Method and system for forming a curved composite charge for a stringer

Abstract

To provide a new method and a new device for forming a bent composite material charge for a stringer.SOLUTION: A composite material stringer can have an in-plane and / or out-plane bend(s) and is formed during the formation of a composite material charge. Concretely, the same is formed using a pallet. The pallet comprises mutually rotatably coupled plural independent pallet parts. A hat part is formed when a part of the charge is suited to cavities in the pallet. The pallet parts are rotated to each other during the formation of the hat part and / or when the hat part is already suited to the cavities. In some embodiments, when the pallet parts are rotated, a die is bent together with the charge. This rotation creates one or more in in-plane and / or out-plane bends. In some embodies, for example, the flange part of the composite material charge is arranged in a temporal direction for enabling the bending of the charge and reducing wrinkles.SELECTED DRAWING: None

Description

Background Art

[0001] Aircraft designs utilize various components such as stringers to support bending loads, torsional loads, shear loads, and direct loads. Stringers are typically formed from lightweight composite materials, such as tapes or fabrics in which fibers are embedded in a resin. The composite layup is typically processed within a forming tool to define the final or semi-final shape of the stringer. However, many applications (such as aircraft) require numerous stringers, and such stringers have various shapes along the length of these stringers, particularly various bends and turns. Having dedicated forming tools for each type of stringer creates procurement issues and significantly increases manufacturing costs. Further, forming bends using conventional forming techniques and tools, such as two-stage forming and bending, can result in undesirable wrinkles.

[0002] More specifically, composite stringers are typically manufactured using a multi-step process. First, in a conventional process, the hat portion of the stringer is shaped using a combination of a die and a cavity within a pallet. At this stage, the stringer is straight and does not have any bends along its length, such as a bend around an axis perpendicular to the major axis of the stringer. If any bends are required, such as in-plane and / or out-of-plane bends, the shaped stringer is transferred to another tool where the stringer is bent into its final stringer shape. Typically, not all surfaces of the shaped stringer are supported during this separate bending operation. This post-shaped bending operation can result in undesirable wrinkles.

[0003] New methods and devices are needed for forming curved composite charges for stringers.

Summary of the Invention

[0004] A method and system for forming a curved composite charge for a stringer are described. Such composite stringers can have in-plane and / or out-of-plane bending. They are formed while shaping the composite charge. Specifically, the composite charge is shaped using a pallet comprising a plurality of independent pallet parts rotatably coupled to each other. A hat portion is formed when a portion of this charge fits into a cavity in the pallet. The pallet parts are rotated relative to each other while the hat portion is being formed and / or after the hat portion has already fit into the cavity. In some embodiments, the die is bent with the charge when the pallet parts are rotated. This rotation generates one or more of in-plane and / or out-of-plane bending. In some embodiments, for example, the flange portion of the composite charge is arranged in a temporary orientation to enable bending of the charge and reduce wrinkling.

[0005] In some embodiments, a method for forming a curved composite charge is provided. The method includes placing the composite charge on a processing surface of a pallet and covering a cavity of the pallet. The composite charge includes a hat portion and a flange portion, the flange portion being integral with and interconnected by the hat portion. The pallet comprises a plurality of pallet parts. Each pallet part of the plurality of pallet parts is rotatably coupled to one or more other pallet parts of the plurality of pallet parts. The cavity extends through each pallet part of the plurality of pallet parts. The composite charge is placed covering and in contact with each pallet part of the plurality of pallet parts. The method includes contacting the hat portion of the composite charge with a die such that the die is aligned with the cavity. The cavity is defined by a cavity surface. The method also includes bending at least the hat portion to conform to the die, inserting the die into the cavity such that the hat portion is disposed between the die and the cavity surface and conforms to each of the die and the cavity surface, and rotating two or more of the pallet parts of the plurality of pallet parts relative to each other about one or more axes, thereby forming a curved composite charge.

[0006] In some embodiments, the method includes inserting a die and a composite charge into a cavity of a pallet. The pallet includes a plurality of pallet parts rotatably coupled to each other. The method includes rotating two or more of the plurality of pallet parts relative to each other about one or more axes, thereby forming a curved composite charge from the composite charge.

[0007] In some embodiments, a stringer forming device includes a pallet including a plurality of pallet parts. Each pallet part of the plurality of pallet parts is rotatably coupled to one or more other pallet parts of the plurality of pallet parts. The pallet further includes a processing surface and a cavity that extends away from the processing surface and into the pallet. The stringer forming device includes a die aligned with the cavity. The die has a cross-section corresponding to a cross-section of the cavity. The die is movable relative to the pallet in a direction perpendicular to the processing surface of the pallet.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0009] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented concepts. In some examples, the presented concepts may be practiced without including some or all of these specific details. In other instances, well-known process steps are not described in detail so as not to unnecessarily obscure the concepts being described. Some concepts are described with reference to specific examples, which are not intended to be limiting.

[0010] Introduction A method and system are described herein for providing in-plane and / or out-of-plane bending capabilities during stringer formation operations. This novel approach combines multiple processing steps (e.g., shaping and bending after being shaped) into one, collectively referred to as the stringer formation operation, which enables reducing the risk of wrinkles and increasing the throughput of the overall process. This approach also provides support for the stringer surface while performing the bending, since the bending operation is carried out using the same forming equipment (e.g., a stringer forming device). Further, various sequences of the shaping and bending operations are specifically selected based on the final shape of the stringer and the characteristics of the composite charge. For example, if the stringer has significant in-plane bending, in some embodiments, the bending is formed after the formation of the hat portion but before, for example, the final orientation of the flange portion with respect to the hat portion.

[0011] Specifically, the composite charge is formed using a pallet comprising a plurality of pallet portions rotatably coupled to each other. The hat portion is formed when a portion of the charge fits into a cavity within the pallet. The pallet portions are rotated relative to each other while or immediately after forming the hat portion, e.g., when the hat portion has already fit into the cavity. In some embodiments, the die bends with the charge being formed while pressing the hat portion into contact with the cavity surface. This rotation of the pallet portions generates one or more of in-plane and / or out-of-plane bending. In some embodiments, the flange portion of the composite charge is disposed in a temporary direction (e.g., away from the pallet) to enable bending of the charge and reduce wrinkles, for example.

[0012] Any type of composite stringer is within the scope of the present disclosure, and some of them will be described next with reference to FIGS. 1A - 1G. FIG. 1A is a schematic cross-sectional view of a stringer 110 having a trapezoidal cross-section. Specifically, the stringer 110 includes a hat 111 and two flanges 116, one on each side of the hat 111. In this embodiment, the hat 111 is formed as a trapezoid and includes a cap 112 and two side walls 114. In some embodiments, the cap 112 is parallel to the flange 116. However, other embodiments are also within the scope. The flange 116 is used to attach the stringer 110 to a lower structure 102 (e.g., the outer skin of an aircraft fuselage).

[0013] FIG. 1B is a schematic cross-sectional view of a stringer 110 having a semi-circular cross-section. In this embodiment, the hat 111 is formed by one continuous arc. Various shapes of this arc (e.g., an arc with a continuous radius, an arc with a varying radius) are also within the scope of this shape. Similar to the embodiment of FIG. 1A, the flange 116 is used to attach the stringer 110 to the lower structure 102.

[0014] Figure 1C is a schematic cross-sectional view of a stringer 110 having an L-shaped contour. Specifically, the stringer 110 includes a flange 116 and an extension 113 that forms a 90-degree angle with respect to the flange 116. However, other orientations of the extension 113 with respect to the flange 116 (e.g., various angles) are also within the scope. Similar to previous embodiments, the flange 116 is used to attach the stringer 110 to the lower structure 102.

[0015] Figure 1D is a schematic cross-sectional view of a stringer 110 having a T-shaped contour. Specifically, the stringer 110 includes two flanges 116 and an extension 113 that forms a 90-degree angle with respect to the flanges 116. The extension 113 is disposed between the two flanges 116. However, other orientations are also within the scope.

[0016] Figure 1E is a schematic cross-sectional view of a stringer 110 having a C-shaped contour. Specifically, the stringer 110 includes a flange 116 and two extensions 113. One of these extensions forms a 90-degree angle with respect to the flange 116, and the other is parallel to the flange 116.

[0017] Figures 1F and 1G are a schematic perspective view and a schematic top view, respectively, of the stringer 110 of Figure 1A. Specifically, Figure 1F shows three out-of-plane bends of the stringer 110 about an axis 103 parallel to the Y-axis. In particular, these axes 103 are also parallel to the flange 116 of the stringer 110. Figure 1G shows two in-plane bends of the stringer 110 about an axis 104 parallel to the Z-axis. In particular, these axes 104 are also perpendicular to the flange 116 of the stringer 110.

[0018] Examples of Stringer Forming Devices Referring to FIG. 4A, the stringer forming device 300 includes a pallet 310 and a die 320. The pallet 310 further includes a processing surface 314 and a cavity 318 that extends away from the processing surface 314 and into the pallet 310. FIG. 4A shows the die 320 and the hat portion 131 of the composite charge 130 disposed within the cavity 318. The combination of the die 320 and the cavity 318 is used to form the hat portion 131. More specifically, the die 320 is aligned with the cavity 318 along the Z-axis. The die 320 is also movable relative to the pallet 310 in a direction along the Z-axis. The Z-axis is perpendicular to the processing surface 314 of the pallet 310. Further, the die 320 has a cross-section corresponding to the cross-section of the cavity 318. In some embodiments, the cross-section of the die 320 has the same shape as the cross-section of the cavity 318, but is smaller to receive the hat portion 131 of the composite charge 130. The size difference between the die 320 and the cavity 318 is determined by the thickness of the composite charge 130.

[0019] The pallet 310 includes a plurality of pallet portions 319 that are rotatably coupled to each other. For example, FIG. 4A shows a plurality of pallet portions 319 including a first pallet portion 311, a second pallet portion 312, and a third pallet portion 313. The second pallet portion 312 is rotatably coupled to each of the first pallet portion 311 and the third pallet portion 313. More specifically, FIG. 4A shows a pivot point 399 between the first pallet portion 311 and the second pallet portion 312. In some embodiments, the first pallet portion 311 is rotatable relative to the second pallet portion 312 about a first axis 391, and the first axis 391 is perpendicular to the processing surface 314 of the pallet 310. The first axis 391 is parallel to the Z-axis. This type of rotation is referred to as in-plane bending. In the same or other embodiments, the first pallet portion 311 is rotatable relative to the second pallet portion 312 about a second axis 392, and the second axis 392 is parallel to the processing surface 314 of the pallet 310. This type of rotation is referred to as out-of-plane bending. The second axis 392 is perpendicular to the main axis of the stringer forming device 300 that extends along the cavity 318. The second axis 392 is also parallel to the Y-axis. FIG. 4A also shows a third axis 393 that is parallel to the X-axis. In some embodiments, the third axis 393 is the main axis of the stringer forming device 300 or at least parallel to its main axis.

[0020] In some embodiments, the plurality of pallet portions 319 include pallet rotation openings 315 disposed between each pair of adjacent pallets, as shown, for example, in FIG. 4A. The pallet rotation openings 315 allow the plurality of pallet portions 319 to rotate relative to each other (e.g., in-plane and / or out-of-plane) without distorting the structure of the plurality of pallet portions 319, e.g., without bending the individual pallets. In some embodiments, the plurality of pallet portions 319 are formed from a bendable material that provides additional flexibility to the plurality of pallet portions 319, in addition to, for example, the pallet rotation openings 315.

[0021] In some embodiments, for example, when die 320 is inserted into cavity 318 and when the plurality of pallet portions 319 rotate relative to each other, die 320 is bendable. This feature rotates the plurality of pallet portions 319 while providing support to the hat portion 131 of composite charge 130, thereby reducing the risk of wrinkles.

[0022] In some embodiments, die 320 includes a die rotation opening 325 disposed at a pivot point, as shown, for example, in FIG. 5C. Die rotation opening 325 allows die 320 to bend when the plurality of pallet portions 319 rotate relative to each other (e.g., in-plane and / or out-of-plane). In some embodiments, die 320 bends without distorting the structure of die 320. In some embodiments, die 320 is formed from a bendable material that provides additional flexibility. The position of die rotation opening 325 corresponds to the position of pallet rotation opening 315, as schematically shown, for example, in FIG. 5C. In some embodiments, die 320 is formed from a bendable material and does not include die rotation opening 325.

[0023] Method embodiments FIG. 2A corresponds to a process flow chart of a method 200 for forming a curved composite charge for a stringer 110 having at least in-plane or out-of-plane bending, according to some embodiments of the present disclosure. In some embodiments, the curved composite charge and corresponding stringer 110 bend in both in-plane and out-of-plane directions. Further, stringer 110 can have any number of in-plane and / or out-of-plane bends.

[0024] The operation of method 200 is performed using stringer forming device 300. Its various embodiments have been described above with reference to, for example, FIG. 4A. Generally, stringer forming device 300 includes pallet 310 and die 320. Now, pallet 310 includes a plurality of pallet portions 319. Thereby, each pallet portion of the plurality of pallet portions 319 is rotatably coupled to at least one other of the plurality of pallet portions 319. Pallet 310 includes cavity 318. Cavity 318 extends through each pallet portion of the plurality of pallet portions 319. Cavity 318 is defined by cavity surface 317.

[0025] In some embodiments, method 200 begins with placing composite charge 130 on processing surface 314 of pallet 310 (block 210 in FIG. 2A). More specifically, composite charge 130 is placed covering cavity 318 of pallet 310, as schematically shown in, for example, FIG. 3A. Furthermore, composite charge 130 is placed covering and in contact with each pallet portion of the plurality of pallet portions 319.

[0026] Generally, any embodiment of composite charge 130 suitable for forming stringer 110 is within the scope of the present disclosure. For example, composite charge 130 includes an uncured pre-impregnated reinforcing tape or fabric that may be referred to as a prepreg. This tape or fabric includes fibers (such as graphite fibers) embedded in a matrix material (such as a polymer, or more specifically, an epoxy or phenolic resin). In some embodiments, the tape or fabric is unidirectional or woven depending on the design and the resulting desired degree of reinforcement in the composite stringer.

[0027] Referring to FIGS. 3A - 3C, the composite charge 130 includes a hat portion 131 and a flange portion 136 that is integral with and interconnected by the hat portion 131. The hat portion 131 is converted into the hat portion of the stringer when the composite charge 130 is formed. In some embodiments, the shape of the flange portion 136 remains substantially unchanged (e.g., remains in the same plane) when the composite charge 130 is formed. In some embodiments, the composite charge 130 is substantially linear / plane at least at this stage of the overall process.

[0028] Referring to FIG. 2A, method 200 proceeds to bring the hat portion 131 of the composite charge 130 into contact with the die 320 (block 220). During this operation, the die 320 is aligned with the cavity 318, as schematically shown in FIG. 3B for example. Note that at this stage, neither the hat portion 131 nor the die 320 protrudes into the cavity. Further, the flange portion 136 remains in contact with the processing surface 314 of the pallet 310.

[0029] Referring to FIG. 2A, method 200 proceeds to insert the die 320 into the cavity 318 (block 225). This die insertion operation includes bending at least the hat portion 131 to conform to the die 320 (block 230), as schematically shown in FIGS. 3C and 3D for example. At this stage, the hat portion 131 is compressed between the die 320 and the surface of the pallet 310 that forms the cavity 318. In this embodiment, the operations represented by blocks 230 and 225 overlap. Alternatively, the operations represented by blocks 230 and 225 are performed at different times. For example, before the die 320 is inserted into the cavity 318, the hat portion 131 is bent to conform to the die 320 using, for example, another device.

[0030] In some embodiments, the bending operation (block 230) includes positioning the flange portion 136 away from the processing surface 314, as schematically shown, for example, in FIG. 3C (block 232). A variety of techniques are within the scope. For example, the edge is slid over the processing surface 314 so as to lift the flange portion 136. In a more specific embodiment, the flange portion 136 is adapted to a sweeper 330, as schematically shown in FIG. 3D (block 234). It should be noted that the flange portion 136 is positioned away from the processing surface 314 either before, after, or during the insertion of the die 320 into the cavity 318. During a later operation, for example, after rotating two or more of the plurality of pallet portions 319 relative to each other, the flange portion 136 is pushed by the sweeper 330 to contact the processing surface 314, as schematically shown, for example, in FIG. 3E.

[0031] A variety of orientations of the flange portion 136 relative to the processing surface 314 are within the scope. For example, the angle (α) between each of the flange portions 136 and the processing surface 314 is between 45 degrees and 90 degrees. In some embodiments, this angle depends on the degree of in-plane bending that the composite charge 130 will undergo. In some embodiments, lifting the flange portion 136 away from the processing surface 314 is performed before bending the composite charge 130. In some embodiments, the flange portion 136 is adapted to a sweeper 330 disposed on the die 320, as schematically shown in FIG. 3D, for example.

[0032] In some embodiments, the bending operation (block 230) is independent of the insertion operation (block 225). For example, the hat portion 131 is formed, at least in part, using other forming tools before inserting the die 320 into the cavity 318, for example.

[0033] Referring to FIG. 2A, method 200 proceeds to rotate two or more of the plurality of pallet portions 319 relative to each other (block 250). The rotation is performed about one or more axes 390, as will be further described below. This rotation operation forms the curved composite charge 140. In some embodiments, while two or more of the plurality of pallet portions 319 are rotated relative to each other, die 320 remains inserted into cavity 318, which results in die 320 bending as will be further described below with reference to block 258. Die 320 provides support at least for hat portion 131 during this rotation operation.

[0034] An embodiment of one or more axes 390 is shown in FIG. 4A and is identified as a first axis 391, a second axis 392, and a third axis 393. Specifically, the plurality of pallet portions 319 comprises a first pallet portion 311 and a second pallet portion 312 that are rotatably coupled to each other. In some embodiments, the first pallet portion 311 and the second pallet portion 312 are rotated relative to each other about the first axis 391 (block 252). This embodiment may be referred to as in-plane rotation. This is because the first pallet portion 311 is perpendicular to the processing surface 314 of the pallet 310, as schematically shown in FIGS. 4C and 4D, for example. FIG. 4A shows a flange portion 136 disposed away from the processing surface 314. It facilitates rotation about the first axis 391 and reduces the risk of wrinkles.

[0035] In some embodiments, the first pallet portion 311 and the second pallet portion 312 are rotated relative to each other about a second axis 392 (block 256). This embodiment may be referred to as out-of-plane rotation. This is because the second axis 392 is parallel to the processing surface 314 of the pallet 310, as schematically shown in FIGS. 6A and 6B. Rotation about the second axis 392 does not require the flange portion 136 to be arranged to move away from the processing surface 314 as in the in-plane rotation described above. In some embodiments, this type of rotation is performed with the flange portion 136 in contact with the processing surface 314. Thus, in some embodiments, method 200, or more specifically the pallet rotation operation (block 250), includes changing the orientation of the flange portion 136 (block 254).

[0036] In some embodiments, the first pallet portion 311 and the second pallet portion 312 are rotated relative to each other about both a first axis 391 and a second axis 392, as also shown in FIGS. 4B and 4C and FIGS. 6A and 6B. For example, these pallet portions 319 are first rotated (relative to each other) about the first axis 391 before being rotated about the second axis 392. More specifically, in some embodiments, once rotation about the first axis 391 is complete, before rotation about the second axis 392, method 200 includes changing the orientation of the flange portion 136 relative to the processing surface 314, e.g., arranging the flange portion 136 to be in contact with the processing surface 314. Alternatively, these pallet portions are rotated (relative to each other) about the first axis 391 and the second axis 392 simultaneously.

[0037] In some embodiments, two or more of the plurality of pallet portions 319 are rotated relative to each other after the die 320 is inserted into the cavity 318 and the hat portion 131 is disposed between the die 320 and the cavity surface 317. In other words, the rotation operation (block 250) also includes bending the die 320 (block 258). As further described below, the die 320 is bendable and enables the hat portion 131 to be supported while the plurality of pallet portions 319 are rotated.

[0038] In some embodiments, the operations represented by blocks 225 and 250 of FIG. 2A overlap in time. Specifically, two or more of the plurality of pallet portions 319 are rotated relative to each other while the die 320 is being inserted into the cavity 318. More specifically, various processing parameters associated with the insertion operation (block 225) and various processing parameters associated with the bending operation (block 250) are also dynamically controlled. For example, the start time of each operation, the speed of each operation, and / or other similar parameters vary during the operation. More specifically, the rotation speed at which two or more of the plurality of pallet portions 319 are rotated relative to each other and the insertion speed at which the die 320 is inserted into the cavity 318 are dynamically controlled.

[0039] In some embodiments, at least two of the plurality of pallet portions 319 have different lengths, as schematically shown in FIGS. 4B and 4C, for example. For example, the length of each pallet portion depends on the required curvature of the stringer 110, e.g., the distance between adjacent bending points. In some embodiments, the pallet 310 is a highly articulated pallet formed from short pallet portions. Thereby, any two adjacent pallet portions can rotate relative to each other about at least two axes.

[0040] In some embodiments, the processing surface 314 of the pallet 310 has one or more notches between each adjacent pair of the plurality of pallet portions 319. The one or more notches enable two or more of the plurality of pallet portions 319 to rotate relative to each other (block 250). These notches are schematically shown in FIGS. 4A - 4C for in - plane rotation and in FIG. 6A for out - of - plane rotation.

[0041] In some embodiments, for example, when the flange portion 136 is previously disposed away from the processing surface 314, the method 200 further includes disposing the flange portion 136 in contact with the processing surface 314 (block 260). The flange portion 136 disposed in contact with the processing surface 314 is schematically shown not only in FIGS. 5A and 5B but also in FIG. 3E. This operation is performed after two or more of the plurality of pallet portions 319 have been rotated relative to each other.

[0042] In some embodiments, the flange - placement operation (block 260) includes sweeping the flange portion 136 using a sweeper 330, as schematically shown in FIGS. 3D and 3E, for example. Specifically, the sweeper 330 moves away from the die 320 and presses the flange portion 136 into contact with the processing surface 314.

[0043] In some embodiments, this flange - placement operation (block 260) includes inflating a bladder 340 disposed between the processing surface 314 and a restraint plate 350, as schematically shown in FIG. 5A, for example. When the bladder 340 inflates, it increases in size and presses the flange portion 136 into contact with the processing surface 314. Further, in some embodiments, the restraint plate 350 moves downward toward the pallet 310. In these embodiments, the bladder 340 pressurizes and consolidates the flange portion 136.

[0044] Referring to FIG. 5B, in some embodiments, the restraint plate 350 includes a plate rotation opening 355 disposed at the pivot point. The plate rotation opening 355 allows the restraint plate 350 to bend as the plurality of pallet portions 319 rotate relative to each other (e.g., in-plane and / or out-of-plane). In some embodiments, the restraint plate 350 bends without distorting the structure of the restraint plate 350. In some embodiments, the restraint plate 350 is formed from a bendable material that provides additional flexibility. The position of the plate rotation opening 355 corresponds to the position of the pallet rotation opening 315, as schematically shown, for example, in FIG. 5B. In some embodiments, each sweeper 330 is coupled to a respective restraint plate 350, and thus, in such an embodiment, the sweeper 330 is also configured to rotate relative to each other.

[0045] In some embodiments, method 200 further includes withdrawing die 320 from cavity 318 (block 270), separating the curved composite charge 140 from pallet 310 (block 272), and curing the curved composite charge 140 to thereby form stringer 110 (block 274).

[0046] FIG. 2B is a process flow chart corresponding to another embodiment of a method for forming a curved composite charge having in-plane and / or out-of-plane bending. This embodiment may be referred to as method 290. Method 290 is similar to method 200 (shown in FIG. 2A) in several respects. Thus, method 290 is described in the general context and with reference to method 200. However, it should be clearly noted that any possibilities and variations described above in connection with method 200 may equally apply to method 290.

[0047] Method 290 includes inserting die 320 and a composite charge (e.g., composite charge 130) into cavity 318 of pallet 310 (block 292). As described above, pallet 310 includes a plurality of pallet portions 319 rotatably coupled to each other. Method 290 includes rotating two or more of the plurality of pallet portions 319 relative to each other about one or more axes 390, thereby forming a curved composite charge 140 from composite charge 130 (block 295).

[0048] Within the scope of the embodiments, inserting die 320 and composite charge 130 into cavity 318 includes bending hat portion 131 of composite charge 130 by inserting die 320 into cavity 318 (block 293).

[0049] Within the scope of the embodiments, rotating includes rotating two or more of the plurality of pallet portions 319 relative to each other about a first axis 391 (block 296) and / or rotating two or more of the plurality of pallet portions (319) relative to each other about a second axis 392 (block 297).

[0050] Within the scope of embodiments of method 290, flange portion 136 of composite charge 130 is disposed to move away from the plurality of pallet portions 319 when two or more of the plurality of pallet portions 319 are rotated relative to each other.

[0051] Within the scope of embodiments of method 290, two or more of the plurality of pallet portions 319 are rotated relative to each other while die 320 is inserted into cavity 318.

[0052] Within the scope of embodiments of method 290, two or more of the plurality of pallet portions 319 are rotated relative to each other after die 320 has been inserted into cavity 318.

[0053] Within the scope of embodiments of method 290, rotating two or more of the plurality of pallet portions 319 relative to each other includes bending die 320 while die 320 is inserted into cavity 318.

[0054] Aircraft embodiments Some of the embodiments, methods, and systems described above are used by aircraft, and more generally, by the aerospace industry. Specifically, these methods and systems can be used not only during the maintenance and servicing of aircraft but also during the manufacture of aircraft.

[0055] Accordingly, the apparatus and methods described above are applicable to the aircraft manufacturing and maintenance method 900 shown in FIG. 7 and to the aircraft 902 shown in FIG. 8. In the pre-manufacture stage, method 900 includes the specification and design 904 of aircraft 902 and the procurement 906 of materials. In the manufacturing stage, the manufacture 908 of the components and sub-assemblies of aircraft 902 and the system integration 910 are performed. Thereafter, aircraft 902 undergoes certification and delivery 912 in order to be put into operation 914. While being operated by the customer, aircraft 902 is scheduled for periodic maintenance and servicing 916, which also includes modifications, reconfigurations, repairs, etc.

[0056] In some embodiments, each of the processes of method 900 can be performed or executed by a system integrator, a third party, and / or an operator, such as, for example, a customer. For the purposes of this description, a system integrator includes, but is not limited to, any number of aircraft manufacturers and subcontractors of major systems, a third party includes, but is not limited to, any number of vendors, subcontractors, and suppliers, and an operator can be an airline, a leasing company, a military entity, a service organization, etc.

[0057] As shown in FIG. 8, an aircraft 902 manufactured by method 900 includes a fuselage 918 having a plurality of systems 920 and an interior 922. Examples of systems 920 include one or more of a propulsion system 924, an electrical system 926, a hydraulic system 928, and an environmental system 930. Any number of other systems may also be included. Although an example of the aerospace industry is shown, the principles of the examples described herein may be applied to other industries such as the automotive industry.

[0058] The devices and methods presented herein may be employed during any one or more of the stages of method 900. For example, components or subassemblies corresponding to manufacturing 908 are fabricated or manufactured in a manner similar to components or subassemblies that are manufactured during operation of aircraft 902. Also, one or more examples of devices, examples of methods, or combinations thereof are utilized during manufacturing 908 and system integration 910, for example, by substantially streamlining the assembly of aircraft 902 or reducing the cost of aircraft 902. Similarly, one or more of the examples of devices, examples of methods, or combinations thereof are utilized during operation of aircraft 902, for example, but not limited to, servicing and maintenance 916.

[0059] Further Examples Furthermore, the description includes examples according to the following clauses. Clause 1. A method for forming a curved composite charge, placing the composite charge on a processing surface of a pallet and covering a cavity of the pallet, wherein the composite charge comprises a hat portion and a flange portion, the flange portion being integral with and interconnected by the hat portion, the pallet comprises a plurality of pallet portions, each pallet portion of the plurality of pallet portions being rotatably coupled to at least one other pallet portion of the plurality of pallet portions, the cavity extending through each pallet portion of the plurality of pallet portions, The composite charge is disposed to cover each of the plurality of pallet portions and to contact each of the plurality of pallet portions, and the composite charge is disposed on the processing surface of the pallet and to cover the cavity of the pallet. Contacting the hat portion of the composite charge with the die such that the die is aligned with the cavity defined by the cavity surface. Bending at least the hat portion to conform to the die. Inserting the die into the cavity such that the hat portion is disposed between the die and the cavity surface and conforming to each of the die and the cavity surface, and A method comprising rotating two or more of the plurality of pallet portions relative to each other about one or more axes, thereby forming a curved composite charge. Clause 2. The method according to clause 1, wherein when the two or more of the plurality of pallet portions are rotated relative to each other, the flange portion is disposed to be away from the processing surface of the pallet. Clause 3. The method according to clause 2, wherein bending at least the hat portion includes disposing the flange portion to be away from the processing surface. Clause 4. The method according to clause 3, wherein disposing the flange portion to be away from the processing surface includes conforming the flange portion to a sweeper disposed on the die. Clause 5. The method according to clause 2, further comprising disposing the flange portion to contact the processing surface after two or more of the plurality of pallet portions are rotated relative to each other. Clause 6. Disposing the flange portion to contact the processing surface includes Sweeping the flange portion with a sweeper disposed on the die. Expanding a bladder disposed between the processing surface and the binding plate, or Using the binding plate to press the flange portion into contact with the processing surface, the method according to clause 5, comprising one or more of the above. Clause 7. The method according to any one of clauses 1 to 6, wherein the one or more axes include a first axis perpendicular to the processing surface of the pallet. Clause 8. The method according to any one of clauses 1 to 7, wherein the one or more axes include a second axis parallel to the processing surface of the pallet. Clause 9. The one or more axes include a first axis and a second axis, The first axis is perpendicular to the processing surface of the pallet, The second axis is parallel to the processing surface of the pallet, The method according to any one of clauses 1 to 8, further comprising rotating two or more of the plurality of pallet portions relative to each other about the first axis and the second axis. Clause 10. The method according to clause 9, wherein two or more of the plurality of pallet portions are rotated relative to each other about the first axis before being rotated about the second axis. Clause 11. The method according to clause 9, wherein two or more of the plurality of pallet portions are rotated relative to each other about the first axis and the second axis simultaneously. Clause 12. The method according to clause 9, further comprising changing the orientation of the flange portion with respect to the processing surface after two or more of the plurality of pallet portions are rotated relative to each other about the first axis and before being rotated about the second axis. Clause 13. Pulling the die out of the cavity, Separating the curved composite charge from the pallet, and The method according to any one of clauses 1 to 12, further comprising curing the curved composite charge, thereby forming a stringer. Clause 14. The method according to any one of clauses 1 to 13, wherein after the die is inserted into the cavity and the hat portion is disposed between the die and the cavity surface, the two or more of the plurality of pallet portions are rotated relative to each other. Clause 15. The method according to any one of clauses 1 to 14, wherein the two or more of the plurality of pallet portions are rotated relative to each other while the die is inserted into the cavity. Clause 16. The method according to clause 15, wherein a rotation speed at which the two or more of the plurality of pallet portions are rotated relative to each other and an insertion speed at which the die is inserted into the cavity are dynamically controlled. Clause 17. The method according to any one of clauses 1 to 16, wherein at least two of the plurality of pallet portions have different lengths. Clause 18. The method according to any one of clauses 1 to 17, wherein rotating two or more of the plurality of pallet portions relative to each other includes bending the die while the die is inserted into the cavity. Clause 19. The processing surface of the pallet includes one or more cutouts between each adjacent pair of the plurality of pallet portions, The method according to any one of clauses 1 to 18, wherein the one or more cutouts enable the two or more of the plurality of pallet portions to be rotated relative to each other. Clause 20. The method according to any one of clauses 1 to 19, wherein rotating two or more of the plurality of pallet portions relative to each other is performed while the flange portion is disposed in contact with the processing surface. Clause 21. Inserting a die and a composite charge into a cavity of a pallet having a plurality of pallet portions rotatably coupled to each other, and rotating two or more of the plurality of pallet portions relative to each other about one or more axes, thereby forming a composite charge curved from the composite charge, a method. Clause 22. The method according to clause 21, wherein when the two or more of the plurality of pallet portions are rotated relative to each other, a flange portion of the composite charge is arranged to be separated from the plurality of pallets. Clause 23. The method according to clause 21 or 22, wherein the two or more of the plurality of pallet portions are rotated relative to each other while the die is inserted into the cavity. Clause 24. The method according to any one of clauses 21 to 23, wherein the two or more of the plurality of pallet portions are rotated relative to each other after the die is inserted into the cavity. Clause 25. The method according to clause 24, wherein rotating two or more of the plurality of pallet portions relative to each other includes bending the die while the die is inserted into the cavity. Clause 26. A pallet having a plurality of pallet portions, each pallet portion of the plurality of pallet portions being rotatably coupled to at least one other pallet portion of the plurality of pallet portions, the pallet further comprising a processing surface and a cavity extending away from the processing surface and into the pallet, a pallet, and A die aligned with the cavity and having a cross-section corresponding to a cross-section of the cavity, the die being movable relative to the pallet in a direction perpendicular to the processing surface of the pallet, a stringer forming device. Clause 27. The stringer forming device according to clause 26, wherein when the die is inserted into the cavity and the plurality of pallet parts rotate relative to each other, the die is bendable. Clause 28. The stringer forming device according to clause 26 or 27, wherein the plurality of pallet parts are rotatable relative to each other about one or more axes including a first axis perpendicular to the processing surface of the pallet. Clause 29. The stringer forming device according to clause 28, wherein the plurality of pallet parts are rotatable relative to each other about one or more axes including a second axis parallel to the processing surface of the pallet. Clause 30. The stringer forming device according to any one of clauses 26 to 29, wherein the plurality of pallet parts are rotatable relative to each other about one or more axes including a second axis parallel to the processing surface of the pallet. Clause 31. The stringer forming device according to any one of clauses 26 to 30, further comprising a sweeper slidably coupled to the die and configured to slide in a direction parallel to the processing surface.

[0060] Conclusion Although the foregoing concepts have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the appended claims. Note that there are numerous alternative manners of implementing the processes, systems, and apparatuses. Therefore, the embodiments herein should be regarded as illustrative and not limiting.

Claims

Claim 1 A method (200) for forming a curved composite charge, comprising: placing a composite charge (130) on a processing surface (314) of a pallet (310) and covering a cavity (318) of the pallet (310) (210), wherein the composite charge (130) comprises a hat portion (131) and a flange portion (136), the flange portion (136) being integral with and interconnected by the hat portion (131), the pallet (310) comprises a plurality of pallet parts (319), each pallet part of the plurality of pallet parts being rotatably coupled to at least one other pallet part of the plurality of pallet parts, the cavity (318) extends through each pallet part of the plurality of pallet parts, placing the composite charge (130) on the processing surface (314) of the pallet (310) and covering the cavity (318) of the pallet (310), wherein the composite charge (130) is disposed to cover each pallet part of the plurality of pallet parts and contact each pallet part of the plurality of pallet parts (210), contacting the hat portion (131) of the composite charge (130) with a die (320) such that the die (320) is aligned with the cavity (318) defined by a cavity surface (317) (220), bending at least the hat portion (131) to conform to the die (320) (230), inserting the die (320) into the cavity (318) such that the hat portion (131) is disposed between the die (320) and the cavity surface (317) and conforms to each of the die (320) and the cavity surface (317) (225), and rotating two or more of the plurality of pallet parts relative to each other about one or more axes (390), thereby forming a curved composite charge (140) (250), wherein the one or more axes (390) include a first axis (391) and a second axis (392), the first axis (391) is perpendicular to the processing surface (314) of the pallet (310), the second axis (392) is parallel to the processing surface (314) of the pallet (310). The method (200) further includes rotating (250) the two or more pallet portions among the plurality of pallet portions (319) relative to each other about the first axis (391) and the second axis (392). **Claim 2** The method (200) according to claim 1, wherein when the two or more pallet portions among the plurality of pallet portions (319) are rotated relative to each other, the flange portion (136) is arranged to be separated from the processing surface (314) of the pallet (310). **Claim 3** The method (200) according to claim 2, wherein bending (230) at least the hat portion (131) includes arranging (232) the flange portion (136) to be separated from the processing surface (314). **Claim 4** The method (200) according to claim 3, wherein arranging (232) the flange portion (136) to be separated from the processing surface (314) includes adapting (234) the flange portion (136) to a sweeper (330) arranged on the die (320). **Claim 5** The method (200) according to claim 2 further includes arranging (260) the flange portion (136) to contact the processing surface (314) after the two or more pallet portions among the plurality of pallet portions (319) are rotated relative to each other. **Claim 6** Arranging (260) the flange portion (136) to contact the processing surface (314) includes sweeping the flange portion (136) with a sweeper (330) arranged on the die (320), inflating a bladder (340) arranged between the processing surface (314) and a binding plate (350), or pushing the flange portion (136) to contact the processing surface (314) using the binding plate (350), and includes one or more of the above, the method (200) according to claim 5. **Claim 7** The method (200) according to any one of claims 1 to 6, wherein at least two of the plurality of pallet portions (319) have different lengths from each other. **Claim 8** The method (200) according to claim 7, further comprising changing (254) the orientation of the flange portion (136) with respect to the processing surface (314) after the two or more pallet portions of the plurality of pallet portions (319) are rotated relative to each other about the first axis (391) and before being rotated about the second axis (392).

9. The processing surface (314) of the pallet (310) includes one or more cutouts between each adjacent pair of the plurality of pallet portions (319), The method (200) according to any one of claims 1 to 8, wherein the one or more cutouts enable (250) two or more of the plurality of pallet portions (319) to be rotated relative to each other.

10. A pallet (310) comprising a plurality of pallet portions (319), each pallet portion of the plurality of pallet portions (319) being rotatably coupled to at least one other pallet portion of the plurality of pallet portions (319), the pallet (310) further comprising a processing surface (314) and a cavity (318) extending away from the processing surface (314) and into the pallet (310), and a die (320) aligned with the cavity (318) and having a cross-section corresponding to the cross-section of the cavity (318), the die (320) being movable relative to the pallet (310) in a direction perpendicular to the processing surface (314) of the pallet (310), rotating two or more of the plurality of pallet portions (319) relative to each other about one or more axes (390), the one or more axes (390) including a first axis (391) and a second axis (392), the first axis (391) being perpendicular to the processing surface (314) of the pallet (310), the second axis (392) being parallel to the processing surface (314) of the pallet (310), A stringer forming device (300) in which two or more of the plurality of pallet portions (319) are rotated relative to each other about the first axis (391) and the second axis (392).

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