The present invention is generally related to ceramic matrix composite (CMC) structures for use in a high temperature combustion environment, and, more particularly, to tooling arrangements and/or techniques for increasing interlaminar shear strength of the CMC structure.
Components made from CMC materials permit higher operating temperatures than do metal alloy materials due to the properties of ceramic materials. One example of a high temperature operational environment occurs in state of the art turbine engine applications. The high temperature capability results in reduced cooling requirements, which results in higher power, greater efficiency, and/or reduced emissions from the engine. Conventional CMC components formed from two-dimensional fiber arrangements have sufficient in-plane strength, but may lack sufficient shear strength to carry interlaminar shear loads.
The invention is explained in the following description in view of the drawings that show:
In accordance with one or more embodiments of the present invention, structural arrangements for fabricating a ceramic matrix composite (CMC) structure are described herein. In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation.
Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. Lastly, the terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated.
The inventors of the present invention propose structural arrangements and techniques designed to increase interlaminar shear strength of a CMC structure. Aspects of the present invention propose tooling arrangements and/or methodology innovatively adapted to introduce an out-of-plane fiber displacement arranged to increase the interlaminar shear strength of the CMC structure.
As shown in
As a result of the urging (e.g., pressure force) applied by the surfaces of the tool against the top and bottom surfaces of the CMC structure, the asperities 30 form a plurality of surface recesses 32 on the surfaces 20 and 21 of the CMC structure. As shown in
For simplicity of illustration just the bottom surface of the tool is shown in the isometric view shown in
In a practical embodiment, the urging force may correspond to a laminate consolidation pressure normally applied during a laminate (e.g., inter-layer) consolidation stage—usually a pressure that in one example embodiment may range from approximately 10 psi to approximately 200 psi. Furthermore, such consolidation normally may be applied by standard tooling (e.g., hard plates) on each side of the laminate. Thus, it is contemplated that a tooling arrangement embodying aspects of the present invention may be integrated into the standard tooling used for consolidation. Thus it is believed that aspects of the present invention do not entail a post-consolidation process step or adding extra manufacturing steps. It will be appreciated that the values of the consolidation pressure may be adjusted based on the needs of a given application, e.g., size and/or pattern of features.
Example variations in the tooling arrangement may include the distribution, spacing, pattern, and depth of the recesses or tooling asperity features. Although example penetration depths explored so far (e.g., ranging from approximately 0.5 mm to approximately 5 mm) and spacing (e.g., ranging from approximately 3 mm to approximately 15 mm) have proven effective, it is contemplated that tooling arrangements that may include pattern variations and/or random depth variation may further strengthen the resistance against interlaminar shear.
As shown in
In another example embodiment, distance L (i.e., spacing between adjacent surface recesses) may be based on thickness t of the structure. An example range for distance spacing L may be from 150 to 500 percent of thickness t of the CMC structure. The distance L may be further based on a depth d of the surface recesses. In this case, an example range for distance L may be from 300 to 1000 percent of the depth d of the adjacent surface recesses.
In the case of discrete asperities, various types of asperity shapes are contemplated. For example, pyramidal-shapes as shown in
It will be appreciated that in accordance with aspects of the present invention, the urging (e.g., pressure force) applied by the surfaces of the tool against the top and bottom surfaces of the CMC structure is arranged to gently and generally uniformly distort the plies (e.g., bulk sinusoidal distortion) throughout the thickness of the CMC structure—thereby reducing or avoiding any potential breakage or cutting damage to fibers and any consequent reduction in the in-plane (fiber dominated) behavior. Thus, it will be appreciated, that this urging is different than what would be required if one desired to introduce localized fiber breakage and/or cutting for improving surface coating adhesion, for example.
While various embodiments of the present invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
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Number | Date | Country | |
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20100291348 A1 | Nov 2010 | US |