초록 ▼

A metal matrix composite lightweight compressor airfoil. The airfoil comprises a braided fabric embedded in a lightweight aluminum-lithium alloy. The airfoils are fabricated by forming a plurality of fiber tows by twisting filaments or fibers. The tows are then braided into a fabric. The fabric may

A metal matrix composite lightweight compressor airfoil. The airfoil comprises a braided fabric embedded in a lightweight aluminum-lithium alloy. The airfoils are fabricated by forming a plurality of fiber tows by twisting filaments or fibers. The tows are then braided into a fabric. The fabric may be impregnated with an optional fugitive polymer that temporarily occupies interstices of the fabric to facilitate handling of the pre-formed braided fabric, but which is subsequently removed. The airfoil may then be formed as a MMC by one of two separate methods. In the first method, aluminum-lithium alloy is pressure augmented casting into a die that includes a preform of fabric impregnated with fugitive polymer. In a second method, a preform is formed using a tool and mandrel by impregnating fabric with aluminum-lithium alloy. Then aluminum-lithium alloy is pressure augmented cast into a die that includes the alloy-impregnated preform.

대표청구항 ▼

1. A composite lightweight compressor airfoil for a turbomachine, comprising: a near surface braided fabric, wherein the braided fabric further comprises a fabric formed from a plurality of twisted fiber tows braided and oriented in a direction so that each of the plurality of tows extend substantia

1. A composite lightweight compressor airfoil for a turbomachine, comprising: a near surface braided fabric, wherein the braided fabric further comprises a fabric formed from a plurality of twisted fiber tows braided and oriented in a direction so that each of the plurality of tows extend substantially parallel to one another and substantially parallel to an axis of the airfoil to a principal direction of the airfoil, wherein the principal direction extends from a first end toward a second end of the airfoil;a core of an aluminum lithium alloy;an outer surface of the aluminum lithium alloy;wherein the aluminum-lithium alloy penetrates interstices of the fabric and the plurality of twisted fiber tows so that the aluminum-lithium alloy is substantially continuous; andwherein the tows are stuffer tows further comprising fiber having a high strength and a low elastic modulus, forming up to about 15% of the volume of the fabric. 2. The composite airfoil of claim 1 wherein the tows are included in a tri-axial braid pattern. 3. The composite airfoil of claim 1 wherein the tows are softening strips further comprising fiber having a high elastic modulus, forming up to about 15% of the volume of the fabric. 4. The composite airfoil of claim 3 wherein the softening strips further comprise fiber selected from the group consisting of carbon fiber, fiberglass fiber, nylon fiber, aramid fiber and combinations thereof. 5. The composite airfoil of claim 1 wherein the aluminum lithium alloy further comprises, in weight percent, about 2.5-3.5% Li, about 0.6-2.5% Cu, about 0.3-1.0% Mg, about 0.1-0.5% Zr, up to about 0.08% Fe, up to about 0.01% Si, up to about 0.03% Ti, the balance Al and incidental impurities. 6. The composite airfoil of claim 1 wherein the stuffer tows further comprise fiber selected from the group consisting of carbon fibers, oxide ceramic fibers, non-oxide ceramic fibers, aramid fibers and combinations thereof. 7. A method for manufacturing a composite lightweight compressor airfoil for a turbomachine, comprising the steps of: forming a plurality of twisted fiber tows;forming a braided fabric from the plurality of twisted fiber tows, the braided fabric having interstices between the tows;providing a female tool and a mandrel in a shape of the airfoil, the tool having faces forming a cavity in the shape of the airfoil, and the mandrel having a near net shape of the airfoil;sandwiching the braided fabric between foils of aluminum-lithium alloy and inserting the sandwich of foil and fabric into the tool;inserting the mandrel into the tool so that the sandwich of foil and fabric fills the cavity and closing the tool;while maintaining a non-oxidizing atmosphere, heating the tool to a superheat temperature above the melting point of the alloy and hot pressing the tool while maintaining the superheat temperature and pressure for a time sufficient to consolidate and infiltrate aluminum lithium alloy into the braided fabric tows, creating a fiber-reinforced metal matrix preform;placing the fiber-reinforced metal matrix preform into a die having a net shape of the airfoil;while maintaining a non-oxidizing atmosphere, pressure-augmenting casting molten aluminum-lithium alloy into the die and against the metal matrix preform to form a metal matrix composite airfoil having an integral aluminum-lithium alloy core and an aluminum-lithium alloy dovetail attachment; andremoving the airfoil from the die after cooling. 8. The method of claim 7 wherein the metal alloy further comprises, in weight percent, about 2.5-3.5% Li, about 0.6-2.5% Cu, about 0.3-1.0% Mg, about 0.1-0.5% Zr, up to about 0.08% Fe, up to about 0.01% Si, up to about 0.03% Ti, the balance Al and incidental impurities. 9. The method of claim 7 wherein the non-oxidizing atmosphere is a vacuum. 10. The method of claim 7 wherein the non-oxidizing atmosphere is an atmosphere selected from the group consisting of an inert gas and nitrogen. 11. The method of claim 7 wherein hot pressing to a superheat temperature includes heating to a temperature about 25-50° C. (45-90° F.) above the melting point of the metal alloy. 12. The method of claim 7 wherein the step of forming the braided fabric additionally includes providing with the braided fabric additional tows selected from the group consisting of stuffer tows and softening strips, the additional tows being substantially parallel to the axis of the airfoil so that the additional tows extend generally in a radial direction with respect to the airfoil, extending from an airfoil tip to an opposite side of the airfoil. 13. A method for manufacturing a composite lightweight compressor airfoil for a turbomachine, comprising the steps of: forming a plurality of twisted fiber tows;forming a braided fabric from the plurality of twisted fiber tows into an airfoil shape, the braided fabric having interstices between the plurality of twisted fiber tows;optionally, impregnating the braided fabric with a fugitive polymer binder to form a preform;providing a die, the die having die faces forming a cavity in the shape of the airfoil, the die producing a near net shape airfoil;inserting the braided fabric into the die, the tows forming the fabric being at an angle to an axis of the airfoil, the axis extending in a radial direction from an airfoil tip to an opposite side of the airfoil;placing the die in a non-oxidizing atmosphere;preheating the die to a first temperature;while maintaining the non-oxidizing atmosphere, pressure augmented casting a metal alloy into the die using a piston to apply a first pressure;then, after the die is filled with molten metal alloy, using the piston to apply a second pressure to infiltrate the interstices of the preform and to penetrate the preform and to volatilize the optional binder, the second metal pressure being greater than the first metal pressure;while maintaining the non-oxidizing atmosphere, cooling the die to form the airfoil, the airfoil having an outer metal alloy surface and a metal alloy core; andremoving the airfoil from the furnace. 14. The method of claim 13 wherein the metal alloy further comprises, in weight percent, about 2.5-3.5% Li, about 0.6-2.5% Cu, about 0.3-1.0% Mg, about 0.1-0.5% Zr, up to about 0.08% Fe, up to about 0.01% Si, up to about 0.03% Ti, the balance Al and incidental impurities. 15. The method of claim 13 further wherein the step of forming the braided fabric into the airfoil shape additionally includes adding stuffer tows to the braided fabric, the stuffer tows being substantially parallel to the axis of the airfoil so that the stuffer tows extend generally in a radial direction with respect to the airfoil tip, from the airfoil tip to the opposite side of the airfoil.