Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Reexamination Certificate
2000-03-02
2003-02-18
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
C428S223000, C428S337000, C264S068000, C264S332000
Reexamination Certificate
active
06521331
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 199 09 675.9, filed on Mar. 5, 1999, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a composite layer structure for use on structural components subject to a danger of erosion damage, including at least one fiber-reinforced synthetic material layer as a substrate, and a cover layer that includes at least one layer of metallic fibers and/or threads arranged adjacent to the substrate. The invention further relates to a method of manufacturing such a layer structure.
BACKGROUND INFORMATION
Layer structures or laminates embodied in the manner of fiber-reinforced composites combine the advantages of a low weight as well as a sufficient strength. Such layer structures based on fiber composite materials, however, have a relatively low resistance to erosive wear. For this reason, such fiber composite layer structures must be protected against erosion when they are used in applications in which they are subjected to fluid mechanical impingement, for example when they are used in the fluid flow path of a fluid flow machine, whereby abrasive particles carried in the fluid as well as varying thermal loading of the components would otherwise have a deleterious effect on the fiber composite layer structure. For this reason, various forms of erosion protection for such a layer structure are known in the art.
German Patent 42 08 842 discloses an erosion protection for use on helicopter rotor blades made of fiber-reinforced synthetic materials. Specifically, the erosion protection includes a metal sheet that is glued or adhesively bonded onto the critical areas of the rotor blade that are especially subjected to erosive wear, and the metal sheet is coated with particles of metallic compounds. In this context, it has been discovered that the reliability and durability of the adhesive bonding of the metal sheet onto the underlying fiber composite structure is problematic and inadequate in practice.
German Patent Publication DE 196 27 860 C1 discloses a blade for a fluid flow machine and a method for its manufacture, whereby in at least partial areas, layers of fiber-reinforced synthetic material are protected with a cover layer of metallic fibers or threads, and this cover layer is bonded or connected using the same synthetic resin binder as the layers of fiber-reinforced synthetic material. In this manner, the desired high adhesion of the cover layer onto the underlying layers of fiber-reinforced synthetic material is ensured. It is desirable, however, to further improve the mechanical properties and particularly the abrasive wear and delamination resistance as well as the erosion resistance of such a structure that is to be exposed to high loads.
German Patent Publication 196 42 983 A1 discloses a layered body or laminate with a substrate, as well as a method for manufacturing it. The layered body includes at least one fiber layer and a cover layer adjacent thereto, wherein the cover layer comprises metallic fibers or threads at least on the side thereof adjoining the fiber layer, and wherein the metallic fibers or threads are saturated or impregnated with a binder agent just as the fiber layer. In order to improve the erosion resistance, particles are embedded in the cover layer in the area of the metallic fibers or threads. Such a layered body, however, does not provide an adequate adhesion ability for various functional layers that are to be applied thereon without chemically or physically attacking the resin matrix. Thus, such a layered body must be further improved with regard to its adhesion ability, especially in combination with functional layers to be applied thereon.
German Patent Laying-Open Publication 19 00 477 discloses a composite part comprising a layer of fiber-reinforced synthetic material and a metallic carrier or substrate, on the outer surface of which a layer of metal fibers in the form of mats, fleeces or woven webs is welded or soldered. The metal fibers establish a form-locking connection with the synthetic material and are saturated or impregnated with a binder together with the synthetic material.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a layer structure of the above described general type, which is improved in such a manner so that the outer surface or skin thereof can be used as a functional outer surface and, for example, provides a good adhesive base for further functional layers applied thereon, whereby the underlying resin matrix is protected during the application as well as the removal of the functional layer or layers. Another object of the invention is to improve the adhesion between an outer metal skin and an underlying fiber-reinforced composite substrate by improving the continuous mutual penetration of a binder agent or matrix material throughout the substrate and the layer of metal fibers and/or threads of the cover layer. It is also an object of the invention to provide a method of manufacturing such a layer structure. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as are apparent from the present specification.
The above objects have been achieved in a composite layer structure according to the invention, comprising a substrate and a cover layer arranged on the substrate. The substrate comprises at least one layer of fiber-reinforced synthetic material including reinforcing fibers and a synthetic resin matrix material. The cover layer includes at least one layer of metallic fibers and/or threads adjacent to the layer of fiber-reinforced synthetic material of the substrate. The metallic fibers and/or threads are impregnated with a synthetic resin binder, and particularly the same synthetic resin binder of the fiber-reinforced synthetic material of the substrate. The cover layer further includes an outer skin comprising a metal sheet that forms an outer surface of the structure and that is connected to the underlying layer or layers of metallic fibers and/or threads at least at a partial area.
The layer of metallic fibers and/or threads has a variable porosity that increases in a direction from the metal sheet or skin toward the fiber-reinforced synthetic material of the substrate. Stated differently, the packing density of the metallic fibers and/or threads increases in a direction from the substrate toward the metal sheet or skin of the cover layer. The varying porosity (or alternatively the varying packing density) may be provided by a porosity (or density) gradient in a single layer of the metallic fibers and/or threads, or especially may be achieved by stacking or layering and laminating a plurality of successive layers of metallic fibers and/or threads, whereby the respective porosity of the successive layers varies layer-to-layer.
Throughout this specification, it should be understood that the terms “outer surface” or “outer skin” or the like can also refer to an exposed surface that is inwardly facing or directed, depending on the particular configuration and construction of the component at hand. For example, if the component is a hollow cylindrical pipe, an “outer surface” or “outer skin” can include the radially inwardly facing interior surface of the pipe wall.
Also, in this specification, the “porosity” of the layer of metallic fibers and/or threads refers to the proportional void space between the fibers and/or threads, especially before impregnation with the binder or matrix material. It should be understood that in the finished layer structure, the binder or matrix material may substantially or entirely fill the void spaces between the metallic fibers and/or threads, so that the finished structure has few or no remaining vacant “pores”, and a contrary implication should not be taken from the term “porosity”. The “packing density” is essentially the inverse of the “porosity” and refers to the volume proportion of the meta
Schober Michael
Schoenacher Reinhold
Sikorski Siegfried
Fasse W. F.
Fasse W. G.
Ferguson Lawrence
Kelly Cynthia H.
MTU Aero Engines GmbH
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