GLASS FIBER METAL MATRIX COMPOSITES Field ofthe Invention [0001] The invention relates to fiber reinforced metal matrix composites. More particularly, the invention relates to glass fiber reinforced metal matrix composites and methods for making the same. ground of the Invention [0002] The next generation of high technology materials for use in aerospace and aircraft applications will need to possess high temperature capability combined with high stiffness and strength. Plates and shells fabricated from laminated metal matrix composites, as opposed to monolithic materials, provide the potential for meeting these requirements and thereby significantly advancing the designer's ability to meet the required elevated temperature and structural strength and stiffness specifications while minimizing weight.

[0003] Efforts to meet these challenges have produced metal matrix composites having relatively long continuous lengths of a reinforcing fibrous material, for example, a ceramic such as aluminum oxide, in a matrix of a metal such as aluminum. However, these composites are often expensive because of the costs of the fibers. In order to make metal matrix composites to be more widely accessible to various markets, there is a need to make metal matrix composites more cost effective.

Summarv of the Invention [0004] The present invention is directed to using glass fibers as the reinforcing material in fiber reinforced metal matrix composites. The invention includes a metal matrix composite having a metal matrix body portion and glass fibers distributed in the metal matrix body portion. The glass fibers may be infiltrated by the metal

matrix. Additionally, the glass fibers may be distributed substantially uniformly in the metal matrix. Still further, at least a portion of the glass fibers may be continuous glass fibers. The glass fibers may be glass fibers, S-glass, E-glass fibers, soda-lime- silica fibers, basalt fibers, quartz fibers, or other similar glassy fibers. Further, the glass fibers may be in the form of woven and/or braided glass fibers, or non-woven glass fibers. The metal matrix is not particularly limited. The metal matrix may include, but is not limited to aluminum, aluminum with 12% silicon, aluminum with 2% copper, and other alloys of aluminum, zinc, and zinc alloys. The invention also includes a metal matrix composite having a plurality of continuous glass fibers substantially encapsulated in a metal matrix comprising aluminum.

[0005] The invention also includes a method for producing a glass fiber reinforced metal matrix composite. The method includes the steps of providing a plurality of glass fibers and embedding the plurality of glass fibers in a metal matrix.

The step of embedding may include infiltrating the glass fibers with the metal matrix.

The plurality of glass fibers may be supplied in a multifiber tow. The method may also include the step of pulling the glass fibers through a partially or fully molten metal bath.

BriefDescription ofthe Drawings [0006] Figure 1 is a diagrammatic view of a glass fiber reinforced metal matrix composite in accordance with an embodiment of the invention.

[0007] Figure 2 is a diagrammatic view of an apparatus for making a glass fiber reinforced metal matrix composite in accordance with an embodiment of the invention.

Detailed Description of Embodiments of the Invention [0008] With reference now to Figure 1, there is shown a glass fiber reinforced metal matrix composite in accordance with an embodiment of the invention designated with the general reference numeral 100. The glass fiber reinforced metal matrix composite includes a plurality of glass fibers, representative glass fibers being represented by the reference numeral 110. The glass fibers 110 are embedded in a metal matrix 120. The glass fibers 110 may be substantially uniformly distributed in the metal matrix 120. Further, the glass fibers 110 may be continuous lengths of fibers extending through the composite 100. The glass fibers 110 may be infiltrated with the matrix metal such that there is substantially no void space between the glass fibers and the metal matrix 120.

[0009] The shape of the glass fiber reinforced metal matrix composite 100 is not particularly limited and may have any number of cross-sectional shapes. Such shapes may include, but are not limited to, circular, elliptical, oval, square, rectangular, triangular, polygonal, irregular polygonal, and the like.

[0010] Generally, the glass fiber 110 may be any type of glass fiber that can maintain some characteristics of a fiber when exposed to the process temperatures and contact with the selected metal. Preferably, the glass fiber improves the mechanical and/or physical properties of the resulting metal matrix composite compared to those of the matrix metal alone. Fibers, depending on the selected matrix metal, may include, but are not limited to, glass fibers, S-glass fibers, E-glass fibers, soda-lime- silica fibers, basalt fibers, quartz fibers, other similar glassy fibers. The diameter of the glass fibers is not particularly limited provided that they may be encapsulated in

the metal matrix. In certain embodiments, the diameter of the glass fibers may range from about 5am to about 30um.

[0011] The matrix metal 120 is not particularly limited, as long as the matrix metal is capable of embedding the selected glass fibers such that the glass fibers retain some characteristic of a fiber during the formation of the composite. Matrix metals, depending on the selected fibers, may include, but are not limited to, aluminum, aluminum with 12% silicon, aluminum with 2% copper, zinc, and zinc alloys including alloys and combinations thereof, as well as other metals and metal alloys.

In certain embodiments, the matrix metal becomes fluid enough for processing at temperatures below those temperatures at which the selected glass fibers are too soft for processing.

[0012] A method for making a glass fiber reinforced metal matrix composite will be described. Glass fibers are provided for embedding in a metal matrix composite.

The glass fibers may be in the form of continuous lengths of individual fibers.

Further the glass fibers may be a plurality of fibers in the form of continuous lengths of tows, yarns, or the like. Further, the glass fibers may be in the form of a woven material where one or more glass fibers are woven in an arrangement to form a fabric like structure. Additionally, the glass fiber may be in the form of a non-woven material. Such non-woven material may include a sheet, mat, batting, and the like.

[0013] With reference now to Figure 2, there is shown an apparatus for forming a glass fiber reinforced metal matrix composite, the apparatus being represented by the reference numeral 200. The apparatus 200 may be used to form continuous lengths of composite material through an infiltration process. As shown in Figure 2, glass fibers 210 are provided and submersed in a metal bath 220 containing the metal will become

the metal matrix. The metal bath is typically contained in a furnace 222 sufficient to maintain the temperature of the metal above its softening point. The submersed glass fibers 210 may be infiltrated with the metal from the metal bath 220 by passing the glass fibers near a sonic waveguide 230. The waveguide 230 directs sonic energy from a sonic processor 235 to the fibers and the metal bath surrounding the fibers.

The sonic processor 235 may provide ultrasonic energy. The metal wets the fibers so that each individual fiber of the fiber bundle is substantially surrounded or encapsulated by the metal, preferably leaving no or minimal void spaces and forms a softened metal matrix infiltrated glass fiber bundle 240.

[0014] The softened metal matrix infiltrated glass fiber bundle 240 may then be pulled through an optional shaping die 250 to shape the infiltrated glass fiber bundle and control the fiber density in the infiltrated fiber bundle. In certain embodiments, the softened metal infiltrated glass fiber bundles may be continuously drawn through the shaping die 250. The fibers may be drawn through the apparatus 200 manually or by mechanically means. The shaping die 250 provides a glass fiber reinforced metal matrix composite having a desired cross-sectional shape. Once the matrix metal has sufficiently solidified, the glass fiber reinforced metal matrix composite may be taken up on a reel, spool, or provided in continuous lengths.

[0015] Without intending to limit the scope of the invention the following example is provided to illustrate certain embodiments of the invention.

Example [0016] High strength S-2 glass fibers listed in Table I were infiltrated with a metal matrix by passing the glass fibers into an aluminum bath, passing the fibers near an ultrasonic waveguide, and removing the infiltrated fibers from the aluminum bath.

The glass fibers were supplied from Advanced Glassfiber Yarns.

[0017] TABLE I. Glass Fibers ID Loss on Yield Tex Denier Filament Filament Ignition (LOI) (yds/lb) Count Diameter (%) (Um) 721B-AA-750 0.65 750 660 5940 1730 14 365-225-TRL288 0.7 225 2200 19,800 1730 23 933-AA-375 0.23 375 1325 11,880 16,320 9 933-AA-750 0.23 750 660 5940 8160 9 463-AA-750 1.0 750 660 5940 8160 9 449-AA-250 0.65 250 1980 17820 24, 480 9

[0018] A pure aluminum bath and an aluminum with 12% silicon bath were used in the process. The aluminum bath temperature was held constant at 1350°C. The ultrasonic probe positioned was varied between 0.125 and 0.250 inches from the glass fibers. The ultrasonic amplitude was varied between settings of 30 and 60 and the processing speed was varied between 36 inches per minute and 294 inches per minute.

Under certain conditions, ultrasonic amplitudes below 30 did not achieve infiltration and amplitudes above 60 began to damage the fibers. All fibers produced a glass fiber reinforced metal matrix composite. Micrographs showed good infiltration of the glass fibers. Samples produced ultimate tensile strengths of 46.8 ksi and an elastic modulus of 8. 8 Msi.

[0019] The above examples are not to be considered limiting and are only illustrative of a few of the many types of composites that may be prepared. The present invention may be varied in many ways without departing form the scope of the invention and is only limited by the following claims.