Method of forming a mandrel for forming a composite structure, method of forming a composite structure, and related tooling

Abstract

A tool for forming a composite structure can have two or more segments (102, 104) formed from a polymeric material. The tool can further have a crush insert (106) disposed between the two or more segments. The tool can also have a support shaft connected between the two or more segments. A method of forming a mandrel can include forming the segments of the mandrel through an additive manufacturing process. The method can further include assembling the segments relative to one another. The method can further include disposing a crush insert between each of the segments. A method of making a composite structure is also disclosed.

Description

[Technical Field]

[0001] This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63 / 169,662, filed April 1, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to methods of forming composite structures. In particular, embodiments of the present disclosure relate to methods of forming composite structures and associated tools and systems. [Background technology]

[0003] When forming a composite structure, a hard-surfaced mandrel may be used to assemble the layers of insulating rubber and composite material. The mandrel can support the insulation, composite membrane material, and skirt material during the winding process, in which the fiber filaments that will form the composite are wound around the insulation, composite membrane material, skirt material, and mandrel. The mandrel also maintains rigidity during the curing of the rubber and composite material. During the curing process, heat and pressure are applied to the composite structure and mandrel as the rubber and composite material harden. After curing, the mandrel is removed from the composite structure, leaving a cavity where the mandrel was located. Therefore, the mandrel should be formed in a manner that allows it to be removed without any damage or deformation to the inner rubber or composite material. Summary of the Invention [Means for solving the problem]

[0004] Embodiments of the present disclosure may include a method of forming a mandrel for forming a composite structure. The method may include forming segments of the mandrel through an additive manufacturing process. The method may further include assembling the segments to one another. The method may further include disposing crush inserts between adjacent segments.

[0005] Another embodiment of the present disclosure may include a tool for forming a composite structure. The tool may have two or more segments formed from a polymeric material. The tool may further include a crush insert disposed between the two or more segments. The tool may further include a support shaft connected between the two or more segments.

[0006] Another embodiment of the present disclosure may include a method of making a composite structure. The method may include assembling a mandrel. Assembling the mandrel may include forming segments of the mandrel through an additive manufacturing process. Assembling the mandrel may further include assembling the segments relative to one another. Assembling the mandrel may further include disposing a crush insert between each of the segments. Assembling the mandrel may further include coupling the segments to a support shaft. The method of making a composite structure may further include coupling the support shaft to a winding machine. The method may further include winding composite fibers around the mandrel to form the composite structure. The method may further include heating the composite structure. The method may further include separating the mandrel from the composite structure.

[0007] While the specification concludes with claims particularly pointing out and distinctly claiming embodiments of the present disclosure, the advantages of embodiments of the present disclosure may be more readily ascertained from the following description of embodiments of the present disclosure when read in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a mandrel according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a perspective view of a mandrel assembly according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a side view of a crush insert according to an embodiment of the present disclosure. [Figure 4] 3A-3C illustrate processing steps for forming a composite structure over the mandrel of the embodiment shown in FIGS. 1 and 2. FIG. [Figure 5] 3A-3C illustrate processing steps for forming a composite structure over the mandrel of the embodiment shown in FIGS. 1 and 2. FIG. [Figure 6] 3A-3C illustrate processing steps for forming a composite structure over the mandrel of the embodiment shown in FIGS. 1 and 2. FIG. [Figure 7] 3A-3C illustrate processing steps for forming a composite structure over the mandrel of the embodiment shown in FIGS. 1 and 2. FIG. [Figure 8] 3A-3C illustrate processing steps for forming a composite structure over the mandrel of the embodiment shown in FIGS. 1 and 2. FIG. [Figure 9] 9A-9C illustrate processing steps for removing the mandrel from the composite structure formed by the processing steps shown in FIGS. 4-8. [Figure 10] 9A-9C illustrate processing steps for removing the mandrel from the composite structure formed by the processing steps shown in FIGS. 4-8. [Figure 11] 9A-9C illustrate processing steps for removing the mandrel from the composite structure formed by the processing steps shown in FIGS. 4-8. DETAILED DESCRIPTION OF THE INVENTION

[0009] The illustrations presented herein are not intended to be actual representations of any particular tooling for making composite structures or components of composite structures, but are merely idealized representations employed to explain example embodiments. The drawings are not necessarily to scale.

[0010] As used herein, the term "substantially" when referring to a given parameter means and includes the degree to which one skilled in the art would understand that the given parameter, characteristic, or condition conforms to small variations, such as within acceptable manufacturing tolerances. For example, a parameter that conforms substantially can conform at least about 90%, at least about 95%, at least about 99%, or even at least about 100%.

[0011] As used herein, relative terms such as "first," "second," "top," "bottom," and the like are generally used for clarity and convenience in understanding this disclosure and the accompanying drawings, and do not imply or rely on any particular preference, orientation, or order unless the context clearly indicates otherwise.

[0012] As used herein, the term "and / or" means and includes any and all combinations of one or more of the associated listed items.

[0013] As used herein, the terms "vertical" and "lateral" refer to the orientation depicted in the figures. Large hollow composite structures, such as pressure vessels and rocket engines, can be formed on hard-surfaced mandrels to define hollow cavities within the composite structure. Hard-surfaced mandrels can be used to assemble layers of insulating rubber and composite material into a desired shape. The mandrel can serve many functions, such as supporting the insulator, composite membrane material, and skirt material during the winding process. The mandrel also maintains rigidity during curing of the insulating rubber and composite material. Heat and pressure are applied to the mandrel as the insulating rubber and composite material solidify during the curing process. After curing, the mandrel is removed from the resulting composite structure. Therefore, the mandrel should be formed in a manner that allows it to be removed without significantly damaging or deforming the inner insulating rubber or composite material. Thermal expansion of the mandrel during the curing process is one factor that can determine the interior shape of the composite structure. Typically, a material with a hard, low thermal expansion is desired for the mandrel. This is because such materials exhibit predictable properties under load.

[0014] The mandrel may be formed from a metallic material such as steel. Steel offers high strength, high stiffness, and low thermal expansion. Steel is also strong and less susceptible to wear compared to other materials. However, steel mandrels can be heavy and expensive to produce. In some instances, steel mandrels can take months, if not years, to design, procure, and implement. Additionally, steel mandrels can have complex assembly and disassembly processes.

[0015] Another material that can be used to form the mandrel is plaster, such as plaster of Paris. Plaster can be rigid when hardened and can have low thermal expansion. Gypsum materials can be inexpensive and relatively easy to obtain. However, plaster requires a rigid framework for support. This framework can be formed from a metal material, such as steel. The framework can be designed to prevent the plaster from cracking during wrapping and hardening. Forming a mandrel from plaster can require a significant amount of time to add the plaster to the framework. Furthermore, plaster can be brittle and easily damaged, which can damage the mandrel and incur additional loss and expense. Adding plaster over an underlying framework can take several weeks. After wrapping and hardening, the plaster can be removed from the composite structure by allowing water to soften the plaster and scraping it from the interior of the composite structure.

[0016] Silica sand can also be used to make the mandrel. The sand can be formed in an outer mold to form the desired shape of the sand. After the sand hardens, it can be removed from the mold and processed in preparation for wrapping. Like gypsum, the silica sand mandrel can be fragile and easily damaged. Therefore, care must be taken not to crack the sand during wrapping. After wrapping and curing, water is used to wash the sand from the interior of the composite structure.

[0017] Forming reusable mandrels from low-cost, strong, rigid materials that can be easily assembled and disassembled can reduce the cost of forming composite structures, such as pressure vessels, rocket engines, etc. Additionally, reusable mandrels that can be procured on short notice can encourage innovation by allowing design changes to be implemented and / or tested without requiring excessive lead times and costs to make changes to the mandrel.

[0018] 1 illustrates an embodiment of a mandrel 100 according to an embodiment of the present disclosure. The mandrel 100 may be formed from multiple segments, such as a wedge segment 102 and a connecting segment 104. The wedge segment 102 and / or the connecting segment 104 may be formed from a rigid material, such as a metallic or polymeric material. The wedge segment 102 may have a generally wedge-shaped cross-section, and the connecting segment 104 may be disposed between two adjacent wedge segments 102.

[0019] The material of the segments 102, 104 may be configured to be stable (e.g., rigid rather than flexible) at the curing temperature of the composite material of the associated composite structure. For example, the material may be stable at temperatures between about 200°F and about 400°F (e.g., between about 285°F and about 320°F, etc.).

[0020] The segments 102, 104 may be formed through an additive manufacturing process (e.g., 3D printing), such as fused filament fabrication (FFF), large scale additive manufacturing (LSAM), stereolithography (SLA), digital light processing (DLP), multijet fusion (MJF), polyjet, selective laser sintering (SLS), direct deposition modeling (DDM), direct metal laser sintering (DMLS), continuous carbon fiber manufacturing, or electron beam melting (EBM). The type of additive manufacturing process may be selected based on the size of the associated segments 102, 104. For example, some additive manufacturing processes may be less expensive and more effective for producing smaller parts, whereas more expensive additive manufacturing processes may be more effective for producing larger parts. In some cases, an inexpensive process may be used for some segments 102, 104, and an expensive process may be used for segments 102, 104 that are too large to be formed by the inexpensive process. In some cases, the size and configuration of the segments 102, 104 may be determined based on the desired additive manufacturing process. For example, the mandrel 100 may be formed from a larger number of relatively small segments 102, 104 to aid in forming the segments 102, 104 through an inexpensive additive manufacturing process. In other cases, the mandrel 100 may be formed from a fewer number of relatively large segments 102, 104 to save time in assembling and disassembling the mandrel 100. In some embodiments, the type of material used to form the segments 102, 104 may determine the type of additive manufacturing process.

[0021] In some cases, the segments 102, 104 may be formed by fusing individual layers of material onto one another to form the desired shape of the segments 102, 104. Forming the segments 102, 104 as layers can help customize internal structures, such as support ribs, within the associated segments 102, 104. Accordingly, internal support structures can be constructed to support areas of each segment 102, 104 (areas that may experience the greatest loads during layup and curing processes). This can further help create voids within the associated segments 102, 104, thereby reducing the weight and material costs of the associated segments 102, 104. Surface finish may be related to layer thickness. For example, forming thinner layers may result in a smoother surface finish, whereas forming thicker layers may result in a rougher surface finish. Similarly, the amount of time to form each segment 102, 104 may be related to the thickness of the individual layers due to the number of passes used to reach the desired thickness. For example, forming the associated segments 102, 104 to a desired thickness with thinner individual layers may take a greater amount of time than forming the same segments 102, 104 to a desired thickness with thicker individual layers. As layer thickness increases, the definition of more intricate features of the individual segments 102, 104 may decrease. In some cases, a rough surface finish and / or intricate features with insufficient solidity may be corrected through processes such as machining, sanding, polishing, etc.

[0022] The segments 102, 104 may be formed from a polymeric material, such as a polyetherimide material (e.g., ULTEM® 1010 and ULTEM® 9085), glass-filled ULTEM® (e.g., 30% glass-filled ULTEM®), or carbon-filled ULTEM® (e.g., 30% carbon-filled ULTEM®). The polymeric material may be configured to withstand cure temperatures exceeding approximately 160°C (320°F). The polymeric material may have a coefficient of thermal expansion (CTE) significantly higher than that of steel, gypsum, or silica sand. To account for the expansion of the segments 102, 104 formed from a polymeric material, the joint 106 between the segments 102, 104 may include a crush insert 300, which will be described in more detail below in connection with FIG. 3. The crush insert 300 may allow the segments 102, 104 to expand while substantially maintaining the same outer shape of the mandrel 100. The crush insert 300 may be secured within the joint 106 between the segments 102 and 104. For example, the crush insert 300 may be secured by frictional interference between the joined segments 102, 104 and the crush insert 300. In some cases, the crush insert 300 may be secured by an adhesive substance, such as glue, epoxy, or tape. In some embodiments, the segments 102, 104 may have retention features configured to capture and retain the crush insert 300 during assembly of the mandrel 100. In some embodiments, the crush insert 300 may be formed directly on the associated segment 102, 104, as described in more detail below.

[0023] In some embodiments, intricate details may be formed on the segments 102, 104 using a removable material, such as a single-use material. For example, a soluble polymer (e.g., a water-soluble polymer or a mild acid-soluble polymer) may be used to form intricate details on the outer surface of the associated segments 102, 104. A composite material may then be formed over the associated mandrel with the intricate details formed from the soluble polymer. The composite material may conform to the contours of the soluble polymer. After the composite material has hardened, a solution configured to dissolve the soluble polymer may be disposed between the mandrel and the composite material to dissolve the soluble polymer to leave a conforming contour formed in the composite material.

[0024] The mandrel 100 can have a bore 108 defined through a central portion of the mandrel 100. The bore 108 can be configured to couple the mandrel 100 to a support shaft 202 ( FIG. 2 ) that can be used to secure the segments 102, 104 relative to one another and / or to secure the mandrel 100 relative to a winding tool, such as a winding machine, winding jig, etc. The bore 108 can have one or more alignment features 110, such as keyways, channels, protrusions, etc.

[0025] 2 shows an exploded view of an embodiment of mandrel 100 including a support shaft 202 disposed within bore 108. Support shaft 202 may be formed from a rigid material having a low CTE, such as a metallic material (e.g., steel).

[0026] The support shaft 202 may be configured to interface with a plurality of diverse mandrels 100. For example, the segments 102, 104 of a plurality of diverse mandrels 100 having different sizes and / or shapes may have substantially similar holes 108 and alignment structures 110 configured to receive the same support shaft 202. As a result, it may not be necessary to obtain a new support shaft 202 to change the design of the mandrel 100.

[0027] The support shaft 202 can have complementary alignment structures 204 that can be configured (e.g., sized and shaped) to interface with (e.g., be inserted into, receive, interlock, etc.) the alignment structures 110 in the bore 108. The complementary alignment structures 204 can be configured to secure the segments 102, 104 both rotationally and radially. In other words, when assembled with the segments 102, 104, the complementary alignment structures 204 can at least substantially prevent rotational and radial movement of the segments 102, 104 relative to the support shaft 202. For example, complementary alignment structures 204 may radially secure associated segments 102, 104 to the support shaft 202 such that the secured segments 102, 104 may secure adjacent segments 102, 104 via contact at the joints 106, such as by interference, friction, or complementary features within the joints 106. The complementary alignment structures 204 may also rotationally secure the segments 102, 104 such that the mandrel 100 rotates with the support shaft 202 even when the support shaft 202 rotates.

[0028] The support shaft 202 and complementary alignment structure 204 may be secured to an alignment support 206. The complementary alignment structure 204, e.g., a rod, dowel, or the like, may be separate from the support shaft 202. The alignment support 206 may have recesses configured to receive the complementary alignment structure 204 and circumferentially position the complementary alignment structure 204 relative to one another. The alignment support 206 may further have structure configured to secure the alignment support 206 to the support shaft 202. For example, the alignment support 206 and the support shaft 202 may have alignment holes configured to receive hardware such as pins, screws, bolts, studs, or the like.

[0029] The boss 208 can be coupled to the mandrel 100 through a boss support 210. The boss support 210 can have a plurality of hardware connectors, such as screws, bolts, or holes configured to receive hardware, such as bolts, screws, or studs. The boss 208 can be formed through an additive manufacturing process similar to that of the segments 102, 104.

[0030] The support shaft 202 can be coupled to a drive shaft 212. The drive shaft 212 can be coupled to a winding tool (not shown). The winding tool can control the position, such as the annular or rotational position, of the mandrel 100 via the drive shaft 212 during the winding process. For example, the winding tool can rotate the support shaft 202 along with the drive shaft 212. Rotation of the support shaft 202 can rotate the mandrel 100 due to interference between the alignment structure 204 and the alignment structure 110. The winding tool can also change the angle of the mandrel 100 relative to the winding tool by changing the angle of the drive shaft 212 and the support shaft 202 relative to the winding tool.

[0031] FIG. 3 illustrates a crush insert 300 that may be disposed within the joint 106 between the segments 102, 104 according to embodiments of the present disclosure. The crush insert 300 may be configured to deform under loads associated with thermal expansion of the segments 102, 104 during hardening of the composite structure. Deforming the crush insert 300 can absorb forces that would otherwise act on the composite structure during hardening. Absorbing the forces can significantly reduce deformation and / or degradation of the segments 102, 104 with which the crush insert 300 is associated, such that the segments 102, 104 may be reused with little or no repair required between uses. In some embodiments, the crush insert 300 can deform a constant amount under a given load. In some cases, the crush insert 300 may be "pre-crushed" to allow it to deform a constant amount. In other embodiments, the crush insert 300 can be compressed a non-constant amount under loads applied by thermal expansion.

[0032] The crush insert 300 may be constructed with voids 302 within it that allow the structure to collapse (e.g., deform) under load. For example, the crush insert 300 may be formed from an aluminum honeycomb structure, such as PACL-XR1, sold by PLASCORE®, located in Michigan. In other embodiments, the crush insert 300 may be formed through an additive manufacturing or 3D printing process, such as fused filament fabrication (FFF), large-scale additive manufacturing (LSAM), stereolithography (SLA), digital light processing (DLP), multi-jet fusion (MJF), polyjet, selective laser sintering (SLS), direct deposition modeling (DDM), direct metal laser sintering (DMLS), continuous carbon fiber processing, or electron beam melting (EBM). Additive manufacturing processes may be used to form the structure with voids 302 within it that allow the structure to collapse under load. Forming the crush insert 300 through an additive manufacturing process can allow the crush insert 300 to be designed to have specific compression characteristics, such as a planned compression load, a constant compression change, or a graduated compression change (e.g., a compression change that changes at different loads or during compression at a given load). In some embodiments, the crush insert 300 can be formed directly onto the segment 102, 104 through an additive manufacturing process. For example, after each use, a used crush insert 300 can be removed from the associated segment 102, 104, and a new crush insert 300 can then be formed onto the associated segment 102, 104. Alternatively, the crush insert 300 can be repeatedly displaceable, such as configured to be used multiple times before an additional crush insert 300 needs to be formed.

[0033] Disposing a crush insert 300 between each segment 102, 104 can allow each segment 102, 104 to adjust, expand, and / or move incrementally independently during the curing process. Allowing each segment 102, 104 to adjust independently can improve the consistency of the shape of the mandrel 100 throughout the curing process.

[0034] The mandrel 100 may be assembled by securing each segment 102, 104 to the support shaft 202 through at least one of the interfaces between the alignment structure 110 and the complementary alignment structure 204 or the interfaces between adjacent segments 102, 104.

[0035] After the mandrel 100 is assembled, it may be coupled to a winding tool through the drive shaft 212. A layer of insulation 402 may be formed on the mandrel 100 as shown in FIG. 4. The insulation 402 may be a rubber material. The insulation 402 may be applied as a sheet of material up to a thickness of about 0.1 inches. After one or more layers of insulation 402 are applied onto the mandrel 100, portions of the insulation 402 may be removed through sanding or machining until the desired thickness of the insulation 402 is reached. The desired thickness of the insulation 402 may be between about 0.06 inches and about 0.45 inches.

[0036] In some embodiments, a layer of polytetrafluoroethylene (PTFE) (e.g., TEFLON®) may be formed on the mandrel 100 prior to the insulator 402, so that the layer of PTFE may be between the insulator 402 and the mandrel 100 and may aid in releasing the composite structure from the mandrel 100 after curing.

[0037] After the insulation 402 is applied, a filament of fiber 502 may be applied onto the insulation 402 through a filament winding process, as shown in FIG. 5. The fiber 502 may be wound in various configurations in various layers to provide strength in different directions. For example, the fiber 502 may be wound in a helical configuration, as shown in FIG. 5. In the helical configuration, the fiber 502 may be wound at an angle of about 10° to about 40° (such as an angle between about 20° and about 30°, or an angle of about 27°) relative to the longitudinal axis of the mandrel 100. In other layers, the fiber 502 may be wound in a hoop configuration. In the hoop configuration, the fiber 502 may be wound at an angle of about 80° to about 90° (such as an angle between about 85° and about 90°, or an angle between about 89.5° and about 90°). The winding angle may be controlled by the drive shaft 212. For example, the drive shaft 212 can change the angle of the mandrel 100 relative to the winding tool, as described above. In other embodiments, the wrap angle can be controlled by changing the position of the winding head relative to the mandrel 100.

[0038] FIG. 6 shows the surface of the composite structure 602 after multiple layers of fiber 502 have been wrapped. As discussed above, the fiber 502 can be wrapped at a variety of angles. For example, the fiber 502 can be wrapped as a hoop winding 604, as shown in FIG. 6, or as a helical winding 606, as shown in FIGS. 5 and 6. Different winding angles can improve the strength of the composite structure 602 in different directions. For example, a hoop winding 604 can improve the radial strength of the composite structure 602, while a helical winding 606 can improve the longitudinal strength of the composite structure 602.

[0039] Each layer of fiber 502 can have a thickness of between about 0.16 mm (about 0.0063 inches) and about 0.366 mm (about 0.0144 inches). The composite structure 602 can be formed of between about 1 layer and about 30 layers (between about 10 layers and about 20 layers, or about 16 layers, etc.).

[0040] After the composite structure 602 is formed from multiple layers of fiber 502, an outer layer 702 may be formed over the composite structure 602, as shown in Figure 7. The outer layer 702 may be formed from a protective material, such as PTFE / fiberglass (ARMALON™).

[0041] After the composite structure 602 is formed, the composite structure 602 may be cured at elevated temperatures and / or elevated pressures. For example, the composite structure 602 on the mandrel 100 may be placed in a high temperature chamber, such as an oven or autoclave, for a specified amount of time. For example, the oven or autoclave containing the composite structure 602 may be maintained at a temperature of between about 102°F (48.89°C) and about 400°F (204.4°C) for several hours (e.g., between about 4 hours and about 20 hours).

[0042] In some embodiments, the composite structure 602 may be cured in multiple stages at various temperatures and for various times. For example, the composite structure 602 may first be cured at a lower temperature, such as between about 120°F (about 48.89°C) and about 280°F (about 137.78°C), or about 250°F, for about 4 to about 10 hours (e.g., about 8 hours). The composite structure 602 may then be cured at a higher temperature, such as between about 280°F (about 137.78°C) and about 350°F (about 176.67°C), or about 290°F, for about 4 to about 14 hours (e.g., about 10 hours). During these curing periods, the temperature may be gradually increased and / or decreased to temperatures higher or lower than the curing temperature. After the cure time, the temperature can be slowly decreased until the composite structure 602 can be removed from the chamber. For example, the temperature can be varied at a rate ranging from about 0.056°C / min (about 0.1°F / min) to about 2.778°C / min (about 5°F / min), such as from about 0.056°C / min (about 0.1°F / min) to about 1.25°C / min (about 2.25°F / min).

[0043] FIG. 8 shows the composite structure 602 after the curing process, with the composite structure 602 still coupled to the support shaft 202 and drive shaft 212. The support shaft 202 and drive shaft 212 may be removed from the bore 108, leaving the mandrel 100 within the composite structure 602, as shown in FIG. 9. The individual connecting segments 104 and wedge segments 102 of the mandrel 100 may then be removed from the composite structure 602, as shown in FIGS. 10 and 11. For example, the first connecting segment 104 may be removed as shown in FIG. 10. The geometry of the wedge segments 102 may allow the connecting segment 104, located between two wedge segments 102, to move radially relative to the wedge segments 102 toward the axis of the mandrel 100, while substantially preventing radial movement away from the axis of the mandrel 100. Thus, once the support shaft 202 is removed from the bore 108, the connecting segment 104 may be removed by moving the connecting segment 104 radially into the bore 108. Then, with the first connecting segment 104 removed, the adjacent wedge segment 102 may be removed through the bore 108. Similarly, other connecting segments 104 and additional wedge segments 102 may be removed through the bore 108 until each segment 102, 104 of the mandrel has been removed from the composite structure 602.

[0044] 11 shows the composite structure 602 and mandrel 100 after all segments 102, 104 and crush inserts 300 have been removed. The composite structure 602 can have a cavity 1102 having substantially the same shape as the mandrel 100. The segments 102, 104 of the mandrel 100 can each have substantially the same shape after the winding and curing process as when the mandrel 100 was assembled, such that the segments 102, 104 can be reassembled with new crush inserts 300 to form another mandrel 100 for the purpose of forming another composite structure 602, without having to form an entirely new mandrel 100. The support shaft 202 and associated complementary alignment structures 204, alignment supports 206, etc. can also be reused with the new mandrel 100.

[0045] Embodiments of the present disclosure may enable reusable mandrels to be formed more quickly and at reduced cost compared to traditional (e.g., conventional) metal mandrels. The reduced cost and time required to form a mandrel may allow for greater innovation in composite structures, reducing the time and cost to change to and / or test different designs. Similarly, the reduced time and cost may enable higher production rates, reducing costs to end users of composite structures.

[0046] Non-limiting illustrative examples of the present disclosure include the following embodiments: Embodiment 1: A method for forming a mandrel for forming a composite structure, comprising forming segments of the mandrel through an additive manufacturing process, assembling the segments to one another, and positioning crush inserts between adjacent segments.

[0047] Embodiment 2: The method of embodiment 1, further comprising forming the segments from a polymeric material. Embodiment 3: The method of any one of embodiments 1 or 2, wherein the additive manufacturing process comprises at least one of a fused filament fabrication process or a large-scale additive manufacturing process.

[0048] Embodiment 4: The method of any one of embodiments 1 to 3, wherein assembling the mandrel segments includes securing the mandrel segments to a support shaft.

[0049] Embodiment 5: The method of embodiment 4, wherein securing the mandrel segments to the support shaft further comprises securing the mandrel segments to the support shaft via complementary alignment structures.

[0050] Embodiment 6: The method of any one of embodiments 1 to 5, further comprising forming the crush insert through an additive manufacturing process. Embodiment 7: The method of any one of embodiments 1 to 6, further comprising forming a crush insert of a material that is configured and / or formulated to deform under loads applied by thermal expansion of the mandrel segments during a composite curing process.

[0051] Embodiment 8: The method of any one of embodiments 1 to 7, further comprising configuring a segment of the mandrel to comprise at least two wedge segments and at least one connecting segment.

[0052] Embodiment 9: The method of embodiment 8, wherein assembling the segments to one another includes fixing at least two wedge segments to a support shaft and positioning at least one connecting segment between the at least two wedge segments.

[0053] Embodiment 10: The method of embodiment 9, wherein at least two wedge segments are configured to substantially prevent at least one connecting segment from moving radially away from the axis of the mandrel, and the support shaft is configured to substantially prevent at least one connecting segment from moving radially toward the axis of the mandrel.

[0054] Embodiment 11: A tool for forming a composite structure, the tool comprising two or more segments formed from a polymeric material, a crush insert disposed between the two or more segments, and a support shaft connected between the two or more segments.

[0055] Embodiment 12: The tool of embodiment 11, wherein the crush insert is configured to deform under loads imposed by thermal expansion of the composite structure during a curing process. Embodiment 13: The tool of any one of embodiments 11 or 12, wherein the crush insert comprises an aluminum honeycomb.

[0056] Embodiment 14: The tool of any one of embodiments 11 to 13, wherein the two or more segments include wedge segments, straight segments, or a combination thereof.

[0057] Embodiment 15: The tool of any one of embodiments 11 to 14, wherein two or more segments are formed from a polyetherimide material. Embodiment 16: A method of making a composite structure, the method comprising assembling a mandrel, where assembling the mandrel comprises forming segments of the mandrel through an additive manufacturing process, assembling the segments to one another, placing a crush insert between each of the segments, and coupling the segments to a support shaft; coupling the support shaft to a winding machine; winding composite fibers around the mandrel to form a composite structure; heating the composite structure; and separating the mandrel from the composite structure.

[0058] Embodiment 17: The method of embodiment 16, wherein separating the mandrel from the composite structure comprises disassembling segments of the mandrel. Embodiment 18: The method of embodiment 17, further comprising using crush inserts configured to deform to accommodate thermal expansion of the mandrel segments when the composite structure is heated.

[0059] Embodiment 19: The method of any one of embodiments 16 to 18, wherein the mandrel segments comprise at least two wedge segments and at least one connecting segment, and assembling the segments to one another comprises positioning the at least one connecting segment between the at least two wedge segments.

[0060] Embodiment 20: The method of embodiment 19, wherein separating the mandrel from the composite structure includes removing at least one connecting segment from between the at least two wedge segments before removing the at least two wedge segments.

[0061] The embodiments of the present disclosure described above and illustrated in the accompanying drawings do not limit the scope of the present invention, as these embodiments are merely examples of embodiments of the present invention, which are defined by the appended claims and their legal equivalents. Any equivalent embodiments are intended to be within the scope of the present disclosure. Indeed, various modifications of the present disclosure, in addition to the embodiments shown and described herein, may become apparent to those skilled in the art from this description, including alternative useful combinations of the described elements. Such modifications and embodiments are also intended to be within the scope of the appended claims and their legal equivalents.

Claims

1. 1. A method for forming a mandrel for forming a composite structure, comprising: forming segments of the mandrel through an additive manufacturing process; assembling the segments to one another; configuring the segments of the mandrel to include at least two wedge segments and at least one connecting segment; disposing crush inserts between adjacent segments, the crush inserts configured to deform at a predetermined rate in response to an applied load; Including, method.

2. The method of claim 1 further comprising forming the segments from a polymeric material.

3. 10. The method of claim 1, wherein the additive manufacturing process comprises at least one of a fused filament manufacturing process or a large-scale additive manufacturing process.

4. The method of claim 1 , wherein assembling the mandrel segments includes securing the mandrel segments to a support shaft.

5. The method of claim 4 , wherein securing the segments of the mandrel to the support shaft further comprises securing the segments of the mandrel to the support shaft via complementary alignment structures.

6. The method of claim 1 , further comprising forming the crush insert through an additive manufacturing process.

7. 10. The method of claim 1, further comprising forming the crush insert of a material that is configured and / or formulated to deform under loads applied by thermal expansion of the segments of the mandrel during a composite curing process.

8. 8. The method according to claim 1, wherein the step of assembling the segments to one another comprises the steps of fixing the at least two wedge segments to a support shaft and positioning the at least one connecting segment between the at least two wedge segments.

9. 9. The method of claim 8, wherein the at least two wedge segments are configured to substantially prevent the at least one connecting segment from moving radially away from the axis of the mandrel, and the support shaft is configured to substantially prevent the at least one connecting segment from moving radially toward the axis of the mandrel.

10. 1. A tool for forming a composite structure, comprising: two or more segments formed from a polymeric material; a crush insert disposed between the two or more segments and configured to deform at a predetermined rate in response to an applied load; a support shaft connected between the two or more segments; Equipped with tool.

11. the load is applied by thermal expansion of the composite structure during the curing process; The tool of claim 10.

12. the crush insert comprises an aluminum honeycomb; The tool of claim 10.

13. the two or more segments include wedge segments, straight segments, or a combination thereof; The tool of claim 10.

14. the two or more segments are formed from a polyetherimide material; A tool according to any one of claims 10 to 13.

15. 1. A method of making a composite structure, comprising: Assembling a mandrel, forming segments of the mandrel through an additive manufacturing process; assembling the segments to one another; disposing a crush insert between each of the segments; and coupling the segments to a support shaft via complementary alignment structures; assembling a mandrel, connecting the support shaft to a winding machine; winding composite fibers around the mandrel to form the composite structure; heating the composite structure; separating the mandrel from the composite structure; Including, method.

16. The method of claim 15 , wherein separating the mandrel from the composite structure comprises disassembling the segments of the mandrel.

17. The method of claim 16 , further comprising using crush inserts configured to deform to accommodate thermal expansion of the segments of the mandrel when the composite structure is heated.

18. 18. The method of any one of claims 15 to 17, wherein the segments of the mandrel comprise at least two wedge segments and at least one connecting segment, and assembling the segments to one another comprises positioning the at least one connecting segment between the at least two wedge segments.

19. 20. The method of claim 18, wherein separating the mandrel from the composite structure comprises removing the at least one connector segment from between the at least two wedge segments before removing the at least two wedge segments.

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