The present disclosure is directed to a method of forming a composite component. The method includes laying one or more layers of uncured composite material onto a mandrel. The mandrel which includes a plurality of conductive media dispersed in a thermoplastic material. An electric current is supplied to the mandrel to resistively heat the one or more layers of uncured composite material to a temperature sufficient to cure the one or more layers of uncured composite material to form a cured composite component. The mandrel is removed from the cured composite component.

FIELD OF THE INVENTION

The present disclosure generally relates to a method of forming a composite component and, more particularly, a method of forming a composite component using resistive heating.

BACKGROUND OF THE INVENTION

Many aircraft components (e.g., airfoils, ducts, panels, etc.) are typically constructed from composite materials such as polymeric matrix composites and ceramic matrix composites. Generally, such composite components are formed by placing uncured composite material into a mold or onto a mandrel having the desired shape of the finished composite component. The mold/mandrel and the uncured composite material are then placed into an oven or an autoclave, which heats the uncured composite material to a temperature sufficient for curing thereof.

Nevertheless, curing the uncured composite material in an oven or an autoclave is an expensive and time-consuming process. More specifically, the oven/autoclave takes a long time to reach the proper temperature before the uncured composite component may be placed therein. Similarly, the oven/autoclave also takes a long time to cool to a safe temperature before the cured composite component may be removed therefrom. This heating and cooling time greatly increases the cycle time necessary to make composite components using conventional methods. This increased cycle time increases the manufacturing cost of the composite component. Accordingly, a method of forming a composite component that does not require the use of an oven or an autoclave for curing thereof would be welcomed in the technology.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, the present disclosure is directed to a method of forming a composite component. The method includes laying one or more layers of uncured composite material onto a mandrel. The mandrel includes a plurality of conductive media dispersed in a thermoplastic material. An electric current is supplied to the mandrel to resistively heat the one or more layers of uncured composite material to a temperature sufficient to cure the one or more layers of uncured composite material to form a cured composite component. The mandrel is removed from the cured composite component.

In another aspect, the present disclosure is directed to a method of forming a composite component. The method includes laying one or more layers of uncured composite material onto a mandrel. The mandrel includes a plurality of conductive media dispersed in a thermoplastic material. The thermoplastic material of the mandrel has a glass transition temperature. The uncured composite material has a glass transition temperature. An electric current is supplied to the mandrel to resistively heat the mandrel and the one or more layers of uncured composite material to a temperature above both the glass transition temperature of thermoplastic material of the mandrel and the glass transition temperature of the uncured composite material. The mandrel and the uncured composite material are deformed from a first shape to a second shape. The mandrel is removed from the composite component.

In a further aspect, the present disclosure is directed to a method of forming a thermoplastic component. The method includes laying one or more layers of thermoplastic material onto a mandrel. The mandrel includes a plurality of conductive media dispersed therein, and the one or more layers of thermoplastic material have a glass transition temperature. An electric current is supplied to the mandrel to resistively heat the one or more layers of thermoplastic material to a temperature above the glass transition temperature of the one or more layers of thermoplastic material. The one or more layers of thermoplastic material are allowed to deform from a first shape to a second shape to form a final thermoplastic component. The mandrel is removed from the final thermoplastic component.

DETAILED DESCRIPTION OF THE INVENTION

The term “thermoplastic” is used herein to mean any material formed from a polymer which softens and flows when heated; such a polymer may be heated and softened a number of times without suffering any basic alteration in characteristics, provided heating is below the decomposition temperature of the polymer. Examples of thermoplastic polymers include, by way of illustration only, polyolefins, polyesters, polyamides, polyurethanes, acrylic ester polymers and copolymers, polyvinyl chloride, polyvinyl acetate, etc. and copolymers thereof.

As used herein, the prefix “nano” refers to the nanometer scale (e.g., from about 1 nm to about 999 nm). For example, particles having an average diameter on the nanometer scale (e.g., from about 1 nm to about 999 nm) are referred to as “nanoparticles”.

In the present disclosure, when a layer is being described as “on” or “over” another layer or a mandrel, it is to be understood that the layers can either be directly contacting each other or have another layer or feature between the layers, unless expressly stated to the contrary. Thus, these terms are simply describing the relative position of the layers to each other and do not necessarily mean “on top of” since the relative position above or below depends upon the orientation of the device to the viewer.

The methods of forming a composite component disclosed herein include laying one or more layers of uncured composite material onto a mandrel. The mandrel is formed from a thermoplastic material having a plurality of conductive media dispersed therein. An electric current is supplied to the mandrel to resistively heats the one or more layers of uncured composite material to a temperature sufficient for curing thereof. In this respect, the methods disclosed herein do not require the use of an oven or autoclave for curing, thereby reducing the cycle time and the manufacturing cost of producing the composite components compared to conventional methods.

FIGS. 1A-1Billustrates embodiments of a mandrel10for use in forming a composite component. More specifically, the mandrel10includes a thermoplastic material12having a plurality of conductive media14dispersed therein. In some embodiments, the thermoplastic material12is a polycarbonate. Nevertheless, the thermoplastic material12may be any suitable thermoplastic. As shown inFIG. 1A, the plurality of conductive media14may be macroscopic particles or inclusions randomly dispersed in the thermoplastic material12. Alternatively, the plurality of conductive media14may be microscopic particles or inclusions randomly dispersed in the thermoplastic material12as shown inFIG. 1B. For example, the plurality of conductive media14may be carbon black inclusions, carbon nanotubes, metallic nanowires, or any other suitable material. In the embodiments shown inFIGS. 1A-1B, for example, the mandrel10may have an annular shape for forming a tube-like component. Although, the mandrel10may have any suitable shape (e.g., curved, etc.) for forming the desired composite component.

The thermoplastic material12and the plurality of conductive media14each have a respective glass transition (“Tg”) temperature. As used herein, “glass transition temperature” or “Tg” refers to the temperature at which an amorphous polymer or an amorphous portion of a crystalline polymer transitions from a hard and brittle glassy state to a rubbery state. For example, the Tgmay be determined by dynamic mechanical analysis (DMA) in accordance with ASTM E1640-09. A Q800 instrument from TA Instruments may be used. The experimental runs may be executed in tension/tension geometry, in a temperature sweep mode in the range from −120° C. to 150° C. with a heating rate of 3° C./min. The strain amplitude frequency may be kept constant (2 Hz) during the test. Three (3) independent samples may be tested to get an average Tg, which is defined by the peak value of the tan δ curve, wherein tan δ is defined as the ratio of the loss modulus to the storage modulus (tan δ==E″/E′).

The plurality of conductive media14is present in the thermoplastic material12in a concentration that exceeds a percolation threshold. The “percolation threshold” as used herein refers to a concentration of a conductive component (e.g., the plurality of conductive media14) in a dielectric material (e.g., the thermoplastic material12) that permits the conduction of electricity therethrough. When above the percolation threshold, the plurality of conductive media14conducts electricity through the thermoplastic material12. Below the percolation threshold, however, the plurality of conductive media14is unable to conduct electricity through the thermoplastic material12.

FIG. 2is a flow chart illustrating an exemplary method (100) of forming a composite component in accordance with the embodiments disclosed herein.FIGS. 3-8illustrate various aspects of the method (100).

Referring toFIGS. 2, 3A, and 3B, one or more layers of uncured composite material16(e.g., an uncured composite tape) are laid onto mandrel10in (102). In the embodiment shown inFIGS. 3A-3B, for example, the one or more layers of uncured composite material16are wrapped around the mandrel10to form a tube-like shape.FIG. 3Ashows the one or more layers of uncured composite material16are wrapped around the mandrel10when the plurality of conductive media14is macroscopic.FIG. 3Bconversely shows the one or more layers of uncured composite material16are wrapped around the mandrel10when the plurality of conductive media14is microscopic. In other embodiments, however, the one or more layers of uncured composite material16may be placed on the mandrel10to form other shapes as well based on the particular shape of the mandrel10.

The one or more layers of uncured composite material may be selected from the group consisting of, but not limited to, a ceramic matrix composite (“CMC”), a polymer matrix composite (“PMC”), a metal matrix composite (“MMC”), or a combination thereof. Suitable examples of matrix material for a CMC matrix is ceramic powder, including but not limited to, silicon carbide, aluminum-oxide, silicon oxide, and combinations thereof. Suitable examples of matrix material for a PMC include, but are not limited to, epoxy based matrices, polyester based matrices, and combinations thereof. In particular embodiments, the PMC material may be thermoplastic PMC tape having a polyether ether ketone (“PEEK”) matrix. Suitable examples of a MMC matrix material include, but are not limited to powder metals such as, but not limited to, aluminum or titanium that are capable of being melted into a continuous molten liquid metal which can encapsulate fibers present in the assembly, before being cooled into a solid ingot with incased fibers. The resulting MMC is a metal article with increased stiffness, and the metal portion (matrix) is the primary load caring element.

Referring now toFIGS. 2 and 4, an electric current18is supplied to the mandrel10to resistively heat the mandrel10and the one or more layers of uncured composite material16to a temperature above the Tgof the one or more layers of uncured composite material16in (104). (104) may also include resistively heating the mandrel10and the one or more layers of uncured composite material16to a temperature above the Tgof thermoplastic material12of the mandrel10. In some embodiments, however, the mandrel10and the one or more layers of uncured composite material16are heated to a temperature below the Tgof the thermoplastic material12of the mandrel10.

More specifically with respect to (104), a power supply20(e.g., a power grid, an electrical outlet, a battery, etc.) supplies the electric current18to the mandrel10via a first wire22. The plurality of conductive media14then conducts the electric current18through the mandrel10. A second wire24returns the electric current18to the power supply20or a ground (not shown). The internal resistance of the plurality of conductive media14creates a voltage drop across the mandrel10, thereby creating heat. This resistive heating increases the temperature of the mandrel10, which, in turn, increases the temperature of the one or more layers of uncured composite material16.

As mentioned above, the resistive heating may increase the temperature of the one or more layers of uncured composite material16above its Tg. At such temperatures (i.e., above the Tgof the thermoplastic material12of the mandrel10and above the Tgof the one or more layers of uncured composite material16), the mandrel10and the uncured composite material16may be manipulated to a desired shape. In this respect, the mandrel10and the uncured composite material16may be deformed from a first shape (e.g., the shape shown inFIG. 4) to a second shape (e.g., the shape shown inFIG. 5) in (106). For example, the mandrel10and the uncured composite material16can be curved, bent, or otherwise deformed as desired. Such an optional deformation process is shown through bending of the mandrel10and the uncured composite material16inFIG. 5prior to removing the mandrel10.

In (108), the one or more layers of uncured composite material16are cured. More specifically, heating the one or more layers of uncured composite material16to a temperature above the Tgthereof may be sufficient for curing thereof. In one embodiment, the resistive heating can be performed for a sufficient period of time (e.g., 5 minutes to 30 minutes) such that the one or more layers of uncured composite material16attain the temperature sufficient for curing thereof. As such, the one or more layers of uncured composite material16are transformed into a cured composite component26. In some embodiments, the electric current18may be 10 Amps to 50 Amps, and the voltage drop may be 50 Volts to 100 Volts. Although, the electric current18and/or the voltage drop may be different in other embodiments.

Curing may be accomplished by any suitable method. For PMCs, curing activates or consolidates the matrix material of the whole assembled ply stack. Curing is accomplished by thermal activation of matrix media, usually, resins or polymers used to coat the fibers forming a thermoplastic with fiber encapsulation also known as thermosetting. For MMCs, curing is accomplished through melting of the matrix media, usually, powder metal used to coat the fibers into metallic slurry with fibers present, and then cooled to a continuous metallic with encapsulated fibers when cooled. The metal matrix media includes, but is not limited to, lighter metals such as aluminum, magnesium, or titanium. For CMCs, curing is accomplished by thermal activation of the binder followed by pyrolyzing the binder to form carbon deposits, to encapsulate or bond together the fibers. The encapsulated or bonded fibers are cooled.

Referring now toFIGS. 2 and 6-7, the mandrel10is removed from the cured composite component26in (110). In the embodiment shown inFIG. 6, the mandrel10and the cured composite component26are submerged in a tank30filled with a solvent32. In this respect, the solvent32selectively dissolves the thermoplastic material12of the mandrel10, while leaving the cured composite component26intact. As such, only the cured composite component26remains upon completion of (110). In one embodiment, the solvent32is acetone; although, the solvent32may be any suitable material. For example, in an embodiment where the solvent32is acetone, the thermoplastic material12of the mandrel10may be a polycarbonate and the cured composite component26may include a PEEK matrix as mentioned above. When dipped in the tank30, the acetone dissolves the polycarbonate of the mandrel10, while leaving the PEEK matrix of the cured composite component26intact.

In alternate embodiments, the mandrel10may be removed from the cured composite component26via heating. As is more specifically illustrated inFIG. 7, an external heater34supplies heat36to soften the mandrel10. Once softened, the mandrel10may be removed from the cured composite component26. The heat36may also thermally decompose the mandrel10as well. In further embodiments, the heat36necessary to soften the mandrel10may be supplied by the internal resistance of the plurality of conductive media14.

FIGS. 8A-8Dillustrate various embodiments of the cured composite component26. Specifically,FIGS. 8A-8Drespectively illustrate a tube38, a duct40having a rectangular cross-section, an airfoil42, and a curved panel44. Nevertheless, the cured composite component26may have any suitable form or shape and may be any type of component. In one embodiment, the cured composite component26is an aircraft component (e.g., the airfoil42). Although, the cured composite component26may be a component for use in any suitable application. For example, the cured composite component26can be utilized as a component within a gas turbine engine.

The mandrel10may also be useful in forming thermoplastic components via thermoforming. In this respect,FIG. 9is a flow chart illustrating an exemplary method (200) of forming a thermoplastic component in accordance with the embodiments disclosed herein.FIGS. 10 and 11illustrate various aspects of the method (200).

Referring toFIGS. 8 and 9, one or more layers of thermoplastic material46onto an alternate embodiment of the mandrel10′ in (202). As shown inFIG. 9, the one or more layers of thermoplastic material46do not conform to the mandrel10′ upon completion of (202). That is, the mandrel10′ includes a curved surface28, while the one or more layers of thermoplastic material46are planar. In this respect, the mandrel10′ may be used to form a curved thermoplastic component. Nevertheless, the mandrel10,10′ may have any suitable shape for forming any suitable component. (202) is substantially similar to (102).

In (204), an electric current18is supplied to the mandrel10to resistively heat the mandrel10and the one or more layers of thermoplastic material46to a temperature above a Tgof the one or more layers of thermoplastic material46. (204) is substantially similar to (104).

In (206), the one or more layers of thermoplastic material46are deformed from a first shape (e.g., the shape shown inFIG. 10) to a second shape (e.g., the shape shown inFIG. 11), thereby forming a final thermoplastic component48. That is, the one or more layers of thermoplastic material46deform when heated to a temperature above the Tgthereof. This deformation converts the one or more layers of thermoplastic material46into a final thermoplastic component48as shown inFIG. 11. The final thermoplastic component48is cooled in (208) to a temperature below the Tgthereof. The final thermoplastic component48may be any of the components shown inFIGS. 8A-8Dor any other suitable component.

In (210), the mandrel10′ is removed from the final thermoplastic component48. (210) may be performed in the same manner (e.g., dissolution, heating, etc.) as (110).