A method for manufacturing a composite material profile comprising a pigmented coating, the profile obtained from said method

Abstract

Method for manufacturing a composite material profile comprising a pigmented coating, profile obtained from said method. The invention relates to a method for manufacturing a composite material profile comprising a step of obtaining a preform and a step of applying at least one pigmented layer to the preform, the pigmented layer comprising at least one pigmented film and at least one support structure (44) having a knitted structure (44.1). Since the knitted structure (44.1) is flexible, it is possible to obtain profiles with complex geometries. The invention also relates to a profile obtained from such a method and to a stiffened panel comprising at least one such profile. Figure 5

Description

Title of the invention: A method for manufacturing a composite material profile comprising a pigmented coating, the profile obtained from said method

[0001] The present application relates to a method for manufacturing a composite material profile comprising a pigmented coating, to a composite material profile obtained from this method and to a stiffened panel made from such a profile.

[0002] According to an embodiment visible in [Fig.1], a stiffened panel 10 comprises a wall 12 which has first and second faces 12.1, 12.2 and a plurality of stiffeners 14 substantially parallel to each other, perpendicular to the wall 12 and positioned on the first face 12.1.

[0003] According to a method visible in [Fig.2], a process for manufacturing a stiffened panel made of composite material comprises a step of manufacturing U or L profiles 16 made of composite material, a step of placing mandrels 18 each supporting a profile 16 on a mounting surface 20 as illustrated in part (A) of [Fig.2], the bases 16.1 of the profiles 16 being substantially parallel to the mounting surface 20 and spaced away from the latter, a step of placing a skin 22 made of composite material on the bases 16.1 of the profiles 16 as illustrated in part (B) of [Fig.2], a step of setting up a polymerization or consolidation tool 24 as illustrated in part (C) of [Fig.2] and a polymerization or consolidation step.

[0004] During the mandrel placement step 18, the mandrels are placed on the placement surface 20 and placed side by side in order to press a first wing 16.2 of a profile 16 of a first mandrel 18 against a second wing 16.3 of a profile 16 of a second mandrel 18, the first and second wings 16.2, 16.3 forming, after the polymerization or consolidation step, a stiffener 14 of the stiffened panel 10.

[0005] According to one embodiment, a method for obtaining a U-shaped profile comprises a step of stacking flat layers of structural fibers to form a flat preform 26, a step of deforming the flat preform 26 on a mold 28 so as to bend the two flanges 16.2, 16.3 of the U-shaped profile 16, as illustrated in [Fig. 4], and then a step of at least partial hardening of the bent preform. This method may include other steps such as a compaction step after the deformation step, a cutting step, and a step of protecting the free edges of the flanges 16.2, 16.3 prior to the hardening step.

[0006] According to a procedure, the profiles 16 are subjected to a non-destructive testing process to check their conformity.

[0007] To ensure the reliability of non-destructive testing measurements and to prevent the wave beam used for non-destructive testing from being reflected, at least one surface of the profile is covered with a pigmented coating after the hardening step, promoting the absorption of the wave beam.

[0008] The drying stage of this coating is relatively long, which significantly lengthens the manufacturing time of the profiles 16.

[0009] To overcome this drawback, document FR3059591 proposes a method for obtaining a profile that includes a step of stacking flat structural fiber plies to form a flat preform 26, a step of applying a pigmented layer to the flat preform 26, a step of deforming the flat preform 26 coated with the pigmented layer on a mold 28 so as to bend the two flanges of the profile, and then a step of hardening the bent preform coated with the pigmented layer. This method may include other steps such as a compaction step after the deformation step, a cutting step, and a step of protecting the free edges of the profile prior to the hardening step.

[0010] According to this method, after the hardening step of the profile coated with the pigmented layer, the latter offers the same advantages as a painted coating after the profile's hardening step. Since the pigmented layer is hardened simultaneously with the structural fiber plies of the profile and not in a separate step, this method reduces manufacturing time.

[0011] According to one embodiment, the pigmented layer comprises an extremely thin paint film having a thickness less than or equal to 50 µm. To allow easy handling of this paint film without damaging it, the pigmented layer comprises a woven fiber structure 30 supporting the paint film.

[0012] According to a prior art configuration shown in [Fig. 3], the woven fiber structure 30 comprises warp and weft yarns 30.1, 30.2 woven in a plain weave. In this type of weave, each weft yarn 30.2 passes alternately over and then under each warp yarn 30.1 to obtain a square pattern. Each of the warp and weft yarns 30.1, 30.2 is oriented approximately in a straight line.

[0013] Even though this method of obtaining a profile using a pigmented layer which combines a paint film and a woven fiber structure 30 makes it possible to significantly reduce the manufacturing time, it is not fully satisfactory because it is reserved for profiles which have a developable pigmented layer application surface and can hardly be implemented if the application surface is not.

[0014] The present invention aims to remedy all or part of the drawbacks of the prior art.

[0015] To this end, the invention relates to a method for manufacturing a profile in composite material comprising a step of obtaining a preform and a step of placing at least one pigmented layer on the preform, the pigmented layer comprising at least one pigmented film and at least one support structure which has a face against which the pigmented film is applied.

[0016] According to the invention, the support structure of the pigmented layer has a knitted structure.

[0017] Since a knitted structure is more flexible than a woven structure, it is possible, using the process of the invention, to obtain profiles with complex geometries.

[0018] According to another characteristic, the knitted structure is a warp-knitted structure.

[0019] According to another characteristic, the knitted structure is a weft-knitted structure.

[0020] According to another feature, the preform is shaped before the setting step in place of the pigmented layer, the process includes a step of conforming the pigmented layer before the step of placing the pigmented layer on the conformed preform.

[0021] According to another feature, the pigmented film is applied flat against the flat support structure, then the pigmented film and the support structure, pressed against each other, are baked and then deformed simultaneously.

[0022] According to another feature, the support structure and the pigmented film are subjected, during their deformation, to a shaping temperature higher than the glass transition temperature of the pigmented film.

[0023] The invention also relates to a composite material profile obtained from a manufacturing process according to one of the preceding characteristics and to a stiffened panel obtained from such a profile.

[0024] Other features and advantages will become apparent from the following description of the invention, given by way of example only, with reference to the accompanying drawings, among which:

[0025] [Fig-1] is a perspective view of a stiffened panel,

[0026] [Fig.2] is a schematic representation of different manufacturing stages of a panel illustrating a method of execution of earlier art,

[0027] [Fig.3] is a front view of part of a woven fibre structure illustrating a method of implementation of the prior art,

[0028] [Fig.4] is a schematic representation of a tooling for shaping a flat preform to obtain a U-shaped profile

[0029] [Fig.5] is a front view of part of a knitted structure illustrating one embodiment of the invention,

[0030] [Fig.6] is a front view of part of a knitted structure illustrating another embodiment of the invention,

[0031] [Fig.7] is a schematic representation of different stages in shaping a pigmented layer,

[0032] [Fig.8] is a schematic representation of a tool for obtaining a profile illustrating one embodiment of the invention,

[0033] [Fig.9] is a perspective representation of different profiles obtained from the process of the invention.

[0034] According to one method, a process for manufacturing a stiffened panel made of composite material comprises a step of manufacturing U or L profiles made of composite material, a step of placing mandrels each supporting a profile on a mounting surface, the bases of the profiles being substantially parallel to the mounting surface and spaced away from the latter, a step of placing a skin made of composite material on the bases of the profiles, a step of setting up a polymerization or consolidation tooling and a polymerization or consolidation step.

[0035] According to one application, an aircraft comprises at least one stiffened panel obtained by this process. By way of example, a wing center box of an aircraft comprises at least one stiffened panel obtained by this process.

[0036] The manufacturing process for a stiffened panel is not further described because, with the exception of the profile manufacturing step, it can be identical to that of the prior art.

[0037] According to an embodiment shown in [Fig. 8], a method for obtaining a profile 34 (shown in [Fig. 9]) comprises a step of stacking structural fiber plies 36a on a mold 38 so as to obtain a formed preform 36. The mold 38 has a stacking surface F38 which has a geometry approximately identical to that of the profile 34 after the production process. In the case of a profile 34 with a non-developable geometry, the stacking surface F38 also has a non-developable geometry.

[0038] This process may include other steps such as a compaction step during or after the stacking step, a cutting step and a step of protecting the free edges of the preform formed prior to a hardening step.

[0039] The stacking and hardening steps are not described further as they may be identical to those of the prior art.

[0040] Depending on the case, the formed preform may have a U-shaped, L-shaped or other cross-section.

[0041] When the profile is used to produce a stiffened panel, according to a first embodiment, the curing step of the formed preform can be carried out before the step of installing the mandrel supporting the formed preform on the mounting surface. According to a first case, the formed preform can be partially polymerized or consolidated before the mounting step, with the completion of polymerization or consolidation occurring simultaneously with that of the skin. According to a second case, the formed preform is fully polymerized or consolidated before the mounting step.

[0042] According to another embodiment, the hardening step is carried out after the mandrel supporting the formed preform has been placed on the mounting surface. In this case, the formed preform is completely raw when it is placed on the mounting surface.

[0043] The process for obtaining the profile includes a step of placing at least one pigmented layer 40 on the preform before the hardening step.

[0044] According to an embodiment visible in part (A) of [Fig.7], the pigmented layer 40 comprises at least one pigmented film 42 and at least one support structure 44 which has a face against which the pigmented layer 40 is applied.

[0045] According to one configuration, the pigmented film 42 is an extremely thin paint film with a thickness of 50 µm or less. This pigmented film 42 is not further described as it may be identical to prior art paint films.

[0046] In one embodiment, the pigmented film 42 is initially flat. In another procedure, the flat pigmented film 42 is positioned on the flat support structure 44. Subsequently, the pigmented film 42 and the support structure 44, placed against each other, are baked and then simultaneously deformed. The pigmented film 42 is deformed on the already shaped support structure 44. In one configuration, the pigmented film 42 has a glass transition temperature (Tg) lower than the shaping temperature. Thus, during deformation, the pigmented film 42 softens and can deform into a non-developable three-dimensional shape.

[0047] According to another method, the pigmented film 42 is partially baked before being applied against the support structure 44. The pigmented film 42 and the support structure 44 are then joined by gluing.

[0048] According to another embodiment, the pigmented layer 40 comprises only a support structure 44 impregnated with pigments.

[0049] According to a particular feature of the invention, the support structure 44 is a knitted structure 44.1, 44.2, as illustrated in Figures 5 and 6. Thus, the knitted structure 44.1, 44.2 comprises interconnected loops of yarn. This type of structure is more flexible than a woven structure and can conform to a non-developable surface without creases, unlike a woven structure.

[0050] According to a first embodiment visible in [Fig. 5], the knitted structure 44.1 is a warp-knitted structure. It comprises only warp yarns 44.1a positioned lengthwise along the knitted structure 44.1, each of them forming loops interlaced with the loops of another warp yarn 44.1a so as to form columns of stitches oriented along the length of the knitted structure.

[0051] According to a second embodiment visible in [Fig. 6], the knitted structure 44.2 is a weft-knitted structure. It comprises only weft yarns 44.2a positioned across the width of the knitted structure, each of them forming loops interlaced with the loops of another weft yarn 44.2a so as to form rows of stitches oriented along the width of the knitted structure.

[0052] Like the prior art woven fiber structure, the knitted structure 44.1, 44.2 protects the pigmented film 42. Unlike the prior art woven fiber structure 30, which can only conform without creases on a developable surface, the knitted structure 44.1, 44.2 can conform without creases on a non-developable surface. Thus, thanks to the knitted structure 44.1, 44.2, it is possible to obtain U-shaped or L-shaped profiles 34, 34, 34'' with complex geometries.

[0053] According to an embodiment visible in part (A) of [Fig.9], a U profile 34 comprises a base 34.1 and two flanges 34.2, 34.3, the base 34.1 and the upper edges of the flanges 34.2, 34.3 each comprise a step 34.1d, 34.2d, 34.3d.

[0054] According to another embodiment visible in part (B) of [Fig.9], an L-shaped profile 34' comprises first and second curved wings 34.1', 34.2'.

[0055] According to another embodiment visible in part (C) of [Fig.9], an L-profile 34” comprises first and second wings 34.1”, 34.2”, the second wing 34.2” having a non-constant thickness.

[0056] Of course, the invention is not limited to these embodiments for the profile.

[0057] According to one method, the process for obtaining a profile 34 comprises a step of obtaining a preform 36 which has a stack of structural plies 36a and a surface to be covered with a pigmented layer 40, a step of obtaining a pigmented layer 40 shaped approximately like the surface to be covered of the preform 36, a step of placing the pigmented layer 40 on the preform 36 and a step of co-firing the preform 36 and the pigmented layer 40 so as to obtain a profile 34 at least partially coated with a pigmented layer 40.

[0058] According to an embodiment more particularly adapted for a profile 34 which has a non-developable geometry, during the step of obtaining the preform 36, the latter is shaped like the profile 34 to be obtained, the structural folds 36a being placed on a stacking surface F38 which has a geometry approximately identical to that of the profile 34 to be obtained.

[0059] In parallel, during the step of obtaining a formed pigmented layer 40, the pigmented film 42 is applied flat against the support structure 44, which is also flat. Subsequently, the pigmented film 42 and the support structure 44 are baked and then deformed simultaneously. During this deformation, the support structure 44 and the pigmented film 42 are subjected to a forming temperature higher than the glass transition temperature Tg of the pigmented film 42, which allows the latter to conform to a non-developable geometry and ensures significant cohesion between the support structure 44 and the pigmented film 42. Since the support structure 44 is a knitted structure, it can conform to a non-developable geometry.

[0060] Regardless of the embodiment, the resulting composite material profile includes on the surface a pigmented layer 40 comprising a pigmented film 42 applied to a support structure 44 which has a knitted structure 44.1, 44.2.

[0061] According to an embodiment shown in [Fig. 7], a shaping tool 46 for the pigmented layer 40 comprises at least one mold 48 having a mounting surface 48.1 that has the same geometry as the surface of the shaped preform 36 against which the pigmented layer 40 is to be placed, and at least one support 50 configured to support the flat pigmented layer 40 and press it against the mold 48. In one configuration, the shaping tool 46 includes a heating system 52 configured to heat the pigmented layer 40 to soften it so that it conforms to the mounting surface 48.1 and / or to cure it. In one arrangement, the support 50 is a frame and the heating system 52 is positioned above the mold 48. The latter includes a sealing system 54 around the mounting surface 48.1 and a suction system 56 configured to draw the gas present between the mold 48 and the pigmented layer 40 and press it against the mounting surface 48.1. According to one operating procedure, the pigmented layer 40 is connected to the support 50 positioned between the mold 48 and the heating system 52 as illustrated in part (A) of [Fig. 7]. Subsequently, the heating system 52 is activated to soften the pigmented layer 40. When the latter is sufficiently softened, the support 50 is moved towards the mold 48 until the pigmented layer 40 is in contact with the sealing system 54. During this movement, the softened pigmented layer 40 is deformed against the mounting surface 48.1. As illustrated in part (B) of [Fig.7], the suction system 56 is activated so that the pigmented layer 40 conforms to the application surface 48.1. After a determined time, the heating system 52 and the suction system 56 are deactivated.After a cooling period, the deformed pigmented layer 40 is removed from the mold 48 and detached. of the support 50, as illustrated in part (C) of [Fig.7]. According to one procedure, the pigmented film 42 is baked when it is flat before being deformed.

Claims

Demands

1. A method for manufacturing a composite material profile comprising a step of obtaining a preform (36) and a step of placing at least one pigmented layer (40) on the preform, the pigmented layer (40) comprising at least one pigmented film (42) and at least one support structure (44) which has a face against which the pigmented film (42) is applied; characterized in that the support structure (44) of the pigmented layer (40) has a knitted structure (44.1, 44.2).

2. A manufacturing method according to claim 1, characterized in that the knitted structure (44.1) is a warp-knitted structure.

3. A manufacturing method according to claim 1, characterized in that the knitted structure (44.2) is a knitted structure with a weft.

4. A manufacturing process according to any one of the preceding claims, characterized in that the preform (36) is formed before the step of placing the pigmented layer (40) and in that the process includes a step of forming the pigmented layer (40) before the step of placing the pigmented layer (40) on the formed preform (36).

5. A manufacturing method according to the preceding claim, characterized in that the pigmented film (42) is applied flat against the flat support structure (44), the pigmented film (42) and the support structure (44) pressed against each other being subsequently baked and deformed simultaneously.

6. A manufacturing process according to the preceding claim, characterized in that the pigmented film (43) has a glass transition temperature (Tg) and in that the support structure (44) and the pigmented film (42) are subjected, during their deformation, to a shaping temperature higher than the glass transition temperature (Tg) of the pigmented film (42).

7. Composite material profile obtained from a manufacturing process according to one of the preceding claims, said profile comprising a support structure (44), on which is attached a pigmented film (42), which has a knitted structure (44.1, 44.2).

8. Stiffened panel obtained from profiles according to claim 7.

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