Method for manufacturing an external casing for flying objects

Abstract

The invention relates to a method for manufacturing an external casing for a flying object made of a fibrous composite material, the external casing having an opening for a door device. The method comprises the following steps: providing a molding tool for manufacturing an external casing with an opening, such that the molding tool has a smooth forming surface, designed to impart its shape to the external flow surface of the external casing with the opening, and includes, in the tool surface, in the area of ​​the opening to be made, a core-forming tool that overhangs the rest of the tool surface by a dimension equal to the door thickness; introducing a first fibrous material into the molding tool, depositing it on the tool surface in a portion bordering the opening, all around the core-forming tool, in the form of a wedge rising towards the core-forming tool.Introduce at least a second fibrous material into the molding tool, depositing it on the tool surface outside the opening and on top of the first fibrous material already deposited within the opening, so that the second fibrous material extends beyond the core of the tool to form an internal stop for the opening on the outer casing. Manufacture the outer casing with the opening by consolidating the unconsolidated matrix material that embeds the fibrous material. Figure for the abbreviation: 2a,

Description

Title of the invention: “Method for manufacturing an exterior covering for flying objects”

[0001] The invention relates to a method for manufacturing, for a flying object, an outer covering made of a fibrous composite material comprising a fibrous material and a matrix material embedding the fibrous material, the outer covering having an outer flow surface, an inner side opposite the outer flow surface and, in the flow surface, an opening for a door device for opening and closing the opening, the latter constituting, in the closed position, the outer flow surface portion of the opening.

[0002] The invention also relates to an exterior covering thus produced.

[0003] The outer covering of a flying object is a kind of shell or casing intended to protect the interior space or the interior of a flying object and to delimit the inner area from the outer area surrounding the flying object. Towards the outside, such an outer covering has an (aerodynamic) flow surface around which an external medium can flow. Such an outer covering therefore serves to delimit an inner area of ​​the flying object from an area outside the flying object, the outer covering having an outer flow surface oriented towards the outer area and around which an external medium can flow, and an inner side opposite the outer flow surface and oriented towards the inner area.

[0004] The outer covering of a flying object, for example an aircraft, is also referred to in the area of ​​the fuselage and wings as "skin" or "aircraft skin". But also in other places, for example the thrusters, the technical elements of the interior space are protected by an outer covering. In the area of ​​the thrusters, such an outer covering is also referred to as a "nacelle". Only in this way can the functional safety of the flight be ensured.

[0005] For maintenance purposes in particular, it is often necessary to be able to access the interior area of ​​the flying object from the exterior area. Therefore, the exterior casing of the thrusters generally includes one or more access doors (also called "access doors"), in order to allow, among other things, maintenance operations on the thrusters. As they are included in the flow surface of the exterior casing, these access doors must be fixed in the exterior casings so as to avoid accidental or untimely opening during flight.

[0006] Such access doors or maintenance doors are generally not entry doors allowing a human to pass through to enter or leave the space. interior of the flying object. In the case of access doors or maintenance doors, these are not the classic aircraft doors, used for example for boarding passengers and crew to enter the aircraft. Rather, they are access elements that must allow a technician to access the technical elements located behind the exterior trim. In the case of such access doors or maintenance doors, these are door elements placed in the exterior trim, which can be opened if necessary to allow access to the technical elements of the flying object located behind it.

[0007] In practice, such access doors or maintenance doors are often fixed by screws or rivets, so that to allow access to the technical elements located behind, it is first necessary to detach the screws or rivets before manually removing the access doors or maintenance doors. But access doors or maintenance doors are also known in practice which are fixed to a hinge and can be opened by means of one or more levers. Such access doors or maintenance doors are very often found in the exterior trim of aircraft turbines.

[0008] Such fastening concepts known in practice for the removable fastening of these access doors or maintenance doors have the major disadvantage that the elements retained for fastening the door, such as for example hinges, handles or screws, protrude from the outer face of the outer cladding, thus constituting an obstacle in the flow surface of the outer cladding. The natural maintenance of the laminar flow regime around the outer flow surface is disturbed and the boundary layer prematurely changes from laminar flow to turbulent flow.

[0009] It has been found that increasing the surfaces conducive to laminar flow makes it possible to significantly reduce the resistance due to friction when flying objects are in flight. The natural maintenance of the laminar regime assumes a flow surface free from any disturbance, free from obstacles such as undulations, differences in level or heads of conventional connecting elements, levers and hinges, which promote a premature transition from the boundary layer to a turbulent flow.

[0010] [Fig.l] shows an access door or maintenance door in the outer casing of a thruster hull, as well as a schematic cross-section. This fastening concept, as shown in [Fig.l], is very frequently used in the prior art for fastening access doors or maintenance doors to a thruster hull. A support or stop mounted on the inner face of the outer casing is fixed to the outer casing by rivets passing through the outer flow surface. The rivets used for this purpose are visible in [Fig.l] in the area bordering the opening of the outer casing. This support or stop here also an opening, smaller than the opening in the drainage surface of the exterior cladding and intended to be closed by the corresponding access or maintenance door. The access or maintenance door can thus be screwed onto the support extending into the opening, so that it can be removed at any time to allow access to the technical elements behind it. The screws used in [Fig.l] are visible in the edge area of ​​the access or maintenance door.

[0011] The fastening concept shown in [Fig.l] to illustrate the state of the art has several drawbacks. Due to the fastening means present in the outer flow surface, the boundary layer tends to change from laminar flow to turbulent flow. Indeed, both the support or stop and the access door itself are fixed using fastening means which pass through the outer flow surface of the outer cladding and thus constitute a disturbance on the outer flow surface. The access doors which are provided in an advanced position in the outer cladding, relative to the direction of flow, consequently promote a very early change of the boundary layer from laminar flow to turbulent flow, which increases the resistance due to friction.

[0012] Another problem with such attachment concepts often arises at the transition between the outer cladding and the access door. Due to variations in the thickness of the components, which frequently occur, especially in the manufacture of the outer cladding and the access door from a fiber composite material, the transition from the flow surface of the outer cladding to the flow surface of the access door is not flat, smooth or flush. On the contrary, due to the varying thickness of the components of the outer cladding and / or the access door, level differences may result, which are also likely to promote an early transition of the boundary layer from laminar flow to turbulent flow.

[0013] When using a fibrous composite material, there is also the problem that each fastening means passing through the fibrous material damages the fibrous structure, which compromises the stability of the component. This is remedied by thickening the material, but this makes the flying object even heavier.

[0014] A concept is known from WO 2013 / 000447 A1 which provides for the subsequent covering of the connecting elements. The bolts connecting the leading edge of the wing and the joining surface occupy a groove, below the aerodynamic flow surface. After assembly, the groove is filled with a filling mass which closes it in a jointed manner with leveling.

[0015] This method has the disadvantage of requiring precise placement of the filler mass. Because the filler masses usually found on the market shrink considerably, both during their curing and under the effect of low external temperatures such as those encountered by airliners in flight, deviations occur in flight conditions from the desired target contour which may disrupt the maintenance of laminar flow. In addition, in the event of replacement, if necessary, of the component, this solution requires first releasing the screws or bolts under the filler mass. This is not feasible in practice, particularly when it comes to access doors which, unlike for example the leading edges of wings or empennages, are regularly dismantled or opened. For example, the access door for checking the oil level in the propellers is opened almost daily, so that it is not realistic to plan for the application of a filler mass and compliance with the curing times until the aircraft's next flight.

[0016] US 5,213,286 A discloses a concept for access doors or maintenance doors comprising a hinge mechanism actuated by a crank. The entire hinge mechanism is located in the interior of the flying object and takes up a considerable amount of space there, which is then no longer available for the actual technical devices. In addition, the hinge mechanism makes the flying object heavier, which goes against the principle of lightweight construction, particularly accompanying the use of a fiber composite material. Another disadvantage is that since the maintenance hatch opens by tilting outwards, its use seems unthinkable in places with corners or locations where the exterior area is cluttered.

[0017] A similar concept is also described in US 7,789,347 A, originally relating to a structure designated as a fan protection door, intended to allow wide access to the engine located in the nacelle. This door opens by tilting forward. In the closed state, the door is engaged in a receiving space while being pressed against the support at the rear, by means of an actuator or a spring preload.

[0018] US 5,368,258 describes a concept for actively maintaining laminar flow in a structure arranged in an intrinsically unfavorable manner. The problem of large gaps between the access door and the peripheral structure is solved by active suction of the boundary layer. The disadvantage here is to add a complex technical system to the aircraft which must be maintained and adds weight, in contradiction with the concept of lightweight construction.

[0019] Against this background, the aim of the present invention is to propose an improved method for manufacturing an external covering made of a fibrous composite material, with an access door, for flying objects, which makes it possible to manufacture, for flying objects, external coverings with an access door which promote a laminar boundary layer flow. Statement of the invention

[0020] The aim is achieved with a method for manufacturing such an exterior cladding as well as with an exterior cladding according to the invention. Advantageous embodiments are also proposed.

[0021] According to the invention, there is provided a method for manufacturing, for a flying object, an outer covering made of a fibrous composite material comprising a fibrous material and a matrix material embedding the fibrous material, the outer covering having an outer flow surface, an inner side opposite the outer flow surface and, in the flow surface, an opening for a door device for opening and closing the opening, the latter constituting, in the closed position, the outer flow surface portion of the opening. In particular, the inner side is generally neither exposed to the flow of an external medium nor visible from the outside, whereas the outer face or flow surface is generally visible from the outside.

[0022] The outer covering therefore has, in the flow surface, an opening intended to allow access to the inner zone of the flying object from the outer zone. The outer covering furthermore has, for opening and closing the opening, a door device which, in the closed position, constitutes the part of the outer flow surface of the opening. When the door device is in the closed position, the entire flow surface of the outer covering therefore consists on the one hand of the flow surface of the door device and on the other hand of the flow surface of the rest of the structure of the outer covering (outer covering with opening) which is provided all around the opening.

[0023] The fiber composite material can, in this case, be provided for the manufacture of the outer cladding in such a way that initially the fiber material and the matrix material are present separately. One can then speak of dry fiber material. Only after the fiber material has been introduced into the appropriate molding tool is the matrix material infused by an infusion process into the dry fiber material. However, the fiber composite material can also be provided in such a way that the fiber material is already infused with the matrix material, and one can then speak of "prepregs". In this case, the fiber material already infused with the matrix material is introduced into the appropriate molding tool, without it having to subsequently undergo an infusion process. Of course, this can nevertheless be carried out retrospectively, depending on the fiber composite material used.

[0024] According to the present invention, for the manufacture of the exterior cladding with opening (this refers to the exterior cladding without a door device in place), one provides first of all a molding tool having a smooth forming surface, which will give its shape to the outer flow surface of the outer covering with opening. The forming surface of the tool is here shaped so as to be able to reproduce the outer flow surface of the outer covering to be produced.

[0025] In the area of ​​the opening to be provided in the outer cladding, there is a core tool in the forming surface of the tool which corresponds to the door device in terms of shape and geometry. The core tool overhangs the remainder of the tool surface surrounding the core tool by a dimension corresponding to the door thickness, so that no fibrous material is deposited in this area intended to produce the opening in the outer cladding. Thus, in the area of ​​the core tool, the tool surface is occupied by the core tool in order to be able to form the corresponding opening in the outer cladding.

[0026] A first fibrous material is now introduced into the molding tool, by depositing it on the tool surface in a portion bordering the opening, all around the core-forming tool, in the form of a wedge rising towards the core-forming tool. This first fibrous material introduced into the molding tool is deposited inside the portion bordering the opening, in such a way that starting from the outer edge of the portion bordering the opening and starting from the forming surface of the tool, the first deposited fibrous material increases continuously, in a wedge shape, towards the upper edge of the core-forming tool. The first fibrous material is thus deposited in the portion bordering the opening by forming on the forming surface of the tool a ramp starting from the outer edge of the portion bordering the opening towards the core-forming tool.

[0027] Thus, after deposition on the forming surface of the tool, in the area of ​​the portion bordering the opening, the first fibrous material is configured in a ramp in the direction of the core-forming tool, so as to form a regular path from the forming surface of the tool located outside the portion bordering the opening, in the direction of the core-forming tool up to the upper edge of the latter, the latter overhanging the forming surface of the tool by the thickness of a door. In particular, there are no edges or projections on this regular path, which will allow an excess of fibrous material to be deposited there.

[0028] In the next step, after the introduction of the first fibrous material, at least a second fibrous material is introduced into the molding tool, depositing it on the tool surface outside the part bordering the opening and on the first fibrous material already deposited in the part bordering the opening, in such a way that the second fibrous material protrudes on the core-forming tool in order to constitute, on the external covering with opening, an internal stop of the opening.

[0029] The ramp or corner formed by the first fibrous material in the bordering portion the opening of the molding tool, now serves to deposit the second fibrous material which will essentially constitute the actual structure of the outer covering. Outside the portion bordering the opening, the second fibrous material serves to constitute the outer flow surface, while in the portion bordering the opening, it is the first fibrous material which constitutes the outer flow surface. In the direction of the core tool, the second fibrous material is deposited beyond the portion bordering the opening, until it protrudes at least partially over the core tool and at least partially covers it. The portion of the second fibrous material which protrudes over the core tool constitutes a stop for the opening which, seen from the outside, extends inwards into the area of ​​the opening when the component is demolded.

[0030] Then, the outer covering is manufactured by ensuring the consolidation of the matrix material in which the fibrous material is embedded. A matrix material that has already been consolidated will not be consolidated again.

[0031] The present manufacturing method has two major advantages. Firstly, the core tool, having the predefined door thickness corresponding to the thickness of a door element of the door device, makes it possible to produce in the area of ​​the opening a stop depth (distance between the outer flow surface and the stop of the opening) which, in the manufacturing process, is not dependent on variations in the thickness of the fiber composite material. On the contrary, the variations in thickness are kept as small as possible in order to contain the projection height with the greatest possible rigor. It is thus possible to produce in the opening, in a reproducible manner and framed by a reliable process, a stop depth corresponding to the thickness of the door element of the door device.If the gate device comprising the gate element is produced with the same precision, no edges or projections are formed on the outer flow surface in the closed state of the gate device, which would promote the transition of the boundary layer to a turbulent flow.

[0032] On the other hand, thanks to the core-forming tool and the deposition of the first fibrous material, the stop of the opening, formed in the opening of the outer covering, can be made of the same material from which the outer flow surface is made outside the part bordering the opening. In the area of ​​the opening, this same fibrous material from which the outer flow surface is made outside the part bordering the opening, is offset towards the interior space, so that it is unnecessary to attach a stop to the inner side of the outer covering using fixing means passing through the outer flow surface. It is therefore possible to dispense with these fixing means by which such a stop is fixed to the inner side of the outer covering (see [Fig.l]). On the contrary, the stop of the opening is integrally formed in the fibrous material of the core tool, the latter constituting the external flow surface outside the portion bordering the opening.

[0033] Another advantage of this method lies in the use of open-design molding tools for manufacturing the outer covering with an opening. Indeed, this method according to the invention does not require a closed molding tool to manufacture the outer covering in accordance with the desired dimensions. Instead, an open molding tool can be used, although open-design molding tools lead, in practice, to variations in thickness. Thus, after the introduction of all the fibrous materials, a vacuum is created under which the introduced fibrous material is sealed. The fibrous material is then placed under a vacuum and, if necessary, infused with a matrix material. Under the action of pressure and / or temperature, for example in an autoclave, the matrix material is consolidated under vacuum.Despite the resulting variations in the dimensional tolerance in the thickness direction, it is thus possible to ensure, within the framework of a reliable process, a well-defined stop depth for the gate device, in order to promote, for a corresponding gate device, a suitable laminar flow of the boundary layer.

[0034] The door device for closing the opening in the exterior cladding has, in this case, a door element which, from the point of view of the extent of its surface, corresponds to the shape and geometry of the opening and which, in particular, has, within the tolerances, a thickness corresponding to the door thickness, i.e. to the depth of the stop. The door device may also have other elements intended to improve stability.

[0035] According to one embodiment, the molding tool for manufacturing the exterior trim being a first molding tool, a second molding tool is provided for manufacturing the corresponding door device, such that the second molding tool has on the one hand a forming surface intended to give its shape to the outer flow surface of the door device and on the other hand a cavity whose depth corresponds to the door thickness dimension of the core tool of the first molding tool, fibrous material is introduced into the second molding tool by depositing the fibrous material in the intended cavity of the second molding tool, and the door device is manufactured by consolidating the matrix material embedding the fibrous material.

[0036] Thus, in a subsequent step of the method, it is also possible to manufacture the door device for the exterior cladding. The door device is manufactured using a second molding tool having a cavity whose depth corresponds to the door thickness dimension of the core tool of the first molding tool. The bottom of the cavity can, in this regard, constitute a forming surface of this tool, giving its shape to the outer flow surface of the door device. This makes it possible to manufacture, in a reliable process, a door device whose door element has a thickness corresponding to the door thickness dimension or the stop depth of the outer cladding with opening.

[0037] Because the two methods match each other for the door thickness dimension, an outer covering is obtained with a door device which, in the closed position, has no projection or edge likely to tend to change the boundary layer from laminar flow to turbulent flow.

[0038] According to one embodiment in this regard, a second at least partially closed molding tool is provided, which comprises on the one hand a first molding tool half having the cavity and on the other hand at least one second molding tool half, and after the introduction of the fibrous material into the cavity of the first molding tool half, the second molding tool is closed by means of the at least one second molding tool half, so that the second molding tool half covers the fibrous material at least in an edge portion adjacent to the edge of the cavity.

[0039] The use of a closed molding tool exclusively for the door device makes it possible to significantly reduce the manufacturing costs of an outer cladding with a door device, since the outer cladding with an opening is manufactured in a molding tool of open design. The closed molding tool for the door device is, in this case, more advantageous during manufacturing and ensures, in a reliable process, compliance with the appropriate door thickness dimension, which must correspond to the door thickness dimension or the stop depth of the outer cladding. Thus, it is possible to manufacture, in a reliable process, an outer cladding with a door device conducive to laminar flow of the boundary layer.

[0040] According to one embodiment, the molding tool for manufacturing the exterior trim is a first molding tool, a second molding tool is provided for manufacturing the corresponding door device, such that the second molding tool has a forming surface intended to give its shape to the outer flow surface of the door device, fibrous material is introduced into the second molding tool, depositing it on the surface of the second molding tool to form a fibrous preform for manufacturing the door device, a vacuum blanket is established above the fibrous preform, the door device is manufactured by consolidating the matrix material embedding the fibrous material, and, while continuously detecting the thickness of the fiber preform using a sensor device during consolidation of the matrix material, using a control device, parameters of the consolidation process are adjusted depending on the detected thickness of the fiber preform and a predefined thickness setpoint.

[0041] In this embodiment, a molding tool of open design can also be used for the production of the door device, the thickness of the door element or the door device being monitored using a sensor device. If a deviation from the predefined thickness setpoint is detected by means of the sensor device, then, using a control device, the adjustable parameters of this process are adjusted or changed during the consolidation process in order to approach the predefined setpoint. The adjustable parameters of such a process can be, for example, those of an autoclave process. In this case, it is in particular parameters such as the temperature and / or pressure curve or the temperature and / or pressure that can be adjusted.

[0042] According to one embodiment, it is provided that after having provided a suitable door device, it is inserted into the opening of the exterior cladding produced and it is applied by a part of the edge of the door against the stop of the opening of the exterior cladding.

[0043] According to one embodiment, provision is made in this regard to apply the door device with gluing against the stop of the opening of the exterior cladding.

[0044] According to one embodiment, by means of several mechanical connecting elements, the door device is applied by clamping and / or locking against the stop of the opening of the exterior cladding by introducing the connecting elements into the stop of the opening of the exterior cladding, from the outside through the edge part of the door.

[0045] In this embodiment, the door device is fixed to the inner stop of the opening by clamping and / or locking, using screws or rivets passing through the outer flow surface of the door device. If necessary, the connecting elements can be loosened and the door device removed in order to allow access to the interior space.

[0046] According to one embodiment, it is provided to insert the connecting elements only on two opposite sides of the edge portion of the door. On the other two sides of the edge portion of the door, no connecting elements are then inserted.

[0047] In this case, it may be provided that the two sides of the edge portion of the door where the connecting elements are provided extend along a main direction of flow passing through the outer flow surface under the conditions of use in accordance with the intended purpose. The connecting elements are thus arranged one behind the other relative to the main direction of flow, which makes it possible to to minimize the harmful influence of these connecting elements, which constitute a disturbance in the external flow surface. It is therefore only along these sides that the boundary layer switches to a turbulent flow, while a laminar flow of the boundary layer remains favored in the other areas of the gate device.

[0048] The other two sides of the door edge part, not provided with connecting elements, are then oriented transversely to the main flow direction.

[0049] According to a particular embodiment, it is provided that the molding tool provided for the manufacture of the outer covering is such that the smooth forming surface of the tool has a curvature in at least one direction of curvature to give the outer covering a curved outer flow surface, and a door device is provided having in this at least one direction of curvature, a curvature less than that of the outer covering.

[0050] .

[0051] If the door device is now inserted into the opening of the outer cladding, which also follows the curvature of the outer cladding, the door device can only rest with the entire circumference of its door stop against the stop of the opening of the outer cladding if the door device adopts the curvature of the outer cladding. It is therefore particularly advantageous if the door device is only fixed against the opening stop of the outer cladding on those sides of the door edge part which each form a respective end of the curvature. The door device can thus be inserted under tension into the opening of the outer cladding, which allows the door device to rest with the other two sides against the opening stop and to be pressed against it.

[0052] According to a particular embodiment, it is provided to provide, from the first fibrous material, a wedge-shaped insert comprising a recess for the core-forming tool, and the wedge-shaped insert is deposited on the tool surface in the part bordering the opening, by introducing the core-forming tool into the recess of the wedge-shaped insert.

[0053] The wedge-shaped insert is here formed from the first fibrous material and is introduced in one piece into the molding tool. In this case, it can be provided that the wedge-shaped insert has been manufactured separately in a prior step of the process. In this case, the wedge-shaped insert can be obtained from dry fibrous material, pre-impregnated fibrous material (prepreg), or be partially consolidated, pre-consolidated or perfectly consolidated. "Partially consolidated" means here that the matrix material is only consolidated in certain parts of the wedge-shaped insert. "Pre-consolidated" means that the matrix material is not yet completely consolidated.

[0054] According to one embodiment, it is provided to form the wedge-shaped insert from a material containing glass or carbon fibers, as the first fibrous material.

[0055] According to one embodiment, provision is made to provide at least one internal locking mechanism which is fixed to the inner side of the outer cladding and to an inner side of the door device, and which is brought into interaction with an actuating lever accessible from the outside, so that by means of the internal locking mechanism, the door device is brought from an open position to the closed position in which the door device is pressed by its door stop against the internal stop of the opening of the outer cladding

[0056] It is thus possible to hold the door device from the inside, so that connecting elements passing through the outer flow surface to fix the door device can be dispensed with. Only the actuating lever remains in the outer flow surface, which minimizes the tendency of the boundary layer to adopt a turbulent flow.

[0057] The invention will be explained below through its characteristics and the following combinations of characteristics.

[0058] Method for manufacturing, for a flying object, an outer covering made of a fibrous composite material comprising a fibrous material and a matrix material embedding the fibrous material, the outer covering having an outer flow surface, an inner side opposite the outer flow surface and, in the flow surface, an opening for a door device for opening and closing the opening, the latter constituting, in the closed position, the outer flow surface portion of the opening, characterized in that the method comprises the following steps:

[0059] - providing a molding tool for manufacturing an outer covering with an opening, such that the molding tool has a smooth forming surface, intended to give its shape to the outer flow surface of the outer covering with an opening and comprises, in the tool surface located in the area of ​​the opening to be produced, a core-forming tool which overhangs the rest of the tool surface by a dimension corresponding to a door thickness, - introducing a first fibrous material into the molding tool, by depositing it on the tool surface in a part bordering the opening, all around the core-forming tool, in the shape of a wedge rising towards the core-forming tool, - introducing at least a second fibrous material into the molding tool, by depositing it on the tool surface outside the bordering part the opening and on the first fibrous material already deposited in the part bordering the opening, in such a way that the second fibrous material protrudes on the core-forming tool in order to constitute, on the external covering with opening, an internal stop of the opening, manufacture the exterior cladding with opening by consolidation of the unconsolidated matrix material embedding the fibrous material.

[0060] Advantageously, the method is further characterized in that the tool of molding for the manufacture of the exterior cladding is a first molding tool, the process having the following additional steps:

[0061] provide a second molding tool for the manufacture of the device corresponding gate, such that the second molding tool has on the one hand a forming surface intended to impart its shape to the outer flow surface of the gate device and on the other hand a cavity whose depth corresponds to the gate thickness dimension of the core tool of the first molding tool, introducing fibrous material into the second molding tool by depositing the fibrous material in the intended cavity of the second molding tool, and manufacture the door device by consolidating the matrix material embedding the fibrous material.

[0062] According to one of its improvements, the method is characterized in that that a second, at least partially closed molding tool is provided, which comprises on the one hand a first molding tool half having the cavity and on the other hand at least one second molding tool half, and that after the introduction of the fibrous material into the cavity of the first molding tool half, the second molding tool is closed by means of the at least one second molding tool half, so that the second molding tool half covers the fibrous material at least in an edge portion adjacent to the edge of the cavity.

[0063] Advantageously, the method according to the invention is further characterized in that the molding tool for manufacturing the exterior trim is a first molding tool, the method comprising the following additional steps:

[0064] provide a second molding tool for the manufacture of the device corresponding gate, such that the second molding tool has a forming surface intended to impart its shape to the outer flow surface of the gate device, introducing fibrous material into the second molding tool, depositing it on the surface of the second molding tool to form a fiber preform for the manufacture of the door device, - establishing a vacuum cover over the fiber preform and manufacturing the door device by consolidating the matrix material embedding the fiber material, - while the thickness of the fiber preform is continuously detected using a sensor device during the consolidation of the matrix material and, using a control device, parameters of the consolidation process are adjusted according to the detected thickness of the fiber preform and a predefined thickness setpoint.

[0065] After obtaining a suitable door device, it can be inserted into the opening of the exterior cladding produced and applied by a part of the edge of the door against the stop of the opening of the exterior cladding. Advantageously, the door device is applied with adhesive against the stop of the opening of the exterior cladding.

[0066] By means of several mechanical connecting elements, the door device can be clamped and / or locked against the stop of the opening of the outer covering by inserting the connecting elements into the stop of the opening of the outer covering from the outside through the edge portion of the door. Advantageously, the connecting elements are inserted only on two opposite sides of the edge portion of the door.

[0067] In one embodiment, the molding tool provided for manufacturing the outer covering is such that the smooth forming surface of the tool has a curvature in at least one direction of curvature to give the outer covering a curved outer flow surface, and a door device is provided having, in this at least one direction of curvature, a curvature less than that of the outer covering.

[0068] According to the invention, it may be provided that from the first fibrous material a wedge-shaped insert is provided having a recess for the core-forming tool, and the wedge-shaped insert is deposited on the tool surface in the portion bordering the opening, by introducing the core-forming tool into the recess of the wedge-shaped insert. Advantageously, the wedge-shaped insert provided may be partially consolidated, pre-consolidated or fully consolidated and, if appropriate, the wedge-shaped insert may be formed from a material containing glass or carbon fibers, as the first fibrous material.

[0069] In one embodiment of the invention, at least one internal locking mechanism is provided which is fixed to the inner side of the outer trim and to an inner side of the door device, and which is brought into interaction with an operating lever accessible from the outside, so that by means of the locking mechanism internal rusting, the door device is brought from an open position to the closed position in which the door device is pressed by its door stop against the internal stop of the opening of the external cladding.

[0070] The invention also comprises an exterior covering obtained in accordance with the method defined above. List of figures

[0071] The invention will now be described further by means of examples using the attached figures. They show:

[0072] [Fig.l]: Principle of attachment to a nacelle, according to the state of the art

[0073] [Fig.2a]: Schematic representation of the manufacture of the exterior cladding with opening

[0074] [Fig.2b]: Representation of an exterior cladding manufactured according to [Fig.2a]

[0075] [Fig.3]: Schematic representation of the manufacture of the door device

[0076] [Fig.4]: Schematic representation of a fixing principle in accordance with a first embodiment

[0077] [Fig.5]: Schematic representation of a fixing principle in accordance with a second embodiment

[0078] [Fig. 1] shows a principle of attachment to the outer casing of a thruster casing, as known from the state of the art. All around the existing opening in which the door is intended to be inserted (also called "access door"), a support mounted on the inner side is held by means of fastening means passing through the outer flow surface. The door is screwed onto the part of the support which protrudes into the opening. [Fig. 1] shows in the outer flow surface both the means for fastening the support to the outer casing and the means for fastening the door to the support, which constitute a disturbance on the outer flow surface. The present invention aims to avoid this.

[0079] [Fig.2a] schematically illustrates the manufacture of an exterior covering 10 with opening 13, in cross-section. We begin by providing a first molding tool 100, having a forming surface 110 which will have to give its shape to the future external flow surface 11 of the external covering 10. In the exemplary embodiment presented, the first forming surface 110 of the tool is of flat conformation, which, in practice, will however generally be replaced by a curved or slightly curved surface in order to reproduce in a corresponding manner the desired shape for the external covering. Such a slightly curved component is moreover shown in [Fig.2b], as it can be manufactured according to the method of [Fig.2a].

[0080] In the embodiment of [Fig.2a], a core forming tool 120 is also provided, placed on a part of the forming surface 110 of the core forming tool. molding 100. But it is also conceivable that the core-forming tool 120 is an integral part of the molding tool 100. The core-forming tool 120 is, in this case, introduced into the area where the future opening 13 of the outer covering 10 to be manufactured will be located. The core-forming tool 120 thus occupies the space that the future opening 13 will take, so as to prevent any deposit of fibrous material there.

[0081] The core forming tool 120 rises a gate thickness dimension d above the remainder of the forming surface 110 of the tool. The gate thickness dimension d ultimately defines the depth of the opening to a stop which will be discussed in detail later.

[0082] In the first step, a first fibrous material 20 is deposited in a portion 130 bordering the opening of the forming surface 110 of the tool and extending over a certain distance all around the core-forming tool 120. The portion 130 bordering the opening thus defines a portion which extends all around the core-forming tool 120 and which will constitute, once the component has been created, a portion bordering the opening 13.

[0083] In this portion 130 bordering the opening, the first fibrous material 20 is now deposited in the form of a wedge or ramp rising towards the core-forming tool, such that the first fibrous material 20 stops, flush, at the upper edge 122 of the core-forming tool 120. From the forming surface 110 of the molding tool 100, the first fibrous material 20 rises in the form of a wedge or ramp to this upper edge 122 of the core-forming tool 120, thus extending regularly and rising continuously above the forming surface 110 of the tool, up to the upper edge 122 to which a surface 124 of the core-forming tool is connected.

[0084] The first fibrous material 20 is here deposited in this manner, preferably all around the entire core-forming tool 120.

[0085] In the next step, a second fibrous material 21 is introduced into the molding tool 100 and is deposited on the one hand on the molding surface 110 of the tool, outside the portion 130 bordering the opening, but also on the first fibrous material 20 deposited in the shape of a wedge or ramp on the portion 130 bordering the opening, as well as partially on the upper surface 124 of the core-forming tool 120. The portion of the second fibrous material 21 deposited at least partially on the upper surface 124 of the core-forming tool therefore protrudes at least partially over the core-forming tool 120, thus forming an inner stop 14 of the opening, against which the door device (not shown), which will be inserted later, will abut in the closed position.

[0086] Due to the core forming tool 120 and the first fibrous material 20 deposited in a wedge or ramp shape in the portion 130 bordering the opening of the core forming tool core 120, the second fiber material which constitutes the outer flow surface 11 outside the opening 13 and the portion 130 bordering the opening, is deflected inwards or towards the interior space or towards the inner side 12, so that an opening stop 14 offset inwards is integrally formed in the second fiber material 21, which constitutes the outer flow surface 11 itself. It is thus not necessary to provide additional connecting elements in the portion 130 bordering the opening for fixing an additional inner stop, as is the case in the prior art (see [Fig.l]).

[0087] The outer flow surface 11 of the outer covering 10 is in this case, in the area of ​​the part 130 bordering the opening, formed not only from a part of the second fibrous material 21 but also from the first fibrous material 20.

[0088] It is here possible to deposit the second fibrous material 21 over the entire upper surface 124 of the core-forming tool. In this case, in a later step of the process, an opening will be made in the second fibrous material 21 in order to allow appropriate access to the interior space. This simplifies the deposition of the second fibrous material 21 but requires an additional step in the process.

[0089] This method for manufacturing an outer covering 10 also makes it possible to reproduce, within the framework of a reliable process, the gap between the outer flow surface 11 of the outer covering and the stop 14 of the opening, independently of the thickness variations which occur during the consolidation of the matrix material, so that the stop depth thus defined (gap between the outer flow surface 11 and the stop 14 of the opening) no longer depends only on the tolerances allowed in the manufacture of the core-forming tool 120.

[0090] Represented schematically in [Fig.2a], the structure developed for the manufacture of the outer covering 10 may further be covered by a vacuum assembly (not shown) before being placed under vacuum, to allow the matrix material to be infused into the fibrous material and then consolidated in an autoclave process. It thus becomes possible to manufacture such outer coverings for flying objects in a molding tool of open design, without having to fear variations in the stop depth which would then result in ridges or projections in the outer flow surface 11 after closing of the door device, conducive to a turbulent boundary layer.

[0091] [Fig. 3] schematically represents the manufacture of the corresponding door device 30, by means of a molding tool of closed design. For this purpose, a second molding tool 200 is provided which, in a first half of the molding tool 210, has a cavity 230 into which the fibrous material 31 is introduced. Then, when the cavity 230 is filled with fibrous material 31, the molding tool 200 is closed by means of a corresponding second tool half 220. The matrix material, contained in the fibrous material 31 of the cavity 230 or which can be infused into the fibrous material 31 after introduction thereof, is now consolidated in order to produce the door device 30.

[0092] The use of a molding tool of closed design makes it possible to reproduce, within the framework of a reliable process, the thickness of the door device 30, given by the predefined height h of the cavity 230 (defined between the bottom of the cavity 230 and the inner face of the upper half of the molding tool 220), so that the thickness variations depend solely on the manufacturing precision of the molding tool 200. The height h of the cavity 230 corresponds here to the height of the core tool 120, which in turn corresponds to the thickness dimension of the door. The door device to be manufactured 30 is thus perfectly adapted to the opening of the outer covering 10 formed using the core tool 120, without leaving any edges or projections in the outer flow surface.With this manufacturing process, it is possible to use an open design molding tool at least for the manufacture of the outer casing in order to produce an outer casing that promotes laminar flow.

[0093] The first fibrous material 20 shown in [Fig. 2a] can be introduced here in the form of a wedge-shaped insert having a recess into which the core tool 120 can be introduced. The wedge-shaped insert is, in this case, preconfigured so that it can be inserted entirely into the portion 130 bordering the opening. The wedge-shaped insert thus already has the desired wedge or ramp shape.

[0094] [Fig. 4] is a cross-section AA of the area of ​​the stop 14 of the opening as shown in [Fig. 2a]. The outer covering 10 has in the embodiment example of [Fig. 4] a curvature that the door device 30 that will be inserted must follow, in order to be able to perfectly cover the opening 13 in the closed position of the door device 30. The latter has, in this case, a smaller curvature than that of the outer covering 10. In other words, the radius of curvature of the outer covering 10 is here less than the radius of curvature of the door device 30. The door device 30 may also have no curvature and be configured as a planar or flat element.

[0095] The door device 30 is first fixed using connecting elements 40 on a first side 41 of a door edge portion. On the second, opposite side 42 of the door edge portion, the door device is somewhat spaced from the stop 14 of the opening of the outer covering 10, because the door device 30, instead of following the curvature of the outer covering 10, has a lesser curvature than that of the outer cladding 10, or even has no curvature at all. The door device is then pressed by its second opposite side 42 onto the stop 14 of the opening of the outer cladding 10 and then it is also fixed on its second side 42 to the outer cladding 10, using connecting elements 40, for example screws or rivets. This forces the door device 30 to adopt the curvature of the outer cladding 10, so that it rests flush against the peripheral stop 14 of the opening of the outer cladding 10. It is thus possible to fix such a door device 30 only on the two sides transverse to the direction of the curvature: these are generally the sides of the outer cladding which lie along the main flow direction. This makes it possible to reduce disturbances on the outer flow surface to a minimum.

[0096] The door device 30 is then fixed under a certain prestress against the stop 14 of the opening. The connecting elements 40 are here arranged in such a way that for each side, the alignment axis of the connecting elements 40 corresponds to the main flow direction to which the door device 30 is exposed in the context of use in accordance with the intended purpose. The main flow direction generally corresponds to the straight-line movement of the flying object.

[0097] [Fig. 5] shows another embodiment in which a locking mechanism 50 holds the door device 30 in the closed position from the inside. A lever device 51, cooperating with an actuating lever 52, exerts a closing force on the door device 30 in the closed position in the direction of the inner side 12 of the outer casing 10, in order to hold the door device 30 in the closed position. The door device 30 is, in this case, pressed by its door stop 32 against the stop 14 of the opening of the outer casing. By acting on the lever 52, the closing force exerted on the door device 30 is released via the lever device 51, and the door device 30 can be extracted from the opening 13 and brought into the open position.

[0098] In this embodiment, only the actuating lever 52 constitutes a disturbance on the external flow surface, while it is possible to dispense with any other connecting element. List of references

[0099] 10 Exterior cladding

[0100] 11 Outer flow surface

[0101] 12 Inner side

[0102] 13 Opening

[0103] 14 Opening stop

[0104] 20 First fibrous material

[0105] 21 Second fibrous material

[0106]

[0107]

[0108]

[0109]

[0110] [YES]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124] 30 Door device 31 Fiber material of the door device 32 Door stop 40 Connecting elements 41 First side of the door stop / opening stop 42 Second side of the door stop / opening stop 50 Locking mechanism 51 Lever device 52 Actuating lever 100 Molding tool / first molding tool 110 Forming surface of the first molding tool 120 Core forming tool 122 Upper edge of core forming tool 124 Surface of core forming tool 130 Portion bordering opening 200 Molding tool / second molding tool 210 First half of second molding tool 220 Second half of second molding tool 230 Cavity of second molding tool

Claims

1. Claims Method for manufacturing, for a flying object, an outer covering (10) from a fibrous composite material comprising a fibrous material and a matrix material embedding the fibrous material, the outer covering (10) having an outer flow surface (11), an inner side (12) opposite the outer flow surface and, in the flow surface, an opening (13) for a door device (30) for opening and closing the opening (13), the latter constituting, in the closed position, the outer flow surface portion (11) of the opening (13), characterized in that the method comprises the following steps: - providing a molding tool for producing an outer covering (10) with an opening (13), such that the molding tool has a smooth forming surface, intended to give its shape to the outer flow surface (11) of the outer covering (10) with an opening (13) and comprises, in the tool surface located in the region of the opening (13) to be produced, a core tool (120) which overhangs the remainder of the tool surface by a dimension corresponding to a door thickness, - introducing a first fibrous material (20) into the molding tool, by depositing it on the tool surface in a portion (130) bordering the opening, all around the core-forming tool (120), in the shape of a wedge rising towards the core-forming tool (120), - introducing at least one second fibrous material (21) into the molding tool, by depositing it on the tool surface outside the portion (130) bordering the opening and on the first fibrous material (20) already deposited in the portion (130) bordering the opening, in such a way that the second fibrous material (21) protrudes onto the core-forming tool (120) in order to constitute, on the outer covering (10) with opening (13), an inner stop (14) of the opening, - manufacture the exterior cladding (10) with opening (13) by consolidating the unconsolidated matrix material embedding the fibrous material.

2. Method according to claim 1, characterized in that the molding tool for manufacturing the outer trim (10) is a first molding tool (100), the method having the following additional steps: - providing a second molding tool (200) for manufacturing the corresponding door device (30), such that the second molding tool (200) has on the one hand a forming surface intended to impart its shape to the outer flow surface (11) of the door device (30) and on the other hand a cavity whose depth corresponds to the door thickness dimension of the core tool (120) of the first molding tool (100), - introducing fibrous material into the second molding tool (200) by depositing the fibrous material in the provided cavity (230) of the second molding tool (200),and - manufacturing the door device (30) by consolidating the matrix material embedding the fibrous material.,

3. Method according to claim 2, characterized in that a second molding tool (200) is provided which is at least partially closed, and which comprises on the one hand a first molding tool half (210) having the cavity and on the other hand at least one second molding tool half (220), and in that after the introduction of the fibrous material into the cavity of the first molding tool half (210), the second molding tool (200) is closed by means of the at least one second molding tool half (220), so that the second molding tool half (200) covers the fibrous material at least in an edge portion adjacent to the edge of the cavity.

4. Method according to claim 1, characterized in that the molding tool for manufacturing the exterior cladding (10) is a first molding tool (100), the method comprising the following additional steps: providing a second molding tool (200) for manufacturing the corresponding door device (30), such such that the second molding tool (200) has a forming surface intended to impart its shape to the outer flow surface (11) of the gate device (30), - introducing fiber material into the second molding tool (200), depositing it on the surface of the second molding tool (200) to form a fiber preform for manufacturing the gate device (30), - establishing a vacuum cover over the fiber preform and manufacturing the gate device (30) by consolidating the matrix material embedding the fiber material, - while the thickness of the fiber preform is continuously detected by means of a sensor device during the consolidation of the matrix material and, by means of a control device, parameters of the consolidation process are adjusted depending on the detected thickness of the fiber preform and a predefined thickness setpoint.

5. Method according to one of the preceding claims, characterized in that after having provided a suitable door device (30), this is inserted into the opening (13) of the outer covering (10) produced and is applied by an edge part of the door against the stop (14) of the opening of the outer covering (10).

6. Method according to claim 5, characterized in that the door device (30) is applied with glue against the stop (14) of the opening of the external cladding (10).

7. Method according to claim 5 or 6, characterized in that by means of several mechanical connecting elements (40), the door device (30) is applied by clamping and / or locking against the stop (14) of the opening of the outer covering (10) by introducing the connecting elements (40) into the stop (14) of the opening of the outer covering, from the outside through the edge part of the door.

8. Method according to claim 7, characterized in that the connecting elements (40) are inserted only on two opposite sides of the door edge part.

9. Method according to one of the preceding claims, characterized in that the molding tool provided for the manufacture of the external covering (10) is such that the smooth forming surface of the tool has a curvature in at least one direction of curvature to give the outer covering (10) a curved outer flow surface (11), and a door device (30) is provided having in this at least one direction of curvature, a curvature less than that of the outer covering (10).

10. Method according to one of the preceding claims, characterized in that from the first fibrous material (20), a wedge-shaped insert is provided having a recess for the core-forming tool (120), and the wedge-shaped insert is deposited on the tool surface in the part bordering the opening (130), by introducing the core-forming tool (120) into the recess of the wedge-shaped insert.

11. A method according to claim 10, characterized in that the wedge-shaped insert provided is partially consolidated, pre-consolidated or fully consolidated.

12. A method according to claim 10 or 11, characterized in that the wedge-shaped insert is formed from a material containing glass or carbon fibers as the first fiber material (20).

13. Method according to one of the preceding claims, characterized in that at least one internal locking mechanism (50) is provided, which is fixed to the inner side (12) of the outer covering (10) and to an inner side (12) of the door device (30), and which is brought into interaction with an actuating lever (52) accessible from the outside, so that by means of the internal locking mechanism (50), the door device (30) is brought from an open position to the closed position in which the door device (30) is pressed by its door stop (32) against the internal stop (14) of the opening of the outer covering (10).

14. Exterior cladding (10) obtained in accordance with the method according to one of the preceding claims.

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