Pulse pressure consolidation of braided preforms for composite parts.

Abstract

To provide a system and method for consolidating a preform of braided fiber.SOLUTION: A method includes: acquiring a braided preform 160 comprising fibers of a unidirectional material that have been woven into a shape having a closed cross-section 162; disposing the braided preform 160 within a mandrel 150; disposing an inflatable bladder 170 within the closed cross-section 162 of the braided preform 160; and iteratively applying pressure to the braided preform 160 via the bladder 170 to consolidate the braided preform 160 against the mandrel 150.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] TECHNICAL FIELD This disclosure relates to the field of fabrication, and in particular to composite fabrication. [Background technology]

[0002] Braided fiber reinforced composite parts may be utilized for a variety of purposes. For example, braided composite parts form fuel supply tubes for transporting jet fuel between or within aircraft. Although braided composite parts provide a substantial amount of strength, fabrication of these composite parts can be difficult. For example, during consolidation, preforms for braided composite parts may exhibit shear locks or otherwise have friction locking issues at the intersections between fibers that cross each other in the weave. When this occurs, the resulting braid of the composite part may be uneven or out of tolerance, necessitating rework or scrapping.

[0003] It would therefore be desirable to have a method and apparatus that takes into account at least some of the above-mentioned problems, as well as possible other problems. Summary of the Invention

[0004] The embodiments described herein provide pulse pressure consolidation of braided preforms for composite parts. By repeatedly applying increasing and decreasing consolidation pressure, areas within the weave that are subject to friction or shear locking relax, releasing the lock and allowing consolidation to continue during the next application of pressure.

[0005] One embodiment is a method for consolidating a braided fiber preform that includes obtaining a braided preform including fibers of unidirectional material woven into a shape having a closed cross-section, placing the braided preform within a mandrel, placing an inflatable bladder within the closed cross-section of the braided preform, and repeatedly applying pressure to the braided preform via the bladder to consolidate the braided preform against the mandrel.

[0006] A further embodiment is a non-transitory computer readable medium having programmed instructions embodied therein that, when executed by a processor, are operable to perform a method for consolidating a braided fiber preform, the method including obtaining a braided preform including fibers of a unidirectional material woven into a shape having a closed cross-section, placing the braided preform within a mandrel, placing an inflatable bladder within the closed cross-section of the braided preform, and repeatedly applying pressure to the braided preform via the bladder to consolidate the braided preform against the mandrel.

[0007] A further embodiment is an apparatus for consolidating a braided fiber preform, the apparatus including a mandrel sized to receive the braided preform, a bladder sized to fit within a closed cross-section of the braided preform, and a controller for repeatedly applying pressure to the braided preform through the bladder to consolidate the braided preform against the mandrel.

[0008] Yet another embodiment is a method for consolidating a braided preform. The method includes obtaining a braided preform including fibers of a unidirectional material woven into a shape having a closed cross-section, increasing a consolidation force applied to the braided preform, and determining whether the fibers in the braided preform are shear locked. In response to determining that the fibers in the braided preform are not shear locked, the method includes further increasing the consolidation force. In response to determining that the fibers in the braided preform are shear locked, the method further includes decreasing the consolidation force.

[0009] Other exemplary embodiments, such as methods and computer readable media relating to the above-mentioned embodiments, are described below. The above-mentioned features, functions, and advantages may be realized alone in various embodiments or may be combined in other embodiments. Further details of these embodiments are described with reference to the following description and drawings.

[0010] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings in which the same reference numbers represent the same elements or same types of elements, and in which: [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a block diagram of a consolidation system for a braided preform in an exemplary embodiment. [Diagram 2] FIG. 1 is a flow diagram illustrating a method for operating a compaction system in an exemplary embodiment. [Diagram 3] FIG. 1 illustrates a perspective view of consolidation of a braided preform via a consolidation system in an exemplary embodiment. [Figure 4] FIG. 1 illustrates a perspective view of consolidation of a braided preform via a consolidation system in an exemplary embodiment. [Diagram 5] FIG. 1 illustrates a perspective view of consolidation of a braided preform via a consolidation system in an exemplary embodiment. [Figure 6] FIG. 1 illustrates a perspective view of consolidation of a braided preform via a consolidation system in an exemplary embodiment. [Figure 7] FIG. 1 illustrates a perspective view of consolidation of a braided preform via a consolidation system in an exemplary embodiment. [Figure 8] 1 is a graph illustrating a pulsed compression technique for performing consolidation in an exemplary embodiment. [Figure 9] 1 is a graph illustrating a pulsed compression technique for performing consolidation in an exemplary embodiment. [Figure 10]1 is a graph illustrating a pulsed compression technique for performing consolidation in an exemplary embodiment. [Figure 11] 1 is a graph illustrating a pulsed compression technique for performing consolidation in an exemplary embodiment. [Figure 12] FIG. 11 is a flow diagram illustrating a further method for operating a compaction system in an exemplary embodiment. [Figure 13] FIG. 1 is a flowchart illustrating an aircraft manufacturing and service method in an illustrative embodiment. [Figure 14] FIG. 1 is an illustration of a block diagram of an aircraft in an illustrative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The accompanying drawings and the following description provide specific exemplary embodiments of the present disclosure. Therefore, it should be understood that those skilled in the art can devise various configurations that embody the principles of the present disclosure and are included in the scope of the present disclosure, although not explicitly described or illustrated herein. Furthermore, any examples described herein are intended to help understand the principles of the present disclosure, and should not be construed as being limited to the specifically described examples and conditions. As a result, the present disclosure is not limited to the specific embodiments or examples described below, but is limited by the scope of the claims and their equivalents.

[0013] First, a composite part, such as a carbon fiber reinforced polymer (CFRP) part, is laid up in multiple layers, collectively referred to as a preform. The individual fibers within each layer of the preform are aligned parallel to one another, but different layers may exhibit different fiber orientations to increase strength along different dimensions of the resulting composite part. The preform may contain a viscous resin that solidifies to solidify the preform into a composite part (e.g., for use in aircraft). Carbon fibers impregnated with uncured thermosetting or thermoplastic resins are called "prepregs." Other types of carbon fibers include "dry fibers" that are not impregnated with thermosetting resins, but may include a tackifier or binder. Dry fibers can be infused with resin before curing. For thermosetting resins, solidification is a unidirectional process called curing, while for thermoplastic resins, the resin can reach a viscous form if reheated.

[0014] 1 is a block diagram of a consolidation system 100 for a braided preform 100 in an exemplary embodiment. Consolidation system 100 includes any suitable system for applying a consolidation pressure to a braided preform that includes interwoven fibers of material that form a closed cross-sectional shape. Examples of such preforms include tubular braided preforms.

[0015] In this embodiment, the compaction system 100 includes a braiding machine 110 (e.g., an industrial three-dimensional (3D) braiding machine) that utilizes bobbins arranged around a frame and moving in a predetermined orbital path relative to each other according to a predefined program to form a braid.

[0016] In one embodiment, the controller 112 operates the braiding machine 110 according to instructions stored in an NC program in the memory 114 to fabricate a braided preform 160 having a closed cross section 162. For example, the braiding machine 110 utilizes a tape 180 including fibers 182 and a thermal plastic 184 as input to the fabrication process (interweaving). The thermal plastic 184 may include polyetheretherketone (PEEK) or polyetherketoneketone (PEKK). The braided preform 160 may include fibers 182 (e.g., carbon fiber, glass fiber) interwoven with one another and may be impregnated with the thermal plastic 184. The braided preform 160 is disposed within a void 154 defined by portions 152 and 153 of the mandrel 150. A bladder 170 (eg, a polyimide bladder), which is flexible but capable of retaining its physical integrity at or near the melting point of the thermoplastic, is sized to fit within the closed cross section 162 of the braided preform 160 .

[0017] During consolidation, controller 112 controls the amount of pressure (P) applied to expand interior 172 of bladder 170 via pressure supply 116 (e.g., a reservoir of compressed gas). The pressure forces bladder 170 against braided preform 160, consolidating braided preform 160 between bladder 170 and mandrel 150. When held in contact with one another, the portions of mandrel 150 define a boundary (e.g., perimeter) of the preform.

[0018] The heater 118 applies heat during consolidation (i.e., between repeated applications of pressure). In one embodiment, the heater 118 raises the temperature of the braided preform 160 to a processing temperature (e.g., within 30 degrees Fahrenheit) below the melting point of the thermoplastic within the braided preform 160 during consolidation. The heater 118 may include a susceptor, a radiant heating element, a resistive heater, or other components. Operation of the heater 118 is performed by the controller 112. The controller 112 may be implemented, for example, as a custom circuit, as a hardware processor executing programmed instructions, or some combination thereof to operate actuable valves or other components.

[0019] Exemplary details of the operation of consolidation system 100 are described with reference to Figure 2. This embodiment assumes that a braided preform 160 has been produced by braiding machine 110, and that braided preform 160 is ready for consolidation into a desired shape.

[0020] Figure 2 is a flow diagram illustrating a method for operating a compaction system, in one exemplary embodiment. The steps of method 200 are described with reference to compaction system 100 of Figure 1, but one of ordinary skill in the art will appreciate that method 200 may be implemented in other systems. The steps of the flow diagram described herein are not exhaustive and may include other steps not shown. The steps described herein may also be implemented in a different order.

[0021] In step 202, a braid preform 160 is obtained. The braid preform 160 is fully braided and includes fibers of unidirectional material (e.g., carbon fibers) woven into a shape having a closed cross-section 162. For example, the braid preform 160 may include a tube having a square cross-section, an oval cross-section, a circular cross-section, etc. Obtaining the braid preform 160 includes operating an end effector or pick and place machine that picks up or otherwise removes the braid preform 160 from the braiding machine.

[0022] In step 204, braided preform 160 is placed within mandrel 150. In one embodiment, this involves placing braided preform 160 within portion 153 of mandrel 150 and then placing a complementary portion 152 of mandrel 150 over braided preform 160 to form void 154.

[0023] In step 206, an inflatable bladder (i.e., bladder 170) is placed within the closed cross section 162 of the braided preform 160. This involves sliding the bladder 170 into position within the space enclosed by the closed cross section 162 while the bladder 170 is in an uninflated state.

[0024] In step 208, the controller 112 operates the pressure supply 116 to repeatedly apply pressure to the braided preform 160 via the bladder 170, thereby consolidating the braided preform 160 into a shape for solidification into a composite part. As used herein, repeatedly applying pressure includes repeatedly increasing and decreasing the amount of pressure applied. In one embodiment, the repeatedly applying pressure is performed cyclically, where each cycle includes applying an incrementally increasing amount of pressure and then returning to a baseline pressure. In one embodiment, the cycles are applied in a gradient of 5 to 10 pounds per square inch (PSI) increments, which increase over time (e.g., 5 to 15 PSI, 15 to 20 PSI, 20 to 35 PSI, etc.) until a desired peak pressure (e.g., 100 PSI, 30 PSI, etc.) is reached. In a further embodiment, the bladder includes multiple independently controllable cells capable of applying different amounts of pressure from one another.

[0025] Repeated pressure application in this manner allows the intersections of the fibers that are locked under pressure to relax. This allows for the angle of the fibers in each intersection to be adjusted in small increments, which prevents the intersections from locking the next time pressure is applied. This technique may be performed over multiple cycles performed simultaneously with multiple cells or bladders. Additionally, the controller 112 may operate the heater 118 during all or part of step 208 to further facilitate consolidation of the fibers and thermoplastic within the braided preform 160. Once consolidation is complete, the preform is solidified into a composite part for use in any suitable structure, such as a fuel line used within a portion of an aircraft. Thus, the above technique uses a bladder to stretch the preform to remove out-of-tolerance conditions and to apply a desired shape and / or thickness to the preform.

[0026] The method may further include removing the bladder 170 from the braided preform 160 and removing the braided preform 160 from the mandrel 150.

[0027] Method 200 provides a substantially superior technique for consolidating braided fiber reinforced thermoplastic composite preforms over the prior art because it allows the intersections between the fibers to relax while pressure is applied, which then allows the fibers to move relative to one another, thereby preventing shear lock or other undesirable friction locking as pressure is increased.

[0028] 3-7 are perspective views of the consolidation of a braid preform via a consolidation system in one example embodiment. Specifically, FIG. 3 shows a portion 300 of a consolidation mandrel including a cutout 310 for receiving a braid preform. FIG. 4 shows the insertion of a braid preform 410, laid up on a layup mandrel 420, into the cutout 310. At this point, the braid preform 410 is unconsolidated and therefore in some embodiments does not fit completely into or border the cutout 310. In FIG. 5, another portion of the consolidation mandrel (i.e., portion 500) is placed over and aligned with portion 300. Portion 500 includes a cutout 510 that is complementary to cutout 310 to form a void.

[0029] 6, lay-up mandrel 420 is removed from braided preform 410 and bladder 600 (e.g., an inflatable bladder) is inserted into braided preform 410. In FIG. 7, bladder 600 is repeatedly pressurized to consolidate braided preform 410 against cutouts 310 and 510.

[0030] 8-11 are graphs illustrating pulse compression techniques for performing consolidation in exemplary embodiments. In particular, FIGs. 8-11 illustrate exemplary compression techniques that may be utilized to perform pulse compression.

[0031] FIG. 8 is a graph 800 illustrating a pulsed pressurization technique 810 in which a pressure P is applied to the braided preform by a bladder over a time T. During a first phase, the pressure is increased from a lower bound P0 to an upper bound P1 defining a first range of pressure, held at P1, and then decreased back to P0, repeating the cycle N times (where N is 3). During a second phase, the pressure is then increased from a lower bound P1 to an upper bound P2 defining a second range of pressure, held at P2, and returned to P1, repeating the cycle N times. This pattern continues, with the controller repeatedly applying pressure by increasing the pressure from the lower bound to the upper bound in each of a number of ranges of pressure until a desired peak pressure is reached. In a further embodiment, N varies depending on the pressure used. In yet a further embodiment, heat is applied to the braided preform during one or more of the above phases to raise the temperature of the braided preform to just below (e.g., within 30 degrees Fahrenheit) the melting point of the thermoplastic in the braided preform. In yet another embodiment, the controller varies the rate of pressure rise between cycles or phases such that certain cycles or phases (eg, those earlier in time) have a lower rate of pressure rise.

[0032] 9 is a graph 900 illustrating a pulsed pressurization technique 910 in which a pressure P is applied by a bladder to a braided preform over a time period T. The pressure is cycled N times from pressure P0 to pressure P1 and back to P0, then from P1 to P2 and back to P1, etc. An initial cycle is performed at ambient temperature (e.g., room temperature) and further cycles are performed while heat is applied.

[0033] 10 is a graph 1000 illustrating a pulsed pressurization technique 1010 in which a pressure P is applied to a braided preform by a bladder over a period of time T. The pressure rises from pressure P0 to pressure P2, then immediately drops to P1, and so on. The pressure then rises to P3 and drops to P2 in a zigzag pattern.

[0034] 11 is a graph 1100 illustrating a pulse pressurization technique 1110, where a pressure P is applied to a braided preform by a bladder over a time period T. The pressure follows a jagged pattern, rising from pressure P0 to pressure P1, back to P0, rising to P2, falling to P1, rising to P3, falling to P2, rising to P4, falling to P3, etc. In further embodiments, any suitable combination of the above techniques may be utilized to implement the pulse pressurization.

[0035] Any of the various techniques described above can be employed to reduce the likelihood of shear lock or other friction lock issues occurring during consolidation of braided thermoplastic parts. Thus, use of the techniques described above reduces the likelihood of the fabricated composite part being out of tolerance, which increases efficiency, reduces costs, and reduces labor.

[0036] 12 is a flow diagram illustrating a further method 1200 for operating a consolidation system in an exemplary embodiment. According to the method 1200, step 1202 includes obtaining a braided preform including fibers of a unidirectional material woven into a shape having a closed cross-section. A mandrel is placed around the braided preform and a bladder is inserted into the space defined by the closed cross-section. The bladder is also allowed to expand until it contacts the preform and applies a consolidation force.

[0037] Step 1204 includes increasing the consolidation force applied to the braided preform, and step 1206 includes determining whether the fibers in the braided preform are shear locked. This can be determined based on the amount of reaction force applied by the braided preform to the bladder over time as the pressure is increased, or by other means. For example, if the braided preform immediately resists the application of pressure without deformation, it is determined that a shear lock is present between the fibers in the preform. For example, this can be determined based on manual inspection, or automatically based on the value of the pressure increasing faster than expected over time. That is, if a shear lock is not present, a certain amount of gas added to the bladder will expand the preform, thereby increasing the volume of the bladder. As the volume of the bladder increases, the pressure does not increase as much as it would if the bladder held its shape. That is, according to the ideal gas law, the increase in the volume of space occupied by the gas at least partially compensates for the additional amount of gas. In contrast, when shear locks are present, adding a volume of gas to the bladder causes an immediate pressure rise because the shear locks in the preform prevent the bladder from increasing in volume or changing shape at one or more locations, and therefore the pressure rises at a higher rate than if shear locks were not present, which can be detected as a difference in the rate of pressure rise.

[0038] In response to determining that the fibers in the braided preform are not shear locked, the consolidation force is further increased at step 1204. Alternatively, in response to determining that the fibers in the braided preform are shear locked, step 1208 includes lowering / reducing the consolidation force applied by the bladder (e.g., by reducing the pressure applied to the bladder). The steps of method 1200 can be performed repeatedly over time to shape the braided preform into a desired shape.

[0039] Working Example In the following examples, additional processes, systems, and methods are described in the context of a consolidation system for thermoplastic preforms.

[0040] Referring more specifically to the drawings, embodiments of the disclosure may be described in relation to an aircraft manufacturing and service method 1300 as shown in FIG. 13 and an aircraft 1302 as shown in FIG. 14. During pre-production, the method 1300 may include specification and design 1304 of the aircraft 1302 and sourcing 1306 of materials. During production, manufacturing 1308 of components and subassemblies of the aircraft 1302 and system integration 1310 occurs. The aircraft 1302 may then undergo certification and delivery 1312 and be placed into service 1314. While in service by a customer, the aircraft 1302 is scheduled for routine maintenance and service 1316, which may include modification, reconfiguration, refurbishment, etc. Apparatus and methods embodied herein may be employed during one or more of any suitable stages of manufacturing and maintenance described in method 1300 (e.g., specification and design 1304, materials procurement 1306, component and subassembly manufacturing 1308, system integration 1310, certification and delivery 1312, operation 1314, maintenance and maintenance 1316) and / or with any suitable components of aircraft 1302 (e.g., airframe 1318, systems 1320, interior 1322, propulsion system 1324, electrical system 1326, hydraulic system 1328, environmental system 1330).

[0041] Each process of method 1300 may be performed or carried out by a system integrator, a third party, and / or an operator (e.g., a customer). For purposes of this description, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major system subcontractors, a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers, and an operator may be an airline, a leasing company, a military entity, a service organization, etc.

[0042] 14 , aircraft 1302 produced by method 1300 may include an airframe 1318 with a number of systems 1320 and an interior 1322. Examples of systems 1320 include one or more of a propulsion system 1324, an electrical system 1326, a hydraulic system 1328, and an environmental system 1330. Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry.

[0043] As mentioned above, the apparatus and methods embodied herein may be employed during any one or more stages of manufacturing and service described in method 1300. For example, components or subassemblies corresponding to component and subassembly manufacturing 1308 may be fabricated or manufactured in a similar manner as components or subassemblies manufactured while the aircraft 1302 is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during component and subassembly manufacturing 1308 and system integration 1310, for example, by substantially streamlining the assembly of the aircraft 1302 or reducing the cost of the aircraft 1302. Similarly, one or more of the apparatus embodiments, method embodiments, or a combination thereof may be utilized during the operation of the aircraft 1302, such as, but not limited to, during maintenance and service 1316. For example, the techniques and systems described herein may be used for material procurement 1306, component and subassembly manufacturing 1308, system integration 1310, operation 1314, and / or maintenance and service 1316, in addition to or instead of airframe 1318 and / or interiors 1322. The techniques and systems may also be utilized for systems 1320, including, for example, propulsion system 1324, electrical system 1326, hydraulic system 1328, and / or environmental system 1330.

[0044] In one embodiment, a part comprises a portion of the airframe 1318 and is manufactured during component and subassembly manufacturing 1308. The part may then be assembled into an aircraft in system integration 1310, after which it may be used in service 1314 until wear renders it unusable. The part may then be scrapped and replaced with a newly manufactured part in maintenance and service 1316. Components and methods of the present invention may be used throughout component and subassembly manufacturing 1308 to manufacture new parts.

[0045] Any of the various control elements (e.g., electrical or electronic components) shown or described herein may be implemented as hardware, processor-implemented software, processor-implemented firmware, or any combination thereof. For example, an element may be implemented as dedicated hardware. A dedicated hardware element may be referred to as a "processor," "controller," or some similar terminology. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by one or more individual processors, some of which may be shared. Furthermore, explicit use of the terms "processor" or "controller" should not be construed as referring only to hardware capable of executing software, but may implicitly include, without limitation, digital signal processor (DSP) hardware, network processors, application specific integrated circuits (ASICs) or other circuitry, field programmable gate arrays (FPGAs), read only memory (ROM) for storing software, random access memory (RAM), non-volatile storage, logic, or any other physical hardware component or module.

[0046] Also, a control element can be implemented as instructions executable by a processor or computer to perform the function of the element. Some examples of instructions are software, program code, and firmware. The instructions are operative when executed by a processor and direct the processor to perform the function of the element. The instructions can be stored in a storage device that can be read by the processor. Some examples of storage devices are digital or solid state memory, magnetic storage media such as magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media.

[0047] Additionally, the disclosure includes embodiments according to the following provisions:

[0048] Clause 1. A method for consolidating a braided fiber preform, the method comprising obtaining a braided preform (202) including fibers of a unidirectional material woven into a shape having a closed cross-section, placing the braided preform within a mandrel (204), placing an inflatable bladder (206) within the closed cross-section of the braided preform, and repeatedly applying pressure to the braided preform via the bladder (208) to consolidate the braided preform against the mandrel.

[0049] Clause 2. The method of clause 1, wherein applying pressure includes increasing the pressure from a lower bound to an upper bound of a pressure range.

[0050] Clause 3. The method of clause 1 or 2, wherein repeatedly applying pressure includes increasing the pressure from a lower bound to an upper bound in each of a plurality of pressure ranges.

[0051] Clause 4. The method of clause 3, wherein the repeatedly applying pressure includes increasing the pressure from a lower bound to an upper bound in a first pressure range and increasing the pressure from a lower bound to an upper bound in a second pressure range, each pressure in the second pressure range being equal to or greater than each pressure in the first pressure range.

[0052] Clause 5. The method of any one of clauses 1 to 4, further comprising pre-impregnating the braided preform with a thermal plastic and heating the braided preform to a processing temperature below the melting point of the thermal plastic while repeatedly applying pressure.

[0053] Clause 6. The method of any one of clauses 1 to 5, further comprising removing the bladder from the braided preform and removing the preform from the mandrel.

[0054] Clause 7. The method of any one of clauses 1 to 6, wherein the braided preform is dried.

[0055] Clause 8. The method of any one of clauses 1 to 7, further comprising holding portions of the mandrel in contact to define a boundary of the preform.

[0056] Clause 9. The method of any one of clauses 1 to 8, further comprising automatically determining whether the fibers in the braided preform are shear locked during the repeated application of pressure.

[0057] Clause 10. Any part of an aircraft assembled in accordance with any one of clauses 1 to 9.

[0058] Clause 11. A non-transitory computer readable medium embodying programmed instructions operable, when executed by a processor, to perform a method for consolidating a braided fiber preform, the method including obtaining a braided preform (202) including fibers of a unidirectional material woven into a shape having a closed cross-section, placing the braided preform within a mandrel (204), placing an inflatable bladder (206) within the closed cross-section of the braided preform, and repeatedly applying pressure to the braided preform via the bladder (208) to consolidate the braided preform against the mandrel.

[0059] Clause 12. The medium of clause 11, wherein applying pressure includes increasing the pressure from a lower limit to an upper limit of the pressure range.

[0060] Clause 13. The medium of clause 11 or 12, wherein the repeated application of pressure includes increasing the pressure from a lower bound to an upper bound in each of a plurality of pressure ranges.

[0061] Clause 14. The medium of clause 13, wherein the repeated application of pressure includes increasing the pressure from a lower bound to an upper bound in a first pressure range and increasing the pressure from a lower bound to an upper bound in a second pressure range, each pressure in the second pressure range being equal to or greater than each pressure in the first pressure range.

[0062] Clause 15. The medium of any one of clauses 11 to 14, wherein the braided preform is pre-impregnated with a thermoplastic, the method further comprising heating the braided preform to a processing temperature below the melting point of the thermoplastic while repeatedly applying pressure.

[0063] Clause 16. The medium of any one of clauses 11-15, wherein the method further comprises removing the bladder from the braided preform and removing the preform from the mandrel.

[0064] Clause 17. The method according to any one of clauses 11 to 16, wherein the braided preform is dried.

[0065] Clause 18. The medium of any one of clauses 11 to 17, wherein the method further comprises holding portions of the mandrel in contact to define a boundary of the preform.

[0066] Clause 19. The medium of any one of clauses 11-18, wherein the method further includes automatically determining whether the fibers in the braided preform are shear locked during the repeated application of pressure.

[0067] Clause 20. A part of an aircraft assembled in accordance with a method defined by instructions stored on a computer readable medium of any one of clauses 11 to 19.

[0068] Clause 21. An apparatus for consolidating a braided fiber preform, the apparatus comprising: a mandrel sized to receive the braided preform; a bladder sized to fit within a closed cross-section of the braided preform; and a controller for repeatedly applying pressure to the preform through the bladder to consolidate the braided preform against the mandrel.

[0069] Clause 22. The apparatus of clause 21, wherein the controller applies pressure by increasing the pressure from a lower bound to an upper bound of a pressure range.

[0070] Clause 23. The apparatus of clause 21 or 22, wherein the controller repeatedly applies pressure by increasing the pressure from a lower bound to an upper bound in each of a plurality of pressure ranges.

[0071] Clause 24. The apparatus of any one of clauses 21 to 23, wherein the controller repeatedly applies pressure by increasing the pressure from a lower bound to an upper bound in a first pressure range and by increasing the pressure from a lower bound to an upper bound in a second pressure range, each pressure in the second pressure range being greater than or equal to each pressure in the first pressure range.

[0072] Clause 25. The apparatus of any one of clauses 21 to 24, wherein the braided preform is pre-impregnated with a thermal plastic, the apparatus further comprising a heater (118) for heating the braided preform to a processing temperature below the melting point of the thermal plastic.

[0073] Clause 26. The apparatus of any one of clauses 21 to 25, wherein the mandrel includes a plurality of portions held in contact to define the boundaries of the preform.

[0074] Clause 27. The apparatus of any one of clauses 21 to 26, wherein the braided preform is dried.

[0075] Article 28. Construction of a part of an aircraft using any of the devices of Articles 21 to 27.

[0076] Clause 29. A method for consolidating a braided preform, comprising obtaining a braided preform including fibers of a unidirectional material woven into a shape having a closed cross-section, increasing a consolidation force applied to the braided preform, and determining whether the fibers in the braided preform are shear locked, further increasing the consolidation force in response to determining that the fibers in the braided preform are not shear locked, and decreasing the consolidation force in response to determining that the fibers in the braided preform are shear locked.

[0077] Clause 30. The method of clause 29, in which the determination is carried out repeatedly over time.

[0078] Clause 31. The method of clauses 29 or 30, wherein the compacting force is applied via an inflatable bladder.

[0079] Clause 32. The method of any one of clauses 29 to 31, further comprising placing a mandrel around the braided preform.

[0080] Article 33. A part of an aircraft assembled in accordance with any one of Articles 29 to 32.

[0081] Clause 34. A non-transitory computer readable medium having programmed instructions embodied therein, the instructions being operable, when executed by a processor, to perform the method of any one of clauses 1-9 or clauses 29-32 for consolidating a braided fiber preform.

[0082] Clause 35. Apparatus according to clause 21, wherein the controller is configured to carry out the method of any one of clauses 1 to 9 or clauses 29 to 32. Although specific embodiments are described herein, the scope of the disclosure is not limited to these specific embodiments, but is defined by the claims and their equivalents.

Claims

1. 1. A method for consolidating a braided fiber preform, comprising: Obtaining a braided preform (202) including fibers of a unidirectional material woven into a shape having a closed cross section; placing the braided preform within a mandrel (204); disposing an inflatable bladder within the closed cross section of the braided preform (206); repeatedly applying pressure to the braided preform through the bladder to compact the braided preform against the mandrel (208); and automatically determining whether fibers in the braided preform are shear-locked during repeated application of pressure. The method includes:

2. The method of claim 1 , wherein repeatedly applying pressure comprises increasing the pressure from a lower bound to an upper bound in each of a plurality of pressure ranges.

3. 3. The method of claim 2, wherein repeatedly applying pressure comprises increasing the pressure from a lower bound to an upper bound in a first pressure range and increasing the pressure from a lower bound to an upper bound in a second pressure range, each pressure in the second pressure range being equal to or greater than each pressure in the first pressure range.

4. The braided preform is pre-impregnated with a thermoplastic, the method comprising: heating the braided preform to a processing temperature below the melting point of the thermoplastic while repeatedly applying pressure. The method of claim 1 , further comprising:

5. removing the bladder from the braided preform; and Removing the preform from the mandrel. The method of claim 1 , further comprising:

6. holding portions of the mandrel in contact to define a boundary of the preform; The method of claim 1 , further comprising:

7. 1. An apparatus for consolidating a braided fiber preform (160), comprising: A mandrel (150) having dimensions to receive the braided preform; a bladder (170) having dimensions to fit within the closed cross-section (162) of said braided preform; a controller (112) for repeatedly applying pressure to the braided preform through the bladder to compact the preform against the mandrel; and Means for determining whether the fibers in said braided preform are shear locked. An apparatus comprising:

8. 8. The apparatus of claim 7, wherein the controller applies pressure by increasing the pressure from a lower bound to an upper bound of a pressure range.

9. 9. The apparatus of claim 7 or 8, wherein the controller repeatedly applies pressure by increasing the pressure from a lower bound to an upper bound in a first pressure range and increasing the pressure from a lower bound to an upper bound in a second pressure range, each pressure in the second pressure range being equal to or greater than each pressure in the first pressure range.

10. The braided preform is pre-impregnated with a thermoplastic, and the apparatus comprises: a heater (118) for heating the braided preform to a processing temperature below the melting point of the thermoplastic; The apparatus of claim 7 , further comprising:

11. 11. Apparatus according to any one of claims 7 to 10, wherein the mandrel comprises multiple portions held in contact to define a boundary of the preform.

12. 1. A method for consolidating a braided preform, comprising: Obtaining a braided preform (1202) including fibers of a unidirectional material woven into a shape having a closed cross section; increasing a consolidation force applied to the braided preform (1204); and Determining whether the fibers in the braided preform are shear-locked (1206). Including, further increasing (1204) the consolidation force in response to determining that the fibers in the braided preform are not shear locked; and decreasing the consolidation force in response to determining that the fibers in the braided preform are shear locked (1206). method.

13. The method of claim 12 , wherein the determining is performed repeatedly over time.

14. 14. The method of claim 12 or 13, wherein the compacting force is applied via an inflatable bladder.

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