Patent Application
20140099484
The present invention relates generally to ceramics and more specifically to a ceramic matrix composite, a method of forming ceramic matrix composite, and a pre-preg composite ply.
In a laminate assembly of ceramic matrix composites, the melt infiltration process exposes the laminate to temperatures above 1000° F. The production process for making laminates for ceramic matrix composites limits the choice of materials that can be used in the inner laminate layers to non-organic material. Non-organic materials, such as ceramics, may be able to withstand high temperatures but are not as flexible as composite materials. Structural and thermal loading on the inner material may exceed the monolithic ceramic strain limits, especially if no reinforcement is available to redistribute stain loading. Monolithic ceramic fillers are prone to cracking due to excessive strains. Using unidirectional CMC tape, although it may resist cracking when placed under structural or thermal related strain increases cost.
Therefore, composite, a method making a composite, and a pre-preg composite ply that do not suffer from the above drawbacks is desirable in the art.
Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
According to an exemplary embodiment of the present disclosure, a composite is provided. The composite includes a first layer, a second layer, and a third layer. The first layer includes at least one ply of a unidirectional tape. The second layer is adjacent the first layer and the second layer includes at least one composite ply. The at least one composite ply of the second layer includes a thin continuous matrix ply sheet having a plurality of randomly oriented unidirectional tape segments thereon. The third layer is adjacent the second layer and the third layer includes at least one ply of the unidirectional tape. The composite provides about 15% to about 20% strength relative to a composite comprising all unidirectional plies and the composite has a bending length of 3 cm to 25 cm based on a Shirley stiffness test.
According to another exemplary embodiment of the present disclosure, a method of forming composite is provided. A first layer having a unidirectional orientation is provided and the first layer includes at least one ply of a unidirectional tape. A second layer having random fiber orientation is applied to the first layer, the second layer includes at least one composite ply, the composite ply comprising a thin continuous matrix ply sheet having a plurality of randomly oriented unidirectional tape segments thereon. A third layer having unidirectional orientation is applied to the second layer and the third layer includes at least one ply of a unidirectional tape. The first layer, the second layer, and the third layer are cured to form a composite. The composite provides about 15% to about 20% strength relative to a composite comprising all unidirectional plies and the ceramic matrix composite has a bending length of 3 cm to 25 cm based on a Shirley stiffness test.
According to another exemplary embodiment of the present disclosure, a pre-preg composite ply is provided. The pre-preg composite ply includes a thin continuous matrix ply sheet having a plurality of randomly oriented unidirectional tape segments thereon. The plurality of randomly oriented unidirectional tape segments occupy about 50% to about 99% of a surface area of the thin continuous matrix ply sheet.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
Provided is an economically viable method of forming a composite, a method making a composite, and a pre-preg composite ply that do not suffer from the drawbacks in the prior art. The present disclosure is generally applicable to composites including ceramic matrix composites (CMCs), polymer matrix composites (PMCs) and metal matrix composite (MMCs). One advantage of an embodiment of the present disclosure is that the composite construction provides strain loading to CMCs, PMCs, and MMCs. Yet another advantage of the present disclosure is a composite that withstands cracking under thermal strain. Another advantage of an embodiment of the present disclosure is reduced ply lifting. Yet another advantage of an embodiment of the present disclosure includes reduced voids in CMCs, PMCs, MMCs and components made using the CMCs, PMCs and MMCs. Another advantage is easier processing to form CMCs, PMCs, MMCs and components resulting in higher part yields. Yet another advantage of an embodiment of the present disclosure is a lower cost in forming CMCs, PMCs, MMCs and components formed therefrom.
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In one embodiment, unidirectional tape 300, is a CMC, and plurality of fibers 302 are ceramic fibers selected from, but not limited to, carbon, silicon-carbide (SiC), silicon-dioxide (SiO2), aluminum-oxide (Al2O3), mullite, zirconium dioxide (ZrO2), silicon carbide incorporating Ti, Zr or Al, silicon oxy-carbinde (SiOxCy), silicon boro-carbo-nitride (SiBxCyNz), and combinations thereof. In an alternative embodiment, unidirectional tape 300 is a PMC, and the plurality of fibers 302 include fibers suitable for reinforcement of polymers, selected from, but not limited to, carbon, aramid, glass, boron, poly-paraphenylene terephthalamide (KEVLAR®), and combinations thereof. In another embodiment, unidirectional tape 300 is a MMC, and plurality of fibers 302 are fibers or particles suitable for reinforcement of metal matrix composites, selected from, but not limited to, carbon, silicon carbide, boron carbide, diamond, transition metal carbides, nitrides and silicides, metallic wires, and combinations thereof.
Unidirectional tape 300 is formed using known manufacturing methods and includes a pre-preg matrix that holds fibers 302 in place. Suitable examples of pre-preg matrix, include, but are not limited to, resins or polymers that are thermoplastic or thermosetting. For example, CMC based unidirectional tapes are constructed from oxide based fibers and a binding mixture of an oxide based matrices and an organic binder, the organic binder, includes, but is not limited to, epoxy, polyurethane, or polyvinyl acetate (PVA). Another example includes, CMC based unidirectional tapes constructed from non-oxide or silicon carbide fibers and a binding mixture of non-oxide based matrices and an organic binder that are wound circumferentially around a drum wall or linearly aligned on a plane to form uniformly spaced fibers intermixed with a matrix slurry with forms a unidirectional tape.
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In building composite 100, the same chemistry is used, only CMC, only PMC, or only MMC, the underlying composite chemistries are not mixed to make composite 100. Composite ply 400 is constructed by assembling a set of randomly aligned mini-strips or unidirectional tape segments 404 on top of a thin matrix layer. Thickness of matrix layer is about 0.0762 millimeters (0.003 inches) to about 0.3048 millimeters (0.012 inches). The matrix layer is used to create a surface of continuity that unidirectional tape segments 404 are applied to, thereby building up composite ply 400. The disclosure provides up to provide 100 percent coverage of the base matrix layer with at least one and up to three overlaying/overlapping unidirectional tape segments 404, each additional unidirectional tape segment 404 filling in the exposed matrix regions and being shifted or reoriented if the stacking exceeds more than three layers of unidirectional tap segments 404. After placing unidirectional tape segments 404 in matrix, the resulting assembly is then placed under pressure to compact the assembly of unidirectional tape segments into a dense ply stack that will act as a uniform ply at the micro level for macro based laminate assembly and the final composite component construction, thereby forming composite ply 400.
Unidirectional tape segments 404 are formed from left over or cut-up unidirectional ceramic composite tapes. Randomly oriented unidirectional tape segments 404 occupy about 50% to about 99%, or alternatively about 60 % to about 90 %, or alternatively about 65% to about 85% of a surface area of the thin continuous matrix ply sheet 402. Randomly oriented unidirectional tape segments 404 have a length of about 25.4 millimeters (1 inch) to about 508.0 millimeters (20 inches), or alternatively about 50 millimeters to about 400 millimeters, or alternatively about 75 millimeters to about 300 millimeters. Randomly oriented unidirectional tape segments 404 have a width of about 25.4 millimeters (1 inch) to about 203.2 millimeters (8 inches), or alternatively about 30 millimeters to about 190 millimeters, or alternatively about 50 millimeters to about 150 millimeters.
Comparing composite ply 400 of the present disclosure to random orientation fiber tape sheets, composite ply 400 is easier to visually inspect and place when forming CMCs, PMCs, or MMCs. Additionally, composite ply 400 produces fewer voids because it has a bending length of 3 cm to 25 cm based on a Shirley stiffness test, which allows composite ply 400 to conform to complex surface of components compared to random orientation fiber sheets. As used herein, “bending stiffness” is a special property of fabric or fibers and the bending stiffness is the tendency of fabric to keep standing without any support. Bending stiffness is a key factor in the study of handle and drape of fabric and unidirectional ply laminates.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
This invention was made with Government support under contract number DE-FC26-05NT42643 awarded by the Department of Energy. The Government has certain rights in the invention.
