extends along at least a portion of the
length of the substantially continuous, longitudinally aligned,
ceramic oxide fibers, and wherein the substantially continuous,
longitudinally aligned, ceramic oxide fibers have a first Young's
modulus and the ceramic oxide material has a second Young's
modulus, and wherein the first Young's modulus is greater than the
second Young's modulus; and
[0104] preparing, based on the resulting design, a porous, sintered
ceramic oxide pre-form comprising the ceramic oxide material
securing tows comprised of the substantially continuous, ceramic
oxide fibers in place, wherein the ceramic oxide material extends
along at least a portion of the length of the substantially
continuous ceramic oxide fibers, and wherein the substantially
continuous ceramic oxide fibers are essentially longitudinally
aligned.
[0105] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0106] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers having
lengths of at least 5 cm,, wherein the metal matrix composite
material to comprise at least one ceramic oxide pre-form comprising
ceramic oxide material extends along at least a portion of the
length of the substantially continuous, longitudinally aligned,
ceramic oxide fibers, and wherein the substantially continuous,
longitudinally aligned, ceramic oxide fibers have a first Young's
modulus and the ceramic oxide material has a second Young's
modulus, and wherein the first Young's modulus is greater than the
second Young's modulus; and
[0107] preparing, based on the resulting design, a porous, sintered
ceramic oxide pre-form comprising the ceramic oxide material having
an open porosity of at least 85% by volume securing substantially
continuous ceramic oxide fibers in place, wherein the ceramic oxide
material extends along at least a portion of the length of the
substantially continuous ceramic oxide fibers.
[0108] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0109] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers, wherein
the metal matrix composite material to comprise at least one
ceramic oxide pre-form comprising ceramic oxide material extends
along at least a portion of the length of the substantially
continuous, longitudinally aligned, ceramic oxide fibers, and
wherein the substantially continuous, longitudinally aligned,
ceramic oxide fibers have a first Young's modulus and the first
ceramic oxide material has a second Young's modulus, and wherein
the first Young's modulus is greater than the second Young's
modulus; and
[0110] preparing, based on the resulting design, a porous, sintered
ceramic oxide pre-form comprising the ceramic oxide material having
an open porosity of at least 85% by volume securing tows comprised
of the substantially continuous ceramic oxide fibers in place,
wherein the ceramic oxide material extends along at least a portion
of the length of the substantially continuous ceramic oxide
fibers.
[0111] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0112] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers having
lengths of at least 5 cm;
[0113] preparing, based on the resulting design, an elongated
pre-form comprising the substantially continuous, longitudinally
aligned, ceramic oxide fibers and binder material bonding fibers
together;
[0114] preparing a green ceramic oxide pre-form comprising green
ceramic oxide material extending along at least a portion of the
length of the elongated pre-form; and
[0115] heating the green ceramic oxide pre-form to provide a
porous, sintered ceramic oxide pre-form comprising ceramic oxide
material securing the substantially continuous, longitudinally
aligned, ceramic oxide fibers in place, wherein the ceramic oxide
material extends along at least a portion of the length of the
substantially continuous ceramic oxide fibers, and wherein the
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned.
[0116] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0117] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers;
[0118] preparing, based on the resulting design, an elongated
pre-form comprising tows comprised of the substantially continuous,
longitudinally aligned, ceramic oxide and binder material bonding
tows comprised of substantially continuous, longitudinally aligned,
ceramic oxide fibers together;
[0119] preparing a green ceramic oxide pre-form comprising green
ceramic oxide material extending along at least a portion of the
length of the elongated pre-form; and
[0120] heating the green ceramic oxide pre-form to provide a
porous, sintered ceramic oxide pre-form comprising ceramic oxide
material securing the tows of substantially continuous,
longitudinally aligned, ceramic oxide fibers in place, wherein the
ceramic oxide material extends along at least a portion of the
length of the substantially continuous fibers, and wherein the
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned.
[0121] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0122] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers having
lengths of at least 5 cm;
[0123] preparing, based on the resulting design, an elongated
pre-form comprising the substantially continuous, longitudinally
aligned, ceramic oxide and binder material bonding fibers
together;
[0124] preparing a green ceramic oxide pre-form comprising green
ceramic oxide material extending along at least a portion of the
length of the elongated pre-form; and
[0125] heating the green ceramic oxide pre-form to provide a
porous, sintered ceramic oxide pre-form comprising ceramic oxide
material having an open porosity of at least 85% by volume securing
the substantially continuous, longitudinally aligned, ceramic oxide
fibers in place, wherein the ceramic oxide material extends along
at least a portion of the length of the substantially continuous
ceramic oxide fibers.
[0126] In another embodiment, the present invention provides a
method for making a porous, sintered ceramic oxide pre-form for an
article comprising metal matrix material, the method
comprising:
[0127] designing an article to comprise metal matrix composite
material reinforced, at least in part, with substantially
continuous, longitudinally aligned, ceramic oxide fibers;
[0128] preparing, based on the resulting design, an elongated
pre-form comprising tows comprised of the substantially continuous,
longitudinally aligned, ceramic oxide and binder material bonding
tows comprised of substantially continuous, longitudinally aligned,
ceramic oxide fibers together;
[0129] preparing a green ceramic oxide pre-form comprising green
ceramic oxide material extending along at least a portion of the
length of the elongated pre-form; and
[0130] heating the green ceramic oxide pre-form to provide a
porous, sintered ceramic oxide pre-form comprising ceramic oxide
material having an open porosity of at least 85% by volume securing
the substantially continuous, longitudinally aligned, ceramic oxide
fibers in place, wherein the ceramic oxide material extends along
at least a portion of the length of the substantially continuous
ceramic oxide fibers.
[0131] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
and metal matrix material, wherein the ceramic oxide pre-form
comprises substantially continuous ceramic oxide fibers having
lengths of at least 5 cm and a porous, sintered ceramic oxide
material extending along at least a portion of the length of the
substantially continuous ceramic oxide fibers, wherein the
substantially continuous ceramic oxide fibers are essentially
longitudinally aligned, and wherein the porous ceramic oxide
material is infiltrated with at least a portion of the metal matrix
material extending into the porous, sintered ceramic oxide
material.
[0132] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
and metal matrix material, wherein the ceramic oxide pre-form
comprises tows comprised of substantially continuous ceramic oxide
fibers and a porous, sintered ceramic oxide material extending
along at least a portion of the length of the tows, wherein the
tows are essentially longitudinally aligned, and wherein the porous
ceramic oxide material is infiltrated with at least a portion of
the metal matrix material extends into the porous, sintered ceramic
oxide material.
[0133] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
and metal matrix material, wherein the ceramic oxide pre-form
comprises substantially continuous, longitudinally aligned, ceramic
oxide fibers having lengths of at least 5 cm and a porous, sintered
ceramic oxide material having an open porosity of at least 85% by
volume extending along at least a portion of the length of the
substantially continuous ceramic oxide fibers, and wherein the
porous, sintered ceramic oxide material is infiltrated with at
least a portion of the metal matrix material.
[0134] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
and metal matrix material, wherein the ceramic oxide pre-form
comprises tows comprised of ceramic oxide fibers and a porous,
sintered ceramic oxide material having an open porosity of at least
85% by volume extending along at least a portion of the length of
the tows, and wherein the porous, sintered ceramic oxide material
is infiltrated with at least a portion of the metal matrix
material.
[0135] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
pre-form and metal matrix material, wherein the ceramic oxide
pre-form comprises:
[0136] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0137] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material and substantially continuous ceramic oxide fibers having
lengths of at least 5 cm, the porous, sintered ceramic oxide
material securing the substantially continuous ceramic oxide fibers
in place, wherein the porous, sintered ceramic oxide material
extends along at least a portion of the length of the substantially
continuous fibers, and wherein the substantially continuous ceramic
oxide fibers are essentially longitudinally aligned, and
[0138] wherein the porous, sintered ceramic oxide material is
infiltrated with at least a portion of the metal matrix
material.
[0139] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
pre-form and metal matrix material, wherein the ceramic oxide
pre-form comprises:
[0140] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0141] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material securing tows comprised of substantially continuous
ceramic oxide fibers in place, wherein the porous, sintered ceramic
oxide material extends along at least a portion of the length of
the substantially continuous fibers, and wherein the tows are
essentially longitudinally aligned, and wherein the porous ceramic
oxide material is infiltrated with at least a portion of the metal
matrix material.
[0142] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
pre-form and metal matrix, wherein the ceramic oxide pre-form
comprises:
[0143] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0144] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material having an open porosity of at least 85% by volume and
substantially continuous ceramic oxide fibers having lengths of at
least 5 cm, the porous, sintered ceramic oxide material securing
the substantially continuous, longitudinally aligned, ceramic oxide
fibers in place, wherein the porous, sintered ceramic oxide
material extends along at least a portion of the length of the
substantially continuous, longitudinally aligned, ceramic oxide
fibers, and
[0145] wherein the porous ceramic oxide material is infiltrated
with at least a portion of the metal matrix material.
[0146] In another embodiment, the present invention provides a
metal matrix composite article comprising a porous ceramic oxide
pre-form and metal matrix, wherein the ceramic oxide pre-form
comprises:
[0147] a first porous, sintered ceramic article including an
aperture for receiving a porous ceramic oxide; and
[0148] a second ceramic article positioned in the aperture, the
second ceramic article comprising porous, sintered ceramic oxide
material having an open porosity of at least 85% by volume securing
tows comprised of substantially continuous, longitudinally aligned,
ceramic oxide fibers in place, wherein the porous, sintered ceramic
oxide material extends along at least a portion of the length of
the substantially continuous, longitudinally aligned, ceramic oxide
fibers, and
[0149] wherein the porous ceramic oxide material is infiltrated
with at least a portion of the metal matrix material.
[0150] Ceramic oxide pre-forms according to the present invention
are useful, for example, to provide reinforcement material in metal
matrix composite articles. One advantage of an aspect of the
present invention is that it allows for an existing article made of
one metal (e.g., cast iron) to be redesigned to be made from
another metal (e.g., aluminum) reinforced with ceramic oxide
material including substantially continuous, ceramic oxide fibers
such that the latter (i.e., the metal matrix composite version of
the article) has certain desired properties (e.g., Young's modulus,
yield strength, and ductility) at least equal to that required for
the use of the original article made from the first metal.
[0151] Optionally, the article may be redesigned to have the same
physical dimensions as the original article.
BRIEF DESCRIPTION OF THE DRAWINGS
[0152] FIG. 1 is a perspective view of a porous ceramic oxide
according to the present invention.
[0153] FIG. 2 is a perspective view of a ceramic fiber ribbon used
to make a porous ceramic oxide according to the present
invention.
[0154] FIG. 3 is a perspective view of an apparatus for making
ceramic oxide pre-forms according to the present invention.
[0155] FIG. 4 is a perspective view of another ceramic oxide
pre-form according to the present invention.
[0156] FIG. 5 is a perspective view of a brake caliper
incorporating a ceramic oxide pre-form according to the present
invention.
[0157] FIG. 6 is a perspective view of another brake caliper
incorporating a ceramic oxide pre-form according to the present
invention.
[0158] FIG. 7 is a digital SEM photomicrograph of a polished
cross-section of a fracture surface of a portion of a brake caliper
according to the present invention.
[0159] FIGS. 8 and 9 are digital SEM photomicrographs of a fracture
surface of a portion of a brake caliper according to the present
invention.
[0160] FIG. 10 is a perspective view of a porous ceramic oxide
pre-form according to the present invention.
[0161] FIG. 11 is a perspective view of a metal matrix composite
article made from the porous ceramic oxide pre-form shown in FIG.
10.
[0162] FIG. 12 is a perspective view of an alternative pre-form
according to the present invention utilizing multiple plies of
longitudinally aligned alpha alumina fibers wherein the
longitudinal axles of the plies are positioned at an angle greater
than zero relative to one another.
[0163] FIG. 13 is a perspective view of a grouping of substantially
continuous alpha alumina fibers spirally wrapped with another group
of substantially continuous alpha alumina fibers.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0164] The present invention provides ceramic oxide pre-forms and
metal matrix composite articles comprising at least one ceramic
oxide pre-form (including ceramic oxide pre-forms according to the
present invention) comprising substantially continuous ceramic
oxide fibers. Preferably, ceramic oxide pre-forms, as well as the
metal matrix composite articles, according to the present invention
are designed for the particular application to achieve an optimal,
or at least acceptable balance of desired properties, low cost, and
ease of manufacture.
[0165] Typically, a porous ceramic oxide(s) pre-form according to
the present invention is designed for a specific application and/or
to have certain properties and/or features. For example, an
existing article made of one metal (e.g., cast iron) is selected to
be redesigned to be made from another metal (e.g., aluminum)
reinforced with ceramic oxide material including substantially
continuous, ceramic oxide fibers such that the latter (i.e., the
metal matrix composite version of the article) has certain desired
properties (e.g., Young's modulus, yield strength, and ductility)
at least equal to that required for the use of the original article
made from the first metal. Optionally, the article may be
redesigned to have the same physical dimensions as the original
article.
[0166] The desired metal matrix composite article configuration,
desired properties, possible metals and ceramic oxide material from
which it may be desirable for it to be made of, as well as relevant
properties of those materials are collected and used to provide
possible suitable constructions. A preferred method for generating
possible constructions is the use of finite element analysis (FEA),
including the use of FEA software run with the aid of a
conventional computer system (including the use of a central
processing unit (CPU) and input and output devices). Suitable FEA
software is commercially available, including that marketed by
Ansys, Inc., Canonsburg, Pa. under the trade designation "ANSYS".
FEA assists in modeling the article mathematically and identifying
regions where placement of the continuous ceramic oxide fibers and
possibly other ceramic oxide materials would provide the desired
property levels. For a non-linear geometry, it is typically
necessary to run several iterations of FEA to obtain a more
preferred design.
[0167] Referring to FIG. 1, ceramic oxide pre-form according to the
present invention 10 comprises substantially continuous,
longitudinally aligned, ceramic oxide fibers 12 and porous ceramic
oxide material 14. Certain preferred porous ceramic oxide material
(including porous, sintered ceramic oxide material) comprises alpha
alumina.
[0168] The continuous reinforcing fibers of the present invention
are substantially longitudinally aligned such that they are
generally parallel to each other. While these fibers may be
incorporated into the ceramic oxide pre-forms as individual fibers,
they are more typically incorporated into the pre-form as a group
of fibers in the form of a bundle or tow. Fibers within the bundle
or tow are maintained in a longitudinally aligned (i.e. a generally
parallel) relationship with one another. When multiple bundles or
tows are utilized in the pre-form, the fiber bundles or tows are
also maintained in a longitudinally aligned (i.e. generally
parallel) relationship with one another. Typically, it is preferred
that all of the continuous reinforcing fibers are maintained in an
essentially longitudinally aligned configuration where individual
fiber alignment is maintained within .+-.10.degree., more
preferably .+-.5.degree., most preferably .+-.3.degree., of their
average longitudinal axis. Continuous reinforcing fibers in the
form of woven, knitted, and the like fiber constructions typically
are not capable of achieving the higher fiber packing densities
realized with longitudinally aligned fibers. Thus, metal
infiltrated articles based on pre-forms utilizing woven, knitted,
or the like fiber constructions typically exhibit lower strength
properties than metal infiltrated articles having longitudinally
aligned continuous reinforcing fibers and hence are less
preferred.
[0169] For some pre-form constructions, it may be desirable or
necessary for the longitudinally aligned, ceramic oxide fibers to
be curved, as opposed to straight (i.e., do not extend in a planar
manner). Hence, for example, the longitudinally aligned, ceramic
oxide fibers may be planar throughout the fiber length, non-planar
(i.e., curved) throughout the fiber length, or they may be planar
at some portions and non-planar (i.e., curved) at other portions,
wherein the continuous reinforcing fibers are maintained in a
substantially non-intersecting, curvilinear arrangement (i.e.
longitudinally aligned) throughout the curved portion of the
pre-form. In preferred embodiments, the fibers are maintained in a
substantially equidistant relationship with each other throughout
the curved portion of the pre-form. For example, FIG. 6C, which is
a perspective schematic of the substantially continuous alpha
alumina fiber insert 208 of FIGS. 6A and 6D, illustrates
longitudinally aligned, alpha alumina fibers 67. Longitudinally
aligned, alpha alumina fibers 67 are planar between section lines
BB and CC and between section lines DD and EE, and curved between
section lines CC and DD. Alternatively, the longitudinally aligned,
ceramic oxide fibers may be non-planar throughout their lengths.
For example, referring to FIG. 10, ceramic oxide pre-form according
to the present invention 100 comprises longitudinally aligned,
ceramic oxide fibers 102 and porous ceramic oxide material 104,
wherein longitudinally aligned, ceramic oxide fibers 102 are curved
throughout their lengths. An example of a metal matrix composite
article which can be made from the latter type of pre-form is an
aluminum metal matrix composite ring, such as shown in FIG. 11.
Ring 110 is comprised of metal 112 and ceramic oxide pre-form 100
(see FIG. 10). Such rings are useful, for example, in high speed
rotating machinery where they are subject to large centrifugal
forces.
[0170] In another aspect, for some pre-form constructions it may be
desirable, or required, to have two, three, four, or more plies of
the longitudinally aligned, ceramic oxide fibers (i.e., a ply is at
least one layer of substantially continuous, longitudinally
aligned, ceramic oxide fibers (preferably, at least one layer of
tows comprised of substantially continuous, longitudinally aligned,
ceramic oxide fibers)). The plies may be oriented with respect to
each other any of a variety of ways. Examples of the relationships
of the plies to each other are shown in FIGS. 12 and 13. Referring
to FIG. 12, ceramic oxide pre-form according to the present
invention 120 comprises first and second plies of longitudinally
aligned, ceramic oxide fibers 121 and 122 secured in porous ceramic
oxide material 124, wherein first ply of longitudinally aligned,
ceramic oxide fibers 121 is positioned 45.degree. with respect to
second ply of longitudinally aligned, ceramic oxide fibers 122,
although depending on the particular application, the difference in
position of a ply with respect to another ply(s) may be anywhere
between greater than zero degrees to 90.degree.. Preferred
positioning of a ply with respect to another ply(s) for some
applications may be in the range from about 30.degree. to about
60.degree., or even, for example, in the range from about
40.degree. to about 50.degree. C. Optionally, porous ceramic oxide
material can be between two or more plies.
[0171] A grouping of fibers may also benefit from being wrapped
with fibers such as shown in FIG. 13, wherein ceramic oxide fibers
131 are spirally wrapped around longitudinally aligned, ceramic
oxide fibers 132. An example of a metal matrix composite article
which may benefit from the properties offered by plies of
longitudinally aligned, ceramic oxide fibers include is an article
that under use is subjected to bending forces about two
perpendicular axes.
[0172] Substantially continuous reinforcing fibers used to make a
porous ceramic oxide pre-form according to the present invention
preferably have an average diameter of at least about 5
micrometers. Preferably, the average fiber diameter is no greater
than about 250 micrometers, more preferably, no greater than about
100 micrometers. For tows of fibers, the average fiber diameter is
preferably, no greater than about 50 micrometers, more preferably,
no greater than about 25 micrometers.
[0173] Preferably, fibers have a Young's modulus of greater than
about 70 GPa GPa, more preferably, at least 100 GPa, at least 150
GPa, at least 200 GPa, at least 250 GPa, at least 300 GPa, or even
at least 350 GPa.
[0174] Preferably, the ceramic oxide fibers have an average tensile
strength of at least about 1.4 GPa, more preferably, at least about
1.7 GPa, even more preferably, at least about 2.1 GPa, and most
preferably, at least about 2.8 GPa.
[0175] Examples of substantially continuous fibers that may be
useful for making metal matrix composite materials according to the
present invention include alpha alumina fibers, such as alpha
alumina fibers aluminosilicate fibers, and aluminoborosilicate
fibers. Ceramic oxide fibers are available commercially as single
filaments, or grouped together (e.g., as yarns or tows). Yams or
tows preferably comprise at least 750 individual fibers per tow,
and more preferably at least 2550 individual fibers per tow. Tows
are well known in the fiber art and refer to a plurality of
(individual) fibers (typically at least 100 fibers, more typically
at least 400 fibers) collected in a rope-like form. Ceramic oxide
fibers, including tows of ceramic oxide fibers, are available in a
variety of lengths. The fibers may have a cross-sectional shape
that is circular or elliptical.
[0176] Methods for making alumina fibers are known in the art and
include the method disclosed in U.S. Pat. No. 4,954,462 (Wood et
al.), the disclosure of which is incorporated herein by reference.
Preferably, the alumina fibers are polycrystalline alpha
alumina-based fibers and comprise, on a theoretical oxide basis,
greater than about 99 percent by weight Al.sub.2O.sub.3 and about
0.2-0.5 percent by weight SiO.sub.2, based on the total weight of
the alumina fibers. In another aspect, preferred polycrystalline,
alpha alumina-based fibers comprise alpha alumina having an average
grain size of less than 1 micrometer (more preferably, less than
0.5 micrometer). In another aspect, preferred polycrystalline,
alpha alumina-based fibers have an average tensile strength of at
least 1.6 GPa (preferably, at least 2.1 GPa, more preferably, at
least 2.8 GPa). Preferred alpha alumina fibers are commercially
available under the trade designation "NEXTEL 610" from the 3M
Company, St. Paul, Minn. Another alpha alumina fiber, which
comprises about 89 percent by weight Al.sub.2O.sub.3, amount 10
percent by weight ZrO.sub.2, and about 1 percent by weight
Y.sub.2O.sub.3, based on the total weight of the fibers,
commercially available from the is that marketed under the trade
designation "NEXTEL 650".
[0177] Suitable aluminosilicate fibers are described in U.S. Pat.
No. 4,047,965 (Karst et al.), the disclosure of which is
incorporated herein by reference. Preferably, the aluminosilicate
fibers comprise, on a theoretical oxide basis, in the range from
about 67 to about 85 percent by weight Al.sub.2O.sub.3 and in the
range from about 33 to about 15 percent by weight SiO.sub.2, based
on the total weight of the aluminosilicate fibers. Some preferred
aluminosilicate fibers comprise, on a theoretical oxide basis, in
the range from about 67 to about 77 percent by weight
Al.sub.2O.sub.3 and in the range from about 33 to about 23 percent
by weight SiO.sub.2, based on the total weight of the
aluminosilicate fibers. One preferred aluminosilicate fiber
comprises, on a theoretical oxide basis, about 85 percent by weight
Al.sub.2O.sub.3 and about 15 percent by weight SiO.sub.2, based on
the total weight of the aluminosilicate fibers. Another preferred
aluminosilicate fiber comprises, on a theoretical oxide basis,
about 73 percent by weight Al.sub.2O.sub.3 and about 27 percent by
weight SiO.sub.2, based on the total weight of the aluminosilicate
fibers. Preferred aluminosilicate fibers are commercially available
under the trade designations "NEXTEL 720" and "NEXTEL 550" from the
3M Company.
[0178] Suitable aluminoborosilicate fibers are described in U.S.
Pat. No. 3,795,524 (Sowman), the disclosure of which is
incorporated herein by reference. Preferably, the
aluminoborosilicate fibers comprise, on a theoretical oxide basis:
about 35 percent by weight to about 75 percent by weight (more
preferably, about 55 percent by weight to about 75 percent by
weight) Al.sub.2O.sub.3; greater than 0 percent by weight (more
preferably, at least about 15 percent by weight) and less than
about 50 percent by weight (more preferably, less than about 45
percent, and most preferably, less than about 44 percent)
SiO.sub.2; and greater than about 5 percent by weight (more
preferably, less than about 25 percent by weight, even more
preferably, about 1 percent by weight to about 5 percent by weight,
and most preferably, about 2 percent by weight to about 20 percent
by weight) B.sub.2O.sub.3, based on the total weight of the
aluminoborosilicate fibers. Preferred aluminoborosilicate fibers
are commercially available under the trade designations "NEXTEL
312" and "NEXTEL 440" from the 3M Company.
[0179] Commercially available substantially continuous ceramic
oxide fibers typically include an organic sizing material added to
the fiber during their manufacture to provide lubricity and to
protect the fiber strands during handling. It is believed that the
sizing tends to reduce the breakage of fibers, reduces static
electricity, and reduces the amount of dust during, for example,
conversion to a fabric. The sizing can be removed, for example, by
dissolving or burning it away.
[0180] It is also within the scope of the present invention to have
coatings on the ceramic oxide fibers. Coatings may be used, for
example, to enhance the wettability of the fibers, to reduce or
prevent reaction between the fibers and molten metal matrix
material. Such coatings and techniques for providing such coatings
are known in the fiber and metal matrix composite art.
[0181] Porous ceramic oxide pre-forms can be made, for example, by
casting a slurry of discontinuous ceramic oxide fibers (including
whiskers) around the continuous fibers. Typically, the continuous
fibers are positioned in a cavity (e.g., mold), and the slurry
added to the mold. The continuous fibers are positioned within the
cavity such that they will be properly positioned in the resulting
ceramic oxide material. The cavity is configured to provide the
desired shape, although it is also within the scope of the present
invention to reshape the resulting ceramic oxide material, for
example, by machining, to provide the desired configuration of the
ceramic oxide pre-form.
[0182] Suitable discontinuous ceramic oxide fibers (including
whiskers) include those made of alumina, including alpha alumina
and transitional aluminas (such as delta alumina), aluminosilicate
fibers, and aluminoborosilicate fibers, and methods of making
and/or sources of such materials, are known in the art.
Discontinuous fibers can be made, for example, by cutting or
chopping continuous fibers (including the continuous fibers
discussed above). Examples of commercially available discontinuous
ceramic oxide fibers include those marketed under the trade
designation "SAFFIL:" from J&J Dyson, Widness, UK, "KAOWOOL"
from Thermal Ceramics Inc., Augusta, Ga., and "FIBERFRAX" from
Unifrax, Niagara Falls, N.Y.
[0183] Typically, the discontinuous fibers have a diameter in the
range from about 1 micrometer to about 20 micrometers, preferably,
from about 3 micrometers to about 12 micrometers, and are up to
about 2.5 cm long, preferably, less than 1.2 cm long, although
whiskers typically have a length in the range from about 6
micrometers to about 12 micrometers long.
[0184] Optionally, the slurry may further comprise ceramic oxide
particles such as alumina (including alpha alumina) particles,
aluminosilicate particles, and aluminoborosilicate particles.
Typically, the preferred average particle size of the particles is
in the range from about 0.05 micrometer to about 50 micrometers.
The slurry may further comprise ceramic oxide bonding materials
such as colloidal silica, colloidal alumina, and the like which can
aid in enhancing the integrity (e.g., by reaction with other
components used to make the porous ceramic oxide pre-form to make
other phases (e.g., the silica may react with alumina to form
mullite)).
[0185] A suitable slurry can be formed using techniques known in
the art. Typically, slurries are formed by dispersing discontinuous
fibers in a liquid medium such as water. To aid in the handling and
positioning of the continuous fibers, a fiber insert (e.g., ribbon)
can be used. A fiber insert comprises a plurality of the continuous
fibers held together with a binder material. Referring to FIG. 2,
fiber insert 20 comprises substantially continuous, longitudinally
aligned, ceramic oxide fibers 22 and fugitive binder material 24,
which serves to secure fibers 22 (as shown in tows 23) into fiber
insert 20. Binder material 24 contacts the fibers only to the
extent necessary to form fiber insert 20, and may not necessarily
be in contact with all fibers. For example, internal fibers may not
be in contact with the binder material.
[0186] In selecting the binder material for making a fiber insert,
consideration is given to adverse effects, if any, the binder
material may have on the properties of the ceramic oxide pre-form,
as well as the impact, if any, the binder material may have on the
use of the ceramic oxide pre-form (e.g., consideration is given to
adverse effects, if any, the binder material may have on the
properties of a metal matrix composite article made from the
ceramic oxide pre-form).
[0187] The binder material is used to temporarily bond the
continuous fibers together, as well as aid in handling and
ultimately placing the fibers in the ceramic oxide pre-form. The
binder material may preferably be a fugitive material, which
preferably burns out at relatively low temperature during the
calcining stage of the pre-form fabrication process leaving no
residue or ash. One preferred fugitive binder material is wax
(e.g., paraffin), which can be heated above its melting point,
applied to the fibers, and then solidified to hold the fibers as
desired. Other preferred fugitive binder materials include water
soluble polymers such as polyvinyl alcohol (PVA), polyvinyl
pyrrolidone (PVP), and combinations thereof. Other suitable
fugitive binder materials may include epoxies such as that marketed
by Cytec Industries, West Patterson, N.J. (formerly marketed by the
3 M Company under the trade designation "SP381 SCOTCHPLY
ADHESIVE").
[0188] As discussed above, the ceramic oxide pre-form is typically
designed for a certain purpose, and as a result, is desired to have
certain properties, have a certain configuration, and be made of
certain materials. Typically, the mold is selected or made to
provide the desired shape of the article to be cast to form a near
net shape. Forming a net-shaped, or near net-shaped article, can,
for example, minimize or eliminate the need for and cost of
subsequent machining or other post-casting processing of the cast
article. The cavity is selected or made to have a desired shape for
the resulting ceramic oxide material. Typically, the cavity is made
or adapted to hold the continuous fibers in a desired location such
that the continuous fibers are properly positioned in the resulting
ceramic oxide pre-form. Techniques for making suitable cavities are
known to those skilled in the art. Such cavities may be made of
rigid material such as of wood, plastic, graphite, and steel (e.g.,
stainless steel). To facilitate the removal of liquid from the
slurry, one or more apertures can be provided in the mold.
[0189] A green ceramic oxide pre-form according to the present
invention can be made, for example, by positioning the continuous
fiber in a cavity, introducing a slurry comprising discontinuous
ceramic oxide fibers into the cavity, and removing liquid from
slurry. Typically, the liquid is removed via apertures in the
cavity. Removal of the liquid through the apertures can be enhanced
with the aid of a vacuum. Preferably, the vacuum is less than 1000
mbars, more preferably, less than 850 mbars. Alternatively, or in
addition to the vacuum, removal of liquid from the cavity can be
enhanced by the application of pressure.
[0190] Unless the green pre-form is dried in the cavity, it is
typically dried after removal from the cavity before calcining or
sintering. Preferably, pre-form is dried to at least one
temperature in the range from about 70.degree. C. to about
100.degree. C, more preferably, from about 85.degree. C. to about
100.degree. C., and typically most preferably, at about 100.degree.
C.
[0191] The green pre-form is typically calcined prior to sintering.
Calcining is heating a material to a temperature(s) to eliminate
free water, and preferably at least about 90 wt-% of any bound
volatiles constituents, but without fusion, as opposed to sintering
wherein material is heated to a temperature(s) bonding of by
solid-state reactions at temperatures lower than those required for
the formation of a liquid phase.
[0192] Typical calcining temperatures are in the range from
400.degree. C. to about 800.degree. C., preferably from about
600.degree. C. to about 800.degree. C. Typical sintering
temperatures are in the range from 900.degree. C. to about
1150.degree. C., preferably from about 950.degree. C. to about
1100.degree. C., more preferably from about 950.degree. C. to about
1100.degree. C.
[0193] The drying, calcining, and sintering times may depend, for
example, on the materials involved, as well as the configuration
(including size) of the pre-form.
[0194] The orientation of the discontinuous fibers with respect to
the length of the continuous fibers may be adjusted by the
fabrication process used to make the ceramic oxide pre-form
according to the present invention. For example, the positioning
apertures in the bottom of the cavity used to hold the slurry to
preferentially remove the liquid from the bottom (or top) of the
cavity (as opposed to the sides) may result in the largest
dimension of the discontinuous fibers preferentially being more
parallel to the length of continuous fibers positioned parallel to
the lengths of the sides of the cavity than perpendicular. For
example, referring to FIG. 3, fiber insert or ribbon 31, which
comprises plurality of the continuous fibers 32 held together with
binder material 33, is positioned in cavity 34. The length of
continuous fibers 32 is parallel to sides of cavity 34, and
perpendicular to bottom 36 of cavity 34. Liquid from slurry 37 is
removed from via apertures 38, such that the largest dimension of
discontinuous fibers preferentially being more perpendicular to the
length of continuous fibers 32 than parallel.
[0195] Preferably, removal of the liquid is aided by a vacuum. For
example, a fiber insert may be affixed in the mold such that it
held in the desired location by clips at each end of the fiber
insert. In one vacuum forming technique, a screen is placed on one
side of the mold for water removal under vacuum. The placement of
the screen is determined by the desired orientation of the
discontinuous fibers. For example, if it is desired to
preferentially align discontinuous fibers to be perpendicular to
the fiber the lengths of continuous, longitudinally aligned fibers,
the screen can be positioned at one of the ends of the fiber
lengths, perpendicular to the length of the fibers. The slurry can
be added, for example, by submersing the mold in the slurry, then
removing or pumping the slurry from the mold. A vacuum can be
applied to the screen side of the mold to draw out the liquid. When
the liquid is removed, the discontinuous fibers are preferentially
aligned with respect to the lengths of the continuous fibers.
Subsequent pressure may be applied to the fibers to force out more
water, and may also aid in densifying the discontinuous fiber.
[0196] Similarly, for example, positioning apertures or holes in
the sides of the cavity used to hold the slurry to preferentially
remove the liquid from the sides of the cavity (as opposed to the
top an bottom) may result in the largest dimension of the
discontinuous fibers preferentially being more perpendicular to the
length of continuous fibers positioned parallel to the lengths of
the sides of the cavity than parallel.
[0197] Ceramic oxide pre-form according to the present invention
may comprise more than one grouping (e.g., two groupings, three
groupings, etc.) of substantially continuous, longitudinally
aligned, ceramic oxide fibers, wherein a grouping of substantially
continuous, longitudinally aligned, ceramic oxide fibers is spaced
apart from another grouping(s) with the porous ceramic oxide
material there between. For example, referring again to FIG. 1
ceramic oxide pre-form according to the present invention 10
comprises groupings 12A, 12B, and 12C of substantially continuous,
longitudinally aligned, ceramic oxide fibers 12 and porous ceramic
oxide material 14.
[0198] The ceramic oxide pre-form may be in any of a variety of
shapes, including a rod (including a rod having a circular,
rectangular, or square cross-section), an I-beam, or a tube. The
ceramic oxide pre-form may be elongated and have a substantially
constant cross-sectional area.
[0199] For some applications, a porous ceramic oxide pre-form
comprising substantially continuous, longitudinally aligned,
ceramic oxide fibers and porous ceramic oxide material, such as
ceramic oxide pre-form 10 in FIG. 1, can be used as an insert or as
a pre-form for reinforcing a metal matrix composite article. For
some uses of the ceramic oxide pre-form, it may be desirable to
prepare a second ceramic oxide pre-form having at least one
aperture to receive one or more ceramic oxide pre-forms according
to the pre-sent invention. For example, referring to FIG. 4,
ceramic oxide pre-form 40 is comprised of porous ceramic oxide
material 42 and has apertures 44A, 44B, 44C, 44D, and 44E, for
receiving ceramic oxide pre-form according to the present
invention. As shown, apertures 44A, 44B, 44C, 44D, and 44E are
designed to each receive a porous ceramic oxide pre-form 10 (see
FIG. 1). The second ceramic oxide pre-form can be made as described
above, as well as by techniques known in the art. In one preferred
embodiment according to the present invention, the Young's modulus
of the first porous material is greater than the Young's modulus of
the second porous material, and the Young's modulus of the
continuous fibers is greater than the Young's modulus of the first
porous material.
[0200] It is also within the scope of the present invention to form
the ceramic oxide material which secures the continuous fibers,
including providing aperture(s) therein for the continuous fibers,
then inserting the fibers into the aperture(s).
[0201] For additional details regarding the formation of ceramic
oxide pre-forms, see, for example, U.S. Pat. No. 5,394,930
(Kennerknecht) and Great Britain Pat. Doc. Nos. 2,182,970 A and B,
published May 28, 1987 and Sep. 14, 1988, respectively, the
disclosures of which are incorporated herein by reference. Other
techniques and other preferred conditions may be apparent those
skilled in the art after reviewing the disclosure herein.
[0202] A preferred use for ceramic oxide pre-forms according to the
present invention is as reinforcement in a metal matrix composite.
An example of a metal matrix composite article according to the
present invention made from a porous ceramic oxide pre-form
according to the present invention is shown in FIGS. 6A, 6B, 6C,
and 6D. Brake caliper 60 for a motor vehicle (e.g., a car, sports
utility vehicle, van, or truck, is comprised of metal (e.g.,
aluminum) 62 and ceramic oxide pre-form according to the present
invention 200. FIGS. 6D and 6E are cross-sectional views of FIG. 6B
along lines FF and GG, respectively. In FIG. 6D and 6E, ceramic
oxide pre-form 200 comprises porous ceramic oxide material 202 and
204 and substantially continuous, longitudinally aligned, ceramic
oxide fiber inserts 206 and 208 which include substantially
continuous, longitudinally aligned, ceramic oxide fibers, 68 and
67, respectively.
[0203] Another exemplary construction of a brake caliper
incorporating a porous ceramic oxide pre-form according to the
present invention, as well as a brake system for a motor vehicle
(e.g., a car, sports utility vehicle, van, or truck utilizing the
brake caliper, is shown in FIG. 5. An example of a disc brake for a
motor vehicle comprises a rotor; inner and outer brake pads
disposed on opposite sides of the rotor and movable into braking
engagement therewith; a piston for urging the inner brake pad
against the rotor; and the brake caliper comprising a body member
having a cylinder positioned on one side of the rotor and
containing the piston, an arm member positioned on the other side
of the rotor and supporting the outer brake pad, and a bridge
extending between the body member and the arm member across the
plane of the rotor. Referring again to FIG. 5, disc brake assembly
50 comprises brake caliper housing 51 formed of body member 52, arm
member 54, and bridge 56 connected at one end to body member 52 and
at other end to arm member 54. Body member 52 has a generally
cylindrical recess 53 therein which slideably receives piston 55 to
which is pressed inner brake pad 57. Inner face 46 of arm member 54
supports outer brake pad 59 which faces inner brake pad 57. Brake
rotor 47, connected to a wheel (not shown) of a vehicle, lies
between inner and outer brake pads 57, 59, respectively. Ceramic
oxide pre-form 10a', comprising continuous alpha alumina oxide
fibers 12a' and porous ceramic oxide material 14a', is located in
bridge 56.
[0204] Hydraulic, or other, actuation of piston 55 causes inner
brake pad 57 to be urged against one side of rotor 47 and, by
reactive force, causes caliper housing 51 to float, thereby
bringing outer brake pad 59 into engagement with the other side of
rotor 47, as is well known in the art.
[0205] Examples of disc brakes for using metal matrix composite
brake calipers incorporating ceramic oxide pre-forms according to
the present invention include fixed, floating and sliding types.
Additionally details regarding brake calipers and brake systems can
be found, for example, in U.S. Pat. Nos. 4,705,093 (Ogino) and
5,234,080 (Pantale), the disclosures of which are incorporated
herein by reference.
[0206] Other examples of metal matrix composite articles which can
be made from ceramic oxide pre-forms according to the present
invention include automotive components (e.g., automotive control
arms and automotive wrist pins) and gun components (such as barrel
support for rifled steel liner).
[0207] Typically, metal matrix composite articles made from ceramic
oxide pre-forms according to the present invention comprise, in the
region comprising the continuous ceramic fibers, in the range from
about 30 to about 45 percent (preferably about 35 to about 45
percent, more preferably, about 35 to about 40 percent) by volume
metal and in the range from about 70 to about 55 percent
(preferably about 65 to about 55 percent, more preferably, about 60
to about 65 percent) by volume continuous ceramic fibers, based on
the total volume of the region. Further, the region comprising the
porous ceramic oxide material which secures the continuous ceramic
fibers, typically comprises in the range from about 20 to about 95
percent (preferably about 60 to about 90 percent, more preferably,
about 80 to about 85 percent) by volume metal and in the range from
about 80 to about 5 percent (preferably about 60 to about 10
percent, more preferably, about 15 to about 5 percent) by volume
porous ceramic oxide material, based on the total volume of the
region.
[0208] The fiber and metal volume content of the metal matrix
composite in the continuous fiber region is generally governed by
the desired to produce a homogeneous composite without significant
movement of the continuous fibers during the metal infiltration. If
the fiber content is too low, it is more difficult to prevent or
minimize movement of the continuous fibers during the metal
infiltration. In the discontinuous fiber region the fiber and metal
volume content of the composite is, in general, governed by balance
between increased strength and stiffness versus decreased ductility
and machinability. The metal comprising the metal matrix composite
is preferably selected such that the matrix material does not
significantly react chemically with the ceramic oxide material,
(i.e., is relatively chemically inert with respect to the-metallic,
refractory material), particularly the continuous fibers, for
example, to eliminate the need to provide a protective coating on
the fiber exterior. Preferred metal matrix materials include
aluminum, zinc, tin, and alloys thereof (e.g., an alloy of aluminum
and copper). More preferably, the matrix material includes aluminum
and alloys thereof. For aluminum matrix materials, the matrix
preferably comprises at least 98 percent by weight aluminum, more
preferably, at least 99 percent by weight aluminum, even more
preferably, greater than 99.9 percent by weight aluminum, and most
preferably, greater than 99.95 percent by weight aluminum.
Preferred aluminum alloys include aluminum and copper such as an
alloy comprising at least about 98 percent by weight Al and up to
about 2 percent by weight Cu. Although higher purity metals tend to
be preferred for making higher tensile strength materials, less
pure forms of metals are also useful.
[0209] Suitable metals are commercially available. For example,
aluminum is available under the trade designation "SUPER PURE
ALUMINUM; 99.99% Al" from Alcoa of Pittsburgh, Pa.. Aluminum alloys
(e.g., Al-2 percent by weight Cu (0.03 percent by weight
impurities) can be obtained from Belmont Metals, New York, N.Y.
Other useful aluminum alloys include those commonly designated
"295," "319," "354," "355," "356," "357," "380," "295," "713,"and
"6061". Zinc and tin are available, for example, from Metal
Services, St. Paul, Minn. ("pure zinc"; 99.999% purity and "pure
tin"; 99.95% purity). Examples of tin alloys include 92 wt. % Sn-8
wt. % Al (which can be made, for example, by adding the aluminum to
a bath of molten tin at 550.degree. C. and permitting the mixture
to stand for 12 hours prior to use). Examples of tin alloys include
90.4 wt. % Zn-9.6 wt. % Al (which can be made, for example, by
adding the aluminum to a bath of molten zinc at 550.degree. C. and
permitting the mixture to stand for 12 hours prior to use).
[0210] The particular fibers, matrix material, and process steps
for making metal matrix composite articles are selected to provide
metal matrix composite article with the desired properties. For
example, the fibers and metal matrix materials are selected to be
sufficiently compatible with each other and the article fabrication
process in order to make the desired article. Additional details
regarding some preferred techniques for making aluminum and
aluminum alloy matrix composites are disclosed, for example, in
co-pending applications having U.S. Ser. Nos. 08/492,960, filed
Jun. 21, 1995 and 09/616,589, 09/616,593, and 09/616,594, filed
Jul. 14, 2000, and PCT application having publication No. WO
97/00976, published Jan. 9, 1997, the disclosures of which are
incorporated herein by reference.
[0211] Fabrication of metal matrix composites using ceramic oxide
pre-forms according to the present invention can be conducted using
techniques known in the art. Such fabrication includes infiltrating
the porous pre-form with molten metal. Typically, it is preferably
for the ceramic oxide pre-form(s) to be at an elevated temperature
(e.g., 750-800.degree. C.) when the molten metal is contacted with
it. Such techniques are known in the art and include heating the
pre-form before it is positioned in the cavity or mold that forms
the metal, or heating the cavity or mold after the ceramic oxide
pre-form has been positioned therein.
[0212] Additional details regarding making metal matrix composites
from ceramic oxide pre-forms can be found, for example, in U.S.
Pat. Nos. 4,705,093 (Ogino) and 5,234,080 (Pantale), and 5,394,093
(Kennerknecht), the disclosures of which are incorporated herein by
reference.
[0213] Further, for additional details regarding the formation of
ceramic oxide pre-forms, and metal matrix composite article made
from ceramic oxide pre-forms see, for example, provisional
applications having U.S. Serail Nos. 60/236,091 and 60/236,110,
filed Sep. 28, 2000 and applications having U.S. Ser. Nos.
______and _______filed the same date as the instant application
(Attorney Docket Nos. 55954US002 and 56046US007), the disclosures
of which are incorporated herein by reference.
[0214] In addition to being used as reinforcement in metal matrix
composites, ceramic oxide pre-forms according to the present
invention can also be useful as filters, thermal insulation, and
catalytic substrates.
EXAMPLE
[0215] This invention is further illustrated by the following
example, but the particular materials and amounts thereof recited
in these examples, as well as other conditions and details, should
not be construed to unduly limit this invention. Various
modifications and alterations of the invention will become apparent
to those skilled in the art. All parts and percentages are by
weight unless otherwise indicated.
EXAMPLE
[0216] A cast iron brake caliper was selected to be made from
aluminum reinforced with continuous alpha alumina fibers (available
under the trade designation "NEXTEL 610" from the 3M Company, St.
Paul, Minn.; 10,000 denier; Young's modulus of about 370 GPa;
average tensile strength of about 3 GPa). The aluminum brake
caliper was designed to have the same dimensions as the cast iron
brake caliper, as well as have at least the same bending stiffness
minimally in the area of the caliper bridge (i.e., that portion of
the caliper extending from the portions of the caliper that
straddle the brake rotor). To obtain optimum performance from the
composite construction that utilizes alpha alumina fibers having a
relatively high Young's modulus and the aluminum matrix that has a
relatively low Young's modulus, the caliper design incorporated a
porous ceramic oxide pre-form comprising discontinuous alumina
fibers (obtained under the trade designation "SAFFIL" from J&J
Dyson, Widness, UK) to provide a transition zone having an
intermediate modulus between the continuous alpha alumina fibers
and the unreinforced aluminum. That is, this ceramic region when
infiltrated with aluminum provided an intermediate modulus zone as
a result of a lower fiber density shorter fiber length, and lower
fiber Young's modulus than produced by the continuous fiber
reinforced zone. The ceramic region formed from the discontinuous
fiber also served to provide secure continuous fibers together, as
well as aided in mechanically supporting the fibers during the
formation of the aluminum brake caliper.
[0217] Finite element analysis (FEA) using a computer code obtained
under the trade designation "ANSYS" from Ansys, Inc., Canonsburg,
Pa., was used to model the caliper mathematically and identify
regions where placement of the continuous alpha alumina fibers
would have the highest impact on the bending stiffness of the
caliper. The caliper design started with the cast iron model to set
requirements for the geometry and bending stiffness. The software
was then used to run 19 iterations to determine the preferred
placement for the continuous fiber reinforcement, as well as to
minimize the amount of continuous fiber required. FIGS. 6A and 6B,
illustrate the upper and lower sides of the brake caliper pre-form,
and show the preferred locations for placement of the continuous
fiber reinforcement. The FEA modeling determined the volume content
of the continuous reinforcing fibers and the discontinuous fiber
("SAFFIL") region in the bridge area as well as the discontinuous
fiber ("SAFFIL") volume content in the transition modulus zones
needed to produce the desired modulus and strength in the aluminum
infiltrated composite construction based on the physical properties
of the alpha alumina fibers ("NEXTEL 610"), the discontinuous
alumina fibers ("SAFFIL"), and the aluminum matrix. The Young's
modulus used for calculations was 185 GPa for the discontinuous
alumina fibers ("SAFFIL") infiltrated with aluminum, and 70 GPa for
aluminum only. The final design provided a porous pre-form that was
sufficiently robust to facilitate handling without breaking while
having sufficient porosity to achieve good infiltration.
[0218] Six of the redesigned aluminum matrix composite brake
calipers were prepared as follows. Tows of 10,000 denier alpha
alumina fiber ("NEXTEL 610") with a filament diameter of 12
micrometers were saturated with water and wound on a square winder
drum to a thickness of about 3 mm and a width of about 12.5 cm. 570
tows were used for the upper area of the brake caliper (FIG. 6B)
and 691 tows were used in the lower area of the brake caliper (FIG.
6A). Each of the four faces of the aluminum drum were 33 cm in
length and 20 cm in width. The drum was removed from the winder and
placed in a freezer to freeze the water saturated tows. The frozen
fiber tows were die cut to provide the various continuous
reinforcing fiber configurations (i.e., ribbons) dictated by the
FEA (see FIGS. 6D and 6E). The frozen fiber ribbons were about 65
volume percent continuous fibers. The caliper design utilized two
pairs of fiber inserts, the first pair 106 positioned along the top
of the bridge and the second pair 108 positions along the bottom of
the bridge in the metal infiltrated caliper.
[0219] Porous blocks of discontinuous fibers was made for
Applicants by Thermal Ceramics Inc. The following was requested
from Thermal Ceramics. Pre-forms made of 15 volume percent
discontinuous fibers ("SAFFIL")/85 volume percent porosity. The
blocks are to be made using Thermal Ceramics standard process for
making commercially sold pre-forms made from discontinuous fibers
("SAFFIL").
[0220] The open porosity of the porous blocks obtained from Thermal
Ceramics Inc. was determined, based on ASTM C20-97, published Aug.
1998, the disclosure of which is incorporated herein, as follows.
Five 1.6 cm .times.1.6 cm .times.5.5 cm samples (although for
determining the open porosity other sizes and shapes can be used)
were cut from a pre-form. Dust was removed by cleaning the samples
with an air hose. The samples were dried in an oven at 110.degree.
C. (230.degree. F.) overnight (about 18 hrs.) and weighed. Then
samples were then boiled in deionized water for 3 hours, allowed to
cool in the water to room temperature (about 25.degree. C.), then
kept overnight (about 18 hours) in the water. The samples were
weighed suspended in water. The samples were removed from the
water, excess water blotted off with a paper towel, and the weight
of the water saturated sample determined. The samples were again
dried in an oven at 110.degree. C. (230.degree. F.) overnight
(about 18 hours) and weighed. The open porosity, which is the
volume of pores, was determined by subtracting the dry weigh of the
sample from the weight of the water saturated sample, and dividing
the result by the density of the saturating liquid. The density of
the saturating liquid, water was 1 gram/cm.sup.3.
[0221] A piece of the porous block ("SAFFIL"), about 8.3 cm by
about 19.1 cm by about 15.2 cm, was machined to provide the
configuration shown in FIGS. D. The porous pre-form 200 consisted
of two interlocking sections, schematically represented in FIGS. 6D
and 6E, that were slidingly engaged with one another. The frozen
die cut substantially continuous alpha alumina fibers were placed
in the recessed areas of the first pre-form section 202 and the
second pre-form section 204 slidingly engaged with the first
section, thereby locking the substantially continuous alpha alumina
fibers in place. The caliper design utilized two pairs of fiber
inserts, the first pair 206 positioned along the top of the bridge
and the second pair 208 positioned along the bottom of the bridge
in the metal infiltrated caliper.
[0222] A graphite block (obtained from Unocal Poco Graphite,
Decatur, Tex.) was machined into a two component mold (held
together by pins during casting) to provide a net shape mold for
the brake caliper. The ceramic oxide pre-form was placed in the
first component of the graphite mold in the contoured shape
designed for it. The second component of the mold was placed over
the pre-form and mated with the first component of the mold and the
mold pins inserted into the mold components to secure them
together.
[0223] The mold components were designed so that a gate was formed
at the top of the mold that allowed molten aluminum to flow into
the mold. The graphite mold was then placed in an oven and
maintained at about 100.degree. C. for about 24 hours to bake the
water out.
[0224] A pressure caster (obtained from Process Engineering
Technologies, Plaistow, N.H.) was used to cast the brake caliper.
The size of the pressure casting vessel was about 16.9 cm (inner
diameter) by 88.9 cm (in length). The mold was loaded into a
stainless steel can 17 cm in diameter and 76 cm in length. Aluminum
blocks (obtained under the trade designation "ALCOA 6061-T6" from
Alcoa Aluminum Co, Pittsburgh, Pa.), about 15.2 cm in diameter and
22.9 cm in length, were loaded into the can. A hold down rod was
used to hold the mold during pressure casting of the aluminum
metal. Two S thermocouples were attached to the exterior of the
pressure vessel, one on the top of the vessel and one approximately
11.4 cm above the graphite mold at the center of the aluminum
blocks to monitor the temperature during the casting process. The
thermocouples were contained in boron nitride coated stainless
steel tubes.
[0225] The casting chamber was sealed, evacuated to less than about
0.15 torr, and repressurized with argon to approximately 0.3 MPa
(40 psi) and the heating elements activated. On reaching
550.degree. C. the casting chamber was vented and then evacuated to
under 15 torr, and the chamber temperature raised to 710.degree. C.
(the mold temperature was above 670.degree. C. at this point). The
heaters were then turned off and the chamber repressurized to
approximately 8.9 MPa (1300 psi), causing the molten aluminum
(i.e., the heating caused the aluminum blocks to melt) to
infiltrate the porous pre-form in the graphite mold. The chamber
temperature and pressure were allowed to drop to approximately
500.degree. C. and 7.5 MPa (1100 psi), respectively, at which point
the chamber was vented and allowed to cool to approximately
200.degree. C. After the cooled vessel was removed from the
pressure caster, the graphite mold was recovered from the pressure
vessel, and the resulting aluminum matrix composite brake caliper
recovered from the graphite mold. Graphite residues from the mold
adhered to the brake caliper were removed using a conventional bead
blast process wherein glass beads in a high pressure air stream
carrier were impinged on the caliper. The glass bead blasting
equipment was obtained from Econoline Abrasive Products Co., Grand
Haven Mich.), and the beads from McMaster-Carr Supply Co.,
Elmhurst, Ill. The cleaned caliper was then heat-treated at
160.degree. C. for two hours and immediately cooled quenched in a
bucket of cold (about 18-20.degree. C.) tap water for about 5
minutes. The cooled caliper was then heat-treated at 540.degree. C.
for six hours and cooled to room temperature (about 25.degree. C.)
overnight. The resulting aluminum brake calipers each weighed about
52% less than the cast iron brake caliper.
[0226] A brake caliper prepared as described above was subjected to
a destructive burst test wherein the arm member 69 and body member
70 were subjected to hydraulic pressure until the caliper
failed.
[0227] Failure occurred in bridge member 70 along section line A-A
(Section line AA is not shown.) of FIG. 6A, substantially in the
transition area between bridge member 70 and arm member 69. The
fractured arm member 69 portion was subsequently transversely
sectioned into multiple sections relative to the fracture face
utilizing a sectioning saw (available from Struers, Inc., Westlake,
Ohio under the trade designation "DISCOTOM-2"). The surface of one
of the sections was polished, using standard scanning electron
microscopy (SEM) polishing techniques to a 0.05 micrometer
colloidal silica finish prior to obtaining the digitized SEM image
shown in FIG. 7, that shows that the ceramic oxide pre-form was
fully infiltrated with aluminum. Image analysis of the
discontinuous fibers ("SAFFIL")/aluminum region in this SEM image
using "SICON IMAGE for WINDOWS" software (the PC version of NIH
IMAGE that is a public domain image-processing program developed by
the Research Services Branch of the National Institutes of Health)
(available from Sicon Corp., Frederick, Md.). This image analysis
software, which uses density profiling functions based on pixtel
intensities from digitized SEM images to distinguish "SAFFIL"
fibers from the aluminum matrix, calculated the average "SAFFIL"
fiber volume fraction in the brake caliper as 17.6% (based on
"SAFFIL" fiber and aluminum content). Applying the same image
analysis protocol to the continuous aluminum oxide reinforced
region of the SEM, the average volume fraction of the continuous
alpha alumina fibers in the region in which they were present was
determined to be about 62% (based on continuous aluminum oxide
fiber and aluminum).
[0228] The fracture surface of the substantially continuous alpha
alumina fiber region of another section was coated with gold using
standard SEM sample preparation techniques prior to SEM imaging.
The digitized SEM images shown in FIG. 8 and FIG. 9, which is a
higher power magnification of the same region show this fracture
surfaces, illustrating fracture at the continuous alpha alumina
fiber/aluminum region 73 was "brittle fracture", whereas at the
discontinuous fibers ("SAFFIL")/aluminum region it was "ductile
fracture" as shown in FIG. 7.
[0229] A portion of the brake caliper was chemically analyzed using
an inductively coupled plasma (ICP) instrument (obtained under the
trade designation "PERKIN ELMER OPTIMA 3300 DV" from Perkin Elmer,
Norwalk, Conn.). The following elements and amounts, by weight,
were found: 96% Al, 0.33% Cr, 0.33% Cu, 1.2% Fe, 0.85% Mg, 0.11%
Mn, 0.13% Ni, 0.43% Si, 0.022% Ti, 0.052% Zn, and 0.0031% Zr. It is
noted that the ASTM standard for 6061 aluminum is G611A, by weight,
for non-Al elements: 0.04-35% Cr, 0.14-0.40% Cu, less than 0.70%
Fe, 0.8-1.2% Mg, 0.15% Mn, 0.4-0.8% Si, 0.15% Ti, and 0.25% Zr.
[0230] Various modifications and alterations of this invention will
become apparent to those skilled in the art without departing from
the scope and spirit of this invention, and it should be understood
that this invention is not to be unduly limited to the illustrative
embodiments set forth herein.
* * * * *