Mould for curved panels

Abstract

The present invention relates to a mould (1) for forming curved parts (9) with large dimensions. The mould (1) comprises a first part (10), a second part (20), bearing devices (30, 40) and sliding areas (51, 52) located between the first part (10) and one (30) of the bearing devices (30, 40) and between the second part (20) and the other (40) of the bearing devices (30, 40). The mould (1) allows the first part (10) and the second part (20) to slide horizontally, while the bearing devices (30, 40) apply a vertical pressure thereto.

Description

[Technical field]

[0001] The present invention relates to a mould for shaping and polymerising under pressure curved and large sized panels made of composite material. [Background technology]

[0002] Composite materials include one or more reinforcing materials impregnated with a polymeric resin.

[0003] Known moulds making it possible to mould curved panels with large dimensions made of composite material, for example airfoil panels for aircraft wings, comprise on the one hand a moulding surface and on the other hand a vacuum membrane or bag. The pressure applied for moulding is sometimes atmospheric pressure, via evacuation between the mould and the bag or membrane, or in other cases by autoclave, typically rising between 6 and 8 bar. A pressure of 6 to 8 bar is usually necessary to limit the porosity of the composite to an acceptable value, typically less than 2% of the volume. The mould is heated, typically at 180°C, to polymerise the resin of the composite. The heating rate allowed is generally 3°C / min, but is most often limited to 1°C / min for autoclave curing, in order to maintain the overall thermal homogeneity of the mould and of the part produced. We typically aim for an overall homogeneity of + / - 5°C.

[0004] In most cases, the resin is already present in the reinforcement when the mold is closed by the vacuum membrane or bag, or is injected there after ejection. In some cases, the resin is partially present during ejection and the complement is injected.

[0005] Additionally, if the part incorporates protruding elements, such as reinforcements, these are typically formed above the opposing forming surface by an external device located below the vacuum bag that is difficult to position relative to the forming surface.

[0006] An alternative to curing under pressure and temperature in an autoclave on a single-sided mold closed by a vacuum bag is the method called SQRTM (Same Qualified Resin Transfer moulding), which is known to allow curing under pressure and temperature in a double-sided mold of male / female moulds. This SQRTM method makes it possible to reproduce the pressure and temperature levels of the autoclave process. SQRTM makes it possible to produce composites of at least the same quality as those produced in an autoclave.

[0007] There are many methods for injecting resin during molding of composite panels. This method is commonly called RTM (Resin Transfer moulding) and is available in many variations, depending on when the mould is fully closed, whether a vacuum, external pressure on the mould, a single-sided mould with a vacuum bag, or a male / female mould is involved. Parts of suitable quality are generally obtained with a male / female mould where a vacuum is applied prior to pressure injection.

[0008] The use of autoclaves to apply closing pressure and heat to the molds is known to be a very energy inefficient process (gas needs to be heated which heats the molds by convection) and consumes ancillary materials such as vacuum bags which are discarded after each use or membranes which are discarded after a few uses.

[0009] For aircraft wing panels, the composite reinforcement is carbon fiber and the resin is most often epoxy. The particularity of carbon fiber is that it hardly expands during the molding cycle between 20 ° C and 180 ° C. It is common for molded parts with large dimensions on one-sided molds made of materials with a thermal expansion coefficient close to that of carbon fiber, such as Invar steel or carbon fiber-based composites. Invar is an expensive material. Carbon fiber-based composites are relatively weak as mold materials. It has been shown that during molding by SQRTM or RTM of parts with large dimensions under pressure and temperature in male / female molds, it is possible to omit the use of mold materials whose expansion coefficient is close to that of carbon fiber. Typically, aluminum or steel molds are used. Summary of the Invention

[0010] The object of the present invention is to provide a mould for parts such as panels, made of composite material, curved, with large dimensions and polymerised under pressure and temperature. The mould allows for good control of the thickness of the panel and of the position of any protruding elements. The mould can also be made of materials whose coefficient of expansion differs significantly from that of the reinforcement of the composite part, for example steel or aluminium for carbon fibre reinforcement. The mould according to the invention allows for the production of high quality parts with attractive yields.

[0011] For this purpose, the invention proposes a mould for moulding at least a part of a curved part, the part having a first part surface and a second part surface separated by a thickness, the mould comprising: a shell, a first part having a first molding surface for molding a first part surface and a first external surface opposite the first molding surface; a second part comprising a second molding surface for molding a second part surface and a second external surface opposite the second molding surface, wherein at least one of the first external surface and the second external surface is non-planar; a shell comprising: - a bearing system, a first bearing device mechanically coupled to the first portion of the shell and configured to urge the first portion of the shell in a first direction; a second bearing device mechanically coupled to the second portion of the shell and configured to urge the second portion of the shell in the first direction; and A bearing system comprising: Equipped with The mold is configured to allow sliding movement between the first portion of the shell and the first bearing device, and between the second portion of the shell and the second bearing device, in at least one direction perpendicular to the first direction.

[0012] In a mold according to the invention, each of the first and second surfaces of the part is defined by one of the forming surfaces, and the thickness of the part is defined by the distance between the forming surfaces of the mold. The mold is preferably slidable in any direction perpendicular to the first direction.

[0013] Since the first part of the shell slides against the first bearing device and the second part of the shell slides against the second bearing device in at least one direction perpendicular to the first direction, the stress exerted by the bearing devices on the forming surface is only in the first direction. This allows pressure to be in the first direction while being free to move in at least one perpendicular direction. Thus, during forming, when the forming surface increases in temperature and expands, the forming surface is constrained in the first direction while having a degree of freedom to extend perpendicular to the first direction. As a result, the thermal expansion of the forming surface mainly results in deformation perpendicular to the first direction, and the thickness of the part, i.e. its extension in the first direction, is very well controlled, despite the thermal expansion due to pressure in the first direction. For example, if the first direction is vertical, the shell can be considered to slide horizontally between the bearing devices that remain fixed horizontally. As a result, the thermal expansion of the forming surfaces primarily results in an increase in the gap between the bearing devices, and this gap (and therefore the thickness of the part) is very well controlled by the pressure that the clamping device exerts on the bearing system. Thus, during forming, the thickness of the part is controlled by pressing in a first direction.

[0014] During molding, the injected resin exerts a pressure that tends to separate the first and second parts of the shell. In the mold according to the invention, this outward pressure is mainly counteracted by the clamping device, which exerts an inward pressure via the bearing system. The balance between the outward and inward pressure makes it possible to obtain the desired part thickness.

[0015] The moulding is carried out at temperatures between 120° C. and 180° C. and under a pressure of 5 to 10 bar. Typically, the vacuum level inside the shell is less than 10 mbar.

[0016] The mold is configured such that a mechanical connection between the first bearing device and the first portion of the shell transmits pressure in a first direction from the first bearing device to the first portion of the shell, and further such that a mechanical connection between the second bearing device and the second portion of the shell transmits pressure in the first direction from the second bearing device to the second portion of the shell.

[0017] Pressure transmission and sliding between the first portion of the shell and the first bearing device occurs at a plurality of first sliding regions, and pressure transmission and sliding between the second portion of the shell and the second bearing device occurs at a plurality of second sliding regions.

[0018] Preferably, the pressure is applied only to a portion of the outer surface of the first part of the shell and of the second part of the shell, this portion accounting for less than 20% of the outer surface. In other words, the first sliding area represents less than 20% of the outer surface and the second sliding area represents less than 20% of the outer surface. This makes it possible to obtain a particularly lightweight mold.

[0019] The shell is provided such that the first part of the shell and the second part of the shell do not slide, or only slightly slide, relative to each other during molding. The first part of the shell is preferably a female part and the second part is preferably a male part. However, the opposite is possible while remaining within the scope of the invention.

[0020] The non-planarity of the outer surface allows it to at least partially follow the curved shape of the molded part or of the molded part of the part, which makes it possible to make the shell particularly light and therefore particularly easy to heat. The same applies to the non-coplanarity of the sliding areas.

[0021] Molding by SQRTM or RTM in a double-sided mold, such as the shell of the invention, under pressure and temperature allows the omission of the use of an autoclave. It has the advantage that the thickness of the part is better controlled than in an autoclave, since it is defined by the air gap of the mold and not by the pressure exerted by the autoclave to limit the porosity. Thanks to the bearing system, the double-sided mold according to the invention is sufficiently rigid so that the air gap does not change too much depending on the pressure exerted inside the mold. Another way to obtain sufficient rigidity is to use such a rigid shell, but such a shell is particularly bulky, which increases the energy required to heat it.

[0022] The first direction is preferably the direction that accounts for the majority of the pressure exerted by the reinforcement and resin on the inside of the mold during molding.

[0023] The first direction is preferably vertical, but can be any (e.g. horizontal), while it is within the scope of the invention. The part extends primarily in the second and third directions, and its thickness extends primarily in the first direction.

[0024] The part preferably comprises a panel. The mould according to the invention has a length of at least 1 m 2 , e.g. at least 10m 2 It may have a length, measured in the second direction, of at least 5 m, such as at least 12 m. It may have a width, measured in the third direction, of at least 1 m, such as at least 2 m.

[0025] The part may be curved, for example having a negative inflection point exhibiting a "saddle" shape. The hollow part may have a depth of at least 30cm, for example at least 80cm.

[0026] The bearing device can be made, for example, of steel or carbon fiber, the latter allowing for reduced mass and thermal expansion.

[0027] The sliding static friction coefficient μ between the first part of the shell and the first bearing device and between the second part of the shell and the second bearing device s The first sliding region and the second sliding region preferably comprise one or several materials such that .gtoreq..times ...

[0028] According to one embodiment, the mechanical coupling between the first external surface and the first bearing device comprises a protrusion extending from the first external surface to the first bearing device and / or a protrusion extending from the first bearing device to the first external surface, and the mechanical coupling between the second external surface and the second bearing device comprises a protrusion extending from the second external surface to the second bearing device and / or a protrusion extending from the second bearing device to the second external surface. Thus, the contact between the bearing device and the first and second parts of the shell does not extend over the entire surface of the shell. This allows the mould to be particularly light. The pressure in the first direction is transmitted via the protrusion.

[0029] According to one embodiment, at least some of the protrusions are provided with ridges. This allows for a particularly uniform pressure transmission. The ridges form the contact line between the shell and the bearing system. Furthermore, the ridge-like protrusions of the external surface allow for stiffening of the shell. However, it is possible, while remaining within the scope of the invention, for at least some of the protrusions to have another form, for example rods or posts.

[0030] According to one embodiment, the mould comprises a heating element fastened to the first external surface and / or to the second external surface and / or to the bearing system and located between the protrusions. The heating element can be, for example, an electric resistor or a magnetic inductor which induces eddy currents in the shell. The arrangement of the heating element as close as possible to the external surface of the shell allows for particularly low energy consumption, since heat transfer is particularly effective.

[0031] In one embodiment of the invention, the bearing system comprises passages configured to pass a heat transfer fluid. The fluid can be a gas, for example, in particular air, passing through holes in the wall forming the protrusion. The cooling can be performed passively or by forced convection. The fluid can be a liquid, in particular if the mould comprises an active cooling system between the moulding surface and the bearing system. For example, the active cooling system can comprise pipes located between the first insulation and through which a cooled liquid circulates. Gas and liquid cooling can be combined.

[0032] According to one embodiment, the mechanical connection between the first external surface and the first bearing device and the mechanical connection between the second external surface and the second bearing device are provided with a first thermal insulation. The heat transfer between the shell and the bearing system is therefore particularly low. This allows for particularly low energy consumption, since the mass of the heated material is limited to the light shell. Furthermore, the bearing system is prevented from thermal deformation. The first thermal insulation has a thermal insulation of, for example, 0.5 Wm -1 K -1 The bearing device may be made of a material having a lower thermal conductivity than , for example, fiberglass and resin-based laminate materials such as Glatherm. The bearing device may also be made of a thermally insulating material, for example, a carbon fiber composite.

[0033] According to one embodiment, the sliding between the first part of the shell and the first bearing device occurs on a plurality of first sliding areas, and the sliding between the second part of the shell and the second bearing device occurs on a plurality of second sliding areas, and the mold is configured such that the distance in the first direction between the first sliding areas and the second sliding areas varies by less than 20% over the entire mold. Thus, the distance in the first direction between the joint points of the shell and the bearing system varies by less than 20% over the entire mold. This allows a particularly uniform application of pressure in the first direction, since when the shell expands through its thickness, all sliding areas move apart in the first direction in the same way (the clamping device responds) and contact is not lost anywhere.

[0034] The distance between the elements of the shell is not constant throughout the mold: in fact, the thickness of the part may vary between two locations in the mold.

[0035] According to one embodiment, the first part of the shell comprises a first segment and a second segment assembled by mechanical fasteners on the outside of the first moulding surface and by welds along the first moulding surface and / or the second part of the shell comprises a first segment and a second segment assembled by mechanical fasteners on the outside of the second moulding surface and by welds along the second moulding surface. Having several segments makes it easier to manufacture and transport the mould and allows the separation of a single segment from the first part of the shell or from the second part of the shell in case of failure of a part of the shell, if one wishes to carry out corrections therein. A mechanical assembly, for example by bolting, allows a particularly resistant and precise separable fastening. Surface welding allows the moulding surface to be made gas-tight. The welds preferably have a maximum thickness of 10 mm. This can be carried out by a laser. Each of the segments preferably has a length of less than 10 meters. The welds are broken during the separation of the segments.

[0036] According to one embodiment, the shell comprises cavities on the first and / or second molding surface, which make it possible to place protruding elements of the part after molding (and therefore polymerization of the resin), for example protruding reinforcements that form the reinforcement.

[0037] The cavity is preferably present only in the first molding surface and not in the second portion of the shell, where the first portion is located below the second portion, which allows for a simple, lightweight construction with a first portion that is heavy but has limited handling during the molding process, and a second portion that is removable and subject to the majority of handling.

[0038] According to one embodiment, the mould comprises removable inserts located in the cavities, each insert comprising an open space intended to receive a protruding reinforcement. With the aid of a polymerised resin, the protruding reinforcement is constructed after moulding the protruding elements of the part, typically the reinforcements. The inserts can for example be made of the same material as the shell. They may comprise at least two parts which are removable with respect to each other. The inserts facilitate the moulding of the protruding elements as well as their demoulding.

[0039] According to one embodiment, the mould comprises a removable arm adapted to hold an insert and to be at least partially inserted into the groove of the first moulding surface and / or the second moulding surface. The arm allows the insert, which is a reinforcement constituting a protruding element, a stiffener or other component of the part, to be taken on the system, which prepares the insert for placing in the mould while maintaining its respective position. This makes it possible to prepare the insert by segmenting an insert having a considerable length and placing the insert in a precise relative position. A precise clearance between the insert segments can be defined such that, when placed in the mould and at a given temperature, this clearance between the segments disappears under the effect of the thermal expansion of the insert, without damaging the reinforcement placed therein.

[0040] The arm allows the precise placement of the low-temperature insert and the reinforcement it accommodates on a preheated molding surface, for example between 90 and 120 °C. The reinforcement can then be placed on the molding surface and the insert before the other molding surface is placed. This may also be preheated. This solution saves time in producing the part, as most of the mass to be heated is preheated. Once the part is polymerized, for example at 180 °C, the arm allows the part to be easily demoulded and the quick release of the moulding device, which can then be used to mould another part.

[0041] The invention further proposes a system comprising a mould, a clamping device and a resin infusion system configured to inject resin into and / or around at least one reinforcement located between a first moulding surface and a second moulding surface, preferably between the first and second moulding surfaces. The at least one reinforcement comprises a main reinforcement and optionally one or more other reinforcements, for example protruding reinforcements. In the case of the RTM method, the resin is injected into the at least one reinforcement. In the SQRTM method, the resin is injected around the at least one reinforcement before polymerization in order to control the pressure in the resin during the moulding process. The mould according to the invention is intended to work with, for example, a pneumatic clamping device, where the force is transmitted by compressed gas. The pressure is preferably applied vertically upwards by the lower part of the clamping device (as shown in the figure). The clamping device can be partially fastened to the bearing system or integrated on one side with the first bearing device and on the other side with the second bearing device.

[0042] According to one embodiment, the pressure applied by the clamping device can be controlled by a region that allows for different pressure to be applied to the edge of the shell compared to the center of the shell. The applied pressure can be varied during molding to facilitate infusion of the resin and / or to obtain a desired thickness during polymerization of the resin.

[0043] The invention further proposes a molding method comprising heating the resin and the primary reinforcement in a mold according to the invention in order to mold a composite part incorporating the primary reinforcement and the resin, where a first part surface of the composite part is molded against a first molding surface and a second part surface is molded against a second molding surface. During heating, the resin is preferably injected between the first and second molding surfaces and a pressure in a first direction is applied via a bearing system. The method can be, for example, a resin transfer molding without pre-impregnation of the reinforcement (RTM) or with pre-impregnation of the reinforcement (SQRTM). If the amount of resin already present is such that the desired pressure is reached without injection, the method may not include resin injection (for example a method called "compression molding"). Heating the resin present in the reinforcement allows the polymerization of the resin. The heating is preferably carried out via heating of the shell. The heating makes it possible to reach temperatures, for example, between 120°C and 180°C. The pressure makes it possible in particular to prevent degassing or even boiling of the resin, which would result in unacceptable porosity. The injection is preferably carried out under a pressure of between 5 and 10 bar.

[0044] According to one embodiment, the part is or includes an aircraft wing, an aircraft tail, an aircraft fuselage panel, an aircraft airfoil flap, an aircraft fairing, or an airfoil panel for an aircraft engine part.

[0045] According to one embodiment, the airfoil may comprise an upper panel produced in a mould according to the invention and a lower panel produced in another mould according to the invention. According to another embodiment, the upper panel for one of the moulding surfaces of the shell and the lower panel for the other of the moulding surfaces of the shell are produced in the same mould.

[0046] According to one embodiment, the method comprises inserting an insert into the cavity prior to the injection of resin, and inserting the protruding reinforcements into the open spaces of the insert, whereby the protruding reinforcements, the main reinforcements and the resin are brought together by moulding to form the part. The precision of the inserts and their positioning means that the protruding elements have a particularly well-defined shape.

[0047] According to one embodiment, when the insert is inserted into the cavity, the shell is at a temperature above 40° C., such as between 90° C. and 120° C. For example, the shell can be maintained above 40° C., such as between 90° C. and 120° C., between successive moldings. This allows for a reduction in the amount of energy required to raise the temperature of the shell.

[0048] According to one embodiment, the heating is carried out for the following period: - a period during which the pressure in the first direction is uniform across the shell; and - at least one other period during which the pressure in the first direction on the central shell region differs from the pressure on the peripheral shell region. [Brief description of the drawings]

[0049] Other characteristics and advantages of the present invention will become apparent from a reading of the following detailed description, the understanding of which is based on the accompanying drawings, in which: [Figure 1] FIG. 2 is a vertical schematic view of the shell. [Diagram 2] FIG. 2 is a vertical schematic view of the molding system. [Diagram 3] FIG. 2 is a vertical schematic view of a portion of a mold. [Figure 4a] FIG. 2 shows a first bearing device. [Figure 4b] FIG. 2 shows a second bearing device. [Diagram 5] FIG. 13 is a schematic diagram of an assembly between some segments of the first and second shell parts. [Figure 6a] FIG. 2 is a top view of the second shell portion. [Figure 6b] FIG. 13 is a bottom view of the second shell portion. [Figure 7] FIG. 2 is a top view of the first shell portion. [Figure 8] FIG. 2 is a vertical view showing the insert within the cavity of the first part of the mold. [Figure 9] FIG. 13 is a schematic top view of the protruding reinforcement and insert. [Figure 10] FIG. 2 is a schematic top view of the protruding reinforcements and inserts on the first portion of the shell. [Figure 11a] FIG. 2 is a schematic side cross-sectional view of the protruding reinforcements and inserts on the first portion of the shell prior to injection. [Figure 11b] FIG. 2 is a schematic vertical cross-sectional view of the part in the open mold after injection. [Figure 11c] FIG. 2 is a schematic vertical cross-sectional view of a molded part. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] EMBODIMENTS OF THE PRESENTINVENTION The present invention will be described with reference to particular embodiments and drawings but the invention is not limited thereto. The drawings or figures described are only schematic and are non-limiting. Moreover, the described functions may be performed by structures other than those described herein.

[0051] In the context of this document, the terms "first" and "second" merely serve to distinguish between various elements and do not imply any ordering between these elements.

[0052] In the drawings, the same or similar elements may have the same reference numbers.

[0053] The various elements of the invention are described with reference to a first direction 501, a second direction 502 and a third direction 503. The second direction 502 and the third direction 503 are perpendicular to the first direction 501 and preferably perpendicular to each other. The reference numbers 501, 502 and 503 are particularly shown in Figure 8. The figure corresponds to one embodiment of the invention in which the first direction 501 is vertical.

[0054] FIG. 1 is a vertical schematic view of a shell 2 intended to be used in a mold 1 according to one embodiment of the present invention. The shell 2 comprises a first portion 10 and a second portion 20. When a first direction 501 is vertical, the first portion 10 and the second portion 20 are essentially horizontal, and the first portion 10 is intended to be below the second portion 20. The first portion 10 comprises a first molding surface 11 and the second portion 20 comprises a second molding surface 21, which together define the shape of the part 9 (FIGS. 2 and 3) to be molded by the mold 1. When molded, the part 9 incorporates a primary reinforcement 99, protruding reinforcements 93 (FIG. 11a), and polymerized resin. The primary reinforcement 99 and the protruding reinforcements 93 are made of carbon fiber.

[0055] The first moulding surface 11 makes it possible to mould a first part surface 91 of the part 9, and the second moulding surface 21 makes it possible to mould a second part surface 92 of the part 9. The shell 2 is provided such that, at its periphery, the first part 10 and the second part 20 do not slide, or only slightly, relative to each other. For example, the friction between them at the left and right ends in FIG. 1 may be sufficient to prevent sliding.

[0056] The first portion 10 comprises a first exterior surface 12 opposite the first forming surface 11, and the second portion 20 comprises a second exterior surface 22 opposite the second forming surface 21. The first exterior surface 12 and / or the second exterior surface 22 are non-planar to at least partially follow the bending of the part 9. The first exterior surface 12 preferably comprises facets 14 perpendicular to the first direction 501, and / or the second exterior surface 22 preferably comprises facets 24 perpendicular to the first direction 501.

[0057] 2 is a vertical schematic view of a molding system 100 according to an embodiment of the present invention. The molding system 100 comprises a mold 1 and a clamping device 110, e.g., pneumatic or hydraulic, including a bead 101 arranged to receive a fluid for applying pressure in a first direction 501 to the mold 1. The mold 1 comprises a shell 2 and a bearing system 3. The molding system 100 also preferably comprises a resin infusion system 120 configured to inject resin between the first molding surface 11 and the second molding surface 21.

[0058] The bearing system 3 comprises a first bearing device 30 configured to press the first part 10 in a first direction 501 via a first sliding area 51 and a second bearing device 40 configured to press the second part 20 in the first direction 501 via a second sliding area 52. The first sliding area 51 is not coplanar and / or the second sliding area 52 is not coplanar.

[0059] The first sliding area allows sliding between the first part 10 and the first bearing device 30 perpendicular to the first direction 501 and transmits pressure in the first direction 501 from the first bearing device 30 to the first part 10. The second sliding area allows sliding between the second part 20 and the second bearing device 40 perpendicular to the first direction 501 and transmits pressure in the first direction 501 from the second bearing device 40 to the second part 20.

[0060] In one embodiment of the present invention, the first external surface 12 includes a downwardly extending protrusion 13 and the first bearing device 30 includes an upwardly extending protrusion 31, and the first sliding area is at the interface between the protrusion 13 of the first external surface 12 and the protrusion 31 of the first bearing device 30.

[0061] In one embodiment of the present invention, the second external surface 22 has an upwardly extending protrusion 23 and the second bearing device 40 has a downwardly extending protrusion 41, and the second sliding area is at the interface between the protrusion 23 of the second external surface 22 and the protrusion 41 of the second bearing device 40.

[0062] Preferably, the distance in the first direction 501 between the first and second sliding regions varies by less than 20% across the mould 1 .

[0063] The first bearing device 30 comprises a flat outer surface 39, perpendicular to the first direction 501 and oriented opposite the shell 2. The flat outer surface 39 is in contact with or integral with a first part 111 of the clamping device 110. The second bearing device 40 comprises a flat outer surface 49, perpendicular to the first direction 501 and oriented opposite the shell 2. The flat outer surface 49 is in contact with or integral with a second part 112 of the clamping device 110. The first part 111 of the clamping device 110 and the second part 112 of the clamping device 110 are mechanically coupled 113.

[0064] 3 is a vertical schematic view of a portion of a mould 1 according to an embodiment of the invention. It makes it possible to show some optional features of the invention, in particular the heating element 60 located between the projections 13, 23 of the shell 2, the first insulation 71 located in the sliding areas 51, 52 and the second insulation 72 located on the opposite side of the shell 2 to the heating element 60. The second insulation 72 has a thermal insulation capacity of, for example, 0.5 Wm -1 K -1 It may also be made of a material with a lower thermal conductivity, for example glass wool.

[0065] Heating element 60 preferably abuts exterior surfaces 12, 22, particularly in the case of conductive heating. Heating element 60 preferably faces exterior surfaces 12, 22, particularly in the case of radiative or inductive heating.

[0066] Figures 4a and 4b show a first bearing device 30 and a second bearing device 40, respectively, in an embodiment of the present invention, in which the projections 31, 41 of the bearing devices 30, 40 are ridges. The projections 31, 41 form walls that define compartments 32, 42 or boxes. These walls are preferably crossed by holes that form passages 33, 43 between the compartments 32, 42. Such a structure of the bearing devices 30, 40 makes them particularly light and may in particular facilitate their handling. It also allows dissipation of heat thanks to circulating air, for example by forced convection and by a heat transfer fluid system.

[0067] In general, it is preferred that the bearing devices 30, 40 are at least 50% hollow - in other words, at least 50% of the volume occupied by each of the bearing devices 30, 40 is not made of solid material.

[0068] 5 is a schematic diagram of an assembly between the first segment 17 and the second segment 18 of the first part 10 and between the first segment 27 and the second segment 28 of the second part 20 in an embodiment of the present invention. Each of the assemblies comprises a mechanical fastener 58 located outside the forming surfaces 11, 21 and / or a weld 59 located at least on the forming surfaces 11, 21. The mechanical fastener 58 and the weld 59 are preferably spatially separated from each other. The mechanical fastener 58 may comprise, for example, a flange 16, 26 through which a bolt passes. The weld 59 may have a triangular longitudinal cross section. The interface between the segments 17, 18 or 27, 28 may comprise a seal 57.

[0069] Figure 6a illustrates the second exterior surface 22 of the second shell portion 20 in one embodiment of the present invention. The protrusions 23 of the second portion 20 are ridges. They define facets 24. Similarly, as best illustrated in Figure 10, the protrusions 13 of the first portion are ridges that define facets 14. The second portion 20 includes a first segment 27, a second segment 28, and a third segment 29 that terminate in a flange 26 at their junction.

[0070] FIG. 6b shows the first molded surface 21 of the second shell portion 20 in one embodiment of the present invention.

[0071] 7 shows a first molding surface 11 of a first shell portion 10 in one embodiment of the present invention. The first portion 10 includes a first segment 17, a second segment 18, and a third segment 19. The perimeter 15 of the part 9 is shown on the first molding surface 11. The mold 1 preferably includes a seal 115 around the perimeter 15.

[0072] In one embodiment of the invention, the shell 2 comprises, preferably at the first moulding surface 11, a cavity 81 arranged to receive at least partly a protruding reinforcement 93 (notably shown in Fig. 11a). Additionally or alternatively, it may comprise a part at the second moulding surface 21. The cavity 81 and the protruding reinforcement 93 extend in particular perpendicular to the first direction 501. They extend mainly along the second direction 502. They are not parallel. The main reinforcement 99 and the protruding reinforcement 93 are preformed, i.e. they are already formed before they are incorporated into the part 9 during moulding.

[0073] Shell 2 preferably comprises a groove 85 in first molded surface 11, or possibly in second molded surface 12. Groove 85 is intended to receive arm 84 (shown in FIG. 10). Arm 84 and groove 85 preferably extend, at least partially, in third direction 503.

[0074] The protruding reinforcement 93 is preferably at least partially inserted into the open space 83 of a removable insert 82 for the shell 2, the insert 82 itself being at least partially inserted into the cavity 81 (FIG. 8).

[0075] The insert 82 may be held by an arm 84 (shown in FIG. 10) that is at least partially inserted into a groove 85 in the first molding surface 11 or, optionally, the second molding surface 12 .

[0076] Figure 8 also shows that inserts 82 are preferably at least partially inserted into the cavity 81. The inserts 82 are removable with respect to the shell 2. They are preferably in two parts 82a, 82b, with an open space 83 between the two parts 82a, 82b. They are intended to hold protruding reinforcements 93.

[0077] 9 is a schematic top view of the protruding reinforcements 93 during installation on the inserts 82. The protruding reinforcements 93 can be placed on several inserts 82, separated by intermediate spaces 87. The inserts 82 can then be held by a temporary support system 86. The arm 84 picks up the inserts 82 and the protruding reinforcements 93 on the support system 86, respecting their respective positions, and places them on the first part 10 as shown in FIG.

[0078] 10 is a schematic top view of the protruding reinforcement 93 and insert 82 during installation in the first portion 10. Also shown therein are protrusions 13 in the form of ridges and facets 14 on the first exterior surface 12 of the first portion 10.

[0079] In fact, between the successive mouldings of the two parts 9, the shell 2 remains at a high temperature, for example at about 120°-140° C. The shell 2 remains at a temperature of, for example, at least 40° C. When the arm 84 holding the insert 82 and the protruding reinforcement 93 is placed in the first hot part 10, the insert 82 expands and the intermediate space 87 disappears.

[0080] FIG. 11a is a vertical cross-sectional view showing the correct positioning of the primary reinforcement 99, the insert 82 and the protruding reinforcement 93 in the first portion 10 prior to injection.

[0081] During injection, the main reinforcement 99 and the protruding reinforcement 93 are located in the space between the moulding surfaces 11, 21 and the resin containing and surrounding them is hardened to polymerise. The clamping device 110 exerts pressure in a first direction 501 via the bearing system 3 to prevent the moulding surfaces 11, 21 from moving apart in the first direction 501. Under the effect of temperature (e.g. 160°-180°), the moulding surfaces 11, 21 expand horizontally against the bearing system 3 due to the sliding area. The protruding reinforcement 93, the main reinforcement 90 and the resin are incorporated into the part 9 during the polymerisation of the resin.

[0082] Preferably, the heating comprises a period during which the pressure in the first direction 501 is applied uniformly on the shell 2 and at least one other period during which the pressure in the first direction 501 on the shell central region 2 differs from the pressure on the shell peripheral region 2. For example, during a first period, the pressure in the first direction 501 can be lower in the central region than in the peripheral region to facilitate injection, during a second period, the pressure in the first direction 501 can be uniform to obtain the desired shape of the part, and during a third period, the pressure in the first direction 501 can be lower in the central region than in the peripheral region to avoid the part's center collapsing. Indeed, during heating, when the resin starts to solidify, the part 9 shrinks and the pressure exerted on the shell 2 decreases. The reduction of the pressure of the mould 1 on the part 9, at least in the central region of the shell 2, makes it possible to take this phenomenon into account. By maintaining the periphery 15 (shown in FIG. 7) of the part 9 at a higher pressure than the central area, a seal can be maintained.

[0083] To allow for variation of pressure on parts 9 over time, clamping device 110 is configured such that the pressure can be varied over time. To allow for spatial adjustment of pressure on parts 9, clamping device 110 preferably comprises a central region and a peripheral region surrounding the central region, such that the pressure in the central region can be different from the pressure in the peripheral region.

[0084] Figure lib shows the part 9 when the second portion 20 has been lifted. The arm 84 that remains during injection helps to handle the part 9 during demolding.

[0085] Figure 11c shows part 9 from mould 1. Part 9 includes protruding reinforcements 93 and protruding elements 94 formed from polymerised resin.

[0086] In other words, the invention relates to a mould 1 for moulding curved parts 9 with large dimensions. The mould 1 comprises a first part 10, a second part 20, bearing devices 30, 40 and sliding areas located between the first part 10 and one of the bearing devices 30, 40 and between the second part 20 and the other of the bearing devices 30, 40. The mould 1 allows the first part 10 and the second part 20 to slide horizontally, while the bearing devices 30, 40 apply a vertical pressure thereto.

[0087] Although the present invention has been described with reference to specific embodiments, these are purely illustrative and should not be construed as limiting. In general, the present invention is not limited to the illustrated and / or described examples. The use of the verbs "comprise", "include", "have", or any other variations and conjugations thereof, in no way excludes the presence of elements other than those mentioned. The use of the indefinite article "a", "an", or the definite article "the" to introduce an element does not exclude the presence of a plurality of these elements. Reference numerals in the claims do not limit their scope.

Claims

1. A mold (1) for molding at least a portion of a curved part (9), said part (9) having a first part surface (91) and a second part surface (92) separated by a thickness, said mold (1) comprising: - shell (2), a first part (10) comprising a first moulding surface (11) for moulding said first part surface (91) and a first external surface (12) opposite said first moulding surface (11); a second part (20) comprising a second molding surface (21) for molding said second part surface (92) and a second external surface (22) opposite said second molding surface (21), wherein at least one of said first external surface and said second external surface (12, 22) is non-planar; A shell (2) comprising: - a bearing system (3), a first bearing device (30) mechanically coupled to said first part (10) and configured to press said first part (10) in a first direction (501); a second bearing device (40) mechanically coupled to said second part (20) and configured to press said second part (20) in said first direction (501); A bearing system (3) comprising: Equipped with the mould (1) is configured to allow sliding between the first part (10) of the shell and the first bearing device (30) and between the second part (20) of the shell and the second bearing device (40) in at least one direction perpendicular to the first direction (501), Mold (1).

2. 2. The mold of claim 1, wherein the mechanical coupling between the first external surface (12) and the first bearing device (30) comprises a protrusion (13) extending from the first external surface (12) to the first bearing device (30) and / or a protrusion (31) extending from the first bearing device (30) to the first external surface (12), and the mechanical coupling between the second external surface (22) and the second bearing device (40) comprises a protrusion (23) extending from the second external surface (22) to the second bearing device (40) and / or a protrusion (41) extending from the second bearing device (40) to the second external surface (22).

3. The mold of claim 2 , wherein at least some of the protrusions (13, 23, 31, 41) comprise ridges.

4. 4. The mold according to claim 2 or 3, comprising a heating element (60) fastened to the first external surface (12) and / or to the second external surface (22) and / or to the bearing system (3) and located between the protrusions (13, 23, 31, 41).

5. 5. The mold according to any one of claims 1 to 4, wherein the bearing system (3) comprises passages (33, 43) configured to pass a heat transfer fluid.

6. 6. The mold according to claim 1, wherein the mechanical connection between the first external surface (12) and the first bearing device (30) and the mechanical connection between the second external surface (22) and the second bearing device (40) comprise a first thermal insulation material (71).

7. 7. The mold according to claim 1, wherein the sliding between the first part (10) and the first bearing device (30) occurs over a plurality of first sliding regions, and the sliding between the second part (20) and the second bearing device (40) occurs over a plurality of second sliding regions, and the mold (1) is configured such that the distance in the first direction (501) between the first sliding region and the second sliding region varies by less than 20% over the entire mold (1).

8. 8. The mold of claim 1, wherein the first portion (10) comprises a first segment (17) and a second segment (18) assembled by mechanical fasteners (58) external to the first forming surface (11) and by welds (59) along the first forming surface (11) and / or the second portion comprises a first segment (27) and a second segment (28) assembled by mechanical fasteners (58) external to the second forming surface (21) and by welds (59) along the second forming surface (21).

9. 9. The mould according to any one of claims 1 to 8, wherein the shell (2) comprises cavities (81) in the first moulding surface (11) and / or the second moulding surface (21), the mould (1) comprises removable inserts (82) located in the cavities (81), each insert (82) comprising an open space (83) intended to receive a protruding reinforcement (93), and the mould (1) comprises removable arms (84) configured to hold the inserts (82) and to be at least partially inserted into grooves (85) in the first moulding surface (11) and / or the second moulding surface (12).

10. 10. A molding system (100) comprising the mold (1) according to any one of claims 1 to 9, a clamping device (110) and a resin injection system (120) configured to inject resin between the first molding surface (11) and the second molding surface (21).

11. 10. A molding method comprising the step of heating resin and primary reinforcements (99) in a mold (1) according to any one of claims 1 to 9 to mold a composite part (9) incorporating said primary reinforcements (99) and resin, wherein a first part surface (91) of said composite part (9) is molded against said first molding surface (11) and a second part surface (92) is molded against said second molding surface (21) while resin is injected between said first molding surface (11) and said second molding surface (21) and pressure in said first direction (501) is applied via said bearing system (3).

12. 12. The method of claim 11, wherein the part (9) comprises an aircraft wing, an aircraft tail, an aircraft fuselage panel, an aircraft airfoil flap, an aircraft fairing, or an airfoil panel for an aircraft engine part.

13. 13. The method according to claim 11 or 12, wherein the mould (1) is the mould according to claim 9, and the method comprises the steps of inserting the insert (82) into the cavity (81) before the resin injection, and inserting the protruding reinforcement (93) into the open space (83), whereby the protruding reinforcement (93), the main reinforcement (99) and the resin are integrated by moulding to form the part (9).

14. 14. The method of claim 13, wherein the shell (2) is at a temperature above 40°C when the insert (82) is inserted into the cavity (81).

15. The heating comprises: a period during which said pressure in said first direction (501) is uniform over the whole of said shell (2); - at least one other period in which said pressure in said first direction (501) on the central shell region (2) is different from said pressure on the peripheral shell region (2); The method according to any one of claims 11 to 14, wherein the method is carried out during

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