METHOD FOR FORMING A RIBLET ON A COMPONENT AND RIBLET MOULD

Abstract

Method for forming a riblet on a component and riblet mould. This invention relates to a method for forming a riblet (3) on a component (1), characterised in that it comprises steps of: printing (106) the riblet on the component (1), comprising applying a film (1) comprising a riblet imprint (6) on the component (1), and peeling (108) the film (4) so as to separate the riblet imprint (6) from the component (1), after printing (106). This invention also relates to a riblet mould (3), the mould comprising a film (4) in which a riblet imprint (6) is formed, the film (4) being adapted to be separated from a component (1) on which a riblet (3) has been printed by means of the riblet mould (3), by peeling the film (4).

Claims

1. A method for forming a riblet on a component, wherein the method comprises: inserting the component in a vacuum bag, printing the riblet on the component, wherein said printing comprises placing the vacuum bag under vacuum by aspiration of the air contained in the vacuum bag using a vacuum pump so that, thanks to the aspiration, the vacuum bag presses a film comprising a riblet imprint against the component, peeling the film so as to separate the riblet imprint from the component, after printing.

2. The method according to claim 1, wherein the film is a wall of the vacuum bag.

3. The method according to claim 1, wherein printing the riblet comprises pressing further the film against the component using a tool situated outside the vacuum bag.

4. The method according to claim 1, further comprising heating the component and the film while the film is applied against the component.

5. The method according to claim 1, comprising applying an anti-erosion coating on the component, wherein the riblet is printed in the anti-erosion coating.

6. The method according to claim 5, wherein the anti-erosion coating consists of a paint and/or of a polymer.

7. The method according to claim 1, wherein the film consists of an elastomer or of a polycarbonate.

8. The method according to claim 1, wherein the riblet forms on the component a groove extending along a longitudinal direction, and wherein the peeling of the film is carried out along the longitudinal direction or following a direction perpendicular to the longitudinal direction.

9. A vacuum bag comprising a pouch, a vacuum pump configured to aspirate the air contained in the pouch and a riblet mould comprising a film in which is formed a riblet imprint, the film being adapted to be separated from a component on which a riblet has been printed using the riblet mould, by peeling the film, the riblet imprint being formed in the internal surface of the pouch (14).

Description

DESCRIPTION OF THE FIGURES

[0030] Other features, aims and advantages of the invention will be revealed by the description that follows, which is purely illustrative and not limiting, and which must be read with reference to the appended drawings in which:

[0031] FIG. 1 illustrates in three-quarters view an aerodynamic component including riblets.

[0032] FIG. 2 shows a known type of riblets.

[0033] FIG. 3 is a section view of a portion of an injection mould, and of a riblet during de-moulding.

[0034] FIGS. 4 and 5 are flowcharts of steps of a method of forming a riblet on a component according to one embodiment of the invention.

[0035] FIG. 6 is a profile view of a riblet mould according to one embodiment of the invention.

[0036] FIG. 7 comprises two three-quarters views of a component during its manufacture in compliance with a method according to one embodiment of the invention.

[0037] FIG. 8 comprises four section views of a component and of a mould used for printing riblets on the component, in compliance with an embodiment of the invention.

[0038] FIG. 9 is a section view of a riblet mould and of a riblet during a de-moulding step according to a first embodiment of the invention.

[0039] FIG. 10 is a three-quarters view of a riblet mould and of a riblet during a de-moulding step according to a second embodiment of the invention.

[0040] In all the figures, similar elements bear identical reference symbols.

DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

[0041] With reference to FIG. 4, an aerodynamic component like that shown in FIG. 1 already discussed, is manufactured by means of the following steps.

[0042] A raw component 1 comprising a surface 2 on which it is desired to form riblets 3 is manufactured in a step 100. The component 1 is for example a portion of a fuselage of an aircraft.

[0043] This manufacture 100 is implemented by casting, but machining a metallic in the mass, by moulding, by stamping for a composite component, etc.

[0044] A film 4 comprising a first surface 5 in which a riblet imprint 6 is formed is manufactured in a step 102.

[0045] The riblet imprint 6 has a profile complementary to that of a riblet 3.

[0046] For example, in an embodiment shown in FIG. 6, the riblet imprint 6 comprises a plurality of ribs with a triangular profile. The ribs extend parallel to one another. The ribs are spaced from one another by planar portions of the surface 5. Other forms of riblet imprint 6, adapted to print riblets of different shapes (slot-shaped or trapezoidal) can of course be used.

[0047] The film 4 also has a second surface 7 opposite to the first surface 5. The second surface 7 is planar.

[0048] The film 4 has suitable stiffness so that the film is not deformed during application and during pressurization at 5 bars, and to resist manual traction during a peeling step which will be described below.

[0049] The film 4 is flexible enough to contact the entire surface of the component (taking into account, for example, shrinkage cavities potentially present on the surface of composite components).

[0050] The film 4 consists for example of elastomer, for example silicone or fluoropolymer or polyurethane. Alternatively, the film 4 is made of polycarbonate, which is a more rigid material than an elastomer. As a variant, the film 4 consists of a polymer or a metal.

[0051] The film 4 has a thickness between its two opposite surfaces 5 and 7 comprised between 0.1 and 0.5 millimetres, preferably 0.3 millimetres.

[0052] In a step 104, an anti-erosion protective coating 8 is applied to the surface 2 of the component 1.

[0053] The application of this anti-erosion coating 8 comprises a preliminary preparation of said surface 2. This preparation comprises sandblasting, degreasing and/or sanding of the surface 2 of the component 1. This preparation has the effect of improving the adhesion of the anti-erosion coating on the surface 2 of the component 1.

[0054] A solution is applied to the surface 2 thus prepared so as to form the anti-erosion coating.

[0055] The anti-erosion coating 8 consists of a material capable of being marked when pressure is applied to it.

[0056] The anti-erosion coating 8 can consist of a polymer film (polyurethane or fluoropolymer for example), or of a thermoplastic material. The anti-erosion coating 8 can also be a paint.

[0057] The anti-erosion coating 8 is attached to the surface 2 of the component 1 by gluing, for example by means of a film of glue, with an adhesive primer in the case of a metal component 1.

[0058] Riblets 3 are then printed 106 onto the anti-erosion coating 8 applied to the component 1 using the film 4.

[0059] In a particular embodiment, of which the steps are illustrated in FIG. 5, the printing comprises the following sub-steps.

[0060] The film is positioned 200 with respect to the component 1, so that the riblet imprint 6 formed in the film 4 faces the anti-erosion coating 8 as shown in FIG. 7.

[0061] For example, as shown in FIG. 8, the component is placed in a cavity of a support element 10, made of foam for example. The first surface 5 of the film 4 is positioned facing the anti-erosion coating 8 previously applied to the component 1. In this manner, the component 1 is sandwiched between the support element 10 and the film 4.

[0062] In a manner known in se, a vacuum bag 12 comprises a pouch 14 and a vacuum pump 16 configured to aspirate the air contained in the pouch 14 and to draw a vacuum there.

[0063] The component 1 is inserted into the interior of the pouch 14 of the vacuum bag 12, likewise the film 14.

[0064] The vacuum bag is placed under vacuum during a step 204 white the component 1 and the film 4 are located in the interior of the pouch 14. To this end, the vacuum pump 16 is activated so as to aspirate the air in the interior of the pouch 14. Thanks to this aspiration, the walls of the pouch 14 of the vacuum bag 12 are pressed against the second surface 7 of the film 4. The riblet imprint 6 formed in the first surface 5 of the film 4, opposite to the surface 7, is then stressed so as to print riblets 3 into the anti-erosion coating 8. The riblets 3 have a shape complementary to that of the riblet imprint 6.

[0065] Although it is optional, the use of the vacuum bag 12 during the printing 106 is advantageous because the walls of the pouch exert a uniform pressure over the entire surface of the riblet imprint 6. The riblets 3 thus obtained are therefore particularly regular, this even when the surface 2 has a complex shape (non-planar in particular).

[0066] In addition, pressure can be exerted 206 by means of a pressing toot situated at the exterior of the vacuum bag 12. The toot presses against the external surface of the pouch 14; the pouch 14 then presses against the second surface 7 of the film 5 contained in the pouch, and the riblet imprint 6 formed on the surface 5 is impressed with greater force into the anti-erosion coating 8. The pressing toots comprises for example a screw and/or ram system.

[0067] The pressure of the riblet imprint 5 against the anti-erosion coating 8 (generated by the vacuum pump 16 and/or the pressing tool situated at the exterior of the pouch 14) is maintained for a period of predetermined length.

[0068] The film 5 and the component 1 can also be heated 208 and maintained at a printing temperature, during this period of predetermined length.

[0069] For example, the pouch 14 of the vacuum bag 12 containing the film 5 and the component 1 is placed in an oven implementing the heating 208.

[0070] Alternatively, the heating 208 is implemented prior to the printing 106. This is advantageous for softening the anti-erosion coating 8, when it has solidified on the surface 2 of the component 1. Such solidification can for example occur typically in the case where the anti-erosion coating 8 is a paint or consists of a thermoplastic.

[0071] The vacuum bag 12 is then opened. A block consisting of the component 1, the anti-erosion coating 8 and the film 4 is withdrawn from the pouch 14.

[0072] The shape of the riblets 3 printed on the anti-erosion coating 8 complies with the prior art. The riblets 3 thus form grooves extending along a longitudinal direction X, complementary to the ribs of the riblet imprint 6. Hereafter the example of riblets 3 with a triangular profile will be used. In the case where the surface 2 is planar the riblets 3 have crests parallel to the longitudinal direction X.

[0073] The component is then de-moulded, i.e. the component is separated from the film used during the printing 106.

[0074] De-moulding comprises peeling the film 4 so as to separated it from the anti-erosion coating 8, and thus reveal the riblets 3 formed in the anti-erosion coating 8.

[0075] Peeling consists of clamping one end of the film 4, manually or using a gripping tool, and displacing this end of the film 4 with respect to the component 1 so as to deform the film 4 and progressively reveal in one direction, hereafter called the peeling direction, the riblets 3 formed on the component 1.

[0076] The flexible character of the film 4 in which the riblet imprint 5 is formed allows a very significant reduction in the shear phenomena encountered when an injection mould is used, this regardless of the peeling direction selected.

[0077] As illustrated in FIG. 9, the peeling direction can be a direction Y orthogonal to the longitudinal direction X of the riblets 3. In a variant illustrated in FIG. 10, the peeling direction is the longitudinal direction X of the riblets 3. These two peeling directions X or Y each allow a maximum reduction of residual sheer, and therefore allow perfectly aerodynamic riblets 3 to be obtained.

[0078] Moreover, the peeling 108 can be manual or assisted, regardless of the selected peeling direction.

[0079] When the film 8 consists of a polymer, the film 8 has a resistance and a flexibility particularly suited to allow its withdrawal by peeling while maintaining the structure of the riblets 3 (few constraints are then exerted on the riblets 3).

[0080] One advantage of the method thus implemented is that the quality can be controlled only once (after the peeling step 108). The improvement of the quality of the riblets and of the repeatability of installation also allows increasing the frequency of sampling. Increasing the frequency of sampling therefore also allows reducing the cost of production of the component.

[0081] The invention is not limited to the embodiments described in relation with the figures, but can be subject to other variants.

[0082] The riblets 3 can be directly formed in the surface 2 of the component, and not in an anti-erosion coating 8. In such a variant, the component can be previously heated, so that the material in which the surface 2 is formed is sufficiently softened so that the riblets 3 can be printed 106 on it.

[0083] As a variant, the film 4 is a component of the pouch of the vacuum bag. The first surface 5 in which the riblet imprint 6 is formed can be a portion of the internal surface of the pouch 14 of the vacuum bag 12. In such a variant, there is no need to insert a film 4 in the interior of the vacuum bag 12, which simplifies the implementation of the printing 106 of the riblets 3.

[0084] In another variant, no vacuum bag is used for pressing the film 4 on the component 1. This pressing is implemented using other pressing means.