Patent Application
20110123823
The subject matter disclosed herein generally relates to graphite fibers joined to a substrate material. More particularly, the subject matter disclosed herein relates to graphite fiber and substrate structures for heat exchanger systems.
Fibercore graphite is a material utilized, for example, in heat exchange applications. The material comprises an array of graphite fibers with a filler of a wax material therebetween. Large pieces of the fibercore are typically bonded to a desired surface, for example, an aluminum component, via an adhesive. Thermal mismatch issues are common between bulk graphite and graphite foam when joined to a metallic substrate. Fibercore graphite is not a monolithic structure and as such accommodates the thermal mismatch by translating with the substrate during thermal processing. Further, the thickness of the fibercore, which is relative to a length of the graphite fibers in the fibercore, is limited due to capability of graphite fiber production. The relatively thin fibercore material is fragile and is subject to breakage and damage when handling and/or shaping by machining or the like into desired shapes. The art would well receive a more robust structure of fibercore, which is not as sensitive to handling and/or other processing and which improves the thermal mismatch issues that exist in current structures.
According to one aspect of the invention, a method of assembling a metallic-graphite structure includes arranging one or more layers of graphite fiber material and locating at least one metallic sheet adjacent to the one or more layers of graphite fiber material. The at least one metallic sheet is secured to the one or more layers of graphite fiber material via brazing.
According to another aspect of the invention, a metallic-graphite structure includes one or more layers of graphite fiber material and at least one metallic sheet located adjacent to the one or more layers of graphite fiber material. The at least one metallic sheet is secured to the one or more layers of graphite fiber material via brazing.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Shown in
A layer of braze filler 18, for example a BNi-2 filler, is utilized between the fibercore graphite layers 12 to join the layers of fibercore graphite 12. In this embodiment, a length of the graphic fibers 14 of the fibercore graphite layer 12 extends substantially from one layer of filler 18 to another layer of filler 18. In some embodiments, at each upper and lower end 20 of the assembly, a metallic sheet 22, which may be a nickel or other suitable material, is brazed to the filler 22. Additionally, in some embodiments, a metallic sheet 22 may be disposed between graphite layers 12 in the assembly. In embodiments where more than one fibercore graphite layer 12 is utilized, brazing of all layers 12 together may be accomplished in a single step. While the embodiments illustrated utilize a nickel metallic sheet 22 and a BNi-2 filler 18, in some embodiments, the metallic sheet 22 may be other nickel-based brazing alloys or of an alloy of titanium and titanium-containing fillers 18 may be utilized therewith.
The sandwich structure is brazed to a substrate 24 formed from, for example, an aluminum material. Alternatively, the substrate 24 may be formed from other materials, such as stainless steel or nickel alloy where increased fluid compatibility is required, for example in a corrosive fluids environment. Brazing of the metallic sheet 22 to the substrate 24 is accomplished via an aluminum braze alloy 26 disposed between the metallic sheet 22 and the substrate 24. In some embodiments, as shown in
In some embodiments, as shown in
The joining of ends of graphite fibers 14 to a metallic sheet 22 into the sandwich structure results in an effectively longer graphite fiber 14 length. The taller fibercore height may be packaged into a more cubic structure (vs. a flat plate) which requires less external support during vibrational loading. Further, the metallic sheet 22/fibercore graphite layer 12 structure is less susceptible to handling damage and can be shaped by a variety of processes, for example, electrical discharge machining (EDM), to produce desired shapes to close tolerances.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
