GB2582629A

GB2582629A - A forming tool

Info

Publication number: GB2582629A
Application number: GB1904350.4A
Authority: GB
Inventors: Wallace Alex; Fry Toby; Kay Matt
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2019-03-28
Filing date: 2019-03-28
Publication date: 2020-09-30
Also published as: GB201904350D0

Abstract

A forming tool 10 for forming a laminate charge, typically a stack of dry fibre plies comprises a base 21 and a plurality of fluid chambers 32. Each fluid chamber includes a distendable wall 38 spaced from the base which distend towards the base when a fluid pressure is applied to provide a load on the laminate charge; preferably, each fluid chamber may be formed from inflatable bladders. The forming tool is configured to sequentially apply fluid pressure to the fluid chambers such that the distendable walls distend sequentially. Preferably the chambers are disposed adjacent to each other and the sequential application may be provided to create a loading wave which aids with the removal of air for debulking and consolidating the charge. A fluid inlet, fluid manifold, valve arrangements and fluid restrictors may be arranged to provide the sequential pressure to the chambers. A pressure control unit may be configured to apply a first load to the charge and subsequently a second, preferably greater, load. A forming tool comprising a plurality of fluid chambers on an upper support and a method of forming a laminate charge are further provided.

Description

A FORMING TOOL

FIELD OF THE INVENTION

[0001] The present invention relates to a forming tool. The present invention also relates to a method of forming a laminate charge. The charge is typically, although not exclusively, either a composite material or a preform which is subsequently infused to form a composite material.

BACKGROUND OF THE INVENTION

[0002] A known method of vacuum moulding a composite material is described in US4562033. Prepregs are placed on a heated former and covered with a sheet of a micro-porous film material, a breather material and an impermeable membrane.

[0003] A problem with some known vacuum moulding processes is that it can be difficult for the charge to be easily sucked onto the forming tool without becoming clamped against the forming tool. Another problem with forming tools for a composite material is that it can be difficult to debulk a stack of plies without the formation of wrinkles.

SUMMARY OF THE INVENTION

[0004] According to an aspect of the invention, there is provided a forming tool for forming a laminate charge, the forming tool comprising: a laminate charge receiving support; and a plurality of fluid chambers; each fluid chamber comprising a distendable wall spaced from the support, wherein the distendable walls are arranged to distend towards the support when a fluid pressure is applied to the fluid chambers to provide a load on the laminate charge receivable on the support; and wherein the forming tool is configured to sequentially apply a fluid pressure to the fluid chambers such that the dispensable walls distend sequentially.

[0005] The above arrangement aids bulk removal for composite manufacturing.

[0006] The distendable wall may be an impermeable sheet. The distendable wall may be a bagging film, a membrane, or any other impermeable and flexible sheet material. The distendable wall may be tensioned.

[0007] Typically the fluid is a gas. The gas may be a compressed gas -for instance from a compressed gas canister.

[0008] The gas may be air, or any other suitable gas. The fluid may be at a temperature higher than atmospheric temperature.

[0009] The plurality of fluid chambers may be disposed adjacent to each other in an array.

[0010] The array of deformable panels may together define a loading surface configured to act on the laminate charge receivable on the support.

[0011] The forming tool may be configured to sequentially apply a fluid pressure to each of the fluid chambers up to a predetermined fluid pressure along the array from a first end of the array to a second end.

[0012] The forming tool may comprise a fluid inlet through which a fluid pressure is applied to the fluid chambers. A fluid pressure generator, such as a motorised pump, may be coupled to the fluid inlet. The fluid pressure generator is arranged to generate the loading force by increasing the fluid pressure in the fluid chambers.

[0013] The forming tool may comprise a first fluid chamber of the plurality of fluid chambers and a second fluid chamber of the plurality of fluid chambers. The fluid inlet may be fluidly connected to the first fluid chamber, with the second fluid chamber fluidly connected in series to the first fluid chamber.

[0014] The forming tool may comprise a flow restrictor in a flow path between the first and second fluid chambers such that, when a fluid pressure is applied at the fluid inlet, the first fluid chamber reaches the applied fluid pressure prior to the second fluid chamber reaching the applied fluid pressure.

[0015] The forming tool may comprise a fluid barrier between the first and second fluid chambers. The flow restrictor may comprise an aperture in the fluid barrier.

[0016] The forming tool may comprise a fluid control valve in a flow path between the first and second fluid chambers.

[0017] The first and second fluid chambers may be fluidly connected in parallel to the fluid inlet.

[0018] The first fluid chamber may comprise a first fluid port and the second fluid chamber may comprise a second fluid port. The first and second fluid ports may be fluidly connected to the fluid inlet.

[0019] The forming tool may comprise a flow restrictor in a flow path between the fluid inlet and the second fluid chamber such that, when a fluid pressure is applied at the fluid inlet, the first fluid chamber reaches the applied fluid pressure prior to the second fluid chamber reaching the applied fluid pressure.

[0020] The forming tool may comprise a first flow restrictor in a flow path between the fluid inlet and the first fluid chamber, and wherein the flow restrictor between the fluid inlet and the second fluid chamber may be a second flow restrictor. The second flow restrictor may apply a greater flow restriction on fluid flow than the first flow restrictor.

[0021] The forming tool may comprise a manifold forming the flow path, wherein the flow restrictor may be in the manifold.

[0022] The forming tool may comprise a fluid control valve between the fluid inlet and the second fluid chamber.

[0023] The forming tool may comprise a first fluid control valve between the fluid inlet and the first fluid chamber. The fluid control valve between the fluid inlet and the second fluid chamber may be a second fluid control valve.

[0024] The forming tool may comprise a fluid pressure control unit configured to operate the first and second fluid control valves, wherein the second fluid control valve is configured to open subsequent to the first fluid control valve.

[0025] The forming tool may comprise a fluid bladder, wherein the fluid bladder forms at least one of the deformable panels.

[0026] The forming tool may comprise a plurality of fluid bladders, wherein each fluid bladder defines a fluid chamber.

[0027] The or each fluid bladder may define at least two fluid chambers [0028] The fluid bladder comprises a diaphragm in the fluid bladder dividing the fluid bladder into at least two fluid chambers.

[0029] The forming tool may comprise a pressure control unit, wherein the pressure control unit is configured to apply a fluid pressure at the inlet.

[0030] The pressure control unit may be configured to provide a first fluid pressure at the fluid inlet to apply a first load to the laminate charge, and to subsequently provide a second fluid pressure at the inlet to apply a second load to the laminate charge.

[0031] The first fluid pressure may be greater than atmospheric pressure. [0032] The second fluid pressure may be greater than the first fluid pressure.

[0033] The forming tool may comprise a retaining arrangement configured to retain the laminate charge receiving support; and the plurality of fluid chambers in a spaced relationship.

[0034] The laminate charge receiving support may be non-planar and, optionally, comprises an arcuate face.

[0035] The array may comprise a non-planar arrangement and, optionally, an arcuate arrangement.

[0036] The laminate charge receiving support may include an exhaust vent.

[0037] The forming tool may be configured to form a component forming at least one of a spar, a rib, and a stringer, The forming tool may form at least one of a Z-shaped, L-shaped, U-shaped, and omega-shaped component.

[0038] According to a further aspect of the invention, there is provided a forming tool for forming a laminate charge, the forming tool comprising: a base support arranged to receive a laminate charge; a plurality of fluid chambers on an upper support spaced from the base support; each fluid chamber comprising a deformable wall spaced from the base support; wherein the forming tool comprises a fluid pressure application arrangement arranged to sequentially apply a fluid pressure to the fluid chambers so as to sequentially deform each of the deformable walls towards the base support to provide a load on the laminate charge receivable on the support.

[0039] A method of forming a laminate charge, the method comprising: mounting the laminate charge on a forming tool, the forming tool having a laminate charge receiving support and a plurality of fluid chambers; each fluid chamber comprising a distendable wall spaced from the support; and sequentially apply a fluid pressure to the fluid chambers so that the dispensable walls sequentially distend towards the support to provide a sequentially applied load on the laminate charge.

[0040] The laminate charge comprises a stack of two or more plies, typically ten or more plies. The stack may be planar, or have an alternative profile.

[0041] The laminate charge may comprise a stack of non-fibrous plies, but typically it comprises a stack of fibre plies. The fibres of the fibre plies may be carbon fibres, or fibres made from any other suitable material. Fibre plies are preferred because they can have relatively high porosity.

[0042] The fibre plies may be prepreg plies, each prepreg ply comprising a layer of fibres impregnated with a matrix material. However the laminate charge may comprise a stack of dry-fibre plies, optionally containing a binder. Such dry-fibre plies have a higher degree of porosity than prepreg plies. Optionally the stack of dry-fibre plies includes resin film plies interleaved with the dry-fibre plies, as a precursor for a resinfilm-infusion process.

[0043] Optionally the method further comprises infusing the dry-fibre plies of the laminate charge with a liquid matrix material after the distendable has pressed the third part of the laminate charge against the forming tool. This may be achieved by a resin transfer moulding process, a resin film infusion process, or any other suitable method.

[0044] The dry-fibre plies may be infused on the forming tool, but more typically they are infused on an infusion tool.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the invention will now be described with reference to the accompanying drawings, in which: [0046] Figure 1 is a perspective view of part of a forming tool performing a laminate charge; [0047] Figure 2 is an exploded perspective view of the forming tool of Figure 1 together with the laminate charge; [0048] Figure 3 is another exploded perspective view of the forming tool and the laminate charge; [0049] Figure 4 is a cross-sectional side view of the part of the forming tool shown in Figure 1 in a partially pressurised condition; [0050] Figure 5a, 5b and 5c are cross-sectional side views of the part of the forming tool of Figure 4 showing a sequential application of fluid pressure to fluid chambers of the forming tool so as to provide a pressure wave across the laminate charge; [0051] Figure 6 is an exploded prospective view of another embodiment of part of the forming tool; [0052] Figure 7 is a cut-away plan view of a forming part of the forming tool shown in Figure 6; [0053] Figures 8 and 9 are schematic block diagrams showing different arrangements of a fluid supply of the forming tool shown in Figure 1; [0054] Figure 10 is a schematic block diagram of a fluid supply of the forming tool shown in Figure 6; and [0055] Figure 11 is a schematic block diagram of a fluid supply of an alternative forming tool.

[0056] DETAILED DESCRIPTION OF EMBODIMENT(S)

[0057] A part of a forming tool 10 for forming a laminate charge 100 is shown in Figure 1. A forming tool 10 comprises a mold 20 and a fluid supply 40. Part of the fluid supply is shown in Figure 1 as a plurality of fluid inlet ports 4L The fluid used in the present embodiment is pressurised air, although other fluids such as a liquid or another gas, may be used. The mold 20 is arranged to receive the laminate charge 100. The laminate charge 100 is shown in Figure 2.

[0058] The mold 20 comprises a support base 21. The base 21 forms a laminate charge receiving support. When assembled with the tool 21, the laminate charge 100 is placed on a base surface 22 of the base 21. The base surface 22 is generally configured to correspond with a profile of the laminate charge 100. Retaining walls 23 extend around the base surface 22. The retaining walls 23 act to surround a laminate charge receiving space 26. The mold 20 also comprises a cover 24. The cover 24 is arranged to be assembled with the base 21. The cover 24 is held in spaced relationship with the base 21. The base 21 and cover 24 are mountable together to define a pre-determined height of the laminate charge receiving space 26. The cover 24 has an inner side 25. The inner side 25 of the cover 24 opposes the base surface 22. A mount 27 is used to clamp the base 21 and cover 24. The mount 27 maintains the base 21 and the cover 24 in a spaced relationship.

[0059] In the present arrangement, the mount 27 extends over the cover 24 and mounts to the retaining walls 23. The retaining walls 23 upstand from the base 21. As such, the base and cover 24 enclose the laminate charge 100. The retaining walls 23 may be omitted. The mount 27 prevents movement of the cover 24 when the base 21, cover 24 and mount 27 are assembled together. Fasteners 28 retain the mount in position. It will be understood that alternative fastening arrangements are possible.

[0060] As shown in Figure 3, a forming part 30 is arranged to act on the laminate charge 100. The forming part 30 is received by the mold 20. The forming part 30 is on the inner side 25 of the cover 24. The forming part 30 is configured to apply a load on the laminate charge 100 during operation of the forming tool 10. When assembled, the laminate charge 100 is received between the base 21 and the forming part 30. The forming part 30 is received between the cover 24 and the base 21. The forming part 30 is disposed against the cover 24.

[0061] Exhaust holes 29 are formed in the base 21. The exhaust holes 29 extend from the base surface 22 and provide for the exhaust of gas from the laminate charge receiving space 26. The exhaust holes 29 may be disposed around the periphery of the base 21. Alternatively, or in addition, the exhaust holes 29 are disposed in an array in the base surface 22. The exhaust holes 29 exhaust to external of the forming tool 10.

[0062] The cover 24 is received by the retaining walls 23 to fully enclose the receiving space 26. In alternative arrangement, the retaining walls 23 at least partially extend from the cover 24. The fluid supply 40 includes the injections ports 41. A plurality of injection ports 41 are shown in Figures 1 to 4. The injection ports 41 fluidly communicate with the forming part 30 as will be described below.

[0063] The forming part 30 will now be described in more detail with reference to Figures 3, 4 and 5a to c.

[0064] The forming part 30 extends across the receiving space 26. The forming part 30 is configured to act across the entire upper face 101 of the laminate charge 100. The forming part 30 is arranged to act on the upper surface 101 of the laminate charge 100. The lower surface 102 of the laminate charge 102 is located on the base surface 22.

[0065] The forming part 30 is supported by the cover 24. The forming part 30 forms a loading surface 34. The loading surface 34 is configured to act on the laminate charge 100. The forming part 30 comprises an array of elongate pressurised bags. The pressurised bags act as fluid chambers 32. Each fluid chamber 32 comprises a peripheral wan 38 defining an internal cavity 39. The plurality of fluid chambers 32 are aligned adjacent to each other. The pressurised bags are arranged as an array 31 of fluid chambers 32. The fluid chambers 32 may be formed individually or integrally with each other.

[0066] Each fluid chamber 32 extends from one end of the receiving space 26 to the other end of the receiving space 26. A dividing wall 35, forming part of the peripheral wall 38, is defined between each adjacent pair of fluid chambers 32. The dividing wall 35 may be formed by a wall of the pressure bags or, for example, by a diaphragm dividing a fluid bladder into two separate fluid chambers 32. Each fluid chamber 32 may be formed by an individual fluid bladder. The pressure bag defining each fluid chamber 32 is formed from a deformable, resilient material. Such a resilient material may be a rubber material.

[0067] The fluid chamber 32 has a distendable wall 33. The distendable wall 33 is at a lower side of the fluid chamber 32. The distendable wall 33 comprises part of the peripheral wall 38. Each distendable wall 33 is exposed to the receiving space 26. The distendable wall 33 may be formed by the fluid bladder. Alternatively, the fluid chamber 32 may be formed by rigid walls, for example upper and side walls, with an exposed distendable panel forming the distendable wall 33. The fluid chamber 32 acts as a sealed gas chamber. When a pressure differential is applied across the distendable wall 33, the distendable wall 33 distends into the side with the higher pressure.

[0068] When air is applied in the fluid chamber 32 at an increased pressure to that of the receiving chamber 24, the distendable wall 33 is configured to distend into the receiving space 26. The distendable wall 33 is therefore able to arrange to deform towards the base 21 to apply a load on the laminate charge 100.

[0069] Each of the fluid chambers 32 is disposed adjacent to a pair of fluid chambers 32 on either side of said fluid chamber 32. One fluid chamber 32 at each end of the array 31 of fluid chambers 32 has a single adjacent fluid chamber 32 and therefore defines the edge of the array 31 of fluid chambers 32.

[0070] Each fluid chamber 32 is fluidly connected to an injection port 41. As such, each fluid chamber 32 has a corresponding injection port 41. The injection port 41 provides for the injection of a fluid, in this case air, into the fluid chamber 32. The fluid supply 40 includes the injection ports 41 communicating with each fluid chamber 32. Air is provided to the injection ports 41 by a fluid inlet 42, as shown in Figure 8. A fluid pump 43 supplies pressurized air at the fluid inlet 22. As such, fluid at an increased pressure is supplied to each fluid chamber 32 via fluid inlet 42.

[0071] A fluid manifold 44 forms part of a fluid control system 46. Pressurised air is supplied to the fluid manifold 44 from the fluid inlet 42. The fluid manifold 44 controls the supply of pressurised air to each of the injection ports 41. The fluid manifold 44 distributes the supply of pressurised air to each of the injection ports 41. The fluid manifold comprises a valve arrangement. The valve arrangement comprises a number of valves 45. Each valve 45 controls the flow of fluid to each fluid chamber 32. As shown in Figure 8, three chambers 32, 32b, 32c are shown of the array 31 of fluid chambers 32. Each fluid chamber 32a, 32b, 32c, has an associated valve 45a, 45b, 45c.

[0072] The fluid control system 46 includes a pressure control unit 47. The pressure control unit 47 is configured to control operation of the valves 45 and the fluid pump 43. It will be understood that the pressurised air supply may be the fluid pump 45, or an alternative supply. The pressure control unit 47 is configured to control the fluid pressure in each fluid chamber 32. The pressure control unit 47 comprises a processor and a memory. In order to operate the forming tool 20 the fluid pump 45 acting as a fluid pressure supply is coupled to the fluid inlet 22.

[0073] A method of forming the laminate charge 100 using the apparatus previously described is set out below. The laminate charge 100 is laid up on the base 21 acting as a layout surface. The laminate charge 100 comprises a stack of dry-fibre plies which are laid up on the horizontal base surface 22. The number of plies is typically about 15 plies (for a 3mm charge) up to about 120 plies (for a 40mm charge). Each ply comprises, for example, a knitted or woolen fabric of separate unidirectional fibre layers or stitched into non-crimp fabrics or woven fabrics of carbon fibres or other fibres. Each ply contains binding material and/or a toughener material, typically in the form of a powder or a veil, but it is "dry" in the sense that it is not pre-impregnated with resin and so has a relatively open porous structure. Optionally, the stack includes a peel ply, semipermeable membrane, or any other porous membrane such as a breather layer at the top of/bottom of the stack.

[0074] When the laminate charge 100 is received on the base 21, the forming part 30 and the cover 24 are disposed above the laminate charge 100. The mounts 27 mount the cover 24 and forming part 30 in a spaced relationship with the base 21. As such, the distance between the base surface 22 and inner side 25 of the cover 25 are disposed in a pre-determined spaced relationship. The mold 20 of the forming tool 10 is therefore assembled with the laminate charge 100 between the forming part 20 and the base 21.

[0075] In a forming step, the fluid pump 43 is turned on to generate an increased fluid pressure at the fluid inlet 42. The pressure control unit 47 is operated to control the fluid pressure at each fluid chamber 32. The pressure control unit 47 includes a controller which is arranged to control opening and closing of each valve 45. Each valve is independently operable.

[0076] The pressure control unit 47 is arranged to control opening of each valve in a predetermined sequence. Each valve 45 is opened sequentially. Each valve 45 is opened is a sequential order from one end of the array 31 or fluid chamber 32 to the opposite end of the array 31. When each valve 45 is opened, an increase pressure is applied at each fluid chamber 32. The increased pressure applied to each fluid chamber 32 causes the distendable wall 43 to distend. The distendable wall 43 is therefore caused to distend against the laminate charge 100. The fluid pressure force in each fluid chamber 32 causes the distendable wall 33 to press the laminate charge 100 against the base 21. By pressing the laminate charge 100 with the loading surface 34 of the array 31 of fluid chambers 32, the arrangement enables air present between the plies of the laminate charge 100 to be washed out by the forming process, which achieves a bulk reduction in the laminate charge 100. By loading each fluid chamber 32 sequentially, it is possible to create a loading wave across the laminate charge 100 from one edge to an opposing edge of the laminate charge 100, and so to generate a sequential loading on the laminate charge 100. This aids with washing out the laminate charge 100during the forming process and helps removal of air present between the plies 51. As such, trapped air is restricted. The exhaust holes 29 in the base 21 are used to allow the air released from the laminate charge 100 to be exhausted from the forming tool 10.

[0077] With the present arrangement, the pressure control unit 47 is arranged to sequentially inflate the fluid chambers 32, and so to distend the distendable wall 33 in a sequential manner from one end of the array 31 to the other end of the array 31. This process is demonstrated in figures 5a to 5c. In Figure 5a, fluid chambers 32a-e are shown in which an increased air pressure has been applied to first and second of the chambers 32a, 32b, such that the distendable wall 33 is deformed towards the base 21 so as to apply an increase load on the laminate charge 100. In this partially pressurized condition the fluid control valves 45 connected to fluid chambers 32a, 32b are in an open condition, whereas the valves 45 of each of the fluid chambers 32c, 32d, 32e are retained in the closed condition.

[0078] In Figure 5b, the fluid control valve 45 of fluid chamber 32c is opened such that the distendable wall 33c distends against the laminate charge 100. Similarly, in Figure 5c, the fluid control valve 45 communicating with fluid chamber 32d is opened such that the distendable wall 33d of fluid chamber 32d distends against the laminate charge 100. As such, a pressure wave is applied across the laminate charge from one end to the other end as shown by arrows A as each valve 45 is opened. At the end of the forming step, all of the fluid chambers 32 have an increased fluid pressure applied to them such that all of the distendable walls 33 of the loading surface 34 are applied against the laminate charge 100at a predetermined loading pressure. The pressure wave helps to prevent wrinkles forming in the plies of the laminate charge.

[0079] At the end of this forming step, each of the valves 45 and valve arrangement 46 may be closed to retain the fluid pressure in each fluid chamber 32. The fluid pump 43 is initially at a first fluid pressure. The pressure control unit 47 may be arranged to control the level of fluid pressure applied at the fluid inlet 42 by the fluid pump 43. In a second stage of the forming step, following the fluid valves 45 being closed, the fluid pump 43 may be configured to apply a second, increased, fluid pressure at the fluid inlet 42. The fluid valves 45 of each fluid chamber 32 may then be opened sequentially to then apply the second, increased, fluid pressure at each of the fluid chambers 32, and therefore sequentially increase the load applied by the di stendable wall 33 of each fluid chamber 32 on the laminate charge 100. Such a process may be repeated, such that the load applied to the laminate charge 100 is applied in a stepped configuration.

[0080] The fluid control system may be configured to sequentially apply the increased fluid pressure in the same sequence at each stage, or an alternative configuration may apply the pressure way at alternating ends of the laminate 100.

[0081] In another embodiment, at the end of the forming step, the fluid pressure in each fluid chamber 32 is released or reduced. A second stage of the forming step may then be applied, in which the first stage is repeated to apply the increased fluid pressure sequentially across the fluid chambers 32. Third and subsequently stages of the forming step may then be applied.

[0082] The loading applied to the laminate charge 100 forces air out of the pores in the laminate charge 100, reducing its bulk ready for curing. For example, once the charge has been fully formed, it is may be heated on the forming tool, or an alternative infusion tool (not shown), in which a liquid resin source is applied to the dry fiber plies of the laminate charge 100 to infuse the laminate charge with liquid resin which is then cured and is ready for use in its particular application. One preferred application for the laminate charge is as a component part of a torsion box of an aircraft wing (known as a wing box). Other applications for the charge include automotive (car floor panel), mass transit, wind turbine, marine turbine or engine parts (jet engines).

[0083] In the above described arrangement it will be understood that the fluid pressure is applied from the fluid inlet 42 to each of the fluid chambers 32 in parallel. With such a parallel configuration, the valve arrangement controls the fluid pressure at each of the fluid chambers 32. An alternative parallel arrangement will now be described with reference to Figure 9. Such a parallel arrangement has generally the same configuration as described above, with a similar mold 20. As such, similar reference numerals will be maintained. However in such an arrangement as shown in Figure 9, the valve arrangement is replaced by a flow restrictor arrangement 49.

[0084] The flow restrictor arrangement 49 comprises flow restrictors 48 controlling the rate of fluid flow into each of the fluid chambers 32. The flow restrictors 48 act to choke the fluid flow through the flow restrictor. As such, it is possible to control the rate at which an increased fluid pressure is applied at each of the fluid chambers 32. In the present embodiment, the flow restrictors 48 are in the manifold 44. The manifold controls the flow of fluid to each fluid chamber 32. The fluid control system 46 comprises the pressure control unit 47. The pressure control unit 47 is configured to control the supply of pressurised air.

[0085] In the embodiment as shown in Figure 9, a first flow restrictor 48a is disposed between the fluid inlet 42 and the fluid chamber 32b. Similarly, a second flow restrictor 48b is disposed between the fluid inlet 42 and the fluid chamber 32c. In the shown embodiment, no flow restrictor is disposed between the fluid inlet 42 and the fluid chamber 32a, although it will be understood that such a flow restrictor may be present.

[0086] Each flow restrictor 48 is configured to control the rate at which fluid flows into each fluid chamber 32, and therefore the rate at which fluid chamber 32 is able to be brought up to equalize with the fluid pressure applied at the fluid inlet 42. When the fluid pump 43 is operated, the increased fluid pressure is applied at fluid inlet 42, and is therefore applied at each flow restrictor 48. Due to the presence of the flow restrictors 48, the fluid chamber 32a is configured to achieve the increased fluid pressure prior to fluid chamber 32b, and the fluid chamber 32b is configured to achieve the applied fluid pressure prior to fluid chamber 32c. As such, the fluid pressure is applied to each of the fluid chambers 32 sequentially. Such arrangement may be achieved by the opening at each fluid flow restrictor 48 having a differing size opening. In such an arrangement, the flow restriction of flow restrictor 48b is greater than flow restriction of flow restrictor 48a. In the present arrangement, the flow restrictors 48a, 48b are shown in parallel, although it will be understood that the flow restrictors may be arranged in series. The flow restriction may be defined by the size of the opening of each injection port 41.

[0087] Referring now to Figures 6 and 7 an alternative flow restrictor arrangement is shown. Each of the fluid chambers 32 are connected in series to each adjacent fluid chamber 32. A schematic view of the arrangement is shown in Figure 10. In this arrangement, the flow restrictors 48 are disposed between fluid chambers 32.

[0088] In such an arrangement the fluid inlet 42 is in fluid communication with a single injection port 41 of one fluid chamber 32a of the array of'31 fluid chambers 32. In the embodiment shown in Figures 6 and 7, the injection port 41 is at a first end of the array 31. Fluid passages 103 are formed between adjacent fluid chambers 32. The fluid passages 103 are openings between adjacent fluid chambers 32. With this arrangement, the fluid chambers 32 are defined by diaphragms acting as dividing walls 35 [0089] Each fluid chamber 32 extends from one end of the receiving space 26 to the other end of the receiving space 26. A dividing wall 35, forming part of the peripheral wall 38, is defined between each adjacent pair of fluid chambers 32. The dividing wall 35 may be formed by a wall of the pressure bags or, for example, by a diaphragm dividing a fluid bladder into two separate fluid chambers 32. Each fluid chamber 32 may be formed by an individual fluid bladder. The pressure bag defining each fluid chamber 32 is formed from a deformable, resilient material. Such a resilient material may be a rubber material.

[0090] The openings acting as fluid passages 103 define the flow restrictors 48a, 48b (shown schematically in Figure 10). By determining an opening area it is possible to control the flow rate through the fluid passage 103, and therefore the rate at which each chamber achieves the increased pressure applied at the injection port 41. When an increased air pressure is applied at the fluid inlet 42, the first fluid chamber 32a achieves the fluid pressure value prior to the second fluid chamber 32b due to the flow restriction at the flow restrictor 48a. Similarly, the second fluid chamber 32b achieves the fluid pressure value prior to the second fluid chamber 32c due to the flow restriction at the flow restrictor 48b. The distendable walls 33 distend sequentially, so as to apply a sequential increased load across the laminate charge 100. As such, a pressure wave is applied across the laminate charge from one end to the other end as shown by arrow B. In the arrangement shown in Figure 7, the openings are formed at opposing ends of each fluid chamber 32.

[0091] It will be understood that in an alternative embodiment, the fluid chambers may be formed in a grid. The grid may have a range of configurations, to define different shapes. With such an arrangement sequential inflation of fluid chambers may be provided in multiple directions, for example in perpendicular directions. As such, loading may be applied in multiple directions.

[0092] A further embodiment is shown schematically in Figure 11. In this embodiment, each of the fluid chambers 32 are connected in series to each adjacent fluid chamber 32. The fluid inlet 42 is in fluid communication with a single injection port 41 of one fluid chamber 32a of the array of 31 fluid chambers 32. In the embodiment shown in Figures 6 and 7, the injection port 41 is at a first end of the array 31. Valves 45 are disposed between adjacent fluid chambers 32. Fluid passages 104 fluidly connect adjacent fluid chambers. However, in this embodiment a valve 45 is associated with each fluid passage 104. As such, the flow of air between adjacent fluid chambers 32 is controlled.

[0093] The fluid control system 46 includes the valves 45 of the valve arrangement. The pressure control unit 47 is arranged to sequentially operate the valves 45, and therefore sequentially inflate the fluid chambers 32. The distendable walls are therefore distended in a sequential manner from one end of the array 31 to the other end of the array 31. When the increased air pressure has been applied to the first fluid chamber 32a, the first valve 45a is opened and the increased air pressure is applied to the second fluid chamber 32b. Subsequently, the first valve 45b is opened and the increased air pressure is applied to the third fluid chamber 32c. Such an operation continues across the array of fluid chambers 32. As such, a pressure wave is applied across the laminate charge from one end to the other end as each valve 45 is opened. At the end of the forming step, all of the fluid chambers 32 have an increased fluid pressure applied to them such that all of the distendable walls 33 of the loading surface 34 are applied against the laminate charge 100 at a predetermined loading pressure. A stepped increase in applied fluid pressure may then be applied as described above.

[0094] In the above described embodiments, the forming tool 10 is shown configured to provide a planar laminate charge. However it will be understood that alternative configurations are possible. For example, the forming tool in an alternative configuration is configured to form an arcuate laminate charge. In such an arrangement the base is arcuate and the array of fluid chambers are arranged in an arcuate configuration. More complex shapes may be produced, such as L-shaped configuration or omega-shaped configuration. For example, the forming tool may form at least one of a spar, a rib, cover, and a stringer, The spar, rib, cover, and/or stringer may be Z-shaped, L-shaped, U-shaped, or omega-shaped.

[0095] It will be understood that the generation of a wave across the laminate charge will help to minimise the generation of wrinkles, for example at radii.

[0096] Although in the above described embodiments, air is used as the fluid supplied by the fluid supply, it will be appreciated that alternative fluids may be used. For example, an alternative gas may be supplied. In embodiments, a liquid such as a hydraulic fluid may be supplied.

[0097] In embodiments, a heated fluid is supplied by the fluid supply. The fluid supply in such an arrangement comprises a fluid heater to supply fluid at a raised temperature. Such a fluid is supplied at a temperature greater than the atmospheric air temperature. In one embodiment, the supplied fluid is air at a heated temperature. In another embodiment, the supplied fluid is a heated liquid such as water.

[0098] Where the word 'or' appears this is to be construed to mean 'and/or' such that items referred to are not necessarily mutually exclusive and may be used in any appropriate combination.

[0099] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1 A forming tool for forming a laminate charge, the forming tool comprising: a laminate charge receiving support; and a plurality of fluid chambers; each fluid chamber comprising a distendable wall spaced from the support; wherein the distendable walls are arranged to distend towards the support when a fluid pressure is applied to the fluid chambers to provide a load on the laminate charge receivable on the support; and wherein the forming tool is configured to sequentially apply fluid pressure to the fluid chambers such that the distendable walls distend sequentially.
2. The forming tool of claim 1, wherein the plurality of fluid chambers are disposed adjacent to each other in an array.
3. The forming tool of claim 2, wherein the distendable walls of the array of fluid chambers together define a loading surface configured to act on the laminate charge receivable on the support.
4. The forming tool of claim 2 or claim 3, wherein the forming tool is configured to sequentially apply a fluid pressure to each of the fluid chambers up to a predetermined fluid pressure along the array from a first end of the array to a second end.
5. The forming tool of any preceding claim, comprising a fluid inlet through which a fluid pressure is applied to the fluid chambers.
6. The forming tool of claim 5 comprising a first fluid chamber of the plurality of fluid chambers and a second fluid chamber of the plurality of fluid chambers, wherein the fluid inlet is fluidly connected to the first fluid chamber, and the second fluid chamber is fluidly connected in series to the first fluid chamber.
7 The forming tool of claim 6, comprising a flow restrictor in a flow path between the first and second fluid chambers such that, when a fluid pressure is applied at the fluid inlet, the first fluid chamber reaches the applied fluid pressure prior to the second fluid chamber reaching the applied fluid pressure.
8. The forming tool of claim 7, comprising a fluid barrier between the first and second fluid chambers, wherein the flow restrictor comprises an aperture in the fluid barrier.
9. The forming tool of claim 6, comprising a fluid control valve in a flow path between the first and second fluid chambers.
10. The forming tool of claim 5, wherein the first and second fluid chambers are fluidly connected in parallel to the fluid inlet.
11 The forming tool of claim 10, comprising a flow restrictor in a flow path between the fluid inlet and the second fluid chamber such that, when a fluid pressure is applied at the fluid inlet, the first fluid chamber reaches the applied fluid pressure prior to the second fluid chamber reaching the applied fluid pressure.
12. The forming tool of claim 11, comprising a first flow restrictor in a flow path between the fluid inlet and the first fluid chamber, and wherein the flow restrictor between the fluid inlet and the second fluid chamber is a second flow restrictor, wherein the second flow restrictor applies a greater flow restriction on fluid flow than the first flow restrictor.
13. The forming tool of claim 11 or 12, comprising a manifold forming the flow path, wherein the flow restrictor is in the manifold.
14. The forming tool of claim 10, comprising a fluid control valve between the fluid inlet and the second fluid chamber.
15. The forming tool of claim 14, comprising a first fluid control valve between the fluid inlet and the first fluid chamber, and wherein the fluid control valve between the fluid inlet and the second fluid chamber is a second fluid control valve.
16. The forming tool of claim 15, comprising a fluid pressure control unit configured to operate the first and second fluid control valves, wherein the second fluid control valve is configured to open subsequent to the first fluid control valve.
17. The forming tool of any preceding claim, comprising a fluid bladder, wherein the fluid bladder forms at least one of the deformable panels.
18. The forming tool of claim 17, comprising a plurality of fluid bladders, wherein each fluid bladder defines a fluid chamber.
19. The forming tool of claim 17 or 18, wherein the or each fluid bladder defines at least two fluid chambers.
20. The forming tool of claim 19, wherein the fluid bladder comprises a diaphragm in the fluid bladder dividing the fluid bladder into at least two fluid chambers.
21. The forming tool of claim 21, wherein the pressure control unit is configured to provide a first fluid pressure at the fluid inlet to apply a first load to the laminate charge, and to subsequently provide a second fluid pressure at the inlet to apply a second load to the laminate charge.
22. The forming tool of claim 22 or 23, wherein the second fluid pressure is greater than the first fluid pressure.
23. The forming tool of any preceding claim, configured to form a component forming at least one of a spar, a rib, and a stringer, and optionally, to form at least one of a Z-shaped, L-shaped, U-shaped, and omega-shaped component.
24. A forming tool for forming a laminate charge, the forming tool comprising: a base support arranged to receive a laminate charge; a plurality of fluid chambers on an upper support spaced from the base support; each fluid chamber comprising a deformable wall spaced from the base support; wherein the forming tool comprises a fluid pressure application arrangement arranged to sequentially apply a fluid pressure to the fluid chambers so as to sequentially deform each of the deformable walls towards the base support to provide a load on the laminate charge receivable on the support.
25. A method of forming a laminate charge, the method comprising: mounting the laminate charge on a forming tool, the forming tool having a laminate charge receiving support and a plurality of fluid chambers; each fluid chamber comprising a distendable wall spaced from the support; and sequentially apply a fluid pressure to the fluid chambers so that the dispensable walls sequentially distend towards the support to provide a sequentially applied load on the laminate charge.