Assemblies and methods for forming fiber-reinforced thermoplastic structures with lightning strike protection

A method for forming a fiber-reinforced thermoplastic part may comprise the steps of locating a lightning strike protection layer on a mold surface of a mold tool, locating a thermoplastic layer over the mold tool, heating the thermoplastic layer to a pliable forming temperature, conforming the thermoplastic layer to a mold surface of the mold tool, and depositing a plurality of fiber strips over the thermoplastic layer.

FIELD

The present disclosure relates generally to thermoplastics manufacturing, and more specifically to assemblies and methods for forming fiber-reinforced thermoplastic structures.

BACKGROUND

Various industries include components having multi-dimensional charges for various uses. In particular, the aerospace industry utilizes nacelles for providing a protective housing around gas turbine engine components as well as for providing an aerodynamic surface for reducing drag, among other applications. Various nacelle structures (e.g., inlet, fan cowls, skins, etc.) may be made from fiber-reinforced materials. Fiber-reinforced structures are typically formed using automated fiber placement systems, wherein fiber-reinforced strips, “slit tape” or “tows,” are applied over the surface of a mold tool. Prior to applying the first layer of tows, a patch work of polyimide film is manually taped to the surface of the mold tool so that the initial layer of tows will stay in place on the mold surface. This mold preparation can be cumbersome, error prone, and costly.

SUMMARY

A method for forming a fiber-reinforced thermoplastic part is disclosed herein. In accordance with various embodiments, the method may comprise the steps of locating a lightning strike protection layer on a mold surface of a mold tool, locating a thermoplastic layer over the mold tool, heating the thermoplastic layer to a pliable forming temperature, conforming the thermoplastic layer to the mold surface of the mold tool, and depositing a plurality of fiber strips over the thermoplastic layer.

In various embodiments, conforming the thermoplastic layer to the mold surface of the mold tool comprises forming an airtight seal between the thermoplastic layer and the mold tool and evacuating air from between the thermoplastic layer and the mold surface of the mold tool.

In various embodiments, the lightning strike protection layer is a metallic mesh. In various embodiments, heating the thermoplastic layer to the pliable forming temperature comprises heating the thermoplastic layer with the thermoplastic layer spaced apart from the mold surface and the lightning strike protection layer.

In various embodiments, depositing the plurality of fiber strips over the thermoplastic layer includes depositing a first layer of fiber strips on the thermoplastic layer and depositing a second layer of fiber strips on the first layer of fiber strips. In various embodiments, the pliable forming temperature is greater than or equal to a glass transition temperature of the thermoplastic layer and less than a melting point of the thermoplastic layer.

In various embodiments, locating the thermoplastic layer over the mold tool may comprise disposing an exterior surface of the thermoplastic layer in a concave configuration. The exterior surface may face a plurality of heater units. Heating the thermoplastic layer to the pliable forming temperature may comprise disposing each heater unit of the plurality of heater units in at least substantially equally-spaced relation to the exterior surface.

In various embodiments, evacuating air from between the thermoplastic layer and the mold surface of the mold tool comprises powering on a vacuum fluidly coupled to a channel defined by the mold tool. In various embodiments, the method may further comprise releasing the thermoplastic layer from the mold tool by turning off the vacuum.

An assembly for forming a fiber-reinforced thermoplastic part is also disclosed herein. In accordance with various embodiments, the assembly may comprise a mold tool having a mold surface and a plurality of attachment frames located around a perimeter of the mold surface. Plurality of attachment frames is configured to couple a thermoplastic layer to the mold tool such that the thermoplastic layer is spaced apart from the mold surface. The attachment frames are raised with respect to the mold surface. The assembly further includes a vacuum configured to evacuate air from over the mold surface and a fiber dispensing assembly configured to deposit a plurality of fiber strips over the mold surface.

In various embodiments, a heating element may be configured to heat a thermoplastic layer to a pliable forming temperature. In various embodiments the heating element comprises a plurality of heater units. In various embodiments, each heater unit of the plurality of heater units is at least substantially-equally spaced from the mold surface.

In accordance with various embodiments, a method for forming a fiber-reinforced thermoplastic part may comprise the steps of locating a lightning strike protection layer between a first thermoplastic layer and a second thermoplastic layer and coupling the lightning strike protection layer, the first thermoplastic layer, and the second thermoplastic layer to a mold tool with the lightning strike protection layer, the first thermoplastic layer, and the second thermoplastic layer spaced apart from a mold surface of the mold tool. The method further includes the steps of heating the first thermoplastic layer and the second thermoplastic layer to a pliable forming temperature, conforming the first thermoplastic layer, the lightning strike protection layer, and the second thermoplastic layer to the mold surface, and depositing a plurality of fiber strips over the second thermoplastic layer.

In various embodiments, conforming the first thermoplastic layer, the lightning strike protection layer, and the second thermoplastic layer to the mold surface comprises forming an airtight seal around a perimeter of the first thermoplastic layer, the lightning strike protection layer, and the second thermoplastic layer and evacuating air from between the first thermoplastic layer and the mold surface of the mold tool.

In various embodiments, forming the airtight seal around the perimeter of the first thermoplastic layer, the lightning strike protection layer, and the second thermoplastic layer comprises attaching a tape to the first thermoplastic layer and to a plurality of attachment frames located around a perimeter of the mold surface.

In various embodiments, forming the airtight seal around the perimeter of the first thermoplastic layer, the lightning strike protection layer, and the second thermoplastic layer comprises locating a top frame on an exterior surface of the second thermoplastic layer.

In various embodiments, depositing the plurality of fiber strips over the second thermoplastic layer comprises depositing a first layer of fiber strips on the second thermoplastic layer, consolidating a first fiber strip of the first layer of fiber strips with the second thermoplastic layer and the first thermoplastic layer by heating the first fiber strip, the first thermoplastic layer, and the second thermoplastic layer to a temperature sufficient to melt the first thermoplastic layer, the second thermoplastic layer, and a matrix material of the first fiber strip, and depositing a second layer of fiber strips on the first layer of fiber strips. Consolidating the first fiber strip with the second thermoplastic layer and the first thermoplastic layer may comprise crosslinking the first thermoplastic layer with the second thermoplastic layer through openings in the lightning strike protection layer.

In various embodiments, the method may further comprise the step of consolidating the plurality of fiber strips, the second thermoplastic layer, and the first thermoplastic layer by locating a vacuum bag over the plurality of fiber strips and the mold tool, placing the mold tool in an oven, and applying heat and pressure to the plurality of fiber strips, the second thermoplastic layer, and the first thermoplastic layer. The heat and pressure are sufficient to melt the second thermoplastic layer, the first thermoplastic layer, and a matrix of the plurality of fiber strips.

In various embodiments, the method further comprise releasing the first thermoplastic layer, the lightning strike protection layer, the second thermoplastic layer, and the plurality of fiber strips from the mold tool by turning off a vacuum fluidly coupled to a channel extending to the mold surface.

DETAILED DESCRIPTION

The assemblies and methods, as described herein, may be used to form fiber-reinforced thermoplastic structures having a lightning strike protection layer. The assemblies and methods, described herein, provide relatively quick manufacturing, e.g., as compared to conventional automated fiber placement systems wherein an initial layer of polyimide tape strips are applied to the mold surface. The assemblies and methods, described herein, may provide a manufacturing process for forming a relatively complex geometry, while minimizing, or eliminating, wrinkling.

With reference toFIG.1, a fan cowl100is illustrated, in accordance with various embodiments. Fan cowl100may include a first fan cowl half102and a second fan cowl half104. First fan cowl half102may include a first outer skin110a. Second fan cowl half104may include a second outer skin110b. First outer skin110aand second outer skin110bmay each comprise a semi-cylindrical geometry when viewed from the aft direction, as shown in the illustrated embodiment. First and second outer skins110a,110bmay define a centerline axis108. Stated differently, first and second outer skins110a,110bmay be bent around/disposed about centerline axis108.

First and second outer skins110a,110bmay be made from a fiber-reinforced thermoplastic. In various embodiments, first and second outer skins110a,110bmay formed from a carbon fiber, glass fiber, aramid fiber, or any other suitable fiber in a thermoplastic matrix. Various thermoplastics may be used for forming a fiber-reinforced thermoplastic component, as described herein, including amorphous thermoplastics (e.g., polyetherimide (PEI), polycarbonate (PC), polysulfone (PSU), polyethersulfone (PES)), semi crystalline thermoplastics (e.g., polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK)), or any other suitable thermoplastic.

In accordance with various embodiments, first and second outer skins110a,110bmay be manufactured using an automated fiber placement (AFP) assembly, as described herein. Because first and second outer skins110a,110bserve as an aerodynamic surface in fan cowl applications, it may be desirable for first and second outer skins110a,110bto be formed having a smooth outer surface and to minimize wrinkling during the forming process. In this regard, first and second outer skins110a,110bmay be manufactured using the assemblies and methods, as described herein. While the disclosed methods and assemblies may find particular use in connection with fan cowl skins, various aspects of the disclosed embodiments may be adapted for manufacturing a variety of fiber-reinforced thermoplastic structures. For example, the disclosed methods and assemblies may be used to form other nacelle structures (e.g., inlets, lip skins, thrust reverser components, etc.) and/or any structure that is formed by AFP over a mold surface. As such, numerous applications of the present disclosure may be realized.

With reference toFIG.2, a mold tool120of an AFP assembly130is illustrated, in accordance with various embodiments. Mold tool120is configured to receive and support deposition of fiber strips during an AFP operation. Mold tool120may be formed of metal, metal alloy, and/or any material capable of withstanding the temperatures and pressures applied during the AFP operation. Mold tool120includes a mold surface122. Mold surface122may include various contouring and/or curvatures and/or complex geometries (e.g. protrusions, surface angles, etc.). The shape of mold surface122is configured to produce the desired component surface shape. In this regard, after completion of the AFP operation, the finished component retains and complements the shape of mold surface122. In various embodiments, mold surface122has a contour matching, or complementing, the desired geometry of first and second outer skins110a,110b, with momentary reference toFIG.1.

A lightning strike protection layer128may be located on mold surface122of mold tool120. The lightning strike protection layer128be a metallic mesh. For example, lightning strike protection layer128may be wire mesh having wires of copper, aluminum, titanium, or any other metal or metal alloy. A height (or wire dimeter) of lightning strike protection layer128is such that lightning strike protection layer128displays flexibility relative to the plane formed by the length and width dimensions of lightning strike protection layer128.

With reference toFIG.3A, in accordance with various embodiments, AFP assembly130is configured to deposit a thermoplastic layer132over mold surface122and lightning strike protection layer128. Thermoplastic layer132may be formed of thermoplastic polymer, PEI, PC, PSU, PES, PVDF, PTFE, PPS, PEEK, PEKK, PAEK, or any other suitable thermoplastic. In accordance with various embodiments, thermoplastic layer132is the form of a sheet configured to cover mold surface122. In this regard, thermoplastic layer132may be a single, unibody member that extends continuously from a first edge134of mold surface122to a second, opposing edge136of mold surface122. In accordance with various embodiments, a length and a width of thermoplastic layer132are equal to or greater than the length and the width, respectively, of the final fiber-reinforced thermoplastic part180(FIG.5). Thermoplastic layer132may be formed solely of thermoplastic. In this regard, thermoplastic layer132may be devoid of fibers.

In accordance with various embodiments, thermoplastic layer132may be coupled to the mold tool120. For example, in various embodiments, a sealing member140of AFP assembly130may be located around the perimeter of thermoplastic layer132and may form an airtight seal between thermoplastic layer132and mold tool120. Sealing member140may comprise a tape, clamp, frame, clip, or any other structure capable of forming an airtight seal around thermoplastic layer132. A vacuum142(e.g., a vacuum pump or vacuum generator) may be coupled to mold tool120. Vacuum142may be configured to evacuate the air from between mold surface122and thermoplastic layer132. For example, in various embodiments, mold tool120defines a channel144extending to mold surface122. Vacuum142may be fluidly coupled to channel144, such that vacuum142evacuates the air from between thermoplastic layer132and mold surface122of mold tool120via channel144.

With reference toFIG.3B, in accordance with various embodiments, a heating element150of AFP assembly130is configured to heat thermoplastic layer132to a sufficient pliable forming temperature, wherein the thermoplastic layer132becomes pliable for forming purposes. Prior to heating, thermoplastic layer132may be rigid or generally non-pliable. In accordance with various embodiments, a pliable forming temperature for a thermoplastic material may be between 190° and 750° Fahrenheit (F) (87.8°-398.9° Celsius (C)). In various embodiments, the pliable forming temperature for the thermoplastic layer132is greater than or equal to a glass transition temperature of the thermoplastic material of thermoplastic layer132and less than a melting point of the thermoplastic material of thermoplastic layer132. For example, a thermoplastic layer132formed of a thermoplastic material having a melting point of 649° F. (343° C.) and a glass transition temperature of 249° F. (143° C.) may be heated to a pliable forming temperature of between 249° F. (143° C.) and 649° F. (343° C.). As will be appreciated by those skilled in the art, the suitable pliable forming temperature may vary depending on the particular type of thermoplastic material being used, as well as other factors, such as the thickness of thermoplastic layer132. As used herein, the term “pliable forming temperature” may refer to a range of temperatures, wherein thermoplastic layer132is suitable for forming (usually equal to or greater than the glass transition temperature). In various embodiments, heating element150may be an infrared heater.

In accordance with various embodiments, AFP assembly130is configured to heat thermoplastic layer132with thermoplastic layer132spaced apart from mold surface122and lightning strike protection layer128. In this regard, sealing member140may be configured to couple thermoplastic layer132to mold tool120such that thermoplastic layer132is initially (e.g., prior to heating) spaced apart from mold surface122and lightning strike protection layer128. In response to heating, thermoplastic layer132becomes pliable and begins to translate toward mold surface122and lightning strike protection layer128.

With additional reference toFIG.3C, the pressure created by vacuum142forces thermoplastic layer132, which is at a pliable forming temperature, into contact with lightning strike protection layer128. The vacuum force further causes pliable thermoplastic layer132to conform to mold surface122such that thermoplastic layer132takes the shape (e.g., complements the contouring, curvatures and/or geometries) of mold surface222. The force applied by thermoplastic layer132against lightning strike protection layer128forces conform to mold surface122such that lightning strike protection layer128also takes the shape (e.g., complements the contouring, curvatures and/or geometries) of mold surface222.

A thickness of thermoplastic layer132and the pressure applied by vacuum142are configured such that thermoplastic layer132completely covers lightning strike protection layer128. For example, while portions of thermoplastic layer132may be located in the open area between the wires of the metal mesh and/or may contact mold surface122at least a portion of thermoplastic layer132remains over the wires, such that during fiber strip deposition described below, the fiber strips contact the thermoplastic layer132rather than wires of the lightning strike protection layer128.

FIG.3Dshows thermoplastic layer132formed on mold surface122(and lightning strike protection layer128). Heating element150may be removed (e.g., powered off) in response to thermoplastic layer132conforming to mold surface122. In various embodiments, sealing member140may be removed and/or vacuum142may be turned off in response to thermoplastic layer132conforming to mold surface122. In various embodiments, thermoplastic layer132may remain secured to mold tool120(e.g., via sealing member140or another means of securement) and/or under vacuum pressure (e.g., via vacuum142), during the AFP process described below with reference toFIGS.4A,4B,4C, and4D. Locating thermoplastic layer132on lightning strike protection layer128tends to reduce, or prevent, movement of lightning strike protection layer128during the AFP process.

With referenceFIGS.4A and4B, in accordance with various embodiments, a fiber dispensing assembly160is configured to dispense (e.g., deposit) fiber strips162over thermoplastic layer132. Fiber dispensing assembly160may dispense fiber strips162adjacent to one another. In this regard, each new fiber strip162may be laid directly adjacent to the previously laid fiber strip162.

With momentary reference toFIGS.6A and6B, a plan view and a cross-section view, respectively, of a portion of a fiber strip162are illustrated. In accordance with various embodiments, fiber strip162comprises a plurality of fibers164. Fibers164extend in a first direction or along the length L of fiber strips162. In this regard, fiber strips162include a length (or first dimension) L, a width (or second dimension) W, and a height (or third dimension) H. Height H may be substantially less than the length L and width W, such that fiber strips162display flexibility relative to the plane formed by the length and width dimensions.

Fibers164may be carbon fibers, glass fibers, ceramic fibers, synthetic fibers such as poly-paraphenylene terephthalamide (KEVLAR), or any other suitable fiber. In various embodiments, fibers164are located within a matrix166of fiber strip162. Matrix166may comprise a thermoplastic. In various embodiments, fiber strips162may comprise pre-impregnated carbon fiber tow, slit fiber tape, or any other fiber-reinforced material. In various embodiments, matrix166and thermoplastic layer132(FIG.4A) are the same thermoplastic material.

Returning toFIGS.4A and4B, in various embodiments, fiber dispensing assembly160may include a consolidation element170. Consolidation element170may be configured to apply heat and/or pressure to deposited fiber strips162. The application of heat and/or pressure by consolidation element170melts the matrices of fiber strips162and thermoplastic layer132, such that in response to consolidation, the matrices of fiber strips162are bonded (e.g., cross-linked) together and to thermoplastic layer132. Consolidation element170is configured to heat fiber strips162and thermoplastic layer132above their respective melting points. The pressure applied by consolidation element170tends to force fiber strips162and/or thermoplastic layer132toward lightning strike protection layer128and also forces the lightning strike protection layer128into the melted matrix and thermoplastic layer132. Stated differently, the melted matrix/thermoplastic layer flows into porosity of the metallic mesh, such that after consolidation, lightning strike protection layer128is secured with the matrix and thermoplastic layer132. The force applied by consolidation element170also forces the matrix and thermoplastic layer132toward mold surface122thereby further facilitating the conformation of fiber strips162and/or thermoplastic layer132to the shape of mold surface122.

With additional reference toFIG.4C, fiber dispensing assembly160may deposit a plurality of layers of fiber strips162on top of one another. For example, a first layer L1of fiber strips162is deposited directly on (i.e., in contact with) surface133of thermoplastic layer132. Surface133is opposite surface135of thermoplastic layer132. Surface135contacts mold surface122. Fiber dispensing assembly160then deposits a second layer L2of fiber strips162on the first layer L1of fiber strips162. WhileFIG.4Cillustrates the fiber strips162of adjacent fiber strip layers L1, L2being deposited in the same direction (e.g., parallel to first and second edges134,136), it is contemplated and understood that fiber dispensing assembly160may deposit fiber strips162in any direction and/or combinations of directions. For example, in various embodiments, the fiber strips162of second layer L2may be laid in a direction substantially perpendicular to the direction in which the fiber strips162of first layer L1were laid. Consolidation element170may be configured to apply heat and/or pressure to deposited fiber strips162of second layer L2. The application of heat and/or pressure by consolidation element170may simultaneously melt the matrices of the fiber strips162of first layer L1and second layer L2, such that in response to consolidation, the matrices of the fiber strips162of layer L1and of second layer L2are bonded (e.g., cross-linked) together.

With additional reference toFIG.4D, fiber dispensing assembly160continues depositing fiber strips162until a part180having the desired number of fiber strip layers is formed (e.g., when a desired part thickness is achieved). WhileFIGS.4A,4B,4C, and4D, show fiber strips162as distinguishable from one another, it is contemplated and understood that after consolidation (e.g., after the matrices have been melted together) fiber strips162are generally indistinguishable from one another. In various embodiments, fiber strips162may be consolidated after the desired number of fiber strip layers have been deposited (e.g., desired part thickness is achieved). For example, in various embodiments, after all of the fiber strips162are deposited, mold tool120and the fiber strip layup formed thereon may be placed in an oven and/or in a vacuum bag, wherein heat and vacuum pressure are applied to the fiber strips162. Consolidating all of the fiber strips162simultaneously tends to decrease manufacturing times.

FIG.5shows part180after removal from mold tool120. With combined reference toFIG.5andFIG.4D, after the final fiber strip layer is consolidated, part180is removed from mold tool120. In various embodiments, the part180(and thermoplastic layer132, which now part of part180) may be removed from mold tool120by turning off vacuum142(FIG.4A). With the vacuum pressure removed, the part180may be pulled off of mold surface122. In various embodiments, part180may be trimmed, or cut, to the desired dimensions after removing the part180from mold tool120. In various embodiments, part180may be first outer skin110a.

In various embodiments, stiffeners, doublers, or other buildup layers may be added to part180. The additional buildup layers may be located on fiber strip162over mold tool120. The buildup layers may be attached to part180using any suitable attachment technique (e.g., ultrasonic welding, thermo-pressing, etc.). The buildup layers may be applied after consolidation of fiber strips162or prior to consolidation, such that attachment (e.g., bonding) of the buildup layers occurs during consolidation of fiber strips162.

With reference toFIG.7A, an AFP assembly230for forming a fiber-reinforced thermoplastic part is illustrated, in accordance with various embodiments. AFP assembly230includes a mold tool220defining a mold surface222. Mold tool220is configured to receive and support deposition of fiber strips during an AFP operation. Mold tool220may be similar to mold tool120, as described above, with reference toFIG.2.

AFP assembly230is configured to deposit a first thermoplastic layer234, a second thermoplastic layer236, and a lightning strike protection layer228on mold surface122. Each of first thermoplastic layer234and second thermoplastic layer236may be formed of thermoplastic polymer, PEI, PC, PSU, PES, PVDF, PTFE, PPS, PEEK, PEKK, PAEK, or any other suitable thermoplastic. In accordance with various embodiments, first and second thermoplastic layers234,236may each in the form of a sheet configured to cover mold surface222. In this regard, first and second thermoplastic layers234,236may each be a single, unibody member that extends continuously from a first edge233of mold surface222to a second, opposing edge235of mold surface222. In accordance with various embodiments, a length and width of each of first and second thermoplastic layers234,236are equal to or greater than the length and width, respectively, of the final composite part. First and second thermoplastic layers234,236may be formed solely of thermoplastic. In this regard, first and second thermoplastic layers234,236may be devoid of fibers.

Lightning strike protection layer228may be located between first thermoplastic layer234and second thermoplastic layer236. Lightning strike protection layer228be a metallic mesh. For example, lightning strike protection layer228may be wire mesh having wires of copper, aluminum, titanium, or any other metal or metal alloy. A height (or wire dimeter) of lightning strike protection layer228is such that lightning strike protection layer228displays flexibility relative to the plane formed by the length and width dimensions of lightning strike protection layer228.

In accordance with various embodiments, first thermoplastic layer234, lightning strike protection layer228, and second thermoplastic layer236may be coupled to the mold tool220For example, in various embodiments, a sealing member240of AFP assembly230may be located around the perimeter of first thermoplastic layer234, lightning strike protection layer228, and second thermoplastic layer236and may form an airtight seal between the mold tool120and first thermoplastic layer234, lightning strike protection layer228, and second thermoplastic layer236. Sealing member240may comprise a tape, clamp, frame, clip, or any other structure capable of forming an airtight seal. A vacuum242(e.g., a vacuum pump or vacuum generator) may be coupled to mold tool220. Vacuum242may be configured to evacuate the air from between mold surface222and first thermoplastic layer234. For example, in various embodiments, mold tool220defines a channel244extending to mold surface222. Vacuum242may be fluidly coupled to channel244, such that vacuum242evacuates the air from between first thermoplastic layer234and mold surface222via channel244.

With reference toFIG.7B, in accordance with various embodiments, a heating element250of AFP assembly230is configured to heat first and second thermoplastic layers234,236to a sufficient pliable forming temperature, wherein the thermoplastic material of each of first and second thermoplastic layers234,236becomes pliable for forming purposes. Prior to heating, first and second thermoplastic layers234,236may be rigid or generally non-pliable. In accordance with various embodiments, a pliable forming temperature for a thermoplastic material may be between 190° and 750° Fahrenheit (F) (87.8°-398.9° Celsius (C)). In various embodiments, the pliable forming temperature for each of first and second thermoplastic layers234,236is greater than or equal to a glass transition temperature of the thermoplastic material of first and second thermoplastic layers234,236and less than a melting point of the thermoplastic material of first and second thermoplastic layers234,236. As will be appreciated by those skilled in the art, the suitable pliable forming temperature may vary depending on the particular type of thermoplastic material being used for each of first and second thermoplastic layers234,236, as well as other factors, such as the thickness of first and second thermoplastic layers234,236. In various embodiments, heating element250may be an infrared heater.

In accordance with various embodiments, AFP assembly230is configured to heat first and second thermoplastic layers234,236with first and second thermoplastic layers234,236and lightning strike protection layer228spaced apart from mold surface222. In this regard, sealing member240may be configured to couple first and second thermoplastic layers234,236and lightning strike protection layer228to mold tool220such that first and second thermoplastic layers234,236and lightning strike protection layer228are initially (e.g., prior to heating) spaced apart from mold surface222. In response to heating, thermoplastic material of first and second thermoplastic layers234,236becomes pliable and begins translating toward mold surface222.

With additional reference toFIG.7C, the pressure created by vacuum242forces first and second thermoplastic layers234,236, which are at a pliable forming temperature, toward mold surface222. Lightning strike protection layer128, which is sandwiched between first thermoplastic layer234and second thermoplastic layer236, is also forced toward mold surface222by first and second thermoplastic layers234,236. The vacuum forces first thermoplastic layer234into contact with mold surface222and causes first and second thermoplastic layers234,236and lightning strike protection layer228to conform to mold surface222. The force applied by second thermoplastic layer236against lightning strike protection layer228, along with the flexibility of lightning strike and pliability of first and second thermoplastic layers234,236, forces lightning strike protection layer228to conform to mold surface222.

FIG.7Dshows fiber dispensing assembly160, as described above with reference toFIGS.4A,4B, and4C, depositing fiber strips162on second thermoplastic layer236. A thickness of each of first and second thermoplastic layers234,236and the pressure applied by vacuum242are configured such that, after conforming to mold surface222, second thermoplastic layer236completely covers lightning strike protection layer228. For example, while portions of second thermoplastic layer236may be located in open areas between the wires of the metal mesh, at least a portion of second thermoplastic layer236remains over the wires, such that during the fiber strip deposition, the fiber strips162contact second thermoplastic layer236rather than the wires of lightning strike protection layer228.

In various embodiments, sealing member240may be removed and/or vacuum242may be turned off prior to the deposition of fiber strips162. In various embodiments, first and second thermoplastic layers234,236and lightning strike protection layer228may remain secured to mold tool220(e.g., via sealing member240or another means of securement) and/or under vacuum pressure (e.g., via vacuum242), during deposition of fiber strips162. Locating lightning strike protection layer228between first thermoplastic layer234and second thermoplastic layer236tends to reduce, or prevent, movement of lightning strike protection layer228during the AFP process.

Fiber dispensing assembly160continues depositing fiber strips162until a part having the desired number of fiber strip layers is formed (e.g., when a desired part thickness is achieved). In various embodiments, fiber strips162may be consolidated in-situ by consolidation element170. Consolidation element170may apply heat and pressure to the deposited fiber strips162. The heat and pressure applied by consolidation element170to the first layer of fiber strips162is sufficient to melt first and second thermoplastic layers234,236and the matrix166(FIG.6B) of the fiber strips162, such that in response to consolidation, the matrices of fiber strips162are bonded (e.g., cross-linked) together and to first and second thermoplastic layers234,236. Melting first and second thermoplastic layers234,236, with lightning strike protection layer228located therebetween, allows first and second thermoplastic layers234,236to bond (e.g., cross-link) with one another through the openings in the wire mesh of lightning strike protection layer228, thereby securing lightning strike protection layer228within first and second thermoplastic layers234,236. In various embodiments, consolidation is performed after the desired number of fiber strip layers have been deposited (e.g., after the desired part thickness is achieved). For example, in various embodiments, after all of the fiber strips162are deposited, mold tool220and the fiber strip layup formed thereon may be placed in an oven and/or in a vacuum bag, wherein heat and pressure (e.g., vacuum) are applied to the fiber strips162.

After consolidation, the formed part (e.g., part180) is removed from mold tool220. In various embodiments, the part, which includes first and second thermoplastic layers234,236and lightning strike protection layer228, may be removed from mold tool220by turning off vacuum242. With the vacuum pressure removed, the part may be pulled off of mold surface222. In various embodiments, the part may be trimmed, or cut, to the desired dimensions after removing the part from mold tool220. In various embodiments, part may be first outer skin110a.

Referring toFIG.8A, a mold tool320of an AFP assembly330is illustrated, in accordance with various embodiments. Mold tool320and AFP assembly330may be used to form part180(FIG.5). Mold tool320is configured to receive and support deposition of fiber strips during an AFP operation, for example, the AFP process described inFIGS.4A,4B,4C, and4D. Mold tool320includes a mold surface322. Mold surface322may include various contouring and/or curvatures and/or complex geometries (e.g. protrusions, surface angles, etc.). After completion of the AFP operation, the finished component retains and complements the shape of mold surface322. In various embodiments, mold surface322has a contour matching, or complementing, the desired geometry of first and second outer skins110a,110b, with momentary reference toFIG.1.

A lightning strike protection layer328may be located on mold surface322of mold tool320. The lightning strike protection layer328be a metallic mesh. For example, lightning strike protection layer328may be wire mesh having wires of copper, aluminum, titanium, or any other metal or metal alloy. A height (or wire dimeter) of lightning strike protection layer328is such that lightning strike protection layer328displays flexibility relative to the plane formed by the length and width dimensions of lightning strike protection layer328.

Mold tool320includes attachment frames324a,324b,324c, and324d. Attachment frames324a,324b,324c, and324dmay bound mold surface322(e.g., attachment frames324a,324b,324c, and324dmay be located around and/or may surround mold surface322). In various embodiments, attachment frame324aand attachment frame324beach have a curved shape. For example, attachment frame324aand attachment frame324bmay each form a half circle (e.g., approximately 180° of a circle). Attachment frame324bmay be located on an opposite end of mold surface322relative to attachment frame324a. In various embodiments, each of attachment frame324aand attachment frame324bmay be raised relative to mold surface322. In this regard, attachment frame324aand attachment frame324bmay create a lip325relative to mold surface322. Attachment frame324cand attachment frame324deach extend between attachment frame324aand attachment frame324b. Attachment frame324cand attachment frame324dmay each have a generally straight, or planar portion. In this regard, attachment frames324a,324b,324c, and324dmay together form a half cylinder. Attachment frame324dmay be located on an opposite end of mold surface322relative to attachment frame324c. In various embodiments, each of attachment frame324cand attachment frame324dmay be raised relative to mold surface322. In this regard, attachment frame324cand attachment frame324cmay each create a lip326relative to mold surface322.

With reference toFIGS.8B, in accordance with various embodiments, AFP assembly330is configured to deposit a thermoplastic layer332and lightning strike protection layer328over mold tool320. Thermoplastic layer332may be formed of thermoplastic polymer, PEI, PC, PSU, PES, PVDF, PTFE, PPS, PEEK, PEKK, PAEK, or any other suitable thermoplastic. In accordance with various embodiments, thermoplastic layer332is configured to be attach to mold tool320at attachment frames324a,324b,324c,324d. Thermoplastic layer332may be a single, unibody member that extends continuously from attachment frame324ato attachment frame324and from attachment frame324cto attachment frame324. Thermoplastic layer332may be formed solely of thermoplastic. In this regard, thermoplastic material may be devoid of fibers.

FIG.8Cshows a perspective cross section taken along the line8C-8C inFIG.8B.FIG.8Dshows a cross section taken along the line8D-8D inFIG.8B. With combined reference toFIGS.8B,8C, and8D, a tape329(e.g., sealing/tacking tape; of a double-sided adhesive configuration) may be applied between thermoplastic layer332and attachment frames324a,324b,324c, and324dto secure the thermoplastic layer332relative to the mold tool320. As such, the tape329is a representative example of the above-noted sealing member140. Tape329may form an airtight seal between thermoplastic layer332and attachment frames324a,324b,324c, and324d. In various embodiments, a clamp, top frame, clip, or any other structure capable of forming an airtight seal around thermoplastic layer332may be employed instead of, or in addition to, tape329.

A vacuum342(e.g., a vacuum pump or vacuum generator) may be coupled to mold tool320. Vacuum342may be configured to evacuate the air from between mold surface322and thermoplastic layer332. For example, in various embodiments, mold tool320defines a channel344extending to mold surface322. Vacuum342may be fluidly coupled to channel344, such that vacuum342evacuates the air from between thermoplastic layer332and mold surface322of mold tool320via channel344.

With reference toFIG.8E, in accordance with various embodiments, AFP assembly330further includes a heating element350having a plurality of heater units352(e.g., infrared heat lamps) that are collectively positioned to at least generally follow the contour of the mold surface322. The cross-section view of AFP assembly330shown inFIG.8EandFIG.8Fis the same cross section as shown inFIG.8D. The various heater units352may be at least substantially equally-spaced from the thermoplastic layer332. For example, heater units352may be at least substantially equally-spaced from an exterior surface334of thermoplastic layer332. Exterior surface334is oriented away from mold surface322of mold tool320. In various embodiments, exterior surface334may have a generally concave shape prior to heating. One or more of the heater units352may be disposed in a different orientation, including where each heater unit352is disposed in a different orientation.

Heater units352are configured to heat thermoplastic layer332to a sufficient pliable forming temperature, wherein the thermoplastic layer332becomes pliable for forming purposes. In various embodiments, the pliable forming temperature for the thermoplastic layer332is greater than or equal to a glass transition temperature of thermoplastic layer332and less than a melting point of the thermoplastic layer332. As will be appreciated by those skilled in the art, the suitable pliable forming temperature may vary depending on the particular type of thermoplastic material being used, as well as other factors, such as the thickness of thermoplastic layer332. As used herein, the term “pliable forming temperature” may refer to a range of temperatures, wherein thermoplastic layer332is suitable for forming (usually at or above the glass transition temperature). In various embodiments, heating element350may be an infrared heater.

In accordance with various embodiments, AFP assembly330is configured to heat thermoplastic layer332with thermoplastic layer332spaced apart from mold surface322and lightning strike protection layer328. In this regard, attachment frames324a,324b,324c, and324dmay couple thermoplastic layer332to mold tool320such that an interior surface336of thermoplastic layer332is initially (e.g., prior to heating) spaced apart from mold surface322and lightning strike protection layer328. Interior surface336is oriented away from exterior surface334and toward mold surface322and lightning strike protection layer328. In response to heating, thermoplastic layer332becomes pliable and begins to translate toward mold surface322and lightning strike protection layer328.

With additional reference toFIG.8F, the pressure created by vacuum342forces thermoplastic layer332, which is at a pliable forming temperature, into contact with lightning strike protection layer328. The vacuum force further causes pliable thermoplastic layer332to conform to mold surface322such that thermoplastic layer332takes the shape (e.g., complements the contouring, curvatures and/or geometries) of mold surface322. The force applied by thermoplastic layer332against lightning strike protection layer328forces conform to mold surface322such that lightning strike protection layer328also takes the shape (e.g., complements the contouring, curvatures and/or geometries) of mold surface222. A thickness of thermoplastic layer332and the pressure applied by vacuum342are configured such that thermoplastic layer332completely covers lightning strike protection layer328. For example, while portions of thermoplastic layer332may be located in the open area between the wires of the metal mesh and/or may contact mold surface322at least a portion of thermoplastic layer332remains over the wires, such that during fiber strip deposition described inFIGS.4A-4D, the fiber strips contact the thermoplastic layer332rather than wires of the lightning strike protection layer328.

In accordance with various embodiments, once thermoplastic layer332has conformed to mold surface322, an AFP process, as described above with reference toFIGS.4A,4B,4C, and4D, may be performed over thermoplastic layer332. In various embodiments, vacuum342may be turned off in response to thermoplastic layer332conforming to mold surface322. In various embodiments, thermoplastic layer332may remain under vacuum pressure (e.g., via vacuum342), during the AFP process.

With reference toFIGS.9A,9B and9C, in various embodiments, AFP assembly330may include a top frame340. In various embodiments, top frame340may be utilized with lightning strike protection layer328located on mold surface322, as shown inFIGS.8A-8F. In various embodiments, top frame340may be utilized with lightning strike protection layer328located between a first thermoplastic layer354and a second thermoplastic layer356, as shown inFIGS.9A,9B and9C. Top frame340may be located over and/or on the thermoplastic material (e.g., first and second thermoplastic layers354,356) and attachment frames324a,324b,324c,324dto secure first and second thermoplastic layers354,356relative to the mold tool320. As such, the top frame340is a representative example of the above-noted sealing member240(FIGS.7A-7D). Top frame340may generally follow the collective shape of attachment frames324a,324b,324c,324d. In this regard, top frame340may be located around and/or may generally surround the perimeter of mold surface322. Top frame340may define an opening346. The shape of opening346(i.e., the portions of top frame340that define opening346) may generally follow the contour of the mold surface322. Top frame340may force first and second thermoplastic layers354,356toward attachment frames324a,324b,324c,324dand/or otherwise cause an airtight seal to be formed between first and second thermoplastic layers354,356and attachment frames324a,324b,324c,324d. In various embodiments, tape329may located between first thermoplastic layer354and attachment frames324a,324b,324c,324dto enhance the hermetic seal between first and second thermoplastic layers354,356and attachment frames324a,324b,324c,324d.

In accordance with various embodiments, heater units352(e.g., infrared heat lamps) of heating element350are collectively positioned to at least generally follow the contour of the mold surface322and/or the contour of first and second thermoplastic layers354,356. In accordance with various embodiments, first thermoplastic layer354, lightning strike protection layer328, and second thermoplastic layer356are spaced apart from mold surface322prior to heating. The various heater units352may be at least substantially equally-spaced from first and second thermoplastic layers354,356. For example, heater units352may be at least substantially equally-spaced from an exterior surface334of second thermoplastic layer356. Exterior surface334is oriented away from first thermoplastic layer354and mold surface322. In various embodiments, exterior surface334may have a generally concave shape prior to heating. One or more of the heater units352may be disposed in a different orientation, including where each heater unit352is disposed in a different orientation.

Heater units352are configured to first and second thermoplastic layers354,356to a sufficient pliable forming temperature, wherein the first and second thermoplastic layers354,356become pliable for forming purposes. In various embodiments, the pliable forming temperature for first and second thermoplastic layers354,356is greater than or equal to a glass transition temperature of first and second thermoplastic layers354,356and less than a melting point of the first and second thermoplastic layers354,356. As will be appreciated by those skilled in the art, the suitable pliable forming temperature may vary depending on the particular type of thermoplastic material being used, as well as other factors, such as the thickness of first and second thermoplastic layers354,356. As used herein, the term “pliable forming temperature” may refer to a range of temperatures, wherein first and second thermoplastic layers354,356is suitable for forming (usually at or above the glass transition temperature).

The pressure created by vacuum342forces first and second thermoplastic layers354,356, which are at a pliable forming temperature, toward mold surface322. Lightning strike protection layer328, which is sandwiched between first thermoplastic layer354and second thermoplastic layer356, is also forced toward mold surface322by first and second thermoplastic layers354,356. The vacuum forces first thermoplastic layer354into contact with mold surface322and causes first and second thermoplastic layers354,356and lightning strike protection layer328to conform to mold surface222.

In accordance with various embodiments, once first and second thermoplastic layers354,356have conformed to mold surface322, an AFP process, as described above with reference toFIGS.4A,4B,4C, and4D, may be performed over first and second thermoplastic layers354,356. In various embodiments, vacuum342may be turned off during the AFP process. In various embodiments, thermoplastic layer332may remain under vacuum pressure (e.g., via vacuum342), during the AFP process.

AFP assembly330, in combination with the dispensing assembly160and in accordance withFIGS.4A-4D, may be employed to manufacture part180(FIG.5) more quickly as compared to conventional AFP systems wherein multiple polyimide tape strips are applied to the mold surface. Conforming the thermoplastic material to the mold surface while heating the material, in conjunction with applying a vacuum pressure, may allow for more complex mold surface geometries, while minimizing, or eliminating, wrinkling. Locating thermoplastic layer332on lightning strike protection layer328and/or locating lightning strike protection layer328between first thermoplastic layer354and second thermoplastic layer356tends to reduce, or prevent, movement of lightning strike protection layer328during the AFP process.

With reference toFIG.10A, a method400for forming a fiber-reinforced thermoplastic part is illustrated. In accordance with various embodiments, method400may include locating a lightning strike protection layer on a mold surface of (step402), locating a thermoplastic layer over the mold tool (step404), heating the thermoplastic layer to a pliable forming temperature (step406), conforming the thermoplastic layer to the mold surface (step408), and depositing a plurality of fiber strips over the thermoplastic layer (step410).

In various embodiments, step404may include disposing an exterior surface of the thermoplastic layer in a concave configuration and facing a plurality of heater units and step306may include disposing each heater unit in at least substantially equally-spaced relation to the exterior surface of the thermoplastic layer.

With reference toFIG.10B, in various embodiments, step408may include forming an airtight seal between the thermoplastic layer and the mold tool (step408A) and evacuating air from between the thermoplastic layer and the mold surface of the mold tool (step408B). In various embodiments, step408A may include forming an airtight seal between the thermoplastic layer and a plurality of attachment frames located around a perimeter of the mold surface. In various embodiments, forming the airtight seal between the thermoplastic layer and the plurality of attachment frames may include attaching a tape to the thermoplastic layer and to the attachment frames. In various embodiments, forming the airtight seal between the thermoplastic layer and the plurality of attachment frames may include locating a top frame on an exterior surface of the thermoplastic layer. In various embodiments, step406B may include powering on a vacuum fluidly coupled to a channel defined by the mold tool.

In various embodiments, step410may include depositing a first layer of fiber strips on the thermoplastic layer (step410A) and depositing a second layer of fiber strips on the first layer of fiber strips (step410B). In various embodiments, method400may comprise applying heat and pressure to the first layer of fiber strips prior to depositing the second layer of fiber strips. (i.e., prior to step410B). In various embodiments, method400may further comprising releasing the thermoplastic layer from the mold tool by turning off the vacuum (step412).

With reference toFIG.11A, a method450of for forming a fiber-reinforced thermoplastic part is illustrated. In accordance with various embodiments, method450includes locating a lightning strike protection layer between a first thermoplastic layer and a second thermoplastic layer (step452) and coupling the lightning strike protection layer, the first thermoplastic layer, and the second thermoplastic layer to a mold tool with the lightning strike protection layer, the first thermoplastic layer, and the second thermoplastic layer spaced apart from a mold surface of the mold tool (step454). Method450further includes heating the first thermoplastic layer and the second thermoplastic layer to a pliable forming temperature (step456), conforming the first thermoplastic layer, the lightning strike protection layer, and the second thermoplastic layer to the mold surface (step458), and depositing a plurality of fiber strips over the second thermoplastic layer (step460).

With reference toFIG.11B, in various embodiments, step458may include forming an airtight seal around a perimeter of the first thermoplastic layer, the lightning strike protection layer, and the second thermoplastic layer (step458A) and evacuating air from between the first thermoplastic layer and the mold surface of the mold tool (step458B). In various embodiments, step458A may include attaching a tape to the first thermoplastic layer and a plurality of attachment frames located around the perimeter of the mold surface. In various embodiments, step458A may include locating a top frame on an exterior surface of the second thermoplastic layer.

In various embodiments, step460may include depositing a first layer of fiber strips on the second thermoplastic layer (step460A), consolidating a first fiber strip of the first layer of fiber strips with the second thermoplastic layer and the first thermoplastic layer by heating the first fiber strip, the first thermoplastic layer, and the second thermoplastic layer to a temperature sufficient to melt the first thermoplastic layer, the second thermoplastic layer, and a matrix material of the first fiber strip (step460B), and depositing a second layer of fiber strips on the first layer of fiber strips (step460C). In various embodiments, step460B may include crosslinking the first thermoplastic layer with the second thermoplastic layer through openings in the metallic mesh.

With reference toFIG.11C, in various embodiments, method450may further comprising consolidating the plurality of fiber strips, the second thermoplastic layer, and the first thermoplastic layer (step462). In various embodiments, method450may further comprising releasing the first thermoplastic layer, the lightning strike protection layer, the second thermoplastic layer, and the plurality of fiber strips from the mold tool by turning off a vacuum fluidly coupled to a channel extending to the mold surface (step464)

With reference toFIG.11D, in various embodiments, step462may include locating a vacuum bag over the plurality of fiber strips and the mold tool (step462A), placing the mold tool in an oven (step462B), and applying heat and pressure (e.g., vacuum) to the plurality of fiber strips, the second thermoplastic layer, and the first thermoplastic layer, the heat and pressure being sufficient to melt the second thermoplastic layer, the first thermoplastic layer, and a matrix of the plurality of fiber strips (step462C). In various embodiments, step462cmay include crosslinking the first thermoplastic layer with the second thermoplastic layer through openings in the metallic mesh.

Methods400,450and AFP assemblies130,230,330tend to allow fiber-reinforced thermoplastic part180(FIG.5) to be manufactured more quickly as compared to conventional AFP systems wherein multiple polyimide tape strips are applied to the mold surface prior to depositing the fiber strips. Conforming the thermoplastic layer(s)132,234,236,354,356and the lightning strike protection layer128,228,328to the mold surface122,222,322by applying vacuum pressure to the heated/pliable thermoplastic layer(s)132,234,236,354,356may allow for more complex mold surface geometries, while minimizing, or eliminating, wrinkling and/or movement of the lightning strike protection layer128,228,328during the AFP process.