Method of stamping-forming fiber-reinforced thermoplastic composite assemblies and related system

Abstract

To perform stamping-forming of a fiber reinforced thermoplastic composite assembly.SOLUTION: Stamping-forming a composite assembly comprises: applying a low-melt film on an interface surface of at least one spar; loading the spar onto at least one tooling segment such that the interface surface is exposed; and heating the tooling segment to a first temperature that is above a crystallization temperature of the low-melt film and below a melt temperature of a resin of the spar. A second low-melt film may be applied on a fiber-reinforced thermoplastic skin blank. The skin blank is heated to a second temperature above a melt temperature of a resin of the skin blank. The skin blank is then draped around the tooling segment such that at least a part of any second low-melt film contacts the low-melt film on the interface surface of the spar. Stamping-press is then closed to co-consolidate the skin blank and the spar, thereby stamping-forming the composite assembly.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to stamping fiber reinforced thermoplastic composite assemblies, and more particularly to such methods involving co-consolidating skins and spars together. [Background technology]

[0002] Conventional methods of forming thermoplastic closed profile torsion boxes, such as wing boxes for aircraft, include forming the skin and spars separately and then inserting the spars in a second step and fastening or welding them to the skin. Potential drawbacks of such techniques include the multiple steps required to fasten the spars to the skin and the difficulty of inserting the spars into an assembly with closed leading and trailing edges without creating tolerance problems in the final part. Summary of the Invention

[0003] The disclosed methods may improve upon conventional techniques, such as by reducing the number of process steps for forming composite assemblies, such as torsion boxes with closed leading and trailing edges. Generally, such methods include forming a thermoplastic composite skin and co-solidifying the skin with a preformed spar in a single stamping molding operation.

[0004] In one particular example, a method of stamping a fiber reinforced thermoplastic composite assembly according to the present disclosure includes applying a first low melting point film onto at least one faying surface of at least one spar, where each spar of the at least one spar is formed of a fiber reinforced thermoplastic composite material. The at least one spar may be loaded onto at least one tool segment, whereby at least one faying surface is exposed and directed away from the at least one tool segment. The at least one tool segment may be heated to a first temperature, where the first temperature is above a crystallization temperature of the first low melting point film and below a melting temperature of the thermoplastic spar resin of the at least one spar. A second low melting point film (which may be the same film material as the first low melting point film) may be applied, coated, or provided on a first side of the fiber reinforced thermoplastic skin blank. As used herein, a thermoplastic composite skin laminate is referred to as a "skin blank" when it is in a flat or substantially unformed state and when it is pliable due to heating and / or desolidification. Once the skin blank is stamped and solidified, it is referred to simply as a "skin." The skin blank may be heated to a second temperature above the melting temperature of the thermoplastic skin resin of the skin blank. In this manner, the skin blank and any second low melt film thereon may be heated to a point at which the skin blank may be draped or positioned around at least one tool segment such that a first side of the skin blank faces an outer surface of the at least one tool segment. When the skin blank is so draped, at least a portion of any second low melt film on the skin blank may be brought into contact with the first low melt film on at least one faying surface of the spar(s).

[0005] To stamp the composite assembly, a stamping press may be closed around the skin blank and the at least one tool segment to press the skin blank against the at least one tool segment and at least a portion of the optional second low melting film against the first low melting film on at least one faying surface of the spar(s). The skin blank and the at least one spar may co-solidify in the stamping press, resulting in a fiber-reinforced thermoplastic composite assembly formed from the skin and the spar(s). Once co-solidification is complete, the stamping press may be opened to remove the composite assembly and the tool segment from the stamping press. The resulting composite assembly is also within the scope of the present disclosure. For example, the resulting composite assembly may be a closed contour torsion box, such as a wing tip, a winglet, a rotor blade for an unmanned aerial vehicle (UAV), a rotor blade for a helicopter tail rotor, a wing, an aileron, a flap, a rudder, and / or a smaller control surface for a UAV, a helicopter, or a commercial airplane.

[0006] Related systems for carrying out such methods are also within the scope of this disclosure. An exemplary system may include a plurality of tool segments configured to position at least one preformed spar for the stamping molding process, an infrared heater configured to heat a fiber reinforced thermoplastic solidified skin blank to a temperature above a film melting point of a low melting point film to be applied to the at least one preformed spar, a tension element configured to maintain tension on the skin blank as it is draped around the plurality of tool segments such that the skin blank faces an outer surface of the plurality of tool segments, and a stamping press configured to close around the skin blank and the plurality of tool segments such that the stamping press is configured to press the skin blank onto the plurality of tool segments and against the low melting point film on the at least one preformed spar to co-solidify the skin blank with the at least one preformed spar, thereby forming a resulting fiber reinforced thermoplastic composite assembly. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic representation of several non-exclusive examples of a spar having a low melting point film applied on a joining surface. [Diagram 2] 1 is a schematic exploded representation of a plurality of tool segments with a plurality of spars engaged therewith. [Diagram 3] 1 is a schematic representation of a plurality of tool segments closed together to sandwich or clamp respective spars between respective adjacent tool segments; [Figure 4] 1 is a schematic representation of a skin blank coated with a low melting point film being heated in a heater. [Diagram 5] 1 is a schematic representation of a heated skin blank positioned against a number of tool segments and an engaged spar; [Figure 6] 1 is a schematic representation of a heated skin blank draped around a number of tool segments to conform the skin blank to the number of tool segments. [Figure 7] 1 is a schematic representation of the tool segments, spars, and skin blanks enclosed within a stamping press for stamping formation. [Figure 8] 8 is a schematic representation of the stamping press of FIG. 7 , encapsulating the tool segments, spars, and skin blanks; [Figure 9] 9 is a schematic representation of the stamping press of FIGS. 7-8 opened away from the tool segments, skin, and spar; [Figure 10] 1 is a schematic flow chart illustrating a method of stamping a composite assembly according to the present disclosure. [Figure 11] 1 is a schematic representation of an alternative arrangement of stamping press and tool segments according to the present disclosure. [Figure 12] 1 is a schematic representation of an alternative type of stamping press that may be used to stamp a composite assembly in accordance with the present disclosure. [Figure 13] 1 is a schematic representation of a system for stamping a composite assembly according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 1-9 and 11-13 provide exemplary and non-exclusive examples of methods and systems for stamping composite assemblies according to the present disclosure and may not generally be drawn to scale. Elements serving similar, or at least substantially similar, purposes are similarly numbered in each of FIGS. 1-9 and 11-13 and may not be described in detail herein with reference to each of FIGS. 1-9 and 11-13. Similarly, not all elements are numbered in each of FIGS. 1-9 and 11-13, but the reference numbers associated therewith may be used consistently herein. Elements, components, and / or features described herein with reference to one or more of FIGS. 1-9 and 11-13 may be included in and / or used in conjunction with any of FIGS. 1-9 and 11-13 without departing from the scope of the present disclosure. Generally, elements that are likely to be included in a given (i.e., particular) embodiment are shown with solid lines, and elements that are optional for a given embodiment are shown with dashed lines, however, elements shown with solid lines are not required for all embodiments, and elements shown with solid lines may be omitted from a particular embodiment without departing from the scope of the present disclosure.

[0009] FIG. 1 shows a schematic representation of a side elevation of a spar 10. The spar 10 may be a preformed fiber reinforced thermoplastic composite spar 10. The spar 10 generally includes an elongated portion 12. The elongated portion 12 has two opposing flanges 14. The flanges 14 extend from the elongated portion 12 at both ends of the elongated portion 12. A first low melting point film 16 is present on a mating surface 18 of each flange 14. The mating surface 18 is the exterior surface of each flange 14 in this example. The first low melting point film 16 may be coated, applied, glued, and / or laminated onto the mating surface 18 of the spar 10. The first low melting point film 16 should be selected to be compatible with the resin used in the fiber reinforced material used to make the spar 10. The first low melting point film 16 may be applied to the mating surface 18 after the spar 10 is preformed, before the spar 10 is preformed, or simultaneously when the spar 10 is preformed. Several examples of suitable low melting point films, which may be amorphous or semi-crystalline, are disclosed in U.S. Patent Application Publication No. 2022 / 0266541, the entire disclosure of which is incorporated by reference herein.

[0010] FIG. 2 shows a schematic representation of a side elevation view of a plurality of tool segments 20 that may be configured to serve as a mold for producing a cosolidified thermoplastic composite assembly. For example, while FIG. 2 shows the plurality of tool segments 20 having a first tool segment 22, a second tool segment 24, and a third tool segment 26, in other embodiments, the plurality of tool segments 20 may include more or fewer tool segments 20. Additionally or alternatively, one or more of the tool segments may each be formed of multiple pieces that engage with one another. The tool segments 20 may be assembled together or configured to engage with one another when used to stamp a composite part. As best seen in FIG. 3, when the tool segments 20 are assembled together, the outer surfaces 28 of the mating tool segments 20 may form an airfoil or teardrop shape, although other shapes are within the scope of the present disclosure.

[0011] 2 and 3, the tool segments 20 may be configured to receive, support, and / or position one or more spars 10 relative to one another. For example, the tool segments 22, 24, 26 are configured to receive, support, and position two spars 10 (e.g., a first spar 10a and a second spar 10b), although in other embodiments, more or fewer spars 10 may be used. In one illustrated embodiment, the first spar 10a may be positioned on the first tool segment 22 and sandwiched or clamped between the first tool segment 22 and the third tool segment 26 when the tool segments 20 are brought together (e.g., in the configuration shown in FIG. 3). The second spar 10b may be positioned on the first tool segment 22 opposite the first spar 10a and sandwiched or clamped between the first tool segment 22 and the second tool segment 24 when the tool segments 20 are brought together as shown in FIG. 3. When so positioned on the tool segments 20, the spars 10 may be positioned such that the flanges 14 and the first low melting film 16 remain exposed when the tool segments 20 are closed together. Each spar 10 may be said to define a respective channel 50 through the elongated portion 12 and the opposing flanges 14. Said channel 50 of the spar 10 may engage the tool segment 20 when the spar 10 is loaded onto the tool segment 20. For example, a first channel 50a of a first spar 10a may engage the first tool segment 22 and a second channel 50b of a second spar 10b may also engage the first tool segment 22, but is positioned at an opposite end of the first tool segment 22 from the first spar 10a. In some embodiments, the first spar 10a is oriented relative to the second spar 10b as follows: That is, as shown in Figures 2-3, the first channel 50a is oriented to face or point towards the second channel 50b of the second spar 10b.

[0012] In some embodiments, the tool segment 20 may include features such as notches 30 that engage or receive aspects of the spar 10. For example, the flange 14 may be configured to engage with a notch 30 on the first tool segment 22 when the spars 10a, 10b are placed on the first tool segment 22. In other embodiments, the notch 30 may be present on a different tool segment 20 instead of or in addition to the first tool segment 22. In some embodiments, different features of the tool segment 20 may engage with different aspects of the flange 14 and / or the spar 10. In some embodiments, the spar 10 may be oriented differently relative to one another and / or one or more of the tool segments 20.

[0013] A fiber reinforced consolidated skin blank 32 (which may be referred to herein simply as skin blank 32) may include a second low melt film 34 on a first side of the skin blank 32. The second low melt film 34 may be the same type of film as the first low melt film 16 on the spar 10 or a different type of low melt film that matches the first low melt film 16 on the spar 10, although in some embodiments the skin blank 32 may be provided without the optional second low melt film 34. The skin blank 32 and any optional second low melt film 34 on the skin blank 32 may be heated, such as by an infrared (IR) heating system 38, as depicted diagrammatically in FIG. 4. Generally, the skin blank 32 is heated to the following points: That is, the point at which the skin blank 32 may be flexible enough to be formed, such as by being draped around and / or against the tool segment 20, with the skin blank 32 conforming to the shape generated by the outer surface 28 of the tool segment 20. For example, Figure 5 generally represents the skin blank 32 positioned against the tool segment 20 (with the spar 10 engaged with the tool segment 20), while Figure 6 generally represents the skin blank 32 draped around the tool segment 20 such that the skin blank 32 fits the tool segment 20.

[0014] To complete an assembly 40 (see FIG. 9 ) of the skin blank 32 and one or more spars 10, a stamping press 42 may be closed around the skin blank 32 and spars 10. The skin blank 32 and spars 10 may be co-solidified within the stamping press 42. For example, FIG. 7 illustrates a schematic representation of a two-piece stamping press 42. The two-piece stamping press 42 is shown having two halves 42a, 42b, although other configurations and types of stamping presses are within the scope of this disclosure. In FIG. 7 , the stamping press halves 42a, 42b are shown in an open configuration in dashed lines and are then moved toward the skin blank 32 and tool segments 20 as indicated by arrow 44. The stamping press 42 is shown in solid lines in FIG. 7 as closed around the skin blank 32 draped over the tool segments 20. The stamping press 42 (e.g., a custom forming die for the stamping press 42) generally defines a recess or cavity 46 between the halves 42a, 42b configured to receive the tool segment 20 and the skin blank 32 therein. The cavity 46 generally has a shape complementary to that of the tool segment 20. The skin blank 32 is thereby pressed onto one side of the stamping press 42 and receives counter pressure from the tool segment 20 against the first side 36 of the skin blank 32. In this manner, the skin blank 32 is pressed into its desired final shape while at a temperature high enough to allow for the formation of the skin blank 32. The skin blank 32 is configured to retain this desired shape once it solidifies and is removed from the stamping press 42 (e.g., once the skin blank 32 transitions through solidification into the formed skin). FIG. 8 diagrammatically represents the skin blank 32, the tool segment 20, and the spar 10 closed within the stamping press 42. FIG. 9, on the other hand, diagrammatically represents removal of the stamping press 42 by moving the halves 42 a, 42 b (illustrated by arrows 48 ) away from the composite assembly 40 formed from co-consolidating the skin blank 32 and the spar 10 .In Figure 9, the stamping press halves 42a, 42b are shown in solid lines in an open configuration and in dashed lines as closed around the composite assembly 40. The tool segment 20 may then be removed from the resulting composite assembly 40. Although Figures 7-9 show the stamping press 42 in the form of two halves 42a, 42b moving towards and away from the skin blank 32 and tool segment 20 to press or release the skin blank 32 or tool segment 20, respectively, in other embodiments within the scope of the present disclosure, the stamping press 42 may have different configurations and / or orientations relative to the skin blank 32 and tool segment 20.

[0015] FIG. 10 generally provides a flow chart illustrating exemplary, non-exclusive embodiments of a method 100 according to the present disclosure. In FIG. 10, some steps are illustrated in dashed boxes indicating that the steps may be optional or may correspond to optional versions of a method according to the present disclosure. However, not all methods according to the present disclosure need include steps illustrated in solid boxes. The method and steps illustrated in FIG. 10 are not limiting, and other methods and steps (and order of steps) are within the scope of the present disclosure, including methods having more or fewer steps than shown, as will be understood from the description herein. The steps of the method 100 may be described with reference to the schematic representations of FIGS. 1-9 for illustrative purposes, but are not limited to the method 100.

[0016] A method 100 of stamping a fiber reinforced thermoplastic composite assembly includes, at 102, applying a first low melting film (e.g., first low melting film 16) onto at least one faying surface (e.g., faying surface 18) of at least one spar (e.g., spar 10). In such a method 100, the spar is formed of a fiber reinforced thermoplastic composite material. Once the first low melting film has been applied to the spar, the spar is loaded onto one or more tool segments (e.g., tool segment 20) at 104, such that the faying surface of the spar is oriented away from the tool segment. For example, the faying surface is not enclosed by the tool segment at this step, although other aspects of the spar may be enclosed within the tool segment (e.g., elongated portion 12, as best seen in FIG. 3). Thus, the first low melting film on the faying surface is exposed even when the tool segments are assembled together. In some examples, the spar may engage the tool segment. The mating surfaces of the spar are thereby substantially flush with the outer surfaces of the tool segments. In some examples, loading the spar onto the tool segments at 104 includes closing the tool segments together, whereby two or more tool segments engage with one another. In some examples, portions of one or more spars are sandwiched or clamped between adjacent tool segments when loaded onto the tool segments at 104 and when the tool segments are closed together. For example, loading the spar onto the tool segments at 104 may include loading a first spar onto the first tool segment, loading a second spar onto the first tool segment, and / or loading a second spar onto the second tool segment. In such examples, loading the spar onto the tool segments at 104 may also include bringing the first tool segment and the second tool segment together to close the first tool segment and the second tool segment together, thereby sandwiching or clamping the second spar between the first tool segment and the second tool segment.Similarly, loading the spar onto the tool segment at 104 may include bringing a third tool segment together with the first tool segment to sandwich or clamp the first spar between the first and third tool segments.

[0017] The method 100 may also include heating the tool segment, the spar, the faying surfaces of the spar, and / or the ambient temperature at which the tool segment is disposed, at 106, whereby the first low melt film on the spar is raised to a first temperature above the crystallization temperature of the first low melt film and below the melting temperature of the thermoplastic spar resin of the spar. In some examples, the heating at 106 results in heating the tool segment and / or the first low melt film to a temperature near the melting temperature of the first low melt film. By limiting the temperature to which the tool segment and the spar are heated at 106, the method 100 may be configured in some examples to heat sufficiently to co-solidify the first low melt film without de-solidifying the spar. This may increase the resistance to defects in the resulting composite assembly. The heating at 106 may be a localized heating step configured to heat only the first low melting point film and the faying surface of the spar, or the heating at 106 may be a general heating step configured to heat the entire tool segment assembly and / or the entire spar loaded therein. Additionally or alternatively, the heating at 106 may include actively heating one or more of the tool segments. In some examples, the method 100 includes cooling (e.g., actively cooling) the tool segments at one or more periods during the process. In some examples, the heating at 106 may be performed before the spar is loaded onto the tool segments at 104.

[0018] A second low melt film (e.g., second low melt film 34) may be applied to the fiber reinforced thermoplastic skin blank at 108. In some methods 100, the second low melt film is the same material as the first low melt film applied to the faying surface of the spar, while in other embodiments, different films may be applied to the spar and the skin blank at 102 and 108, respectively. In some embodiments, the second low melt film may be applied to the entire surface or side of the skin blank at 108. In other embodiments, the second low melt film may be applied to only a portion of the surface or side of the skin blank. For example, the second low melt film may be applied in an area of ​​the skin blank configured to contact the first low melt film applied to the spar. In some embodiments, the skin blank may be provided without having any second low melt film thereon. Once the optional second low melting film is applied to the skin blank at 108 (generally only on one side of the skin blank, such as the first side 36), the skin blank and the second low melting film are heated at 110. In some embodiments, heating the skin blank at 110 may be performed using an infrared (IR) heater (e.g., the IR heating system 38). Generally, heating the skin blank at 110 is performed to raise the temperature of the skin blank to a second temperature, which is equal to or greater than the melting temperature of the thermoplastic skin resin used in the skin blank. Thus, heating at 110 at least partially desolidifies the skin blank, thereby imparting flexibility to the skin blank so that it may be formed as desired. Heating the skin blank at 110 may be performed simultaneously with heating the tool segments at 106, or one heating step may be performed before or after the other. In some embodiments, the skin blank may be suspended and / or tensioned prior to and / or during heating of the skin blank at 110 .

[0019] Once the skin blank is sufficiently heated at 110 and the faying surface of the spar is sufficiently heated at 106, the skin blank is placed or draped around the tool segment at 112 (as shown diagrammatically in FIGS. 5-6). In some embodiments, draping the skin blank around the tool segment at 112 raises the film temperature of the first low melting point film on the faying surface of the spar above the film melting point, thereby melting the first low melting point film. As the skin blank is draped around the tool segment at 112, tension is applied to both ends of the skin blank, causing it to conform to the shape defined by the outer surface of the tool segment. To drape the skin blank at 112, the skin blank and the tool segment are positioned relative to one another, such that a first side of the skin blank with the second low melting point film thereon (if present) faces the outer surface of the tool segment. In this manner, when the skin blank is draped around the tool segment at 112, at least a portion of any second low melt point film on the skin blank will contact the first low melt point film on the faying surface of the spar engaged with the tool segment.

[0020] Various arrangements for draping the skin blank around the tool segments at 112 are within the scope of the present disclosure. For example, the skin blank and the tool segments may be positioned relative to one another for draping at 112, whereby the skin blank is positioned above the tool segments and then the skin blank is lowered toward the tool segments and / or the tool segments are raised toward the skin blank so that the skin blank fits over the tool segments. In another arrangement, the skin blank may be positioned relative to the tool segments side-by-side as shown diagrammatically in FIG. 11. Draping the skin blank around the tool segments at 112 generally involves maintaining tension on the skin blank during draping at 112, such as with tension elements 52 shown in FIGS. 5-6. The tension elements 52 may be elements such as grippers or springs, for example, although any suitable mechanism or device may be used for this purpose, as will be understood by one of ordinary skill in the art. The tension elements 52 are generally coupled or engaged with opposite ends or edges of the skin blank as shown in Figures 11-12 and are used to hold the skin blank to maintain tension on the skin blank as it is draped or placed around the tooling segments. In this manner, the tension elements may be used to reduce or prevent wrinkles in the resulting composite assembly. In some embodiments, the tension elements may be configured to be rotatable relative to the skin blank.

[0021] With continued reference to FIG. 10 , a stamping press (e.g., stamping press 42) may then be closed around the skin blank and the tool segment at 114, thereby forcing the skin blank against the tool segment and forcing at least a portion of any second low melting point film on the skin blank against the first low melting point film on the faying surface of the spar. Closing the stamping press at 114 may be performed in a variety of ways depending on the given setup used to perform the disclosed method 100. For example, closing the stamping press at 114 may include moving the two halves of the stamping press toward each other to enclose the skin blank and the tool segment within a cavity defined between the two stamping press halves. For example, FIGS. 7-9 show the stamping press halves 42a, 42b moving toward each other and toward either side of the skin blank 32 and the tool segment 20, thereby enclosing the skin blank 32 and the tool segment 20 within the cavity 46 of the stamping press 42. FIG. 11 shows a slightly different arrangement, with the stamping press halves 42a, 42b moved toward the top and bottom of the skin blank 32 and the tooling segments 20. FIG. 12 shows a schematic of yet another embodiment, where the stamping press is closed at 114 by moving one stamping press half toward the other (e.g., moving the stamping press half 42a toward the stamping press half 42b while the stamping press half 42b remains stationary). Arrows 54 in FIGS. 11-12 indicate the general direction of process flow. In the embodiment of FIG. 12, closing the stamping press at 114 also includes using one stamping press half (e.g., stamping press half 42a) to move the tooling segments and skin blank toward the second stamping press half (e.g., stamping press half 42a). Regardless of the placement of the stamping press relative to the tool segments, generally the tension elements remain outside of the stamping press when the stamping press is closed around the skin blank and tool segments at 114.Any tension elements used to smooth the skin blank in place on the tool segments will generally be removed once the resulting composite assembly has co-solidified and is removed from the stamping press. In other words, the tension elements are generally used in assisting in the formation of the resulting composite assembly and do not themselves form a part of the resulting composite assembly.

[0022] The stamping press remains closed around the skin blank and tool segments until the skin blank and spar are co-solidified within the stamping press at 116, thereby forming a fiber reinforced thermoplastic composite assembly of the skin and spar in a single stamping forming operation. In some examples, a certain predetermined pressure or force may be applied to the stamping press while the skin blank and spar are co-solidifying at 116 and / or the stamping press may be actively heated and / or cooled at 128 to aid in the solidification process. In some examples, heating and / or cooling the stamping press at 128 may be performed to maintain a predetermined temperature of the skin blank for a given period of time and / or to change the temperature of the skin blank after a predefined period of time. Co-solidifying at 116 and / or heating and / or cooling at 128 may be performed before or after closing the stamping press at 114 and until or before opening the stamping press at 118.

[0023] Once the skin blank and spar are co-solidified, the stamping press is opened at 118. The resulting composite assembly may be removed from the stamping press and / or tool segments at 120. For example, opening the stamping press at 118 may be performed after the current temperature of the skin and spar is below the crystallization temperature of all of the first thermoplastic resin of the first low melting point film, the second thermoplastic resin of the second low melting point film, the thermoplastic spar resin of the spar, and the thermoplastic skin resin of the skin / skin blank. Additionally or alternatively, opening the stamping press at 118 may be performed after the resulting fiber reinforced thermoplastic composite assembly is below the film melting point of the first low melting point film and any second low melting point film. The resulting composite assembly is a closed contour aerodynamic torsion box in some methods 100. For example, the resulting composite assembly may be a wing tip, a winglet, a rotor blade for an unmanned aerial vehicle (UAV), a rotor blade for a helicopter tail rotor, a wing, an aileron, a flap, a rudder, and / or smaller control surfaces for a UAV, helicopter, or commercial airplane.

[0024] Some embodiments of the method 100 further include trimming the resulting composite assembly at 122 and / or non-destructively inspecting the resulting composite assembly at 124. Additionally or alternatively, the method 100 may include forming the spar at 126 such that the spar is preformed. In various embodiments, the first low melting point film applied at 102 may be applied to a preformed spar at 126. In some embodiments, the spar may be stamped at 126. In some methods 100, the first low melting point film is applied to the faying surface of the spar while stamping the spar at 126, while in other embodiments of the method 100, the first low melting point film may be applied to the faying surface of the spar at 104 before or after the spar is stamped (or otherwise formed) at 126. In some examples, forming the spar at 126 may include laying up the spar as a flat blank with a first low melt film as a surface layer, pre-solidifying the spar in an oven or static press, and then stamping the spar. In another example, forming the spar at 126 may include laying up the spar as a flat blank, and then stamping the spar directly. In yet another example, forming the spar at 126 includes laying up material into the final spar shape using an automated fiber placement device, then solidifying in an oven or press, and adding a low melt film on the faying surfaces of the spar during solidification. In other examples, the spar may be formed at 126 as described above, but the low melt film is added after forming.

[0025] The first and / or second low melt point films generally comprise a thermoplastic resin having a melt temperature below the melt temperature of the thermoplastic resin used in the spar (referred to herein as the spar melt temperature of the spar resin). Similarly, the melt temperature of the low melt point film may generally be below the melt temperature of the thermoplastic skin resin used in the skin blank (referred to herein as the skin melt point of the skin resin). In various examples, the film melt point of the first and / or second low melt point films may be at least 20° F. below the skin melt point, at least 30° F. below the skin melt point, at least 40° F. below the skin melt point, at least 50° F. below the skin melt point, and / or at least 60° F. below the skin melt point. Additionally or alternatively, the film melting point of the first and / or second low melting point films can be at least 20° F. lower than the spar melting point, at least 30° F. lower than the spar melting point, at least 40° F. lower than the spar melting point, at least 50° F. lower than the spar melting point, and / or at least 60° F. lower than the spar melting point.

[0026] FIG. 13 illustrates several examples of a system 60 for stamping a fiber reinforced thermoplastic composite assembly. The system 60 generally includes a plurality of tool segments 20 configured to position at least one preformed spar 10 for the stamping process, an infrared heater 38, a tensioning element 52, and a stamping press 42. As disclosed herein, the heater 38 is configured to heat the fiber reinforced thermoplastic composite assembly to a temperature above the skin melting point of the skin blank resin. The tensioning element 52 maintains tension on the skin blank 32 as it drapes around the tool segments 20, and the stamping press 42 is configured to close around the skin blank 32 and the tool segments 20. The stamping press 42 is thereby configured to press the skin blank 32 onto the plurality of tool segments 20 and against the low melting point film on the at least one preformed spar 10 to co-solidify the skin blank 32 with the one or more spars 10, thereby forming a resultant fiber reinforced thermoplastic composite assembly. In some embodiments, system 60 includes a cooling system 62 configured to actively cool the tool segments 20 and / or the die of the stamping press 42, and / or a heating system 64 configured to actively heat the tool segments 20 and / or the die of the stamping press 42. In some systems 60, a single temperature control system may be configured to actively heat and cool the tool segments 20 (and / or the spar 10 engaged therewith).

[0027] Illustrative, non-exclusive embodiments of the subject matter of the present disclosure are described in the following recited paragraphs.

[0028] A1. 1. A method of stamping a fiber reinforced thermoplastic composite assembly, comprising: applying a first low melting point film onto at least one faying surface of at least one spar, each spar of the at least one spar being formed of a fiber reinforced thermoplastic composite material; loading the at least one spar onto the at least one tool segment such that the at least one joint surface is oriented away from the at least one tool segment; heating the at least one tool segment such that the first low melt point film reaches a first temperature, the first temperature being above a crystallization temperature of the first low melt point film and below a melting temperature of a thermoplastic spar resin of the at least one spar; heating the skin blank to a second temperature, the second temperature being above a melting temperature of a thermoplastic skin resin of the skin blank, the skin blank being a fiber reinforced thermoplastic skin blank; draping the skin blank around the at least one tool segment such that a first side of the skin blank faces an exterior surface of the at least one tool segment; closing a stamping press around the skin blank and the at least one tool segment, thereby pressing the skin blank against the at least one tool segment and pressing the skin blank against the first low melting point film on the at least one faying surface; and co-solidifying said skin blank and said at least one spar in said stamping press, thereby forming said fiber reinforced thermoplastic composite assembly.

[0029] A1.1. The method of paragraph A1, further comprising removing the fiber reinforced thermoplastic composite assembly from the at least one tool segment.

[0030] A1.2. The method of paragraph A1 or A1.1, wherein the first low melt point film comprises a first thermoplastic resin having a first film melt temperature below the spar melt temperature of the thermoplastic spar resin of the at least one spar.

[0031] A1.3. The method of any one of paragraphs A1-A1.2, wherein each spar of the at least one spar includes an elongated portion extending between two opposing flanges.

[0032] A1.4. The method of paragraph A1.3, wherein the at least one mating surface includes an outer surface of each of the two opposing flanges of the at least one spar.

[0033] A1.5. The method of paragraph A1.4, wherein loading the at least one spar onto the at least one tool segment includes loading the at least one spar so that the outer surface of each of the two opposing flanges of the at least one spar is exposed and facing away from the at least one tool segment.

[0034] A1.6. The method of any one of paragraphs A1 to A1.5, further including opening the stamping press to remove the at least one tool segment and the fiber reinforced thermoplastic composite assembly.

[0035] A1.7. The method of paragraph A1.6, wherein opening the stamping press occurs after co-solidifying the skin blank and the at least one spar.

[0036] A1.8. The method of paragraph A1.6 or A1.7, wherein opening the stamping press occurs after the current temperature of the fiber reinforced thermoplastic composite assembly is below the crystallization temperatures of all of the first thermoplastic resin of the first low melt point film, the second thermoplastic resin of the second low melt point film, the thermoplastic spar resin, and the thermoplastic skin resin of the skin blank.

[0037] A1.9. The method of any one of paragraphs A1 to A1.8, further including applying a second low melting point film on the first side of the skin blank.

[0038] A1.10. The method of paragraph A1.9, wherein heating the skin blank includes heating the skin blank having the second low melting point film to the second temperature.

[0039] A1.11. The method of paragraph A1.9 or A1.10, wherein draping the skin blank includes draping the skin blank with the second low melt point film around the at least one tool segment such that the first side of the skin blank faces the outer surface of the at least one tool segment with at least a portion of the second low melt point film in contact with the first low melt point film on the at least one joining surface.

[0040] A1.12. The method of any one of paragraphs A1.9 to A1.11, wherein closing the stamping press includes closing the stamping press around the shell blank and the at least one tool segment, thereby pressing at least a portion of the second low melt point film against the first low melt point film on the at least one faying surface.

[0041] A1.13. The method of any one of paragraphs A1.9 to A1.12, wherein the second low melt point film comprises a second thermoplastic resin having a second film melt temperature below the spar melt temperature of the thermoplastic spar resin of the at least one spar.

[0042] A1.14. The method of paragraph A1.13, wherein the second thermoplastic resin is the same as the first thermoplastic resin of the first low melting point film.

[0043] A2. The method of any one of paragraphs A1 to A1.14, further comprising forming the at least one spar.

[0044] A3. The method of paragraph A2, wherein forming the at least one spar includes stamping the at least one spar.

[0045] A4. The method of paragraph A3, wherein stamping the at least one spar results in applying the first low melting point film to an outer surface of each of two opposing flanges of each spar of the at least one spar.

[0046] A4.1. The method of paragraphs A3 or A4, wherein stamping the at least one spar results in applying the first low melting point film to the at least one joining surface of the at least one spar.

[0047] A5. The method of any one of paragraphs A1 to A4.1, wherein the at least one tool segment includes a first tool segment, and loading the at least one spar includes loading a first spar of the at least one spar onto the first tool segment.

[0048] A6. The method of any one of paragraphs A1 to A5, wherein the at least one tool segment includes a second tool segment, and loading the at least one spar includes loading a second spar of the at least one spar onto the second tool segment.

[0049] A7. The method of any one of paragraphs A1-A6, wherein loading the at least one spar includes loading a second of the at least one spar onto a first tool segment.

[0050] A8. The method of any one of paragraphs A5 to A7, further including bringing the first tool segment and the second tool segment together to close the first tool segment and the second tool segment together.

[0051] A9. The method of any one of paragraphs A5 to A8, wherein loading the at least one spar includes clamping the first spar between the first tool segment and a third tool segment.

[0052] A10. The method of any one of paragraphs A5-A9, wherein loading the at least one spar includes clamping a second spar between the first tool segment and a second tool segment.

[0053] A11. The method of any one of paragraphs A5 to A10, wherein loading the at least one spar includes loading the first spar and the second spar such that a first channel of the first spar faces a second channel of the second spar.

[0054] A12. The method of any one of paragraphs A5-A11, wherein a first channel of the first spar engages the first tool segment.

[0055] A13. The method of any one of paragraphs A5-A12, wherein a second channel of a second spar engages the first tool segment on an opposite side from the first spar.

[0056] A14. The method of any one of paragraphs A5 to A13, wherein the at least one tool segment includes a plurality of tool segments, including a first tool segment, a second tool segment, and / or a third tool segment.

[0057] A15. The method of any one of paragraphs A1-A14, further comprising actively cooling the at least one tool segment.

[0058] A15.1. The method of any one of paragraphs A1-A15, further including actively cooling one or more tools of the stamping press.

[0059] A16. The method of any one of paragraphs A1 to A15.1, further comprising actively heating the at least one tool segment.

[0060] A16.1. The method of any one of paragraphs A1-A16, further including actively heating one or more tools of the stamping press.

[0061] A17. The method of any one of paragraphs A1 to A16.1, wherein heating the skin blank includes infrared heating.

[0062] A18. The method of any one of paragraphs A1-A17, wherein a second low melting point film engages the skin blank while the skin blank is being heated.

[0063] A19. The method of any one of paragraphs A1-A18, further including positioning the skin blank and the at least one tool segment relative to one another such that the skin blank is positioned above the at least one tool segment.

[0064] A20. The method of any of paragraphs A1-A18, further including positioning the skin blank and the at least one tool segment relative to one another such that the skin blank and the at least one tool segment are side-by-side.

[0065] A21. The method of any one of paragraphs A1-A20, wherein draping the skin blank includes lowering the skin blank toward the at least one tool segment.

[0066] A22. The method of any one of paragraphs A1-A20, wherein draping the skin blank includes raising the at least one tool segment toward the skin blank.

[0067] A23. The method of any of paragraphs A1-A22, wherein draping the skin blank includes using a tension element to maintain tension on the skin blank while draping the skin blank.

[0068] A23.1. The method of paragraph A23, wherein the tension element includes a gripper or a spring.

[0069] A24. The method of any one of paragraphs A1 to A23.1, further comprising trimming the fiber reinforced thermoplastic composite assembly.

[0070] A25. The method of any of paragraphs A1-A24, further comprising non-destructively inspecting the fiber reinforced thermoplastic composite assembly.

[0071] A26. The method of any one of paragraphs A1-A25, further including maintaining a predetermined pressure and / or temperature on the shell blank and the at least one tool segment after closing the stamping press, during the co-solidifying, and before opening the stamping press.

[0072] A27. The method of any one of paragraphs A1 to A26, wherein the fiber reinforced thermoplastic composite assembly is a closed contour aerodynamic torsion box.

[0073] A28. The method of any one of paragraphs A1-A27, wherein closing the stamping press includes moving two halves of the stamping press toward each other and toward the at least one tool segment.

[0074] A29. The method of any one of paragraphs A1-A27, wherein closing the stamping press includes moving a first half of the stamping press toward a second half of the stamping press.

[0075] A30. The method of any one of paragraphs A1-A29, wherein closing the stamping press includes using a first half of the stamping press to move the at least one tool segment toward a second half of the stamping press.

[0076] A31. The method of any one of paragraphs A1 to A30, including opening the stamping press, wherein opening the stamping press is performed after the fiber reinforced thermoplastic composite assembly is below the film melting point of the first low melting point film and / or the second low melting point film.

[0077] A32. The method of any one of paragraphs A1 to A31, wherein the film melting point of the first low melting point film and / or the second low melting point film is below the skin melting point of the skin blank.

[0078] A33. The method of paragraph A32, wherein the film melt point is at least 20 degrees Fahrenheit lower than the skin melting point, at least 30 degrees Fahrenheit lower than the skin melting point, at least 40 degrees Fahrenheit lower than the skin melting point, at least 50 degrees Fahrenheit lower than the skin melting point, and / or at least 60 degrees Fahrenheit lower than the skin melting point.

[0079] A34. The method of any one of paragraphs A1 to A33, wherein heating the shell blank is performed prior to closing the stamping press.

[0080] A35. The method of any one of paragraphs A1 to A34, wherein draping the skin blank around the at least one tool segment raises a film temperature of the first low melting point film above a film melting point, thereby melting the first low melting point film.

[0081] A36. The method of any one of paragraphs A1 to A35, wherein the fiber reinforced thermoplastic composite assembly is a wing tip, a winglet, a rotor blade for an unmanned aerial vehicle (UAV), a rotor blade for a helicopter tail rotor, a wing, an aileron, a flap, a rudder, and / or a smaller control surface for a UAV, a helicopter, or a commercial airplane.

[0082] A37. The method of any one of paragraphs A1-A36, wherein the at least one spar is a preformed spar.

[0083] A38. The method of any one of paragraphs A1-A37, wherein the stamping press includes a first half and a second half that together form a cavity configured to receive a plurality of tool segments, the at least one faying surface of the at least one spar, and the skin blank therein.

[0084] B1. A closed contour torsion box made in accordance with the method of any one of paragraphs A1 to A38.

[0085] B2. Wing tips, winglets, rotor blades for unmanned aerial vehicles (UAVs), rotor blades for helicopter tail rotors, wings, ailerons, flaps, rudder, and / or smaller control surfaces for UAVs, helicopters, or civilian airplanes made in accordance with the method of any one of paragraphs A1 to A38.

[0086] C1. 1. A system for stamping a fiber reinforced thermoplastic composite assembly, comprising: a plurality of tool segments configured to position at least one preformed spar for a stamping forming process; an infrared heater configured to heat the fiber reinforced thermoplastic solidified skin blank to a temperature above a skin melting point of the thermoplastic skin resin of the fiber reinforced thermoplastic solidified skin blank; a tension element configured to maintain tension on the skin blank when the skin blank is draped around the plurality of tool segments such that the skin blank faces an outer surface of the plurality of tool segments; and a stamping press configured to close around the skin blank and the plurality of tool segments such that the stamping press is configured to press the skin blank onto the plurality of tool segments and against a low melting temperature film on the at least one preformed spar to co-solidify the skin blank with the at least one preformed spar, thereby forming the fiber reinforced thermoplastic composite assembly.

[0087] C2. The system of paragraph C1, wherein the stamping molding process includes the method of any one of paragraphs A1 to A38.

[0088] C3. The system of paragraph C1 or C2, wherein the low melt temperature film is applied to an exterior surface of each of two opposing flanges of the at least one preformed spar.

[0089] C3.1. The system of any of paragraphs C1 to C3, wherein the low melting point film is applied to at least one faying surface of the at least one preformed spar.

[0090] C4. The system of any one of paragraphs C1 to C3.1, wherein the plurality of tool segments includes a first tool segment, a second tool segment, and a third tool segment, and the first tool segment is configured to be positioned between the second tool segment and the third tool segment.

[0091] C5. The system of paragraph C4, wherein a first spar of the at least one preformed spar is configured to be loaded onto the plurality of tool segments such that the first spar is clamped between the first tool segment and the third tool segment.

[0092] C6. The system of paragraphs C4 or C5, wherein a second spar of the at least one preformed spar is configured to be loaded onto the plurality of tool segments such that the second spar is clamped between the first tool segment and the second tool segment.

[0093] C7. The system of any one of paragraphs C4 to C6, wherein the plurality of tool segments are configured to engage one another and to engage the at least one preformed spar such that a first channel of the at least one preformed spar faces a second channel of the at least one preformed spar.

[0094] C8. The system of any one of paragraphs C1 to C7, wherein the plurality of tool segments are configured to position the at least one preformed spar such that an outer surface of an opposing flange of each respective spar faces outwardly from the outer surface of the plurality of tool segments.

[0095] C8.1. The system of any one of paragraphs C1 to C8, wherein the plurality of tool segments are configured to position the at least one preformed spar such that at least one mating surface of each respective spar faces outwardly from the outer surface of the plurality of tool segments.

[0096] C9. The system of any one of paragraphs C1 to C8.1, further comprising a cooling system configured to actively cool the plurality of tool segments.

[0097] C10. The system of any of paragraphs C1-C9, further comprising a heating system configured to actively heat the plurality of tool segments.

[0098] C11. The system of any of paragraphs C1 to C10, wherein the plurality of tool segments are configured to be moved toward the skin blank as the skin blank is draped around the tool segments.

[0099] C12. The system of any one of paragraphs C1 to C11, wherein the stamping press is configured to maintain a predetermined pressure and / or temperature against the skin blank and the plurality of tool segments for a period of time sufficient to co-solidify the skin blank and the at least one preformed spar.

[0100] C13. The system of any one of paragraphs C1 to C12, wherein the stamping press includes a first half and a second half that together form a cavity configured to receive the plurality of tool segments therein.

[0101] C14. The system described in paragraph C13, wherein the first half and the second half are configured to be moved toward one another to close the stamping press about the plurality of tool segments.

[0102] C15. The system described in paragraph C13, wherein the first half is configured to move itself and the plurality of tool segments toward the second half to close the stamping press around the plurality of tool segments.

[0103] D1. Use of the system of any one of paragraphs C1 to C15 to make a closed contour torsion box.

[0104] D2. Use of the system of any one of paragraphs C1 through C15 to create wing tips, winglets, rotor blades for unmanned aerial vehicles (UAVs), rotor blades for helicopter tail rotors, wings, ailerons, flaps, rudder, and / or smaller control surfaces for UAVs, helicopters, or civilian airplanes.

[0105] As used herein, the terms "selective" and "selectively" mean that an operation, movement, configuration, or other activity of one or more components of a device, or that changes one or more characteristics of a device, is the direct or indirect result of a dynamic process of an aspect or one or more components of the device and / or a user's manipulation of an aspect or one or more components of the device. Thus, the terms "selective" and "selectively" can characterize an activity that is the direct or indirect result of a user's manipulation of an aspect or one or more components of the device, or can characterize a process that occurs automatically, for example, via the mechanisms disclosed herein.

[0106] As used herein, the terms "adapted" and "configured" mean that an element, component, or other object is designed and / or intended to perform a given function. Thus, the use of the terms "adapted" and "configured" should not be interpreted to mean that a given element, component, or other object is merely "capable" of performing a given function, but rather that the element, component, and / or other object has been specifically selected, created, implemented, utilized, programmed, and / or designed for performing that function. It is further within the scope of this disclosure that an element, component, and / or other object listed as being adapted to perform a particular function may additionally or alternatively be described as being configured to perform that function, and vice versa. Similarly, an object listed as being configured to perform a particular function may additionally or alternatively be described as being operable to perform that function.

[0107] As used herein, the phrase "at least one" referring to a list of one or more entities should be understood to mean at least one entity selected from any one or more of the entities in the list of entities, but not necessarily including at least one of every entity specifically named in the list of entities, and does not exclude any combination of the entities in the list of entities. This definition further allows for the optional presence of entities other than those specifically identified in the list of entities associated with the phrase "at least one," whether or not related to those specifically identified entities. Thus, as a non-limiting example, "at least one of A and B" (or, similarly, "at least one of A or B," or, similarly, "at least one of A and / or B") means, in one embodiment, at least one, optionally more than one A, and no B (and optionally including entities other than B); in another embodiment, at least one, optionally more than one B, and no A (and optionally including entities other than A); and in yet another embodiment, at least one, optionally more than one A, and at least one, optionally more than one B (and optionally including other entities). In other words, the terms "at least one," "one or more," and "and / or" are open-ended expressions that are both conjunctive and disjunctive in their operation. For example, the phrases "at least one of A, B, and C," "at least one of A, B, or C," "one or more of A, B, and C," "one or more of A, B, or C," and "A, B, and / or C" can mean A only, B only, C only, A and B together, A and C together, B and C together, A, B, and C together, and optionally combinations of any of the above with at least one other item.

[0108] The various disclosed elements of the apparatus and steps of the methods disclosed herein are not required for all apparatus and methods according to the present disclosure, and the present disclosure includes all novel and non-obvious combinations and subcombinations of the various elements and steps disclosed herein. Moreover, one or more of the various elements and steps disclosed herein may define independent inventive subject matter that is separate and distinct from the entirety of the disclosed apparatus or method. Thus, such inventive subject matter need not relate to the particular apparatus and methods explicitly disclosed herein, and such inventive subject matter may also find utility in apparatus and / or methods not explicitly disclosed herein.

[0109] As used herein, the phrases "for example," "as an example," and / or simply the term "example," when used in connection with one or more components, features, details, structures, embodiments, and / or methods according to the present disclosure, are intended to convey that the described components, features, details, structures, embodiments, and / or methods are exemplary, non-limiting examples of the components, features, details, structures, embodiments, and / or methods according to the present disclosure. Thus, the described components, features, details, structures, embodiments, and / or methods are not intended to be limiting, required, or exhaustive, and other components, features, details, structures, embodiments, and / or methods, including structurally and / or functionally similar and / or equivalent components, features, details, structures, embodiments, and / or methods, are also included within the scope of the present disclosure.

Claims

1. A method (100) for stamping a fiber reinforced thermoplastic composite assembly, comprising: applying (102) a first low melting point film (16) onto at least one faying surface (18) of at least one spar (10), each spar (10) of the at least one spar (10) being formed of a fiber reinforced thermoplastic composite material; loading (104) the at least one spar (10) onto the at least one tool segment (20) such that the at least one joining surface (18) is oriented away from the at least one tool segment (20); heating (106) the at least one tool segment (20) such that the first low melt point film (16) reaches a first temperature, the first temperature being above a crystallization temperature of the first low melt point film (16) and below a melting temperature of a thermoplastic spar resin of the at least one spar (10); heating (110) a skin blank (30) to a second temperature, the second temperature being above a melting temperature of a thermoplastic skin resin of the skin blank (30), the skin blank (30) being a fiber reinforced thermoplastic skin blank (30); draping (112) the skin blank (30) around the at least one tool segment (20) such that a first side (36) of the skin blank (30) faces an exterior surface of the at least one tool segment (20); closing (114) a stamping press (42) around the skin blank (30) and the at least one tool segment (20), thereby pressing the skin blank (30) against the at least one tool segment (20) and pressing the skin blank (30) against the first low melting point film (16) on the at least one joining surface (18); co-solidifying (116) said skin blank (30) and said at least one spar (10) in said stamping press (42), thereby forming said fiber reinforced thermoplastic composite assembly.

2. The method (100) of claim 1, wherein the first low melt point film (16) comprises a first thermoplastic resin having a first film melt temperature below a spar melt temperature of the thermoplastic spar resin.

3. 2. The method (100) of claim 1, wherein each spar (10) of the at least one spar (10) comprises an elongated portion (12) extending between two opposing flanges (14), and the at least one joining surface (18) includes an outer surface of each of the two opposing flanges (14) of the at least one spar (10).

4. 4. The method (100) of claim 3, wherein loading (104) the at least one spar (10) onto the at least one tool segment (20) comprises loading the at least one spar (10) such that the outer surface of each of the two opposing flanges (14) of the at least one spar (10) is exposed and oriented away from the at least one tool segment (20).

5. 2. The method (100) of claim 1, further comprising opening (118) the stamping press (42) to remove the fiber reinforced thermoplastic composite assembly, wherein opening (118) the stamping press (42) is performed after a current temperature of the fiber reinforced thermoplastic composite assembly is below the lowest of a crystallization temperature of a first thermoplastic resin of the first low melt point film (16), a second thermoplastic resin of a second low melt point film (34) on the skin blank (30), the thermoplastic spar resin, and the thermoplastic skin resin of the skin blank (30).

6. 2. The method (100) of claim 1, further comprising stamping the at least one spar (10), wherein stamping the at least one spar (10) results in applying the first low melting point film (16) to an outer surface of each of two opposing flanges (14) of each spar (10) of the at least one spar (10), and the at least one joining surface (18) includes the outer surface of each of the two opposing flanges (14) of each spar (10) of the at least one spar (10).

7. The at least one tool segment (20) includes a first tool segment (22), a second tool segment (24), and a third tool segment (26), and loading (104) the at least one spar (10) includes: loading a first spar (10a) of the at least one spar (10) onto the first tool segment (22); loading a second spar (10b) of the at least one spar (10) onto the first tool segment (22); bringing the first tool segment (22) and the second tool segment (24) together to close the first tool segment (22) and the second tool segment (24) together, thereby clamping the second spar (10b) between the first tool segment (22) and the second tool segment (24); and The method (100) of claim 1, comprising clamping the first spar (10a) between the first tool segment (22) and the third tool segment (26).

8. 2. The method (100) of claim 1, wherein loading (104) the at least one spar (10) comprises loading the first spar (10a) and the second spar (10b) such that a first channel (50a) of a first spar (10a) of the at least one spar (10) faces a second channel (50b) of a second spar (10b) of the at least one spar (10), wherein the first channel (50a) of the first spar (10a) engages a first tool segment (22) of the at least one tool segment (20) and the second channel (50b) of the second spar (10b) engages the first tool segment (22) on a side opposite the first spar (10a).

9. The method (100) of claim 1, wherein heating (110) the skin blank (30) comprises infrared heating.

10. 2. The method (100) of claim 1, further comprising applying (108) a second low melting point film (34) onto the first side (36) of the skin blank (30), the second low melting point film (34) having already been applied onto the skin blank (30) prior to heating (110) the skin blank (30).

11. 2. The method (100) of claim 1, wherein draping (112) the skin blank (30) comprises using a tension element (52) to maintain tension on the skin blank (30) while draping (112) the skin blank (30).

12. The method (100) of claim 11, wherein the tension element (52) comprises a gripper or a spring.

13. The method (100) of claim 1 , wherein the fiber reinforced thermoplastic composite assembly is a closed contour aerodynamic torsion box.

14. The method (100) of claim 1, wherein the first low melt point film (16) has a film melt point below a skin melt point of the skin blank (30).

15. 2. The method (100) of claim 1, wherein draping (112) the skin blank (30) around the at least one tool segment (20) raises a film temperature of the first low melt point film (16) above a film melting point, thereby melting the first low melt point film (16).

16. The method (100) of claim 1, wherein the at least one spar (10) is a preformed spar (10).

17. A closed contour torsion box comprising one or more selected from the group consisting of a wing tip, a winglet, a rotor blade for an unmanned aerial vehicle (UAV), a rotor blade for a helicopter tail rotor, a wing, an aileron, a flap, a rudder, and smaller control surfaces for a UAV, helicopter, or commercial airplane, applying (102) a first low melting point film (16) onto at least one faying surface (18) of at least one spar (10), each spar (10) of the at least one spar (10) being formed of a fiber reinforced thermoplastic composite material; loading (104) the at least one spar (10) onto the at least one tool segment (20) such that the at least one joining surface (18) is oriented away from the at least one tool segment (20); heating (106) the at least one tool segment (20) such that the first low melt point film (16) reaches a first temperature, the first temperature being above a crystallization temperature of the first low melt point film (16) and below a melting temperature of a thermoplastic spar resin of the at least one spar (10); heating (110) a skin blank (30) to a second temperature, the second temperature being above a melting temperature of a thermoplastic skin resin of the skin blank (30), the skin blank (30) being a fiber reinforced thermoplastic skin blank (30); draping (112) the skin blank (30) around the at least one tool segment (20) such that a first side (36) of the skin blank (30) faces an exterior surface of the at least one tool segment (20); closing (114) a stamping press (42) around the skin blank (30) and the at least one tool segment (20), thereby pressing the skin blank (30) against the at least one tool segment (20) and pressing the skin blank (30) against the first low melting point film (16) on the at least one joining surface (18); 2. A closed profile torsion box made according to a method (100) comprising co-solidifying (116) said skin blank (30) and said at least one spar (10) in said stamping press (42), thereby forming said closed profile torsion box.

18. 1. A system (60) for stamping a fiber reinforced thermoplastic composite assembly, comprising: a plurality of tool segments (20) configured to position at least one preformed spar (10) for a stamping forming process; an infrared heater (38) configured to heat the fiber reinforced thermoplastic solidified skin blank (30) to a temperature above the film melting point of a first low melting point film applied to the at least one preformed spar (10); a tension element (52) configured to maintain tension on the skin blank (30) when the skin blank (30) is draped around the plurality of tool segments (20) such that the skin blank (30) faces an outer surface of the plurality of tool segments (20); and a stamping press (42) configured to close around the skin blank (30) and the plurality of tool segments (20) such that the stamping press (42) is configured to press the skin blank (30) onto the plurality of tool segments (20) and against the first low melting point film (16) on the at least one preformed spar (10) to co-solidify the skin blank (30) with the at least one preformed spar (10), thereby forming the fiber reinforced thermoplastic composite assembly.

19. the plurality of tool segments (20) includes a first tool segment (22), a second tool segment (24), and a third tool segment (26), the first tool segment (22) is configured to be disposed between the second tool segment (24) and the third tool segment (26), a first spar (10a) of the at least one preformed spar (10) is configured to be loaded onto the plurality of tool segments (20) such that the first spar (10a) is sandwiched between the first tool segment (22) and the third tool segment (26), 20. The system (60) of claim 18, wherein a second spar (10b) of at least one preformed spar (10) is configured to be loaded onto the plurality of tool segments (20) such that the second spar (10b) is clamped between the first tool segment (22) and the second tool segment (24), and the plurality of tool segments (20) are configured to position the at least one preformed spar (10) such that at least one mating surface (18) of each respective spar (10) faces outwardly from the outer surface of the plurality of tool segments (20).

20. a cooling system (62) configured to actively cool the plurality of tool segments (20); and The system (60) of claim 18, further comprising a heating system (64) configured to actively heat the plurality of tool segments (20).

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