Method of forming an aircraft fluid flow conduit

Abstract

A method of forming an aircraft fluid flow conduit, particularly a fuel stringer duct, comprises forming a conduit preform, wherein forming the conduit preform comprises wrapping a sheet 125 around a

Description

BACKGROUND OFTHE INVENTION [0001 ] The present disclosure relates to aircraft fluid flow conduits.

[0002] The present invention relates to aircraft fluid flow conduits. More particularly, but not exclusively, this invention concerns a method of forming an aircraft fluid flow conduit. The invention also concerns an aircraft fluid flow conduit, an aircraft wing, an aircraft fuel transmission arrangement and an aircraft.

[0003] It is known to provide a fuel stringer duct that both acts as a wing stringer in an aircraft wing and provides a duct for carrying aircraft fuel. One such duct is formed from a ply. A supporting top hat structure is used to provide further structural support and to facilitate attachment of the duct to an aircraft structure. A U-shaped channel member is also provided to provide structural support to the ply. Very few layers extend around the whole perimeter of the duct, and therefore the structural integrity of the duct relies on strong interaction between adjacent parts of the duct (e.g. between the ply and the top hat, and between the ply and the U-shaped channel member).

[0004] The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method of forming an aircraft fluid flow conduit. SUMMARY OF THE INVENTION

[0005] In accordance with a first aspect of the present invention, there is provided a method of forming an aircraft fluid flow conduit, the method comprising: forming a conduit preform, wherein forming a conduit preform comprises: providing at least one layer of braided material under tension around a mandrel, the braided material being capable of forming a composite material with a matrix; providing a curable precursor material to the conduit preform; and curing the curable precursor material to form a matrix.

[0006] The applicant has discovered that an aircraft fluid flow conduit may be formed by providing around a mandrel braided materialthat is capable of forming a composite material. Forming a conduit preform optionally comprises providing a plurality of layers of braided material around the mandrel.

[0007] Optionally, at least two of the plurality of layers of braided material are mutually different. For example, the angle that the strands of material make with a longitudinal axis of the conduit preform may be mutually different in two layers of braid. For example, a first angle that strands of material of a first layer of braided material make with a longitudinal axis of the conduit preform may be different from a second angle that strands of material of a second layer of braided material make with a longitudinal axis of the conduit preform.

[0008] Within a layer of braid, the angle that the strands of material make with a longitudinal axis of the conduit preform need not be constant. For example, a layer of braid may comprise a first region in which the angle that the strands of material make with a longitudinal axis of the conduit preform is a first value, and a second region in which the angle that the strands of material make with a longitudinal axis of the conduit preform is a second value different from the first value.

[0009] Forming a conduit preform optionally comprises providing at least one interlayer between two layers of braided material, at least one of those interlayers optionally comprising a material capable of forming a composite material with a matrix. Optionally, at least one interlayer is not a braided material.

[0010] At least one layer, optionally more than one layer and optionally each layer, of braided material may be applied using a braiding apparatus. Optionally, at least one layer, optionally more than one layer and optionally each layer, of braided material may be maintained under tension during provision of curable precursor materialto the conduit preform. [0011 ] For the avoidance of doubt, there may optionally be at least one layer between the mandrel and the innermost layer of braided material.

[0012] In accordance with a second aspect of the present invention, there is provided a method of forming an aircraft fluid flow conduit, the method comprising: forming a conduit preform, wherein forming the conduit preform comprises: wrapping a sheet around a mandrel such that at least a portion of the sheet overlaps with another portion of the sheet, the sheet comprising fibrous material capable of forming a composite material with a matrix; and curing the sheet to form a matrix.

[0013] The applicant has discovered that it is possible to make an aircraft fluid flow conduit by wrapping a sheet that is capable of forming a composite material around a mandrel. Priorto wrapping the sheet around the mandrel, the sheet may be substantially devoid of curable precursor material. In this case, the method may comprise providing curable precursor material to the sheet after the sheet has been wrapped around the mandrel, such that priorto wrapping the sheet around the mandrel the sheet is substantially devoid of the curable precursor material. Curing the sheet to form the matrix may comprise curingthe curable precursor material to form the matrix. Alternatively or additionally, prior to wrapping, the sheet may comprise the curable precursor material. Wrapping the sheet around the mandrel may therefore comprise wrapping a sheet comprising a curable precursor material around the mandrel. Optionally, the sheet will be provided with the curable precursor material, for example in the form of a pre-preg. Alternatively or additionally, the method may comprise providing curable precursor to a sheet which is substantially devoid of curable precursor material, and then wrapping the sheet around the mandrel. Curingthe sheet to form the matrix may comprise curing the curable precursor material to form the matrix. Even in the event that the sheet, prior to wrapping, comprises curable precursor material, then the method may comprise providing curable precursor material to the sheet after the sheet is wrapped around the mandrel. The method optionally comprises wrapping the sheet around the mandrel such that at least two, optionally at least three, optionally at least four, optionally at least five, optionally at least six, optionally at least ten, optionally at least twelve, optionally at least fifteen and optionally at least twenty thicknesses of sheet are formed around the mandrel. Therefore, the conduit preform optionally comprises at least two, optionally at least three, optionally at least four, optionally at least five, optionally at least six, optionally at least ten, optionally at least twelve, optionally at least fifteen and optionally at least twenty thicknesses of sheet around the mandrel. The method optionally comprises wrapping the sheet around the mandrel such that no more than one hundred, optionally no more than eighty, optionally no more than sixty, optionally no more than forty, optionally no more than thirty, and optionally no more than twenty thicknesses of sheet are formed around the mandrel. Therefore, the conduit preform optionally comprises no more than one hundred, optionally no more than eighty, optionally no more than sixty, optionally no more than forty, optionally no more than thirty, and optionally no more than twenty thicknesses of sheet around the mandrel.

[0014] Wrappingthe sheet around the mandrel may comprise one or more of: moving the sheet around a substantially motionless mandrel; maintaining the sheet in a substantially constant position and moving the mandrel (optionally rotating the mandrel); and moving the sheet around a moving mandrel (optionally rotating the mandrel).

[0015] The sheet optionally comprises at least one layer and optionally more than one layer. At least one, optionally more than one and optionally each layer comprises fibrous material capable for forming a composite material with a matrix.

[0016] Optionally, each layer need not be continuous. For example, at least one layer, and optionally more than one layer, may comprise a first portion of material that is not continuous with a second portion of material. This allows a conduit to be formed in which the conduit has a layer structure that is different in different parts of the conduit.

[0017] Optionally, the sheet may comprise at least one continuous layer. The sheet may comprise a backing layer. The backing layer may be a substantially continuous layer.

[0018] Formingthe conduit preform may optionally comprise wrapping a sheet around the mandrel such that at least a portion of the sheet overlaps with another portion of the sheet, and such that a flap portion of sheet extends from the wrapped mandrel. The flap portion may be used to attach the conduit preform to an aircraft structure or an aircraft structure preform.

[0019] For the avoidance of doubt, the following statements apply to both the methods of the first and second aspects of the present invention.

[0020] The mandrel is optionally expandable and / or contractable. The mandrel is optionally inflatable and / or deflatable. The method may therefore optionally comprise expanding, preferably inflating, the mandrel prior to the formation of the conduit preform. The method may optionally comprise contracting, preferably deflating, the mandrel after curingthe precursor material. [0021 ] The curable precursor material optionally comprises any suitable material, such as resin precursors, that are well-known to those skilled in the art. The curable precursor material may optionally be chosen dependent on the fibrous material used to form the conduit perform (for example, the braided material in the first aspect of the present invention or the sheet in the second aspect of the present invention).

[0022] Curing the curable precursor material may comprise any suitable curing method orstep(s) and may typically depend on the nature of the curable precursor. For example, curing the curable precursor material optionally comprises heating the curable precursor material. The heating conditions (for example, the temperature and duration of heating) may optionally depend on the thickness of conduit preform and curable precursor material being heated and the nature of the curable precursor material. Optionally, curingthe curable precursor material may comprise exposing the curable precursor material to electromagnetic radiation, such as ultraviolet radiation.

[0023] The method optionally comprises providing one or more substrates to facilitate securing the conduit preform to an aircraft structure or to an aircraft structure preform.

[0024] An aircraft structure preform (if present) optionally comprises fibrous material capable of forming a composite material with a matrix. The aircraft structure preform may optionally be impregnated with curable precursor material capable of forming such a matrix. The curable precursor material impregnated in the aircraft structure preform may be the same as, or different from, the curable precursor material provided to the conduit preform.

[0025] Optionally, at least one of the substrates may comprise a sheet, and may comprise more than one layer.

[0026] The method optionally comprises contacting at least one of the substrates with the aircraft structure or aircraft structure preform.

[0027] The method may optionally comprise locating the conduit preform against, or proximate to a surface of an aircraft structure or an aircraft structure preform and contacting at least one of the substrates with the duct perform and with the aircraft structure or the aircraft structure preform.

[0028] The method may optionally comprise providing the conduit preform with at least one of the substrates, and then locating the conduit preform against, or proximate to a surface of the aircraft structure or aircraft structure preform. Locating the conduit preform against, or proximate to, a surface of the aircraft structure or aircraft structure preform may optionally bring the substrate into contact with a surface of the aircraft structure or aircraft structure preform. Alternatively or additionally, the method may optionally comprise contacting the conduit preform, absent at least one of said substrates, with a surface of the aircraft structure or aircraft structure preform, and then providing the conduit preform with at least one substrate.

[0029] The method optionally comprises providing a substrate such that the substrate contacts the aircraft structure or aircraft structure preform to at least one side, and preferably to two sides, of the conduit preform. The substrate may be considered to be omega or Q-shaped.

[0030] Optionally, at least one of said substrates comprises braided material. [0031 ] The method may optionally comprise forming one or more of said substrates comprising braided material so as to provide one or more portions of substrate to facilitate contact of the substrate, and attachment of the conduit preform, to an aircraft structure or aircraft structure preform.

[0032] The method may optionally comprise mounting the conduit preform on a first tool and providing a substrate comprising braided material in tension around the conduit preform and the first tool.

[0033] The method may optionally comprise urging the substrate comprising braided material into contact with the conduit preform. The method may optionally comprise treating the substrate comprising braided material to facilitate urging of the substrate into contact with the conduit preform. For example, the method may optionally comprise cuttingthe braided material.

[0034] The method may optionally comprise urging the substrate into contact with the conduit preform using a second tool. The second tool may be configured to mate with the first tool.

[0035] The aircraft fluid flow conduit is optionally suitable for carrying a liquid, for example, aircraft fuel.

[0036] The aircraft fluid flow conduit is optionally configured to provide structural support. The aircraft fluid flow conduit is optionally configured to transfer forces from an aircraft skin to other structural components. The aircraft fluid flow conduit optionally provides a stringer.

[0037] In accordance with a third aspect of the present invention, there is provided an aircraft fluid flow conduit made in accordance with the method of the first aspect of the present invention.

[0038] In accordance with a fourth aspect of the present invention, there is provided an aircraft fluid flow conduit made in accordance with the method of the second aspect of the present invention.

[0039] In accordance with a fifth aspect of the present invention, there is provided an aircraft wing comprising an aircraft fluid flow conduit in accordance with the third or fourth aspects of the present invention.

[0040] The aircraft fluid flow conduit, or at least a portion thereof, optionally extends from an inboard location of an aircraft wing to an outboard location of an aircraft wing. [0041 ] The aircraft fluid flow conduit is optionally configured to provide structural support. The aircraft fluid flow conduit is optionally configured to transfer forces from an aircraft skin to other structural components. The aircraft fluid flow conduit optionally provides a stringer.

[0042] The aircraft fluid flow conduit may act as a stringer. At least a portion of the aircraft fluid flow conduit may extend from an inboard wing position to an outboard wing position. The aircraft fluid flow conduit may be configured to carry fuel.

[0043] In accordance with a sixth aspect of the present invention, there is provided an aircraft fuel transmission arrangement comprising at least one fuel tank and an aircraft fluid flow conduit in accordance with the third or fourth aspect of the present invention, the aircraft fluid flow conduit being in fluid communication with at least one fuel tank.

[0044] In accordance with a seventh aspect of the present invention, there is provided an aircraft comprising an aircraft wing in accordance with the fifth aspect of the present invention and / or an aircraft fuel transmission arrangement in accordance with the sixth aspect of the present invention.

[0045] It will, of course, be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa. DESCRIPTION OF THE DRAWINGS

[0046] Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings of which:

[0047] Figure 1 is a schematic cross-sectional view of a known fuel stringer duct;

[0048] Figure 2 is a schematic representation of an example of an embodiment of a method of forming an aircraft fluid flow conduit in accordance with the first aspect of the present invention;

[0049] Figure 3 is a schematic cross-sectional representation of a conduit preform used in the method of Figure 2;

[0050] Figure 4A is a schematic cross-sectional representation of the conduit preform used in the method of Figure 2, the conduit preform being located against an aircraft structure preform; [0051 ] Figure 4B is a schematic cross-sectional representation of the conduit preform of Figure 3 being located against an aircraft structure preform in an example of a further embodiment of a method of forming an aircraft fluid flow conduit in accordance with the first aspect of the present invention;

[0052] Figure 5A is a schematic cross-sectional representation of the conduit preform of Figure 3 placed against a first tool, in an example of a further embodiment of a method of forming an aircraft fluid flow conduit in accordance with the first aspect of the present invention;

[0053] Figure 5B is a schematic cross-section representation of the arrangement of Figure 5A, with an enveloping braiding sheet around the conduit preform and first tool;

[0054] Figure 5C is a schematic cross-section representation of the arrangement of Figure 5B, with cutters being used to cut the braiding sheet;

[0055] Figure 5D is a schematic cross-section representation of the arrangement of Figure 5C, with a second tool being brought into proximity to the conduit preform and the first tool;

[0056] Figure 5E is a schematic cross-section representation of the arrangement of Figure 5D, with the braiding sheet having been cut to a desired size;

[0057] Figure 6 is a schematic representation of an example of an embodiment of a method of forming an aircraft fluid flow conduit in accordance with the second aspect of the present invention;

[0058] Figure 7 is a schematic representation of the 4-ply sheet used in the method of Figure 6;

[0059] Figure 8 is a schematic representation of a conduit preform made in accordance with the method of Figure 6;

[0060] Figure 9 is a schematic representation of a 2-ply sheet used in an example of a further embodiment of a method of forming an aircraft fluid flow conduit in accordance with the second aspect of the present invention;

[0061] Figure 10 is a schematic cross-sectional representation of a conduit preform made using the sheet of Figure 9;

[0062] Figure 11 is a schematic cross-sectional representation of a conduit preform placed against an aircraft structure preform in accordance with an example of an embodiment in accordance with a method of forming an aircraft fluid flow conduit in accordance with the second aspect of the present invention;

[0063] Figure 12 is a schematic cross-sectional representation of a conduit preform placed against an aircraft structure preform in accordance with an example of another embodiment in accordance with a method of forming an aircraft fluid flow conduit in accordance with the second aspect of the present invention; and

[0064] Figure 13 is a schematic representation of an example of an embodiment of an aircraft fluid flow conduit in accordance with the third or fourth aspects of the present invention, an example of an embodiment of an aircraft wing in accordance with the fifth aspect of the present invention, an example of an embodiment of an aircraft fuel transmission arrangement in accordance with the sixth aspect of the present invention and an example of an embodiment of an aircraft in accordance with the seventh aspect of the present invention. DETAILED DESCRIPTION

[0065] A known fuel stringer duct will now be described with reference to Fig. 1. The fuel stringer duct is denoted generally by reference numeral 1, and comprises ply 2, top hat 3, U-shaped channel member 4, capping ply 5 and noodles 6. All parts of the stringer duct are formed from composite material, apart from the noodles. Ply 2 is relatively thin and comprises relatively few layers. U-shaped channel member 4 provides structural support for the duct, given that the duct 1 has to withstand pressures associated with the provision of aircraft fuel. Top hat 3 is generally omega or Q shaped, and is relatively thick, providing structural support to the duct 1. The laterally-extending portions 3A, 3B of top hat 3 also facilitate attachment to capping ply 5. Capping ply 5 is attached to aircraft structure 7. Noodles 6 provide suitable radii of curvature for adjacent composite layers. Given that ply 2 is relatively thin, the presence of a relatively thick top hat 3 and a U-shaped channel member 4 is highly beneficial. However, the presence of such features may make manufacture of the fuel stringer duct 1 relatively complicated. Furthermore, very few layers of composite material extend around the whole perimeter of the duct, and therefore the structural integrity of the duct relies on strong interaction between adjacent parts of the duct (e.g. between the ply 2 and top hat 3, and between ply 2 and U-shaped channel member4).

[0066] The applicant has developed alternative and / or improved arrangements of fuel stringer duct, and, in particular, has developed alternative and / or improved methods of forming aircraft fluid flow conduits, in particular, but not exclusively aircraft wing fuel stringer ducts. In this connection, an embodiment of the present invention will now be described by way of example only with reference to Figs. 2,3,4A and 4B. A method of forming an aircraft fluid flow conduit is shown schematically in Fig. 2. The method is denoted generally by reference numeral 10 and comprises: forming 11 a conduit preform, wherein forming 11 a conduit preform comprises providing at least one layer of braided material under tension around a mandrel, the braided material being capable of forming a composite material with a matrix; providing 12 a curable precursor material to the conduit preform; and curing 13 the curable precursor material to form a matrix.

[0067] Togetherthe braided material and matrix form a composite. The method 10 will now be described in more detail with reference to Figure 3,4A and 4B. It should be noted that the arrangements shown in Figures 4A and 4B are alternative arrangements, particularly in relation to how the conduit preform is attached to an aircraft structure. Referring to Figure 3, mandrel 15 is inflated to the generally square cross-sectional shape shown. The mandrel 15 is elongate and has a uniform cross-section along its length. A braiding machine (not shown) is used to provide first braiding layer 21 of conduit preform 20 around mandrel 15. The first braiding layer 21 is formed around the perimeter of the mandrel so that the mandrel is enclosed by the first braiding layer 21. Those skilled in the art will realise that the ends of the mandrel 15 may not be covered by the first braiding layer 21. First braiding layer 21 is maintained in tension. The braid angle in this case is 75 degrees, the braid angle being the angle that the bias yarns make with the longitudinal axis of the conduit preform 20 and the mandrel 15. A first U- shaped layer 22 of non-crimp fabric (often called NCF) is then applied in contact with the first braiding layer 21. A second braiding layer 23 is then applied over the first U-shaped layer 22 of NCF. The second braiding layer is formed around the perimeter of the first U-shaped layer 22 of NCF. The braid angle of the second braiding layer 23 is 45 degrees. A second U-shaped layer 24 of non-crimp fabric (often called NCF) is then applied, with the U-shape having the same orientation as the U-shape of the first U-shaped layer of NCF. Further alternating arrangements of braiding layer and U-shaped layer of NCK may be applied as desired.

[0068] This multi-layer arrangement is then impregnated with a curable composition that, on curing, forms a matrix as part of a composite material with the braiding material and the NCF. Referring to Figure 4A, this uncured, impregnated multi-layer arrangement is placed against an aircraft structure preform 40 that has been impregnated with a curable composition that, on curing, forms a matrix as part of a composite material aircraft structure. A sheet 30 is placed over the top of the multi-layer arrangement described above with reference to Figure 3, so that the sheet 30 forms an omegashaped structure with laterally-extending portions 30A, 30B in contact with impregnated aircraft structure preform 40. Sheet 30 may then be impregnated. The impregnated conduit preform 20 and aircraft structure preform 40 are then subjected to curing. The mandrel 15 may then be deflated and removed.

[0069] An alternative method will now be described with reference to Figure 4B. In the method of Figure 4B, sheets 31 and 32 are provided to facilitate attachment of the conduit preform 20 to aircraft structure preform 40. Sheet 31 provides a lateral portion 31A and sheet 32 provides a lateral portion 32A, which lateral portions 31A, 32A contact the impregnated aircraft structure preform 40. Unlike Figure 4A, in Figure 4B there is no “top hat" sheet that extends over the multi-layer arrangement shown in Figure 3, and which provides laterally-extending portions that facilitate attachment of the conduit preform 20 to the aircraft structure preform 40.

[0070] The braided layers extend around the periphery of the conduit preform, thereby providing a tube of braided material, providing structural strength and stability. Further structural strength is provided by the U-shaped layers of NCF. [0071 ] Another example of an embodiment in accordance with the first aspect of the present invention will now be described with reference to Figures 5A to 5E, in which braided layers may form the “top hat” omega-shaped structure. Referring to Figure 5A, multi-layer arrangement 25 as shown in Figure 3 is moved into contact with first tool 50. Noodles 6A, 6b are placed adjacent to the multi-layer arrangement 25. Multiple layers of braid 55 are formed around first tool 50 and multi-layer arrangement 25, as shown in Figure 5B. Firsttool50 has rounded edges to facilitate tensioning of the braided layers. The braiding layers would then be cut, preferably using an ultrasonic knife, at lines 51, 52 as shown in Figure 5C. A female, second tool 53 is then used to urge the braided layers 55 into contact with the multi-layer arrangement 25 and noodles 6A, 6B. The braiding layers 55 would then be cut to form the laterally-extending portions 55A, 55B as shown in Figure 5E. As described above in relation to Figures 4A and 4B, the conduit preform may then be impregnated and placed adjacent an aircraft structure preform for curing.

[0072] The examples above demonstrate that it is possible to make aircraft stringer ducts using one or more sheets of braiding material. Alternative methods of making such stringer ducts, and aircraft fluid flow conduits in general, will now be described with reference to Figures 6 to 12. These alternative methods involve wrapping a sheet around a mandrel such that at least a portion of the sheet overlaps with another portion of the sheet, the sheet being capable of forming a composite material with a matrix.

[0073] A method of forming an aircraft fluid flow conduit is shown schematically in Fig. 6. The method is denoted generally by reference numeral 100 and comprises forming 101a conduit preform, wherein forming 101 a conduit preform comprises wrapping a sheet around a mandrel such that at least a portion of the sheet overlaps with another portion of the sheet, the sheet comprising fibrous material capable of forming a composite material with a matrix; and providing 102 a curable precursor material to the conduit preform. The method 100 also comprises curing 103 the curable precursor material to form a matrix.

[0074] The method 100 will now be described in more detail with reference to Figures 7 and 8. The sheet 110 used to wrap the mandrel 15 comprises four layers, as shown in Figure 7. First layer 111 is a carrier layer and comprises a NCF in which the mean fibre direction is about 90 degrees to the longitudinal axis (LA) of the sheet 110 and the conduit preform. Second layer 112 is an NCF layer in which the mean fibre direction is about 0 degrees to the longitudinal axis of the sheet 110 and the conduit preform. Third layer 113 is a NCF layer in which the mean fibre direction is about 45 degrees to the longitudinal axis of the sheet 110 and the conduit preform. Fourth layer 114 is an NCF layer in which the mean fibre direction is about 135 degrees to the longitudinal axis of the sheet 110 and the conduit preform. The first 111, second 112, third 113 and fourth 114 layers are lightly attached to one another. Sheet 110 is wrapped around mandrel 15 as shown in Figure 8, with fourth layer 114 adjacent mandrel 15. Portion 110E of sheet 110 overlaps with portion 110A, and portion 110F overlaps with portion 110B. This wrapping process ensures that the perimeter of the mandrel 15 is closed by sheet 110. In practice, the sheet 110 may be wrapped many times around the mandrel 15, providing a structure that, when impregnated and cured, is strong. Wrapped, and impregnated, structure 115 may then be placed adjacent to an aircraft structure preform for curing.

[0075] A further example of an embodiment of a method in accordance with the second aspect of the present invention will now be described by way of example only with reference to Figures 9,10 and 11. Sheet 120 is divided into 8 portions A-H of approximately even width. Portions A, C, D, E, G and H comprise both a first layer (a carrier layer) and a second layer. Portions B and F only comprise the first layer. For the purpose of this example, portion I shown in dashed lines in Figure 9 is not present. Sheet 120 is wrapped around mandrel 15 as shown in Figure 10 to form multi-layer arrangement 125. Single-layer portions B and F of sheet 120 are located in the same position i.e. below the mandrel 15. Multi-layer arrangement 125 is then placed adjacent to an impregnated aircraft structure precursor 40. Noodles 6A, 6B are placed either side of the multi-layer arrangement 125. Attachment portions 65, 66 are placed either side of the multi-layer arrangement 125 to facilitate attachment of the multi-layer arrangement 125 to the aircraft structure precursor 40. Attachment portions 65, 66 comprise laterally-extending portions 65A and 65B to facilitate attachment.

[0076] Yet another example of an embodiment of a method in accordance with the second aspect of the present invention will now be described byway of example only with reference to Figures 9,10 and 12. Sheet 120 comprises 8 portions A-H of approximately even width, and a ninth, wider portion I. Portions A, C, D, E, G, H and I comprise both a first layer (a carrier layer) and a second layer. Portions B and F only comprise the first layer. Sheet 120 is wrapped around mandrel 15 as shown in Figure 12 to form multi-layer arrangement 135. Single-layer portions B and F of sheet 120 are located in the same position i.e. below the mandrel 15. Multi-layer arrangement 135 is then placed adjacent to an impregnated aircraft structure precursor 40. Noodles 6A, 6B are placed either side of the multi-layer arrangement 125. Wider portion I of sheet 120 is placed over noodle 6B to provide a laterally-extending portion IB to facilitate attachment to the aircraft structure precursor. Attachment portion 65 is placed to one side of the multi-layer arrangement 135 to facilitate attachment of the multi-layer arrangement 135 to the aircraft structure precursor 40. Attachment portion 65 comprises laterally-extending portion 65Ato facilitate attachment.

[0077] The examples of methods described above may be used to make an example of an aircraft stringer fuel duct in accordance with the present invention, shown using reference numeral 201 in Figure 13. An example of an aircraft wing in accordance with the present invention is also shown in Figure 13, and is denoted generally by reference numeral 202. Aircraft stringer fuel duct 201 extends from an inboard position 203 to an outboard position 204. Figure 13 also shows an example of an aircraft fuel supply arrangement shown generally by reference numeral 205. The aircraft fuel supply arrangement 205 comprises aircraft stringer fuel duct 201 in fluid communication with fuel tank 206. Figure 13 also shows an example of an aircraft in accordance with the present invention, shown generally by reference numeral 207, the aircraft 207 comprising aircraft wing 202 and aircraft fuel supply arrangement 205.

[0078] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0079] The Examples above describe methods in which the impregnated conduit preform is placed against an impregnated aircraft structure preform before either the impregnated conduit preform or the impregnated aircraft structure preform is subject to curing conditions. Alternatively, the impregnated conduit preform could be subject to curing conditions before being placed against either an impregnated aircraft structure preform or an aircraft structure.

[0080] The Examples described above with reference to Figs. 1 to 5E show a conduit preform comprising two braid layers and two non-crimp fabric (NCF) layers, with the braid layers alternating with the NCF layers. Those skilled in the art will realise that other arrangements are possible. For example, the conduit preform may optionally comprise only one braid layer. Optionally, the conduit preform may comprise one or more braid layers, but with no NCF layers. Optionally, if the conduit preform comprises more than one braid layer and at least one NCF layer, then an NCF layer need not be located between two braid layers. [0081 ] The Examples described above with reference to Figs. 1 to 5E show a conduit preform comprising two braid layers in which the angle of the fibres of the first braid layer to a longitudinal axis of the conduit preform are different from the angle of the fibres of the second braid layer to a longitudinal axis of the conduit preform. This need not be the case. The angle of the fibres of the first braid layer to a longitudinal axis of the conduit preform may be the same as the angle of the fibres of the second braid layer to a longitudinal axis of the conduit preform.

[0082] The Examples described above with reference to Figs. 6 to 12 shows the mandrel being wrapped in a 4-layer or4-ply sheet. Those skilled in the art will realise thatthe sheet need not comprise more than one layer or ply. Those skilled in the art will realise that the sheet need not comprise 4 layers or plies.

[0083] The Examples described above with reference to Figs. 6 to 12 shows the mandrel being wrapped in approximately two layers of sheet, each layer comprising 4 plies. Those skilled in the art will realise that the mandrel may be wrapped in more than two layers. Those skilled in the art will realise that the mandrel may be wrapped in less than two layers, so long as there is overlap between two portions of the sheet.

[0084] The Examples described above with reference to Figures 6 to 12 describe wrapping a “dry”, unimpregnated sheet around the mandrel, and then impregnating the sheet with a curable precursor material. Those skilled in the art will realise that it would be possible to wrap a sheet comprising a curable precursor material around the mandrel. The sheet may be provided as a “pre-preg”, for example.

[0085] The Examples above describe the use of an expandable and contractable mandrel. Those skilled in the art will realise that this need not be the case. The mandrel need not be expandable or contractable.

[0086] The Examples above describe the use of a mandrel that is substantially square in cross-section. Those skilled in the art will realise that other shapes of mandrel are possible. For example, a mandrel may be substantially circular or rectangular in crosssection.

[0087] The Examples above describe methods of making a duct for carrying fuel. Those skilled in the art will realise that the duct may be used to carry other aircraft fluids, such as hydraulic fluid or vent gas.

[0088] The Examples above describe methods of making an aircraft wing stringer. Those skilled in the art will realise that the duct need not operate as an aircraft wing stringer.

[0089] The Examples described above with reference to Figs. 6 to 12 shows the mandrel being wrapped in a sheet, with nothing between the mandrel and the sheet. Those skilled in the art will realise that there may be one or more layers between the mandrel and the sheet which is wrapped about the mandrel.

[0090] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

1. A method of forming an aircraft fluid flow conduit, the method comprising:forming a conduit preform, wherein forming the conduit preform comprises:wrapping a sheet around a mandrel such that at least a portion of the sheet overlaps with another portion of the sheet, the sheet comprising fibrous material capable of forming a composite material with a matrix; andcuring the sheet to form a matrix.

2. A method according to claim 1, wherein wrapping the sheet around the mandrel comprising wrapping a sheet comprising a curable precursor material around the mandrel, and wherein curing the sheet to form the matrix comprises curing the curable precursor material to form the matrix.

3. A method according to claim 1, comprising providing a curable precursor material to the sheet after wrapping the sheet around the mandrel, such that priorto wrappingthe sheet around the mandrel the sheet is substantially devoid of the curable precursor material, wherein curing the sheet to form the matrix comprises curing the curable precursor material to form the matrix.

4. A method according to any preceding claims, comprising wrapping the sheet around the mandrel such that at least two thicknesses of sheet are formed around the mandrel.

5. A method according to any preceding claim, wherein wrapping the sheet around the mandrel comprise one or more of: moving the sheet around a substantially motionless mandrel; maintainingthe sheet in a substantially constant position and movingthe mandrel; and movingthe sheet around a moving mandrel.

6. A method according to any preceding claim, wherein the sheet comprises more than one layer.

7. A method according to claim 6, wherein at least one layer comprises a first portion of material that is not continuous with a second portion of material.

8. A method according to claim 6 or claim 7, wherein the sheet comprises at least one continuous layer.

9. A method according to any preceding claim, wherein forming the conduit preform comprises wrapping a sheet around the mandrel such that at least a portion of the sheet overlaps with another portion of the sheet, and such that a flap portion of the sheet extends from the wrapped mandrel.

10. A method of forming an aircraft fluid flow conduit, the method comprising:forming a conduit preform, wherein forming the conduit preform comprises:providing at least one layer of braided material under tension around a mandrel, the braided material being capable of forming a composite material with a matrix;providing a curable precursor material to the conduit preform; andcuring the curable precursor material to form a matrix.

11. The method according to claim 10, wherein forming the conduit preform comprises providing a plurality of layers of braided material around the mandrel, wherein at least two of the plurality of layers of braided material are mutually different.

12. The method according to claim 11, wherein forming the conduit preform comprises providing at least one interlayer between two layers of braided material.

13. The method according to claim 12, wherein at least one interlayer is not a braided material.

14. A method according to any preceding claim, comprising providing one or more substrates to facilitate securing the conduit preform to an aircraft structure or to an aircraft structure preform.

15. A method according to claim 14, wherein at least one of said substrates comprises a sheet.

16. A method according to claim 14 or claim 15, comprising contacting at least one of the substrates with the aircraft structure or aircraft structure preform.

17. A method according to any of claims 14 to 16, comprising locating the conduit preform against, or proximate to a surface of an aircraft structure or an aircraft structurepreform and contacting at least one of the substrates with the duct perform and with the aircraft structure or the aircraft structure preform.

18. A method according to any of claims 14 to 17, comprising providing the conduit preform with at least one of the substrates, and then locating the conduit preform against, or proximate to a surface of the aircraft structure or aircraft structure preform.

19. A method according to any of claims 14 to 18, comprising providing the substrate such that the substrate contacts the aircraft structure or aircraft structure preform to at least one side of the conduit preform.

20. A method according to any of claims 14 to 19, comprising forming one or more of said substrates comprising braided material so as to provide one or more portions of substrate to facilitate contact of the substrate, and attachment of the conduit preform, to the aircraft structure or aircraft structure preform.

21. A method accordingto any of claims 14 to 20, comprising mounting the conduit preform on a first tool and wherein providing the substrate comprises providing a substrate comprising braided material in tension around the conduit preform and the first tool, and urging the substrate into contact with the conduit preform using a second tool.

22. An aircraft fluid flow conduit made in accordance with the method of any preceding claim.

23. An aircraft wing comprising an aircraft fluid flow conduit in accordance with claim 22.

24. An aircraft fuel transmission arrangement comprising at least one fuel tank and an aircraft fluid flow conduit in accordance with claim 22, the aircraft fluid flow conduit being in fluid communication with at least one fuel tank.

25. An aircraft comprising an aircraft wing in accordance with claim 23 and / or an aircraft fuel transmission arrangement in accordance with claim 24.Application No: GB2411161.9Examiner:Mr Darren WilliamsClaims searched: 1-9Date of search: 23 January 2025Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-3, 5-9 US2016 / 332409 Al (PRICE) see especially figures 6-9 X 1-9 US2011 / 139932 Al (MATHESON) see especially figure 7 X 1-9 GB2040790 A (BUCKLEY) see especially figure 3 v A 1-9 US2009 / 260745 Al (IWAI) see especially figure 2 X 1-9 US2010 / 078259 Al (STEVENSON) see especially figure 1 v A 1-3, 5-9 WO2018 / 207446 Al (KUWAJIMA) see especially figures 4a-e X 1-9 JP2022127466 A (IIO) see especially figures 6A-6CCategories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if p Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:22International Classification:Subclass Subgroup Valid From B29C 0053 / 58 01 / 01 / 2006 B29C 0053 / 08 01 / 01 / 2006 B29C 0053 / 56 01 / 01 / 2006 B29C 0070 / 32 01 / 01 / 2006

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