Apparatus and process for producing structural elements in composite materials - Patents.com

Abstract

The present invention relates to an apparatus (10) for making a structural element (1) of composite material having a longitudinal axis (A) and an axial cavity (2). The apparatus (10) comprises a support frame (11) and a lamination mandrel (12) mounted on the support frame (11) so as to be rotatable about its central axis (B) and defining an outer lamination surface (13), the support frame (11) comprising two vertical headers (14, 15) facing each other and parallel to each other, and longitudinal connection means (16) for longitudinally connecting the headers (14, 15), each header (14, 15) comprising a fixed part (17) and a movable part (18) for coaxially receiving the lamination mandrel (12) and rotatable about the central axis (B) relative to the fixed part (17), the lamination mandrel (12) comprising a central shaft (26, 26'), a plurality of sectors (30) angularly spaced apart about the central axis (B), and a central shaft (26'). , 26') and each of the sectors (30) for moving the sectors (30) themselves between an extended stacking position and a contracted position, and the device (10) further includes first restraining means (35) for releasably connecting the sectors (30) arranged in the extended stacking position to the movable parts (18) of the headers (14, 15), and second restraining means (36) for releasably connecting the linear actuators (31) to the sectors (30) such that, when the sectors (30) are in the extended position and connected to the movable parts (18) of the headers (14, 15) by the first restraining means (35), the linear actuators (31) and the sectors (30) can be removed from the device (10).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application is related to Italian Patent Application No. 102022000007511, filed on April 14, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to an apparatus and process for making structural elements in composite materials having a longitudinal axis and an axial cavity.

[0003] It should be noted that the term "for making a structural element in a composite material" covers not only the operations or steps for making a structural element, including the passage through an autoclave, but also the subsequent operations or steps of inspecting and finishing the previously made structural element, as well as any further operations or steps of assembling this structural element with other structural elements.

[0004] In particular, the invention finds advantageous, but not exclusive, application in the construction of closed or open structural elements, for example aircraft fuselages or fuselage sections. [Background technology]

[0005] In the aerospace sector, to which the following description explicitly refers without loss of generality, structural elements of the type defined above, made of composite materials, are well known, the use of which is driven by the need to reduce the total weight of aircraft and to eliminate or minimize corrosion problems in aircraft structures.

[0006] In the most common solutions, the composite material used is a fibrous material, e.g., carbon fiber, pre-impregnated with epoxy resin, BMI, or other uncured or pre-cured material. The material is deposited in a mold and then processed under temperature and pressure. Other methods use dry fibers, which are usually impregnated with a flowing resin according to well-known processes (e.g., by a method known as "resin transfer molding" or RTM).

[0007] Typically, a structural element of the above mentioned type, such as a fuselage or part thereof, is made by combining a skin in composite material with a number of stiffening stringers, also made of composite material and usually arranged parallel to the axis of the fuselage or part thereof.

[0008] In particular, each stringer typically one or two lateral longitudinal flanges suitable for bonding to the skin; a raised portion of a predetermined shape protruding laterally from the flange; The bar is defined by a thin-walled longitudinal section including:

[0009] The stringers most commonly used in the industry have Omega, T, L, J or Z cross sections.

[0010] The cycle for building these types of structural elements or parts thereof usually consists of the following steps, namely: Fabrication, Trimming and / or drilling, Non-destructive and dimensional inspection, Surface finish, and assembly Includes.

[0011] Of the many processes for producing structural elements of the above type, the most commonly used are listed below.

[0012] According to a first mode of operation, to manufacture a stringer, multiple layers of uncured composite material are placed on a suitably shaped forming tool.

[0013] Once the stringers are manufactured, they are removed from the forming tool and placed into respective recesses in a tool called a mandrel; after this operation, further layers of uncured composite material are laid down and overlapped onto the stringers placed in the recesses of the mandrel to produce the skin.

[0014] The assembly thus formed then undergoes a co-curing operation in an autoclave by applying appropriate pressure and temperature in order to cure the composite material, compress the aforementioned layers together and bond the stringers to the skins.

[0015] In practice, each stringer is rigidly and integrally applied to one face of the skin, normally the face defining the inner wall of the skin, ie the one which, in use, faces the inside of the fuselage.

[0016] This completes the steps for creating the structural element.

[0017] According to another mode of operation, a skin made by laminating together several layers of uncured composite material is bonded by means of a structural adhesive to stringers which have previously been pre-cured after their formation.

[0018] Again, the assembly so formed is placed in an autoclave and subjected to appropriate pressures and temperatures to cure the new composite material, compress the several plies together, and bond the stringers to the skins, an operation commonly referred to in the industry as co-bonding.

[0019] The co-bonding operation can also be performed by pre-curing only the skin and bonding it to the uncured stringers with a structural adhesive.

[0020] According to a further mode of operation, both the skins and stringers can be pre-cured and then bonded together by a structural adhesive, an operation commonly referred to in the industry as bonding, which can be carried out either in an autoclave or cold.

[0021] Depending on the specific application, there are configurations in which longitudinal stringers are integrated into the skins, or other so-called sandwich configurations in which there are two skins separated by a closed or open cell filler.

[0022] Again, the skins are laminated onto a mandrel and cured with appropriate stiffeners (sandwiches, embedded skins, etc.) at appropriate pressures and temperatures.

[0023] In summary, in a co-curing process, the components to be cured (skin and stiffeners) are both "new", in a co-bonding process, one of the elements (skin or stiffener) is already cured, and in a bonding process, both elements are cured.

[0024] Once the curing process is complete, the structural elements thus formed are trimmed (the laminate material of the skin is increased from the nominal value) and, if required, drilled according to the project requirements.

[0025] Once the structural elements are obtained, as required by the project, they will be subjected to non-destructive testing to verify their feasibility.

[0026] The dimensions are also measured to ensure there are no "outside tolerances."

[0027] As a result of this inspection, rework may be required, if necessary, to restore the product characteristics required by the project.

[0028] The application of a protective coating is a necessary preparatory step for the next step, where the composite material must be protected against contact with metallic materials, especially aluminum, UV rays, moisture, and others as required by the project.

[0029] Once all the above work is complete, the flow of fabricating these structural elements is completed by installing on top of them other stiffened and non-stiffened elements as required by the project and which complete the construction.

[0030] There is a need in the field to optimize the process for making these structural elements by minimizing the overall setup time and flow.

[0031] For the same reasons, there is also a need to create a single device that makes it possible to complete the entire production cycle described above in a simple and efficient manner.

[0032] Finally, there is also a need to be able to use the same device to create structural elements with different longitudinal and diametric dimensions relative to the longitudinal axis, allowing the same device to be used for different applications and / or programs. [Prior art documents] [Patent documents]

[0033] [Patent Document 1] EP2644359B1 Summary of the Invention [Problem to be solved by the invention]

[0034] One object of the present invention is to provide an apparatus for producing structural elements in a composite material having a longitudinal axis and an axial cavity, which is reliable, cost-effective and capable of meeting at least one of the requirements defined above and associated with the aforementioned apparatus of known type. [Means for solving the problem]

[0035] According to the invention, this object is achieved by a device as claimed in claim 1.

[0036] Another object of the present invention is to provide a process for making a structural element in a composite material having a longitudinal axis and an axial cavity, which makes it possible to meet in a simple and inexpensive manner at least one of the requirements defined above and associated with the known types of processes described above.

[0037] According to the invention, this object is achieved by a process as defined in claim 13.

[0038] In order that the invention may be better understood, a preferred, non-limiting embodiment will now be described, purely by way of example and with the aid of the accompanying drawings, in which: [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is a perspective view, with parts removed for clarity, of a structural element in composite material, in particular a portion of an aircraft fuselage, made using the apparatus and process according to the invention; [Diagram 2] 2 is a perspective view, with parts removed for clarity, of the support frame of the device according to the invention for producing the structural element in FIG. 1; FIG. [Figure 3A] FIG. 3 is a front view, with parts removed for clarity, of a lamination mandrel of a device according to the invention, mounted on the support frame in FIG. 2 and intended to be placed in a retracted position; [Figure 3B] FIG. 3B is a reduced perspective view of the lamination mandrel in FIG. 3A carried by a handling trolley. [Figure 4] FIG. 4 is a perspective view, with parts removed for clarity, of the central shaft of the lamination mandrel in FIGS. 3A and 3B equipped with a linear actuator; [Diagram 5]FIG. 5 is an exploded perspective view, with parts removed for clarity, of a possible variant of the central shaft in FIG. 4, consisting of a basic module identical to the central shaft in FIG. 4, and an auxiliary module. [Figure 6] FIG. 5 is a perspective view, with parts removed for clarity, of the basic and auxiliary modules of the variant in FIG. 4 during assembly. [Figure 7] FIG. 5 is a perspective view, with parts removed for clarity, of the basic and auxiliary modules of the variant in FIG. 4 assembled together. [Figure 8] FIG. 1 is a perspective view, with parts removed for clarity, of an apparatus according to the invention in a preparatory step for a lamination operation with uncured or precured composite material; [Figure 9] FIG. 9 is a side view, with parts removed and parts enlarged for clarity, of the detail in FIG. 8. [Figure 10A] FIG. 9 is a side view, with parts removed and parts enlarged for clarity, of the inner detail of the lamination mandrel shown in FIG. 8. [Figure 10B] FIG. 9 is a side view, with parts removed and parts enlarged for clarity, of the inner detail of the lamination mandrel shown in FIG. 8. [Figure 11] FIG. 9 is a perspective view, with parts removed and parts scaled down for clarity, of the apparatus shown in FIG. 8 in a further preparatory step for the lamination operation, in which the central shaft and linear actuator in FIG. 4 have been removed from the rest of the apparatus by the trolley shown in FIG. 3B. [Figure 12] 9 is a side view, with parts removed and parts scaled down for clarity, of the apparatus in FIG. 8 at the end of a lamination operation; FIG. [Figure 13] FIG. 13 is a side view of the apparatus in FIG. 12 at the end of the curing and finishing cycle. [Figure 14] 14 is a side view of the apparatus in FIG. 13 after removal of the laying mandrel from the stiffening structural element, at a stage when this structural element is supported only by the support frame. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] With reference to FIG. 1, the number 1 indicates, as a whole, a first example of a structural element in a composite material produced using the device and process that are the object of the present invention.

[0041] In particular, the description makes explicit reference, without thereby losing generality, to structural elements used in the aeronautical field, such as aircraft fuselages or parts of fuselages, and to processes for producing these structural elements.

[0042] According to the preferred embodiment described and illustrated herein, the structural element 1 is intended to be part of an aircraft fuselage (known per se and not illustrated).

[0043] More precisely, the structural element 1 has a longitudinal axis A and is provided with an axial through-bore 2. In practice, the structural element 1 is a body of revolution having an axis A; in the present case, the structural element 1 has a cylindrical shape with axis A.

[0044] Alternatively, the structural element 1 may be substantially similar to a body of revolution having an axis A. For example, it may not have a constant cross-section along the axis A, but may have a tapered configuration towards one of its axial ends. The structural element 1 includes a skin 3 made of composite material and a series of hollow longitudinal stiffening stringers 4 with closed sections.

[0045] The stringers 4 extend parallel to the axis A, in the present case along the entire axial length of the structural element 1 .

[0046] In one embodiment, the composite material used is a fiber material, e.g., carbon fiber, pre-impregnated with epoxy resin, BMI, or other uncured or pre-cured material. The material is deposited in a mold and then processed under temperature and pressure. Other methods use dry fiber, which is usually impregnated with a flowing resin according to well-known processes (e.g., by a method known as "resin transfer molding" or RTM).

[0047] In the solution depicted in the attached figures, the structural element 1 is obtained by rigidly and integrally applying the stringers 4 to the skin 3, such that each stringer 4, together with the skin 3 itself, delimits a hollow section with a closed contour.

[0048] As can be seen in Figure 1, each stringer 4 comprises two lateral flanges 5 suitable for bonding to the skin 3, and a raised portion 6 centrally located between the flanges 5 and projecting relative to them and having a concave shape on one side. In particular, in the example shown, the stringers 4 have an omega cross-section.

[0049] Alternatively, the stringers 4 intended to create a hollow section closed by the skin 3 may have a cross section of different shapes, for example a circular arc, semicircular, rectangular, polygonal, semi-elliptical, semi-oval, etc.

[0050] 2 to 14 show an apparatus (and its components) according to the invention for producing a structural element 1. The apparatus is generally designated by the reference number 10.

[0051] In particular, the apparatus 10 includes a support frame 11 (shown separately in FIG. 2) and a laying mandrel 12 (shown separately in FIG. 3A), which is mounted to the support frame 11 so as to be rotatable about its own central axis B, and which defines an outer laying surface 13 onto which one or more layers of composite material to be cured or pre-cured are intended to be laid, as will be described in more detail below.

[0052] The support frame 11 essentially comprises two vertical headers 14, 15 facing each other and parallel to each other, and one or more, in this case two, longitudinal cross members 16 extending between the headers 14, 15 and connecting them at a predetermined distance.

[0053] More specifically, the headers 14, 15 are capable of receiving the lamination mandrel 12 between them and, for this purpose, extend transversely, in particular perpendicularly, to the axis B of the lamination mandrel 12 itself.

[0054] Each header 14, 15 includes a fixed portion 17 and a movable portion 18 which coaxially receives the lamination mandrel 12 and is rotatable about an axis B relative to the fixed portion 17.

[0055] As can be seen in Figures 2, 8 and 11, the fixed part 17 of each header 14, 15 externally surrounds a respective mobile part 18, which has a cylindrical outer shape of axis B and is mounted through the fixed part 17 itself by the interposition of washers and / or bushings, which are known per se and are not shown, so that the mobile part 18 of each header 14, 15 can rotate about axis B relative to the respective fixed part 17.

[0056] Both movable parts 18 of the headers 14, 15 are centrally provided with respective central through openings 20, 21 which in the present case have a circular contour and are identical to each other.

[0057] According to a possible alternative not shown, the openings in the movable part of the header can have different diameters or sizes, in particular if it is necessary to create a structural element with a tapered configuration towards one of its axial ends.

[0058] Preferably, each header 14, 15 is mounted to a respective pair of height-adjustable guide posts 22. In particular, when stably positioned on a floor surface, the guide posts 22 project downwardly from each header 14, 15 and from the longitudinal cross-members 16 to define respective support legs 23 for resting the support frame 11 on the floor surface.

[0059] The longitudinal cross-members 16 also have an adjustable length parallel to the axis B, and for this purpose, according to a preferred embodiment, each longitudinal cross-member 16 is formed by two bars 16a, 16b mounted coaxially so that they can slide on the guide rods 24.

[0060] Furthermore, the longitudinal cross members 16 are preferably provided with wheels 25, which allow the device 10 to be moved after the headers 14, 15 have slid on their respective guide posts 22 until the wheels 25 themselves come into contact with the floor surface and simultaneously hide the support legs 23.

[0061] All the described adjustments make it possible to adapt the support frame 11 to different sizes of the lamination mandrel 12 and thus of the structural elements 1 to be produced, both in the longitudinal direction, i.e. parallel to the axis B, and in height.

[0062] The height adjustment of the headers 14, 15 also makes it easier to adapt the entire apparatus 10 to different sized autoclaves, as will be explained in more detail below.

[0063] 3A, 3B, 4, 8 and 11, the lamination mandrel 12 is a central shaft 26 (FIG. 4) of axis B, which in this case has a polygonal, in particular hexagonal, profile; a plurality of sectors 30 angularly spaced about an axis B; a plurality of linear actuators 31, in this case telescopic actuators or jacks, extending between the central shaft 26 and the respective sectors 30 for moving the sectors 30 between an extended stacking position (FIGS. 3B, 8 and 11) in which said sectors 30 are adjacent to one another at a maximum distance from the central shaft 26 and define a stacking plane 13, and a retracted position (FIG. 3A) in which said sectors 30 are adjacent to the central shaft 26 and partially overlap one another; Includes.

[0064] Preferably, central shaft 26 carries an externally cantilevered linear actuator 31 .

[0065] According to the variants shown in Figures 5, 6 and 7, a central shaft, here shown as 26', can consist of a basic module 26a' and one or more auxiliary modules 26b', which can optionally be axially connected to one (27) or both (27, 28) of the ends of the basic module 26a', or to the already assembled auxiliary module 26b' itself, in order to increase the axial length of the central shaft 26'.

[0066] In the example shown in Figures 5, 6 and 7, the central shaft 26' consists of a basic module 26a' having the same length as the central shaft 26, and an auxiliary module 26b' connected to the end 27 of the basic module 26a'.

[0067] 3A, 3B, 10A, 10B and 11, the sectors 30 consist of respective curved panels bounded, towards the central shaft 26, by respective inner surfaces 29a and, on the opposite side, by respective outer surfaces 29b forming respective parts of the stacking surface 13.

[0068] The sectors 30 have on their outer surface 29b one or more longitudinal recesses or grooves 32 configured to receive the previously formed stringers 4 prior to the step of contacting them with the skin 3 and to support them during that same step and in subsequent hardening steps or operations, as will be better explained below.

[0069] Advantageously, the process of making the structural element 1 further comprises, following the step of forming the stringers 4 and before the step of bringing them into contact with the skin 3, a not shown longitudinal insert, commonly known as a "bladder", disposed inside the raised portion 6 of each stringer 4, so that when the skin 3 and the respective stringer 4 come into contact with each other, each of said inserts is entirely contained within a cavity formed between them.

[0070] 3A, 3B, 4, 10A and 10B, and 11, each linear actuator 31 includes a hollow casing or tubular sleeve 33 fixed to and cantilevered externally from a central shaft 26, and one or more rods 34 that slide into the sleeve 33 and / or relative to any other rods 34.

[0071] By moving the rod 34, each linear actuator 31 can assume a different overall length ranging from a minimum length to a maximum length, with the rod 34 of each linear actuator 31 protruding from its respective sleeve 33 in at least a configuration other than the minimum length.

[0072] The maximum stroke of the rod 34 of each linear actuator 31 can be adjusted as a function of the morphology of the sectors 30 and the maximum radial occupation of the stacking surface 13 defined by the sectors 30 themselves.

[0073] Advantageously (FIGS. 2, 8, 9, 10A, 10B and 11), the device 10 comprises: a first restraining member 35 for releasably connecting the sector 30 in the extended stack position to the movable portion 18 of the header 14, 15; a second restraining member 36 releasably connecting the linear actuator 31 to the sector 30 such that the central shaft 26 and the linear actuator 31 can be removed from the support frame 11 with the sector 30 placed in the extended position and connected to the movable part 18 of the header 14, 15 by the restraining member 35; Further includes:

[0074] In particular, in the example shown, the restraining members 35 extend parallel to the axis B and include respective bolts 35 a which releasably connect the movable parts 18 of the headers 14 , 15 to both axial edges of the sectors 30 .

[0075] In particular, each bolt 35a engages a corresponding hole 35b, 35c provided in the movable portion 18 of the associated header 14, 15 and in the associated sector 30, respectively.

[0076] The sectors 30 are also connected to one another in the extended stack position by a system of known type described in patent EP 2 644 359 B1 in the name of the same applicant.

[0077] According to a possible alternative, not shown, the arresting member 35 may be a closure or connection that can be electronically operated to make the sector 30 integral with the movable part 18 of the header 14,15.

[0078] In the illustrated example (see in particular Figures 10A and 10B), each restraining member 36 includes an engagement seat 37 provided in the respective sector 30 and a connecting head 38 carried by the end rod 34 of the respective linear actuator 31 and suitable for being connected in a releasable manner to the engagement seat 37 itself.

[0079] In particular, in the solution shown here, the coupling head 38 of each linear actuator 31 is movable between a contracted configuration (FIG. 10A) in which it can freely move in and out of its respective engagement seat 37, and an extended configuration (FIG. 10B) in which it projects radially relative to the remainder of the rod 34 so that it can be held to itself by being coupled to the engagement seat 37.

[0080] Referring to FIG. 14, the headers 14, 15 of the support frame 11 further include a number of gripping members 40 which are movable between a rest position housed within the respective headers 14, 15 and a working position in which they protrude from the respective headers 14, 15 and hold both axial edges of the stiffened structural element 1 to enable the lamination mandrel 12 to be removed from the structural element 1 itself through the central opening 20 of the headers 14.

[0081] In particular, the gripping member 40 is movable between a rest position parallel to the axis B and a working position.

[0082] The gripping members 40 are also carried by the movable portions 18 of the respective headers 14,15.

[0083] With the gripping member 40 positioned in the working position to hold the hardened structural element 1, the linear actuator 31 causes the sector 30 to be displaced from the extended lamination position to the contracted position, making it possible to remove the lamination mandrel 12 from the structural element 1.

[0084] The insertion and removal of the lamination mandrels 12 into and from the support frame 11, as well as the insertion and removal into and from the sectors 30 of the central shaft 26 with the linear actuators 31, is preferably performed by a handling trolley 41 shown in Figures 3B and 11.

[0085] In particular, the handling trolley 41 includes two horizontal longitudinal bars 42 on which wheels 43 are mounted, and headers 44 perpendicular to the longitudinal bars 42 and overlapping respective adjacent ends thereof.

[0086] The longitudinal bar 42 is designed to slide under the longitudinal cross-member 16 of the support frame 11 so that, in use, the header 44 is positioned opposite and parallel to one of the headers 14,15.

[0087] The header 44 of the handling trolley 41 is also equipped with restraining means, known per se and not shown, such as bolts, for integrally connecting the central shaft 26 which is cantilevered perpendicular to the header 44.

[0088] In use, to make a structural element 1, the first step is to prepare the apparatus 10 for the lamination operation.

[0089] In particular, the sectors 30 , which are connected to respective linear actuators 31 by restraining members 36 , are positioned in a retracted position adjacent the central shaft 26 .

[0090] At this point, the lamination mandrel 12 with its sectors 30 in the retracted position is inserted, with the help of a handling trolley 41, through one of the central openings 20, 21 of the headers 14, 15 inside the support frame 11 between the headers 14 and 15 themselves.

[0091] The sectors 30 are then moved to the extended stacked position by actuating the linear actuators 31. The sectors 30, still held in the extended stacked position, are then connected to the movable parts 18 of the headers 14, 15 by means of restraining members 35 (FIG. 8).

[0092] At this point, the restraining members 36 can be released to decouple the linear actuators 31 from their respective sectors 30 and retract the linear actuators 31 towards the central shaft 26 .

[0093] In this state, the central shaft 26 with the linear actuator 31 retracted can be removed from the support frame 11 (Figure 11), again with the help of the handling trolley 41, and thus can be used in parallel for other applications, for example for producing another structural element 1.

[0094] Lamination onto the lamination surface 13 of the lamination mandrel 12 can then begin in a conventional manner.

[0095] In particular, previously formed, uncured or pre-cured stiffening stringers 4 are inserted into the respective grooves 32 of the sectors 30 in combination with noodles and bladders.

[0096] The skin 3 is then formed by laminating several required layers of uncured or pre-cured composite material on the layup surface 13 and on the stringers 4 and on different types of inserts placed in the grooves 32 (Figure 12).

[0097] During the laying operation, the sector 30 is rotated about the axis B together with the movable parts 18 of the headers 14,15.

[0098] Upon completion of the lay-up operation, the apparatus 10 with the laminated composite material is transferred into an autoclave (known per se and not shown) to carry out a curing cycle.

[0099] Transportation can be advantageously effected by hiding the support legs 23 within the respective headers 14, 15 and by resting the wheels 25 on a floor surface on which they can slide.

[0100] At the end of the curing cycle, the support frame 11 and sectors 30 are removed from the autoclave to continue with the conventional steps to complete the fabrication of the structural element 1.

[0101] In particular, the stiffened structural element 1 is trimmed (the laminated material of the skin 3 is increased from the nominal value) and, if required, drilled according to the project requirements. As can be seen in figure 13, both axial edges of the stiffened structural element 1 are cut and subjected to finishing operations (figure 13). These operations are carried out while the laying mandrel 12 remains attached to the support frame 11 and carries the stiffened structural element 1 externally.

[0102] At this point, the central shaft 26 and linear actuator 31 are then reinserted through the central opening 20 of the header 14 and into the sector 30 with the aid of the handling trolley 41. In addition, the linear actuator 31 is reconnected to the sector 30 by the restraining member 36 (FIG. 10B).

[0103] The gripping members 40 are then moved from the rest position to the working position, where they project from the respective headers 14,15 and hold both axial end edges of the structural element 1. In practice, the structural element 1 is mounted on the headers 14,15.

[0104] In this working condition, when the displacement of the sectors 30 from the extended laying position to the retracted position is carried out by the linear actuators 31 , it is possible to remove the laying mandrel 12 from the structural element 1 .

[0105] The lamination mandrel 12 may then be removed from the support frame 11 through one of the central openings 20,21 of the headers 14,15, again with the aid of the handling trolley 41.

[0106] The structural element 1 thus produced has its longitudinal axis A coinciding with the axis B of the laying mandrel 12 .

[0107] In this condition, it is possible that the structural element 1 is connected to the movable parts 18 of the headers 14, 15 and thus that the structural element 1 itself can rotate about its axis A which coincides with axis B, and a series of non-destructive tests can be carried out to verify this possibility.

[0108] The structural element 1 is also subjected to dimensional measurements to ensure there are no "out-of-tolerance" conditions.

[0109] As a result of this inspection, rework may be required, if necessary, to restore the product characteristics required by the project.

[0110] In this step it is also possible to apply a protective paint to the structural element 1, which is thus protected against contact with metal materials, especially aluminium, UV rays, moisture and others as required by the project.

[0111] Once all the above operations are completed, the flow of fabricating the structural element 1 is completed by installing on top of it other stiffening and non-stiffening elements required by the project and which complete the construction.

[0112] This step can also be advantageously carried out by leaving the structural element 1 connected to the movable parts 18 of the headers 14 , 15 of the support frame 11 .

[0113] The advantages made possible by the present invention are apparent from a consideration of the above-described and illustrated features of device 10 and the process for making same.

[0114] In particular, the described solution allows in a simple manner the optimization of the working area required for the manufacture of a structural element 1, such as an aircraft fuselage section with a constant or tapering cross section.

[0115] In fact, the manufacturing process, including the actual fabrication, finishing and drilling operations, quality and dimensional checks, as well as the installation of additional stiffening elements, can be completed entirely on the apparatus 10, and parts of the lamination mandrel 12 (central shaft 26 and linear actuator 31) can be reused in parallel for the manufacture of other structural elements, even if of different size (e.g. axial length and diameter), thereby reducing the cost and time of the manufacturing process.

[0116] Furthermore, the apparatus 10 is very flexible and suitable for use in making structural elements of different axial and radial sizes as well as for adapting to different sized autoclaves.

[0117] Finally, it is apparent that modifications and variations can be made to the device 10 and the process for making said device 10 as described and illustrated herein without departing from the scope of protection defined by the claims. [Explanation of symbols]

[0118] 1 Structural elements 2 cavities 3. Skin 4 Stringer 5 Flange 6 Raised area 10 equipment 11 Support frame 12 Stacked Mandrel 13 Laminated surface 14 Header 15 Header 16 Crosspiece 16a Bar 16b Bar 17 Fixed part 18 Moving parts 20 aperture 21 Aperture 22 Guide post 23 Support legs 24 Guide rod 25 wheels 26 Central shaft 26' central shaft 26a' Basic Module 26b' Auxiliary Module 27 End 28 End 29a Inside 29b External surface 30 sectors 31 Linear Actuator 32 Groove 33 Sleeve 34 Rod 35 First restraining member 35a Bolt 35b hole 35c hole 36 Second restraining member 37 Engagement seat 38 Connecting Head 40 Gripping member 41 Handling Trolley 42 Longitudinal bar 43 wheels 44 Header

Claims

1. An apparatus (10) for producing a structural element (1) of composite material having a longitudinal axis (A) and an axial cavity (2), said apparatus (10) comprising: A support frame (11); a laying mandrel (12) mounted on said support frame (11) in a rotatable manner about its central axis (B) and defining an outer laying surface (13) on which one or more layers of composite material to be cured or precured are intended to be laid; Including, The support frame (11) is two vertical headers (14, 15) facing each other and parallel to each other, extending in use transversely to the central axis (B) of the lamination mandrel (12) and capable of receiving the lamination mandrel (12) itself therebetween; a longitudinal connection means (16) for connecting the headers (14, 15) in the longitudinal direction; Including, Each header (14, 15) includes a fixed portion (17) and a movable portion (18) that coaxially receives the lamination mandrel (12) and is rotatable about the central axis (B) relative to the fixed portion (17); The lamination mandrel (12) is a central shaft (26, 26') defining said central axis (B); a plurality of sectors (30) angularly spaced about said central axis (B); a plurality of linear actuators (31) extending between the central shaft (26, 26') and each of the sectors (30) for moving the sectors (30) themselves between an extended stacking position in which the sectors (30) are adjacent to one another at a maximum distance from the central shaft (26, 26') to define the stacking plane (13) and a contracted position in which the sectors (30) are adjacent to the central shaft (26, 26') and partially overlap one another; Including, The device (10) also includes a first restraining means (35) for releasably connecting the sector (30) in the extended stacked position to the movable portion (18) of the header (14, 15); a second restraining means (36) for releasably connecting the linear actuator (31) to the sector (30) so as to enable the central shaft (26, 26') and the linear actuator (31) to be removed from the device (10) when the sector (30) is placed in the extended stacking position and connected to the movable part (18) of the header (14, 15) by the first restraining means (35); 13. An apparatus comprising:

2. 2. The apparatus of claim 1, wherein the movable part (18) of at least one of the headers (14, 15) has a central opening (20, 21) through which the lamination mandrel (12) or the assembly formed by the central shaft (26, 26') and the linear actuator (31) can be inserted into / removed from the support frame (11).

3. 3. The apparatus according to claim 2, wherein the headers (14, 15) further comprise gripping members (40) which are movable between a rest position housed within the respective headers (14, 15) and a working position protruding from the respective headers (14, 15) and holding both end edges of the hardened structural element (1) to enable the lamination mandrel (12) to be removed from the structural element (1) itself through the central opening (20, 21).

4. 4. Apparatus according to claim 3, wherein the gripping member (40) is movable between the rest position parallel to the central axis (B) and the working position.

5. 5. Apparatus according to claim 3 or 4, wherein the gripping members (40) are carried by the movable parts (18) of the respective headers (14, 15).

6. 6. Apparatus according to any one of claims 3 to 5, wherein displacement of the sectors (30) from the extended laying position to the contracted position by the linear actuator (31) results in removal of the laying mandrel (12) from the hardened structural element (1).

7. 7. The device according to claim 1, wherein each of the linear actuators (31) comprises a tubular sleeve (33) fixed to the outside of the central shaft (26, 26') and at least one rod (34) which slides relative to the tubular sleeve (33) and sets a position protruding by different amounts from the tubular sleeve (33) itself, the maximum stroke of the rod (34) of each of the linear actuators (31) being adjustable as a function of the configuration of the sectors (30) and the maximum radial occupation area of ​​the stacking surface (13) defined by the sectors (30) themselves.

8. 8. The device according to claim 7, wherein the second restraining means (36) comprises, for each of the linear actuators (31), a free end head (38) of the respective rod (34) releasably coupled with an engagement seat (37) of the respective sector (30).

9. 9. Apparatus according to any one of the preceding claims, wherein each of the headers (14, 15) is mounted on a guide post (22) which is height adjustable.

10. 10. The device according to claim 9, wherein the guide posts (22) project downwards from each of the headers (14, 15) to define respective support legs (23) of the support frame (11), and the longitudinal connection means (16) are provided with wheels (25) enabling the device (10) to be moved after the headers (14, 15) have slid on the respective guide posts (22) until the wheels (25) themselves come into contact with the floor surface and at the same time the support legs (23) are hidden.

11. 11. Apparatus according to any one of the preceding claims, wherein the longitudinal connection means comprises at least a pair of longitudinal cross members (16) extending between the headers (14, 15) and having an adjustable length.

12. 12. The apparatus according to claim 1, wherein the central shaft (26') comprises a basic module (26a') and one or more auxiliary modules (26b'), the auxiliary modules (26b') being optionally axially connectable to one or both head ends of the basic module (26a') or to the auxiliary module (26b') itself, once already assembled, in order to increase the axial length of the central shaft (26') itself.

13. A process for producing a structural element (1) of composite material having a longitudinal axis (A) and an axial cavity (2) by means of a device (10) according to any one of claims 1 to 12, comprising: (a) connecting said sector (30) to said linear actuator (31) and positioning said sector (30) itself in said contracted position on said central shaft (26, 26'); (b) mounting the lamination mandrel (12) with the sectors (30) in the retracted position onto the support frame (11); (c) moving the sectors (30) by the linear actuators (31) to the extended stacked position; (d) connecting the sector (30) in the extended stacked position to the movable portion (18) of the header (14, 15) by the first restraining means (35); (e) releasing the second restraining means (36) to decouple the linear actuator (31) from the sector (30); (f) retracting the linear actuator (31) towards the central shaft (26, 26'); (g) removing the central shaft (26, 26') with the linear actuator (31) retracted from the support frame (11); (h) laying an uncured or pre-cured composite material onto said laying surface (13) of said sector (30); (i) transporting said support frame (11) and said sectors (30) attached thereto together with said laminated composite material to an autoclave to carry out a curing cycle; (l) removing the assembly of step (i) from said autoclave; (m) reinserting the central shaft (26, 26') with the linear actuator (31) inside the sector (30) and connecting the linear actuator (31) to the sector (30) itself by the second restraining means (36); (n) attaching the hardened structural element (1) to the headers (14, 15); (o) retracting the sectors (30) by the linear actuator (31) into the retracted position on the central shaft (26, 26') while activating the second restraining means (36); (p) removing said lamination mandrel (12) in said contracted position by said sector (30) from said hardened structural element (1) and said support frame (11); The process includes:

14. 14. The process according to claim 13, wherein step (n) is carried out by moving a gripping member (40) to a working position in which the gripping member (40) holds both end edges of the hardened structural element (1) and thereby fixes them to the headers (14, 15).

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