METHOD FOR MANUFACTURING A COMPOSITE PART WITH REINFORCING ELEMENT AND A COMPOSITE PART OBTAINED BY SUCH A METHOD

Abstract

The invention relates to a method for manufacturing a part (1) made of composite material comprising a fibrous reinforcement (10) embedded in a matrix, the method comprising the following steps: - creating a first structure (11) and a second structure (12) layered and comprising a plurality of superimposed fiber layers, - applying the second structure onto the first structure, - impregnating the first structure and / or the second structure with a matrix, and - densifying the first and second structures to obtain a rigid composite part. According to the invention, the method includes a step of arranging at least one reinforcing element (14) comprising thermoplastic fibers at an interlaminar interface (13) between the first structure (11) and the second structure (12) so as to reinforce the interlaminar interface (13). Figure for the abstract: Fig. 1

Description

Title of the invention: METHOD FOR MANUFACTURING A COMPOSITE MATERIAL PART WITH REINFORCING ELEMENT AND COMPOSITE MATERIAL PART OBTAINED BY SUCH A METHOD Technical field of the invention

[0001] The present invention relates to the field of composite material parts made from a fiber reinforcement densified by a matrix, in particular turbomachine parts. It relates in particular to parts made from laminated structures. Technological background

[0002] Composite material parts are increasingly used to improve their thermomechanical resistance capabilities and reduce their masses. These composite material parts find their application in the aeronautical, automotive, etc. fields where they are exposed to high temperatures.

[0003] Certain composite materials are usually composed of a fibrous reinforcement and a matrix. The fibrous reinforcement may be an arrangement of several laminated structures which are of different shapes and which are bonded together at one or more interlaminar interfaces. A risk of delamination or lack of strength may arise at the interlaminar interfaces, particularly when the part is subjected to high mechanical loads.

[0004] To overcome these drawbacks, tough resins have been used to densify the fiber reinforcement. So-called tough resins are generally loaded with microstructures and are more viscous, and / or include a suitable chemical formulation. However, such a resin can make it difficult to impregnate the fibers of the fiber reinforcement. All of the different laminated structures can be linked by stitching using structural threads for example, which can be expensive.

[0005] There is a need to resolve all or part of the aforementioned drawbacks. Summary of the invention

[0006] The objective of the present invention is to provide a simple, economical and robust solution which makes it possible to reinforce the junction of laminated fibrous structures.

[0007] We achieve this objective in accordance with the invention by means of a method for manufacturing a part made of composite material comprising a fibrous reinforcement embedded in a matrix, the method comprising the following steps: - production of a first laminated structure comprising a plurality of layers of superimposed fibers and intended to form a skin of the part in composite material, - production of a second laminated structure comprising a plurality of layers of superimposed fibers and intended to form a stiffener having a predetermined shape, the stiffener extending from a surface of the skin, - applying the second structure to the first structure so that at least a portion of the second structure is in contact at an interlaminar interface with the first structure, - impregnation of the first structure and / or the second laminated structure with a polymer matrix, and - densification of the first structure and the second laminated structure so as to obtain a part made of rigid composite material, the method comprising a step of arranging at least one reinforcing element comprising fibers of thermoplastic material at the interlaminar interface between the first structure and the second structure so as to reinforce the interlaminar interface.

[0008] Thus, this solution makes it possible to achieve the aforementioned objective. In particular, the thermoplastic fiber reinforcing element makes it possible in a very simple manner to increase the interlaminar cohesion between the first laminated structure and the second laminated structure forming the fiber reinforcement. This induces a significant improvement in the mechanical strength and the peel threshold of the composite material part obtained by this method.

[0009] The method also comprises one or more of the following features and / or steps, taken alone or in combination:

[0010] - the stiffener has a cross section in I, T, C, U, J, L or in Q (in omega capital letter).

[0011] - the matrix comprises a thermosetting resin.

[0012] - the reinforcing element has a surface mass of between 2 and 30 g / m2 and a transverse permeability of at least 5% of its surface.

[0013] - the thermoplastic material of the reinforcing element comprises a polyamide, a polyethylene, a polyetherimide, a polyphenylene sulfide, a polyethylene terephthalate or a combination thereof.

[0014] - the reinforcing element comprises a chemical binder or an organic binder and / or nanotube fillers and / or carbon fibers.

[0015] - the reinforcing element is fixed to at least one of the first and second fibrous structures at the interlaminar interface, for example by sewing or gluing.

[0016] - the second structure comprises fibrous legs intended to form legs of the stiffener, each fibrous leg extending on either side of a lateral portion which is intended to form part of the body of the stiffener.

[0017] - one or more reinforcing elements extend across the width of each leg fibrous and on either side of the lateral portion of the second structure.

[0018] - each fibrous leg comprises two layers which extend in directions opposite and parallel to the direction of the first stratified structure.

[0019] - the reinforcing element comprises layers of fibers which extend along the direction of the first structure and the layers of fibers that extend within each lateral portion.

[0020] - the reinforcing element has an inverted T shape, the reinforcing element forcement is located between the layers of each fibrous leg and at the interlaminar interface.

[0021] - - the reinforcing element is configured to form a connecting node in which a fibrous profile is housed.

[0022] - - the connecting node has a triangular shape.

[0023] - - the reinforcing element has a housing intended to accommodate a structure fibrous.

[0024] - - the reinforcing element comprises a web which extends parallel to the first structure.

[0025] - - the reinforcing element comprises a fibrous profile arranged between the web and a fibrous leg.

[0026] — the reinforcing element comprises a web and a fibrous profile arranged at minus one end of a fibrous leg.

[0027] — the veil is arranged between the first structure and a fibrous profile.

[0028] - the impregnation step is carried out prior to the production steps, prea possibly at the application stage or after the application stage.

[0029] - the first structure and / or the second structure comprises pre-fibers impregnated.

[0030] - the first laminated structure and the second laminated structure are separately densified facing and in that the method comprises a step of fixing the second densified structure on the first densified structure.

[0031] The invention also relates to a composite material part obtained by such a method. The part comprises a skin and at least one stiffener extending from a surface of the skin, the stiffener having a cross-section in the shape of I, T, C, U, L, J, or Q.

[0032] The invention relates to an aircraft turbomachine equipped with such a part made of composite material.

[0033] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given as purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

[0034] - [Fig.l] is a perspective view of a part made of composite material of tur- machine equipped with stiffeners according to the invention;

[0035] - [Fig.2] is a schematic, detailed and perspective view of an example of part made of composite material comprising a fibrous reinforcement embedded in a matrix and having a complex shape according to the invention;

[0036] - [Fig.3] is a perspective view of an example of a fibrous reinforcement or preform with laminated structures according to the invention;

[0037] - [Fig.4] illustrates in a sectional view a fibrous reinforcement with structures laminates bonded together at an interlaminar interface according to the invention;

[0038] - [Fig.5] represents another example of an interlaminar interface between laminated structures according to the invention;

[0039] - [Fig.6] illustrates yet another embodiment of an interlaminar interface between laminated structures of a fibrous reinforcement according to the invention;

[0040] - [Fig.7] illustrates yet another embodiment of a laminar interface between laminated structures according to the invention;

[0041] - [Fig.8] is a sectional view of another embodiment of an interface laminar between laminated structures of a fibrous reinforcement according to the invention;

[0042] - [Fig.9] represents a second structure of a fibrous reinforcement intended to form an I-shaped stiffener according to the invention;

[0043] - [Fig. 10] represents a second structure of a fibrous reinforcement intended to form a J-shaped stiffener according to the invention;

[0044] - [Fig. 11] represents a second structure of a fibrous reinforcement intended to form a T-shaped stiffener according to the invention;

[0045] - [Fig. 12] represents a second structure of a fibrous reinforcement intended to form an L-shaped stiffener according to the invention;

[0046] - [Fig. 13] represents a second structure of a fibrous reinforcement intended to form a C-shaped stiffener according to the invention;

[0047] - [Fig. 14] represents a second structure of a fibrous reinforcement intended to form a U-shaped stiffener according to the invention; and,

[0048] - [Fig. 15] represents an example of a flowchart of a manufacturing process of a part made of composite material according to the invention.

[0049] [Fig. 1] represents a part 1 made of composite material. The part 1 made of composite material comprises a skin 2 and at least one stiffener 3. The part 1 is intended to equip a turbomachine. In particular, the part 1 made of composite material is substantially cylindrical (close to a barrel) with a longitudinal axis X and comprises several stiffeners 3. In [Fig. 1], the part 1 comprises several stiffeners 3. The stiffeners 3 extend around the longitudinal axis X or extend along the longitudinal axis, and rise radially from the skin 2.

[0050] Of course, the part 1 made of composite material could be used in various fields where thermomechanical performance and mass reduction are required, such as automobiles and astronautics.

[0051] Skin 2 can be defined globally in a plane or have a curved surface as is the case in [Fig.l].

[0052] With reference to [Fig. 2], the skin 2 advantageously, but not limitingly, has a thickness el of between 1 mm and 5 mm. Advantageously, but not limitingly, its thickness el is substantially constant according to its dimensions. The thickness el is measured between a first surface 2a and a second surface 2b. The thickness el is less than the length L1 and the width 11 of the skin 1. The length L1 represents the largest dimension in [Fig. 1].

[0053] Each stiffener 3 extends from one of the first surface 2a and second surface 2b of the skin 2. Each stiffener 3 makes it possible to stiffen and / or provide mechanical strength to the skin 2 so as to withstand significant loads and high temperatures. For this purpose, at least one stiffener 3 has a cross-section of predetermined shape such as a Q (capital omega), I, C, U, or T shape. Alternatively, at least one stiffener 3 has a J- or L-shaped cross-section.

[0054] The composite material part 1 illustrated in [Fig.l], comprises a first stiffener 3a in capital I (with tabs at each end), a second stiffener 3b in Q, and a third stiffener in J (with a tab at one of the ends). The second stiffener 3b in Q is arranged between the first stiffener 3a and the third stiffener 3c along the longitudinal axis X. Another arrangement of these stiffeners 3a, 3, 3c could be envisaged.

[0055] The part 1 made of composite material further comprises a fourth stiffener 3d and a fifth stiffener 3e which each extend along the longitudinal axis X. The fourth and fifth stiffeners 3d, 3e each have a Q shape. The fourth and fifth stiffeners 3d, 3e are placed on either side of the second stiffener 3b. In particular, the fourth stiffener 3d extends along the longitudinal axis X between the first stiffener 3a and the second stiffener 3b while the fifth stiffener 3e extends along the longitudinal axis X between the second stiffener 3b and the third stiffener 3c. Other fourth and fifth stiffeners may be arranged diametrically opposite these or be regularly distributed around the longitudinal axis X.

[0056] Advantageously, but not limitatively, each stiffener 3 has a height hl (taken transversely to the skin) of between 5 and 100 mm. Each stiffener 3 is generally elongated and has a length L2 substantially parallel to the surface 2a from which the stiffener 3 extends. The length L2 is greater than a width 12 of the stiffener 3. The width 12 of the stiffener 3 (in a direction parallel to that of the skin) may be between 15 mm and 150 mm. Advantageously, each stiffener 3 has a thickness of between 1 mm and 7 mm.

[0057] Each stiffener 3 formed has a main body 4 and at least one leg 5 which is connected to the skin 2. The main body 4 extends at a distance from the skin 2.

[0058] In the case of [Fig.2], the stiffener has a Q shape. More precisely, the (Omega) stiffener comprises a main body 4 and two legs 5a, 5b which extend transversely from the main body 4. The two legs 5a, 5b are connected to the skin 2.

[0059] The height of the Q-shaped stiffener is between 7 and 70 mm and the width is between 20 and 100 mm. Preferably, the height is 7 mm and the width 40 mm or the height 70 mm and the width 50 mm.

[0060] Alternatively, the stiffener 3 has a T or L shape with a main body 4 and a single tab 5. The tab 5 extends transversely from the main body 4 and is connected to the skin 2. For example, the height of the T or L stiffener has a height which is between 10 mm and 50 mm.

[0061] In the case of a stiffener 3, in particular the first stiffener 3a having an I-shaped section as shown in [Fig.l], the latter comprises a main body 4 which extends transversely between two legs 5a, 5b. The main body 4 extends transversely relative to the surface of the skin 2. One of the legs 5 makes it possible to connect the I-shaped stiffener to the skin 2. Advantageously, the legs 5a, 5b are parallel to each other.

[0062] In the case of the third J-shaped stiffener 3c with reference to [Fig.l], this comprises a main body 4 which extends transversely from a single leg 5. The free end of the stiffener 3c has a curved shape. The main body 4 extends transversely relative to the surface of the skin 2.

[0063] The part 1 made of composite material is made from a fibrous reinforcement 10 and a matrix. The fibrous reinforcement 10 comprises carbon, glass, ceramic, aramid (such as Kevlar®), polyamide fibers or a mixture of these fibers. Preferably, the fibers are carbon fibers.

[0064] The matrix is ​​preferably an organic matrix. This may be a resin thermoplastic or a thermosetting resin. In this description, the terms "resin" and "matrix" are equivalent. The resin may be based on epoxy, vinylester, polyester, polybismaleimides (BMI). Preferably, the resin is based on epoxy.

[0065] With reference to Figures 3 and 4, the fiber reinforcement 10 comprises a first laminated structure 11 and a second laminated structure 12 which are bonded together at an interlaminar interface 13. The first laminated structure 11 is intended to form the skin 2 of the composite part and the second laminated structure 12 is intended to form the stiffener 3 of the composite part. In all cases, the fiber reinforcement 10 comprises at least two laminated fiber structures 11, 12. Each first and second laminated structure 11, 12 comprises at least one layer of fibers. In particular, each layer is composed of fibers woven or sewn to constitute the first structure 11 (or first fiber preform) which extends around an axis of revolution (corresponding to the longitudinal axis X) of the part 1 or to constitute the second structure 12 (or second fiber preform).At least a portion of the second structure 12 extends in elevation transversely of a surface (the innermost or the outermost) of the first structure 11 and at least a portion of the second structure 12 extends parallel to the surface of the first structure 11.

[0066] The first laminated structure 11 comprises several layers 11a, 11b or superimposed plies. In the present example, the first laminated structure 11 comprises two superimposed layers 11a, 11b. Similarly, the second laminated structure 12 comprises two superimposed layers 12a, 12b.

[0067] Each layer 11a, 11b, 12a, 12b of the first structure 11 and of the second structure 12 may comprise long or short fibers and / or continuous or discontinuous fibers. The fibers may be oriented randomly, in all directions, in a plane. Discontinuous long fibers are known by the English acronym “DLF” for “Discontinuous Long Fiber”).

[0068] Each layer 11a, 11b, 12a, 12b of the first structure 11 and of the second structure 12 may be in the form of a fabric, a braid, a sheet or ribbons of unidirectional fibers, non-woven fibers (known by the English expression "Non Crimp Fabrics" and acronym in English NCF), mat or other.

[0069] In the case of a fabric, the latter can be obtained by two-dimensional (2D), three-dimensional (3D) or multi-layer weaving. In the present invention, by "three-dimensional weaving" we mean a weaving in which certain weft threads and warp threads are linked on several weft layers. Three-dimensional weaving promotes good bonding between the layers and good mechanical strength of the preform and subsequently of the composite material part. Weaving can be carried out using a well-known jacquard-type loom with weft threads and warp threads.

[0070] Alternatively, each layer 11a, 11b, 12a, 12b is obtained by draping.

[0071] The fibers of at least one of the layers 11a, 11b, 12a, 12b may be impregnated. The impregnation resin may be a polymeric resin, for example a thermosetting or thermoplastic resin. An example of a thermoplastic impregnation resin is a polyamide, a polyetheretherketone, a polyetherketoneketone, poly(phenylene sulfide) or a polyaryletherketone. The thermosetting resin comprises for example an epoxide or a polyimide.

[0072] The fibrous reinforcement 10 comprises at least one reinforcing element 14 which is placed at the interlaminar interface 13 of the first structure 11 and the second structure 12. The reinforcing element 14 may comprise fibers. Advantageously, but not limitingly, the reinforcing element 14 comprises a web 14V of cut or uncut fibers. The fibers are then entangled with each other.

[0073] Alternatively, the reinforcing element 14 can be obtained by very fine weaving.

[0074] The fibers of the reinforcing element 14 are made of a polymer material. Preferably, the polymer material is a thermoplastic. Advantageously, but not limited to, the thermoplastic material may be a polyamide, a polyetherimide, a polyethylene, a polyphenylene sulfide, a polyethylene terephthalate or a combination thereof.

[0075] According to one embodiment, the reinforcing element 14 may comprise a chemical binder and / or nanotube fillers and / or carbon fibers. The chemical binder may comprise at least one polymer material. The nanotubes may be recycled as may the carbon fibers. The nanoparticles may be of the “core-shell rubber” type which are dispersed in a resin. The binder makes it possible to maintain the shape of the reinforcing element 14. As for the fillers, they make it possible, on the one hand, to improve the mechanical properties of the reinforcing element 14 and, on the other hand, to guarantee good integration between the two structures 11, 12.

[0076] According to another embodiment, the reinforcing element 14 may comprise an organic binder such as a sizing composition (for example comprising acrylic or methacrylic or amine compounds) to hold the fibers together.

[0077] According to yet another embodiment, the carbon nanotubes are dispersed among the fibers of the reinforcing element or are grafted radially to the fibers of the reinforcing element 14. In particular, the carbon nanotubes can be developed around the fibers of the reinforcing element 14 using the techniques of the company N12 technologies.

[0078] The reinforcing element 14 may have a height (along a direction per pendicular to the surface of the first structure 11) between 5 pm and 0.7 mm. Preferably, the height is between 5 pm and 50 pm.

[0079] According to another characteristic, the reinforcing element 14 has a surface mass of between 2 and 30 g / m2. The use of a material with a fine grammage makes it possible to minimize the mass of the reinforcing element 14. Advantageously, but not limitingly, the reinforcing element 14 has a transverse permeability to the fluid, here the resin, of at least 5% of its surface and preferably at least 10%. This configuration allows rapid impregnation of the reinforcing element 14 by the resin.

[0080] With reference to [Fig. 4] which schematically represents a second omega-shaped structure 12, the reinforcing element 14 (here a web 14V) is arranged between each fibrous tab 15 of the second laminated structure 12, and the first laminated structure 11. Each fibrous tab 15 is intended to form the tab 5 of the stiffener 3. At least a portion of the fibrous layers of the second structure 12 extends in elevation transversely to the general surface of the first structure 11 and is continuously extended by at least a portion of the second structure 12 extending parallel to the general surface of the first structure 11. Each fibrous tab 15 extends towards the outside of the portion intended to form the body of the stiffener 3. Each web 14V extends along the width of each fibrous tab 15 and has the same length as the latter.

[0081] Advantageously, the 14V web can be fixed to one of the fibrous structures 11 (respectively 12) against the interlaminar interface 13 with the other fibrous structure 12 (respectively 11). The fixing can be carried out by sewing or stitching in English. In this case, carbon, glass, aramid or polyester fibers or the same thermoplastic constituting the first and second structures 11, 12, can be used to carry out this sewing. The fixing can also be carried out by gluing using an adhesive.

[0082] [Fig. 5] illustrates another arrangement of the fibrous reinforcement 10. The second structure 12 comprises sets of fibers extending transversely to the general surface of the first structure 11 and extending continuously in two parts extending parallel to the general surface of the first structure 11 in opposite directions to the base of the stiffener 3. In particular, in the example illustrated, each fibrous tab 15 extends on either side of a lateral portion 16 of the second structure 12 which is intended to form a part of the body of the stiffener 3. In this way, each lateral portion 16 of the second structure 12 and fibrous tab 15 has a substantially T-shaped cross-section (one of the branches of the T may be shorter). This shape is obtained by folding at least one layer, here layer 12b. Here, layer 12b has portions 12ba, 12bb. extending inwardly and towards each other. The layer 12a has portions 12aa, 12ab extending outwardly. Each pair of portions 12aa, 12ba or 12ab, 12bb form a fibrous leg 5. The web 14V of the reinforcing element 14 extends over the entire width of each fibrous leg 15 and on either side of each lateral portion 16. In other words, there is a single reinforcing element 14 for each fibrous leg 15 and each reinforcing element 14 extends towards the inside of the fibrous body portion and towards the outside of the body as well as at the interlaminar interface 13.

[0083] [Fig. 6] shows another arrangement of the fiber reinforcement 10. This embodiment differs from that of [Fig. 5] in that the reinforcing element 14 has a general inverted T shape. In other words, the reinforcing element 14 comprises layers or extended zones of fibers 14a, 14b, 14c which here extend in the plane of the first structure 11 (or in the direction of the first structure 11) and layers of fibers which extend inside the lateral portion of the main body. Thus the reinforcing element 14 is arranged so as to form a connecting node 17. In particular, three layers or extended zones of fibers 14a, 14b, 14c of the reinforcing element 14 meet at the connecting node 17. Advantageously, but not limitingly, the connecting node 17 has a triangular shape.

[0084] As illustrated in [Fig.6], this connecting node 17 may itself be filled with a complementary fibrous structure. In other words, the connecting node 17 is configured so as to form a housing. The complementary fibrous structure may be in the form of a fibrous profile 18 of complementary shape with the connecting node 17. Here the fibrous profile 18 comprises a triangular section. Advantageously, but not limitingly, the fibrous profile 18 may be made from longitudinal or discontinuous continuous fibers. The fibers may be entangled chopped fibers, braided continuous fibers, and / or be composed of several woven fiber threads forming a strand (roving in English). Advantageously, but not limitingly, the fibrous profile 18 may be made of thermoplastic fibers of the same nature as the reinforcing element 14 or of glass fibers, aramid fibers or carbon fibers.

[0085] In the example of [Fig.6], the layer 12b is continuous. The portions 12ba, 12bb are connected to each other. Of course, the portions 12ba and 12bb can be arranged in a similar manner to that of [Fig.5], or separated from each other.

[0086] [Fig.7] shows yet another embodiment of the fibrous reinforcement 10. The interlaminar interface 13 is shown in detail. In this embodiment, each fibrous tab 15 is formed by the extension of four layers of the second laminated structure 12. Advantageously, each fibrous tab 15 comprises two layers 15a, 15b, 15c, 15d which extend in opposite directions and parallel to the direction of the first laminated structure 11. The reinforcing element 14 is located between the fibrous legs 15 and the first structure 11, and is defined in a plane parallel to that of the first laminated structure 11 (or in the direction of the first structure). The reinforcing element 14 here comprises two webs, represented 14V, 14V' for each lateral portion 16 of the second structure 12. Of course, a single web 14V of the reinforcing element 14 can extend over the entire width of each fibrous tab 15. In this embodiment, each web 14V, 14V' is sewn to the first and second laminated structures 11, 12. Of course, the first structure 11, the second structure 12 and the webs 14V', 14V” are assembled beforehand.

[0087] [Fig. 8] shows another embodiment of the fiber reinforcement 10. This embodiment differs from that of [Fig. 7] in that the reinforcing element 14 has a generally inverted T-shaped section. The reinforcing element 14 is installed between the opposite layers of the fiber legs 15 and at the interlaminar interface 13. In particular, the reinforcing element 14 comprises layers of fibers or extended fiber zones 14a, 14b, 14c extending transversely inside the layer of the lateral portion of the second structure 12 and layers extending between the fiber leg 5 and the first structure 11. The reinforcing element 14 comprises a longitudinal fiber profile 18 arranged at the intersection of the three extended fiber zones 14a, 14b, 14c of the reinforcing element 14.The fiber profile 18 may advantageously be made of glass fibers, aramid or carbon fibers and produced by a braiding or matrix weaving process. The fiber profile 18 may be in the form of strands having several woven fiber threads. The reinforcing element 14 may advantageously be sewn with the longitudinal fiber profile 18 and may also be sewn to one or other of the first and second structures 11, 12 prior to the assembly of the different laminated structures.

[0088] Other examples of fiber reinforcement 10 for producing stiffeners 3 in the shape of I, T, C, U, J, or L and a skin 2 are shown in Figures 9 to 14.

[0089] With reference to [Fig.9], the second structure 12 is intended to form an I-shaped stiffener with two legs at each end of the main body and one of the legs of which makes it possible to connect the I-shaped stiffener to the skin 2. The second structure 12 comprises fibrous legs 15 which are located at each end of the main fibrous body forming the main body 4 of the stiffener. The main fibrous body and the fibrous legs 15 are formed using three layers 12a, 12b, 12c. Each layer 12a, 12b is folded to form portions 12ab, 12ba, 12ba, 12bb. These portions 12ab, 12ba, 12ba, 12bb extend towards the outside of the main fibrous body and in a parallel manner to each other. These portions 12ab, 12ba, 12ba, 12bb are also pa connected to the first structure 11. The layer 12c extends parallel to the first structure 11 and forms with the portions 12ba, 12bb of each layer 12a, 12b a fibrous tab 15 (not connected to the first structure 11). The reinforcing element 14 comprises a web 14V which is arranged between a fibrous tab 15 (formed here by the portions 12ab and 12ba of each layer 12a, 12b) of the second structure 12, and the first structure 11. The web 14V extends along the width of each fibrous tab 15, parallel to the first structure 11 and has substantially the same length as the fibrous tabs 15. A fibrous profile 18 is arranged on the one hand, between each layer 12a, 12b and on the other hand, between the web 14V and the fibrous tab 15 which is intended to be connected to the first structure 11. The other fibrous profile 18 is arranged on the one hand, between each layer 12a, 12b and on the other hand, between the layer 12c and the fibrous tab 15 (opposite the first structure 11).

[0090] [Fig. 10] shows a second structure 12 intended to form a J-shaped stiffener with a single tab for connecting the stiffener to the skin 2. The second structure 12 comprises two layers 12a, 12b. Each layer 12a, 12b has portions 12ab, 12bb which extend in the same direction to form the free end of the stiffener and portions 12aa, 12ba which extend in opposite directions to form at least in part the single fibrous tab 15. The portions 12ab and 12bb may have a curved shape. A web 14V is arranged between the fibrous tab 15 and the first structure 11. Advantageously, the reinforcing element 14 comprises a fibrous profile 18 which is arranged on the one hand, between each layer 12a, 12b and on the other hand, between the web 14V and the fibrous tab 15 intended to be connected to the first structure 11.

[0091] [Fig. 11] shows a second structure 12 intended to form a T-shaped stiffener with a single tab enabling the stiffener to be connected to the skin 2. The second structure 12 comprises two layers 12a, 12b. Each layer 12a, 12b is folded to form a portion 12aa, 12ba extending outwardly from the main fibrous body to form the single fibrous leg 15. In other words, the portions 12aa, 12ba extend in opposite directions and parallel to the first structure 11. A web 14V is arranged between the fibrous leg 15 and the first structure 11. Advantageously, a fibrous profile 18 is arranged on the one hand, between each layer 12a, 12b and on the other hand, between the web 14V and the fibrous leg 15 intended to be connected to the first structure 11.

[0092] [Fig. 12] shows a second structure 12 for forming an L-shaped stiffener with a single tab for connecting the stiffener to the skin 2. The second structure 12 comprises two layers 12a, 12b. Each layer 12a, 12b is folded to form a portion 12aa, 12ba extending outwardly from the main fibrous body to form the single fibrous tab 15. The portions 12aa, 12ba extend along the same directions and parallel to the first structure 11. A web 14V is arranged between the fibrous tab 15 and the first structure 11. Advantageously, but not limitingly, a fibrous profile 18 is arranged on the one hand at one end of the portions 12aa, 12ba (or of the fibrous tab 15). Preferably, the fibrous profile 18 is placed at the level of the folding of the layers to form the portions 12aa, 12ba. The web 14V can extend below the fibrous profile in the plane of [Fig. 12].

[0093] The [Fig. 13] represents a second structure 12 intended to form a C-shaped stiffener with two fibrous tabs, only one of which makes it possible to connect the stiffener to the skin 2. Each layer 12a, 12b of the second structure 12 is folded to form two portions 12aa, 12ba which extend parallel to each other and which are connected to the first structure 11. The portions 12aa, 12ba extend parallel to the first structure 11 and form a fibrous tab 15 connected to the first structure 11. Each layer 12a, 12b is also folded to form two portions 12ab, 12bb which extend parallel to each other and opposite the first structure 11. The portions 12aa, 12ba, 12ab, 12bb extend in the same directions and parallel to the first structure 11. A veil 14V is arranged between the fibrous tab 15 and the first structure 11.Advantageously, but not limitingly, a fibrous profile 18 is arranged at one end of the portions 12ba, 12aa (or of the fibrous tab 15). Preferably, the fibrous profile 18 is placed at the level of the folding of the layers to form the portions 12aa, 12ba. The web 14V can extend below the fibrous profile in the plane of [Fig. 13].

[0094] [Fig. 14] shows a second structure 12 intended to form a U-shaped stiffener. The U-shaped stiffener comprises a main body 4 and a single leg 5 connected to the skin 2. The main body has two branches which extend transversely relative to the skin 2. The branches are here parallel to each other. The single fibrous leg 15 extends transversely between the two branches of the main body. To produce this stiffener, the second structure 12 comprises two layers 12a, 12b which are folded to form two portions 12aa, 12ba which extend parallel to each other and which are connected to the first structure 11. The portions 12aa, 12ba extend parallel to the first structure 11 and form a fibrous tab 15 connected to the first structure 11. The layers 12a, 12b also form two fibrous branches which extend parallel to each other and transversely spaced from the first structure 11.A 14V web is arranged between the fibrous tab 15 and the first structure 11. Advantageously, a fibrous profile 18 is arranged on the one hand at each end of the fibrous tab 15 intended to be connected to the first structure 11. The 14V web can extend below the fibrous profile 18 in the plane of [Fig. 14].

[0095] We will now describe in detail the process of manufacturing a part in composite material. This process is represented in a flowchart in [Fig. 15].

[0096] The method 100 comprises a step 101 of producing a first laminated structure 11 comprising a plurality of layers of superimposed fibers. In our exemplary embodiment, the first structure 11 is intended to form the skin 2 of the part 1 made of composite material. The layers are superimposed on each other.

[0097] The method comprises a step 102 of producing a second laminated structure 12 comprising a plurality of superimposed layers of fibers. This second structure 12 is intended to form the stiffener 3 having a predetermined shape. As we have seen previously, the stiffener 3 has a cross section in the shape of an I, T, C, U, L, J or Q.

[0098] The method comprises a step 103 of placing the first structure 11 in a mold (not shown). Alternatively, the first structure 11 is formed in the mold, i.e. the different layers are superimposed in the mold. In this case, the mold has the shape of the first structure 11.

[0099] The method comprises a step 104 of applying the second structure 12 to the first structure 11 so that at least a portion of the second structure is in contact at an interlaminar interface 13 with the first structure 11. In particular, the fibrous tabs 15 are brought into contact with the first structure 11, and more precisely still with the upper layer. The two assembled laminated structures 11, 12 form the fibrous reinforcement 10. In the case of the second Q-shaped structure 12, the second structure 12 comprises fibrous tabs 15 which bear on the first structure 11. Advantageously, the application step takes place in the mold where the first structure 11 is placed. Alternatively, the second structure 12 is shaped in another mold and then it is placed after its shaping on the first structure 11. In this case, the mold has the shape of the second structure (I-shaped, T-shaped, C-shaped, U-shaped, L-shaped, J-shaped or Q-shaped).

[0100] Optionally, a holding element (not shown) making it possible to maintain the shape of the second structure 12 is placed in the mold during the assembly of the first structure 11 and the second structure 12. The holding element is solid or rigid and may remain in place until the densification of the composite material part.

[0101] The method comprises a step 105 of arranging a reinforcing element 14 comprising fibers of thermoplastic material at the interlaminar interface 13 between the first structure 11 and the second structure 12. The arranging step 105 advantageously takes place prior to the application step 104. The reinforcing element 14 is arranged between the fibrous tabs 5 and the first laminated structure 11. Each reinforcing element 14 has a width substantially equal (plus or minus 0.5 mm) to the width of each fibrous tab 15 as well as a length sen possibly equal (plus or minus 0.5 mm) to the length of each fibrous leg 5. In the case where the reinforcing element 14 is arranged so as to form a triangular-shaped space or the triangular-shaped connecting zone, a fibrous profiled element 18 may be arranged in this space during the arrangement step 15 or subsequently to this step 105.

[0102] The method comprises a step 106 of impregnating the first structure 11 and / or the second structure 12. According to an alternative embodiment, the impregnation step 106 is carried out by injecting a matrix according to RTM technology, this acronym meaning in English Resin Transfer Molding for resin transfer molding, in order to carry out a subsequent densification of the fiber reinforcement 10 and obtain the desired composite material part. The matrix is ​​injected into a mold comprising the first structure 11 and the second structure 12 forming the fiber reinforcement 10 as well as the reinforcing element 14. The latter is in this case a dry fiber reinforcement. This will make it possible to obtain the composite material part in a few operations, or even in a single operation.

[0103] The method comprises a densification step 107 of the first structure 11 and / or the second structure 12 so as to obtain the part made of rigid composite material. During this densification step 107, the fiber reinforcement 10 undergoes a heat treatment which will allow the matrix to be crosslinked and hardened. Generally speaking, and within the framework of the RTM technique, the densification takes place in the same injection mold of the matrix and possibly in parallel with the impregnation step. In other words, the first structure 11 and the second structure 12 as well as the reinforcing element 14 are densified at the same time.

[0104] According to one embodiment, the impregnation step 106 takes place prior to the production step 101, 102 of the first structure 11 and the second structure 12. This is particularly the case where the fibers are pre-impregnated with a matrix. According to yet another alternative, the fibers of each first and second structure 11, 12 are impregnated with the matrix after the respective production steps 101, 102 and are compacted to obtain their shape. The laminated structures 11, 12 are respectively compacted in a mold. The densification step 107 is carried out to harden the matrix which impregnates the fibers. Of course, the reinforcing element 14 is arranged beforehand between the two structures 11, 12 before densification.

[0105] According to another embodiment, the first laminated structure 11 and the second laminated structure 12 are respectively impregnated with a matrix and densified. In other words, the first structure 11 is solidified or densified separately from the second structure 12. In this case, the method comprises a step of fixing the densified second structure to the first structure 11. Furthermore, during this embodiment, the reinforcing element 14 is arranged between the first laminated structure 11 and the second laminated structure 12 which have been densified before the latter is fixed. Advantageously, the fixing is carried out by gluing, for example with matrix injection. The gluing can also be carried out using an epoxy-based adhesive. The reinforcing element 14 is fixed to the first and second structures using this glue.

[0106] In this way, at least a portion of the reinforcing element 14 makes it possible to reinforce the junction, in the layer of material, between the stiffener 3 and skin 2 by being judiciously placed at the interlaminar interface 13 of the structures intended to form the skin and the stiffener respectively.

Claims

Claims

1. Method (100) for manufacturing a part (1) made of composite material comprising a fibrous reinforcement (10) embedded in a matrix, the method comprising the following steps of: - producing (101) a first laminated structure (11) comprising a plurality of superimposed layers of fibers and intended to form a skin (2) of the part made of composite material, - producing (102) a second laminated structure (12) comprising a plurality of superimposed layers of fibers and intended to form a stiffener (3) having a predetermined shape, the stiffener (3) extending from a surface (2a, 2b) of the skin (2), - applying (104) the second structure (11) to the first structure (12) so that at least a portion of the second structure (12) is in contact at an interlaminar interface (13) with the first structure (11), - impregnating (106) the first structure (11) and / or the second structure (12) laminated by a polymer matrix,and - densification (107) of the first structure (11) and / or of the second structure (12) laminated so as to obtain a part made of rigid composite material, characterized in that the method comprises a step of arranging (105) at least one reinforcing element (14) comprising fibers made of thermoplastic material at the interlaminar interface (13) between the first structure (11) and the second structure (12) so as to reinforce the interlaminar interface (13).,

2. Method (100) according to the preceding claim, characterized in that the stiffener has a cross section in I, T, C, U, L, J or Q.

3. Method (100) according to one of the preceding claims, characterized in that the matrix comprises a thermosetting resin.

4. Method (100) according to one of the preceding claims, characterized in that the reinforcing element (14) has a surface mass of between 2 and 30 g / m2 and a transverse permeability of at least 5% of its surface.

5. Method (100) according to one of the preceding claims, characterized in that the thermoplastic material of the reinforcing element (14) comprises a polyamide, a polyethylene, a polyetherimide, a polyphenylene sulfide, a polyethylene terephthalate or a combination of these.

6. Method (100) according to one of the preceding claims, characterized in that the reinforcing element (14) comprises a chemical binder or an organic binder and / or nanotube fillers and / or carbon fibers.

7. Method (100) according to any one of the preceding claims, characterized in that the second structure (12) comprises fibrous tabs (15) intended to form tabs (5) of the stiffener (3), each fibrous tab (15) extending on either side of a lateral portion (16) which is intended to form a part of the body of the stiffener (3).

8. Method (100) according to the preceding claim, characterized in that one or more reinforcing elements (14) extend over the width of each fibrous tab (15) and on either side of the lateral portion (16) of the second structure (12).

9. Method (100) according to claim 7 or 8, characterized in that each fibrous tab (15) comprises two layers (15a, 15b, 15c, 15d) which extend in opposite directions and parallel to the direction of the first laminated structure (11).

10. Method (100) according to claim 7, characterized in that the reinforcing element (14) comprises layers of fibers which extend in the direction of the first structure (11) and layers of fibers which extend inside each lateral portion (16).

11. Method (100) according to one of the preceding claims, characterized in that the reinforcing element (14) is fixed to at least one of the first and second fibrous structures (11, 12) at the interlaminar interface (13) for example by sewing or gluing.

12. Method (100) according to one of the preceding claims, characterized in that the impregnation step (106) is carried out prior to the production steps (101, 102), prior to step (104) or after step (104).

13. Method (100) according to the preceding claim, characterized in that the first structure (11) and / or the second structure (12) comprise pre-impregnated fibers.

14. Method (100) according to any one of the preceding claims, characterized in that the first laminated structure (11) and the second laminated structure (12) are densified separately and in that it comprises a step of fixing the second densified structure (12) on the first densified structure (11).

15. Part (1) made of composite material produced by the manufacturing method (100) according to any one of the preceding claims, the part comprising a skin (2) and at least one stiffener (3) extending from a surface of the skin (2), said at least one stiffener (3) having a cross section in the shape of I, T, C, U, L, J, or Q.

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