Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Composite article making
Reexamination Certificate
1998-10-26
2001-05-15
Yoon, Tae (Department: 1714)
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Composite article making
C264S043000, C264S045300, C523S149000, C523S216000, C524S401000
Reexamination Certificate
active
06231793
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to ceramic matrix composite components and more particularly to “green-state” discontinuous fiber ceramic matrix composite components made from a polymer-derived ceramic precursor resin and a method of rapidly manufacturing these components.
BACKGROUND OF THE INVENTION
Ceramic matrix composite (CMC) is a useful material for making components used in many applications including aircraft and automobiles. Moreover, when the CMC is reinforced with fiber the resulting material can be used to make components that are resistant to extremely high temperatures and surprisingly strong and durable. For example, fiber-reinforced CMC can be used to make components such as piston rings, catalytic converters, exhaust manifolds, brake rotors and brake pads.
A CMC component is typically manufactured by mixing a resin with fibers and filler powders to form a mixture. This mixture is then loaded into a mold in the shape of the desired component. Next, the mixture is cured by raising the temperature of the mold and the mixture to the cure temperature of the resin. Curing occurs when the mixture has set enough such that the component is formed.
The newly formed component is then ejected from the mold. At this stage the component is in a “green-state.” This means that it has not been pyrolized, or raised to a high enough temperature whereby a ceramic is formed. Thus, in its “green-state” the component is a polymer composite that has structural integrity and can be handled but still needs to undergo pyrolysis before the component can be used.
Generally, this fabrication process takes a substantial amount of time. This is partly because resins, especially polymer-derived ceramic precursor resins, tend to cure rapidly when raised to their cure temperature. Consequently, the mold and the mixture must be cool when the mixture is loaded into the mold to ensure that the resin does not cure prior to closing the mold. Instead, the cool mold and the mixture must be heated to the cure temperature. Typically, this heating takes in excess of one hour due to the thermal mass of the forming tool.
One problem with this manufacturing process for CMC components is that it takes a substantial amount of time to manufacture a CMC component. This relatively long manufacturing time of CMC components is one reason why CMC components have difficulty competing in the marketplace with similar components made from traditional materials. This is despite the fact that CMC components are generally lighter, more durable and more efficient traditional materials in widespread use. For example, a traditional brake pad can be manufactured in a matter of seconds. Conversely, a CMC brake pad, which is more resistant to high temperatures and more durable, takes in excess of one hour to manufacture.
Another problem with the manufacturing process of CMC components is that the large discrepancy between manufacturing times has the effect of drastically increasing the cost of a CMC brake pad compared to a traditional brake pad. This, in turn, has hindered the widespread use of CMC components in favor of components made from traditional materials.
Therefore, what is needed is a method of rapidly manufacturing a CMC component that yields a CMC component that retains its resistance to high temperature, strength and durability. Moreover, this method of rapid manufacture would in turn decrease the production costs of the CMC component and would allow the CMC component to compete in the marketplace with similar components made from traditional materials. Furthermore, what is also needed is a method for rapidly manufacturing CMC components that yields a mixture which has a long shelf life. This would permit preparation of the mixture well ahead of production and alleviate slowdowns in manufacturing.
Whatever the merits of the above-mentioned methods of manufacturing CMC components, they do not achieve the benefits of the present invention.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art as described above and other limitations that will become apparent upon reading and understanding the present specification, the present invention includes “green-state” CMC components made from a polymer-derived ceramic precursor resin and a method of rapidly manufacturing these components.
The method of the present invention permits “green-state” CMC components to be manufactured rapidly enough to drastically reduce the production time of the components. This generally leads to decreased production costs. Furthermore, this method yields rapidly manufactured “green-state” CMC components that have at least the temperature resistance, strength and durability of CMC components manufactured by much slower procedures. In addition, the present invention includes a mixture for making rapidly manufactured “green-state” CMC components whereby the mixture can be stored for an extended period of time.
In a preferred embodiment, the present invention includes a method for rapidly manufacturing a “green-state” CMC component. Specifically, a mixture is created by mixing together a polymer-derived ceramic precursor resin, a catalyst, a discontinuous fiber and a filler material. The resultant mixture then is dried and loaded into a preheated mold. The mixture is then cured in the mold until the “green-state” component is formed. Next, the component is ejected from the mold and reinfiltrated with a resin to fill any porosity in the component.
In some embodiments, the mixture includes only a polymer-derived ceramic precursor resin, a catalyst, and fiber. Furthermore, some embodiments omit the step of drying the mixture and the step of reinfiltrating the component with a resin.
The present invention also includes a “green-state” CMC component and the resin/catalyst mixture prepared by using the above methods.
Other aspects and advantages of the present invention as well as a more complete understanding thereof will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. Moreover, it is intended that the scope of the invention be limited by the claims and not the preceding summary or the following detailed description.
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Coonce William Eugene
Strasser Thomas Edward
Anderson Terry J.
Hoch, Jr. Karl J.
Yoon Tae
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