Manufacturing process of a composite panel

Abstract

Method for manufacturing a composite panel The invention relates to a method for manufacturing a composite panel comprising a cellular core interposed between two skins comprising the steps of: - positioning a first layer of resin (4) on a first tool (2), - positioning an element with a cellular structure (6) comprising a cellular structure (8) arranged between two fibrous preforms (10, 12) intended to form the skins, a first of the fibrous preforms (being positioned on the first layer of resin, - positioning a second layer of resin (14) on the second of the fibrous preforms or on a second tool, - positioning one or the second tool, the first tool and the second tool being arranged relative to each other so as to allow relative movement between the two tools,- vacuum cooking generating infiltration of the resin into the honeycomb structure element and relative movement between the two tools. Figure for abstract: Fig. 1a.,

Description

Title of the invention: Method for manufacturing a composite panel Technical field

[0001] The present invention relates to the manufacture of a composite panel comprising a honeycomb core arranged between two skins.

[0002] The invention is more particularly applied to nacelle panels including thrust reverser panels of aircraft propulsion units formed from such a composite panel, for example an acoustic composite panel. Prior art

[0003] The manufacture of a composite panel intended to form a thrust reverser panel can be carried out by different techniques.

[0004] A first of these techniques consists of using a process of draping and polymerization of pre-impregnated fabrics. However, such a solution requires several polymerization stages as well as the bonding of several separately manufactured parts before assembly to form the composite panel, resulting in a high manufacturing cost.

[0005] Another technique is to use a resin infusion process. This technique involves manufacturing the composite panel by arranging different layers of materials on a form, then injecting a resin and ensuring the diffusion of the resin inside these different layers, for example by drainage for its polymerization. However, with such a solution, it is difficult to control the quantity of resin used and extraction steps are generally necessary to remove the excess resin. Statement of the invention

[0006] The invention aims in particular to overcome at least in part one of these drawbacks and aims in particular to propose a solution allowing simplified and less expensive manufacture of a composite panel, by reducing the number of manufacturing steps, in particular by avoiding the multiple polymerization and bonding steps, while making it possible to control the quantity of resin used.

[0007] To this end, the invention relates to a method for manufacturing a composite panel comprising a cellular core interposed between two skins, the method comprising the steps of:

[0008] positioning of a first layer of resin on a first tool,

[0009] positioning of a honeycomb structure element comprising a honeycomb structure arranged between two fiber preforms intended to form the skins, a first of the fiber preforms being positioned on the first layer of resin,

[0010] positioning of a second layer of resin on the second of the fiber preforms or on a second tool,

[0011] positioning of one or the second tool, the first tool and the second tool being arranged relative to each other so as to allow relative movement between the two tools,

[0012] vacuum cooking generating infiltration of the resin into the element with a honeycomb structure and relative movement between the two tools.

[0013] For example, the second tooling may be positioned such that the first tooling and the second tooling are arranged relative to each other so as to allow relative movement between the two tools.

[0014] According to other characteristics of the invention, the method of the invention comprises one or more of the following optional characteristics.

[0015] The relative movement generated between the two tools corresponds to a rapprochement between the two tools.

[0016] Both tools are rigid.

[0017] One of the tools is rigid and the other tool is semi-rigid or flexible.

[0018] The resin layers are resin layers in solid form, for example when the resin layers are positioned, respectively on the first tool and on the second of the fiber preforms, for example in the draping (or assembly) phases.

[0019] The method comprises a preliminary step in which the thickness of the first resin layer and the second resin layer are chosen according to an amount of resin to be used.

[0020] Each of the fiber preforms is a dry fiber preform.

[0021] The initial volume rate of fibers may be of the order of 40 to 45%. The initial volume rate is understood to mean the volume rate of fibers during the positioning of the fiber preforms. The final volume rate of fibers in the skins of the panel which have been manufactured may be greater than 50%, preferably greater than 55%, preferably between 57 and 65%. The final volume rate is understood to mean the volume rate of fibers obtained at the end of the process.

[0022] The positioning of the honeycomb structure element comprises the steps of:

[0023] positioning the first of the fiber preforms intended to form a first of the skins on the first layer of resin,

[0024] positioning a first layer of adhesive on the first fibrous preform

[0025] positioning the honeycomb structure on the first layer of adhesive,

[0026] positioning a second layer of adhesive on the honeycomb structure,

[0027] positioning of the second fiber preform and for example of its resin layer, intended to form a second of the skins on the second adhesive layer.

[0028] The method comprises a step of positioning at least one U-shaped or Z-shaped edge piece at one of the ends of the honeycomb structure element.

[0029] The method comprises a step of positioning a first sealing element and a second sealing element between the two tools and on either side of the stack formed of at least the element with a honeycomb structure and the layers of resins.

[0030] The first sealing member and the second sealing member are configured to accommodate relative movement between the two tools.

[0031] According to another aspect, the invention relates to an assembly for the manufacture of a composite panel comprising a cellular core interposed between two skins, for example obtained at the end of the step of positioning one or the second tool of the method as previously described, the assembly comprising:

[0032] the first tool,

[0033] the first layer of resin positioned on the first tool,

[0034] the first fiber preform positioned on the first layer of resin,

[0035] the honeycomb structure positioned on the first fiber preform,

[0036] the second fiber preform positioned on the honeycomb structure,

[0037] the second layer of resin positioned on the second fiber preform,

[0038] the second tool positioned on the second layer of resin,

[0039] the first tool and the second tool being arranged relative to each other so as to allow relative movement between the two tools.

[0040] For example, one of the tools is rigid and the other tool is semi-rigid or flexible. Brief description of the drawings

[0041] [Fig.1a] [Fig.1a] illustrates a sectional view of an assembly during one of the stages of manufacturing a composite panel according to a first embodiment.

[0042] [Fig.lb] [Fig.lb] illustrates a sectional view of the assembly of [Fig.la] during a later stage of manufacturing the composite panel.

[0043] [Fig.2] [Fig.2] represents a variant of the assembly illustrated in Figure 1 when of one of the stages of manufacturing a composite panel.

[0044] [Fig.3a] [Fig.3a] illustrates a sectional view of an assembly during one of the stages of manufacturing a composite panel according to a second embodiment.

[0045] [Fig.3b] [Fig.3b] illustrates a sectional view of the whole of [Fig.3a] during a subsequent stage of manufacturing the composite panel.

[0046] [Fig.4] [Fig.4] is a perspective view of an assembly according to a third mode of realization.

[0047] [Fig.5] [Fig.5] is a longitudinal sectional view of the assembly illustrated in [Fig.4],

[0048] [Fig.6a] [Fig.6a] illustrates an assembly during one of the stages of manufacturing a composite panel according to an alternative embodiment of the assembly illustrated in Figures 3a and 3b.

[0049] [Fig.6b] [Fig.6b] illustrates a sectional view of the assembly of [Fig.6a] during a later stage of manufacturing of the composite panel.

[0050] [Fig.7] [Fig.7] illustrates an assembly during one of the stages of manufacturing a composite panel according to an alternative embodiment of the third embodiment

[0051] [Fig.8] [Fig.8] represents a variant of the assembly illustrated in Figure 1 during one of the stages of manufacturing a composite panel.

[0052] [Fig.9] [Fig.9] represents a composite panel obtained by the process according to the invention.

[0053] [Fig. 10] [Fig. 10] is an exploded view of an assembly according to another embodiment.

[0054] [Fig.11] [Fig.11] is a sectional view of the assembly of [Fig.10].

[0055] [Fig. 12] [Fig. 12] is a variant of the assembly illustrated in [Fig.4]. Description of the embodiments

[0056] In the remainder of the description of the method according to the invention, the same numerical references designate the same elements.

[0057] A method of manufacturing a composite panel according to the invention is described. The method may be intended for the manufacture of a composite panel comprising, for example, a honeycomb core interposed between two skins according to one embodiment of the invention.

[0058] The composite panel, for example, acoustic, can be used as a nacelle panel, for example as a flap or thrust reverser panel of an aircraft propulsion system, for example as an internal fixed structure (IFS) or external fixed structure (OFS) panel. The panel can be a sandwich panel, for example an acoustic sandwich panel, for example with a honeycomb core.

[0059] The manufacturing method comprises a step of positioning a first layer of resin 4 on a first tool 2. The first layer of resin 4 may be in direct contact with the first tool 2.

[0060] The manufacturing method may comprise a step, for example subsequent to the step of positioning the first layer of resin, of positioning a honeycomb structure element 6 comprising a honeycomb structure 8 arranged between two fibrous preforms 10, 12 intended to form the skins. This step can be carried out so that a first fibrous preform 10 is positioned on the first layer of resin 4, for example in direct contact with the first layer of resin 4.

[0061] The honeycomb structure element 6 for forming the composite panel 24 ([Fig.9]) may comprise a honeycomb structure 8 arranged between a first fiber preform 10 intended to form a first skin of the composite panel and a second fiber preform 12 intended to form a second skin of the composite panel. The honeycomb structure element 6 comprises the honeycomb structure 8 and the two fiber preforms 10, 12.

[0062] The positioning of the element with a cellular structure 6 may comprise the steps, for example successive steps of positioning the first fiber preform 10 intended to form a first skin on the first layer of resin 4, of positioning the cellular structure 8 on the first fiber preform 10 and of positioning the second fiber preform 12 intended to form a second skin on the cellular structure 8.

[0063] For example, the positioning of the cellular structure element 6 may comprise the steps, for example successive steps of positioning the first fiber preform 10 intended to form a first skin on the first resin layer 4, of positioning a first adhesive layer 26 on the first fiber preform 10, of positioning the cellular structure 8 on the first adhesive layer 26, of positioning a second adhesive layer 28 on the cellular structure 8, and of positioning the second fiber preform 12 intended to form a second skin on the second adhesive layer 28.

[0064] The layers of adhesives 26, 28, which are respectively arranged between the cellular structure 8 and one of the fibrous preforms 10, 12, make it possible to improve the cohesion between the cellular structure and the fibrous preforms, for example during the manufacture of the panel.

[0065] The adhesive layers 26, 28 may be in solid form, for example the adhesive layers may be adhesive films.

[0066] The manufacturing method may comprise a step, for example subsequent to the step of positioning the element with a cellular structure, of positioning a second layer of resin 14. The second layer of resin 14 may be positioned on the second fiber preform 12, for example in direct contact with the second fiber preform or on a second tool 16.

[0067] The manufacturing method may comprise a step, for example subsequent to the step of positioning the second layer of resin, of positioning a second tool 16. The second tool 16 may be positioned on the second layer of resin 14, for example in direct contact with the second layer of resin. 14. When the second layer of resin 14 has already been positioned on the second tool 16 during the previous step, the second tool 16 can be positioned so that the second layer of resin 14 is positioned on the second fiber preform 12, for example in direct contact with the second fiber preform 12.

[0068] In the present invention, positioning the elements involves moving the elements.

[0069] At least one of the two tools, for example the two tools 2, 16, may have a shape corresponding to the final shape of the composite panel to be manufactured.

[0070] In the method according to the invention, each resin layer 4, 14 may be a resin layer in solid form, which may be configured to change state, for example to become fluid, for example by a modification of its temperature, for example by an increase in temperature, for example when heating the resin. For example, each resin layer may be a resin film.

[0071] By resin layer in solid form, it is meant that once positioned, the resin layer has a texture and viscosity such that the resin layer does not move, does not flow and does not penetrate between the filaments of the fiber preforms (a phenomenon which can occur by capillarity for insufficiently viscous materials). For example, each resin layer has a minimum viscosity threshold of 10,000 poises.

[0072] Figures 1a, 2, 3a, 6a, 7, 8 and 11 illustrate an assembly 20 obtained at the end of the step of positioning the second tool 16. The assembly 20 comprises a stack of materials 4, 10, 26, 8, 28, 12, 14, 6 between the two tools 2, 16 once the previous positioning steps have been described.

[0073] The manufacturing method may comprise a subsequent step, for example a vacuum cooking step, for example a single step, generating for example an infiltration of the resin into the element with a honeycomb structure.

[0074] During this step, the stack of materials may be heated, for example in an oven. For example, the volume 22 between the two tools 2, 16 is heated. Furthermore, the volume 22 between the two tools 2, 16 is placed under vacuum, for example after sealing the volume between the two tools, for example by suction of the air contained in the volume between the tools, for example by means of a vacuum pump.

[0075] The heating causes a fluidification of the resin, for example of the resin films 4, 14 which will allow the latter to be able to infiltrate into the fiber preforms 10 and 12. The evacuation of the volume between the tools will create a depression between the tools relative to the external ambient pressure generating an infiltration by capillarity of the resin into the element with a cellular structure, for example in pore spaces of the preforms 10 and 12 of the honeycomb structure element 6, that is to say between the strands and the filaments of these preforms.

[0076] During infiltration, the aim is to ensure that the resin reaches the end of the cellular structure 8 in contact with the fibrous preform.

[0077] The use of resin in solid form, for example resin films, will make it possible to choose, before depositing the resin layers, the quantity of resin which will be used during the manufacturing process so that the resin can fill the space between the fibres of the preform and reach at least the base of the cellular structure opposite the preform.

[0078] Furthermore, each layer of resin 4, 14 is respectively positioned opposite one of the two fiber preforms 10, 12. This configuration makes it possible to optimize the process by allowing the resin to infiltrate directly, for example during its fluidification during the vacuum cooking step, into the fiber preform with which it is associated.

[0079] In the method according to the invention, the second tool 16 can be positioned relative to the first tool 2 so as to allow relative movement between the two tools, for example during the vacuum cooking step. The second tool 16 can be positioned relative to the first tool 2 so that the first tool and the second tool are arranged relative to each other so as to allow relative movement between the two tools, for example during the vacuum cooking step. The relative movement generated between the two tools, for example during the vacuum cooking step, can for example correspond to a bringing together of the two tools.

[0080] During the vacuum cooking step, the depression created between the two tools generates a transverse force of attraction of the two tools 2 and 16 towards each other and a compression of the preforms 10 and 12 between the cellular structure 8 and the tools 2 and 16 by means of the resin layers 4 and 14, the compression of the preforms and the penetration of the resin into the preforms generate a relative movement between the two tools, for example a rapprochement between the two tools (figures 1b, 3b, 6b and 11).

[0081] This relative movement is permitted due to the progressive infiltration of the resin into the fiber preforms 10 and 12, for example the pore space of the fiber preforms 10 and 12. The two tools 2, 16 are arranged so as to move closer to each other as the resin fluidizes and infiltrates the element with a cellular structure, and in particular the fiber preforms 10 and 12 up to the cellular structure 8.

[0082] Once the resin has infiltrated into the pore space of the fiber preforms 10 and 12, each tool 2, 16 can be pressed against a respective fiber preform 10, 12. of the honeycomb structure element 6 and apply a force thereto so as to adjust the first and second tools to the desired shape for the desired shape of the composite panel.

[0083] For example, the two tools 2, 16 can approach each other by a distance at least equal to the sum E of the thicknesses e1, e2 of the first layer 4 and of the second layer 14 of resin ([Fig.1a]).

[0084] The manufacturing method according to the invention may comprise a preliminary step, preceding for example the step of positioning the first layer of resin on the first tool, in which the thickness of the first layer of resin and of the second layer of resin are chosen as a function of a quantity of resin to be used which can be determined beforehand. The thickness of the first layer of resin and of the second layer of resin chosen may be identical or different.

[0085] The quantity of resin of each of the resin layers to be deposited is determined so as to be sufficient to fill the pore space of the fiber preform with which it is associated up to the connection with the cellular core. Thus, the thickness of the first resin layer can be chosen so as to allow, for example during vacuum curing, infiltration of the resin into the first fiber preform and up to a portion of the cellular structure in contact with the first fiber preform and the thickness of the second resin layer can be chosen so as to allow, for example during vacuum curing, infiltration of the resin into the second fiber preform and up to a portion of the cellular structure being in contact with the second fiber preform.

[0086] The objective being to obtain light skins, each of the fiber preforms can be a dry fiber preform having, in particular, thanks to vacuum compaction between the tools, a final fiber volume ratio greater than 50%, preferably greater than 55%, preferably between 57 and 65%. The term “final volume ratio” means the volume ratio obtained at the end of the process. The initial fiber volume ratio is of the order of 40 to 45%. The term “initial volume ratio” means the fiber volume ratio when positioning the fiber preforms.

[0087] The quantity of resin required is therefore at least 35% of the fiber volume and preferably between 43% and 50% of the fiber volume.

[0088] For example, for a composite panel where each skin has a predefined thickness, and therefore each fiber preform has said predefined thickness, the thickness of the resin layer to be deposited associated with each skin would be approximately half of said thickness. The two tools must be able to approach the thickness of the two resin layers during the vacuum curing step.

[0089] For example, for a composite panel where each skin has an intended thickness of 1.5 mm, and therefore each fiber preform has a thickness of 1.5 mm, the thickness of the resin layer to be deposited associated with each skin would be 0.75 mm, i.e. an excess thickness before infiltration of the resin during the vacuum cooking step of around 1.5 mm. The two tools must be able to come closer than 1.5 mm during the vacuum cooking step.

[0090] The vacuum curing step may generate, for example after the infiltration of the resin, a solidification of the resin for example by polymerization of the resin, for example for a thermosetting resin. Alternatively, the manufacturing method may comprise a step, for example subsequent to the vacuum curing step, of cooling generating a solidification of the resin, for example for a thermoplastic resin, for example cooling of the volume between the two tools. This makes it possible to finalize the consolidation of the element with a honeycomb structure making it possible to form the skins and the composite panel.

[0091] The method according to the invention makes it possible to manufacture a composite panel in a single polymerization operation, thus reducing the manufacturing cost. In addition, since the fiber preforms have high fiber volume rates, the resin is retained by capillarity in the preforms. By arranging the quantity of resin in relation to the thicknesses of the fiber preforms, the resin will not fill the macro cavities of the cellular core. Thus, there is no need for a prior sealing operation of the cellular structure because the quantity of resin used can be determined beforehand.

[0092] Each of the fiber preforms 10, 12 may be a dry fiber preform. The dry fibers may be woven, sewn, or unidirectional fibers. The dry fibers may be draped, formed manually, or by a mechanized process. A dry fiber is understood to mean a fiber having a limited binder content (for example, less than 5%), which allows the fiber to be essentially porous and thus allow colonization by capillary infiltration of the resin, for example during the vacuum curing step. It is possible to use draped or sewn unidirectional fiber sheets (NCF) or low-hemmed, non-openwork fabrics. For example, carbon fabrics. This type of preform makes it possible to obtain fiber volume contents of between 50 and 65% under the simple effect of the compression on the preforms generated by the vacuum.

[0093] The cellular structure 8 may be a cellular core structure, for example a honeycomb or foam cellular core structure.

[0094] The honeycomb core structure may be a honeycomb core structure made of closed-cell foams (i.e., non-acoustic cells), open-cell foams (e.g., intercommunicating, made of 'lattice' materials, possibly acoustically compatible). Preferably, the honeycomb core structure may be a 'honeycomb type' honeycomb core structure, i.e., comprising macro cells partitioned by thin foils, including for example hexagonal or misshapen cells, or with folded alveolar cores (for example Foldcore type).

[0095] The cellular structure 8 may be formed by a plurality of cellular sections which may be connected to each other by films of intumescent material, i.e. layers of intumescent material in solid form. This makes it possible to provide continuity of material and mechanical continuity between the two adjacent sections of the cellular structure 8.

[0096] The cellular structure 8 may comprise solid inserts, for example metallic or non-metallic, making it possible to meet different needs, for example forming, mechanical strength, through-fastenings, etc. Preferably, cellular cores having contacts every less than 20 mm are used, preferably 15 mm (such as, for example, honeycomb-type cellular cores with cells of size 5 / 8 inch), preferably 10 mm (such as honeycomb-type cellular cores with cells of size 3 / 8 inch).

[0097] Furthermore, the manufacturing method may comprise a step, for example an intermediate step, of positioning a first film of intumescent material (not shown) between the first fibrous preform and the cellular structure and an intermediate step of positioning a second film of intumescent material between the cellular structure and the second fibrous preform.

[0098] In the manufacturing method according to the invention, one of the two tools 2, 16 may be a rigid tool, for example a mold and the other tool 2, 16 may be a rigid or semi-rigid or flexible tool. When the other tool is rigid it may be for example a counter-mold. When the other tool is flexible it may be a flexible membrane, for example an elastomer membrane. It is understood that the tool is rigid relative to the semi-rigid or flexible tool.

[0099] The use of rigid tooling, which for example has sufficient rigidity to give its geometry to the surface of the skin with which the tooling comes into contact during the vacuum cooking step due to the proximity between the two tools, makes it possible to obtain a skin with an aerodynamic surface.

[0100] By rigid mold is meant, which is sufficiently solid and non-deformable to give the panel the geometry of the surface in contact with the tooling.

[0101] For example, the mold may be metallic or composite, for example at least several millimeters thick. The mold may be fixed to a frame or to a stiffening carcass (Figures 10 and 11).

[0102] By rigid counter-mold is meant for example a counter-mold having a stiffness of the order of that of the mold, but preferably without a frame or carcass. rigid counter-mold is configured to be able to deform globally by the few millimeters necessary to bring the two tools 2, 16 together.

[0103] When the second tool is semi-rigid, a semi-rigid counter-mold can also be used. By 'semi-rigid' counter-mold we mean, for example, a composite or metal shell 1 to 3 mm thick, i.e. locally stiff, but globally deformable. The semi-rigid counter-mold has greater flexibility.

[0104] The flexible tooling may be a shell made of silicone or rubber material a few millimeters thick, which may optionally be reinforced with an internal texture. The flexible tooling has even greater flexibility.

[0105] The use of an aerodynamic or acoustic skin perforated with a multitude of orifices allowing fluid communication between the exterior and the interior of the cellular core of the composite, makes it possible to form a composite panel, for example, an acoustic one which can be used as a flap or acoustic panel, for example for a thrust reverser of an aircraft propulsion unit.

[0106] When two rigid tools 2, 16 are used, this makes it possible to obtain a composite panel, each of the skins of which has an aerodynamic surface quality at the end of manufacturing, i.e. a smooth and undulating surface.

[0107] The use of flexible tooling is more economical and makes it easier to produce the composite panel because it eliminates the need for a mold, flexible membrane and counter-mold assembly. Only one mold and one flexible membrane can be used. Furthermore, flexible tooling is more adaptable to the thickness of the stack of materials placed between the two tools.

[0108] For example, one of the two tools may be fixed and the second tool may be movable relative to the first tool so as to allow relative movement between the two tools, for example a bringing together of the two tools, for example during the vacuum cooking step. In such a case, the fixed tool provides the general geometry of the part and the continuity of the first face of the part, and the movable tool provides the continuity of shape of the second face of the part.

[0109] In a variant, the two tools can be mobile, each of them providing continuity to each surface of the part, the general geometry being dependent on the relative movements and deformations of the two tools between them.

[0110] The tools 2, 16 will be described later.

[0111] The examples in Figures 1a, 2, 3a, 6a and 8 illustrate a set obtained at the end of of the positioning step previously described. The assembly 20 comprises a first tool 2 having for example a flat shape, a first layer of resin 4 as previously described which can be positioned, for example directly, on the first tool 2, a first fiber preform 10 such as previously described which can be positioned, for example directly on the first resin layer 4, a honeycomb structure 8 as previously described which can be positioned, for example directly on the first fiber preform 10, a second fiber preform 12 as previously described which can be positioned, for example directly, on the honeycomb structure 8, a second resin layer 14 as previously described which can be positioned, for example directly on the second fiber preform 12, and a second tool 16 having for example a planar shape, positioned on the second resin layer 14.

[0112] Optionally, a first layer of adhesive 26 may be positioned between the first fibrous preform 10 and the cellular structure 8, and a second layer of adhesive 28 may be positioned between the cellular structure 8 and the second fibrous preform 12.

[0113] The method may be intended for the manufacture of a composite panel having a generally planar shape. An assembly for the manufacture of such a panel is illustrated in Figures 1a, 1b, 2 and 8. In this embodiment, each tool has a surface, for example intended to respectively compress a fibrous preform, for example during the vacuum cooking step, which is planar.

[0114] The first tool 2 and the second tool 16 are arranged relative to each other so as to allow relative movement between the two tools 2, 16, for example a bringing together of the two tools 2, 16, for example during vacuum cooking.

[0115] In this embodiment, the first tool 2 and the second tool 16 are moved by translation. The relative movement of one tool with respect to the other is linear, in a direction parallel to the thickness of the resin layers.

[0116] In [Fig. 1b] the assembly 20 is shown after the vacuum curing step. Unlike the methods of the prior art, the resin is not injected but deposited beforehand, for example in the form of a film. During the process, the curing step heats the resin which melts and impregnates the fibers, for example dry fiber preforms. The infiltration of the resin into the fibers frees a space in the volume formed between the two tools allowing a rapprochement between the two tools, generated by the depression created by the evacuation of the volume.

[0117] In a first variant illustrated in figures 1a, 1b, and 8, the two tools 2, 16 can be rigid. For example, the first tool 2 can be a mold, for example rigid, and the second tool 16 can be a counter-mold, for example rigid.

[0118] In an alternative embodiment, the second tool 16 can be directly connected and sealed with the tool 2. The connection between the two tools requires the flexibility of the second tool 16 at least in the peripheral zones between the two part faces. For example, the second tool 16 may comprise a rigid main zone and flexible lateral zones made of elastomer or rubber on the lateral flanks.

[0119] Alternatively, in the example illustrated in [Fig.2], the second tooling 16 may be a flexible membrane that may be configured to cover the top and sides of the stack of materials.

[0120] The method and the assembly can also be intended for the manufacture of a composite panel of radiated, semi-cylindrical or conical shape.

[0121] Such an assembly is illustrated in figures 3a, 3b, 4, 5, 6a, 6b, 7, 8, 10 and 11. The assembly 20 is intended for the manufacture of composite panels having a generally curved shape. For example, the radii of curvature of parts can be between 400 mm and 2.5 m, for panel thicknesses between approximately 20 and 100 mm.

[0122] In a first variant embodiment illustrated in figures 4 to 7, 10 and 11, the two tools 2, 16 can slide relative to each other tangentially to the shape of the honeycomb structure element 6. For example, the first tool 2 can be fixed, and the second tool can be mobile 16, or vice versa, the mobile tool 16 being able to move radially at at least one point and at all other points move radially and tangentially. The movement of the mobile tool relative to the fibers is a combination of translation transverse to the thickness of the resin layers and translation parallel to the shape of the honeycomb structure element.In the case of large curved parts on an angular sector a, considering E the total thickness of resin deposited (for the two fiber preforms) and constituting the excess thickness of the stack, the compaction during the capillary infiltration of the resin will have to cause the changes in thickness according to, h' 1 = hl-E, h'2=h2-E, h'3=h3-E; .

[0123] In this embodiment where the tools can slide freely and one of them can be considered without deformation, and the second tool 16 moving only radially by the value E at the median plane of the angular sector, at the ends of the angular sector the displacement of the second tool will be E in the direction of the thickness and E. a / 2 tangentially.

[0124] For E = 1.5 mm, a =180°= ir; each lateral end slides by s= (ji / 2) xl.5 = 2.3 mm.

[0125] In the case of a curved part, if both tools are rigid, one of the two tools may have a greater curvature to accommodate the reduction in thickness due to the melting of the resin.

[0126] In a variant illustrated in Figures 3a and 3b and 12 the two tools can be arranged relative to each other so as to allow transverse but not tangential movements. For example the two tools can be linked together by means of at least two pins 30. In the example illustrated in Figures 3a and 3b, the two tools 2, 16 can be radially pinned together at several points, including the contours of the tools, that is to say considering that during the infiltration compaction, any normal section from one tool to the other of the circumference remains normal (no tangential sliding of the tools between them), then R'n = hn / (hn+En) x Rn.

[0127] With n corresponding to the index i of the left, middle and right points, Rn corresponding to the local internal radius before compaction and infiltration of the resin, hn corresponding to the local final thickness of the part, En corresponding to the thickness of all the additional resin layers at the given position n or i and R'n corresponding to the local internal radius after the phase of compaction and infiltration of the resin.

[0128] Let for En = 1.5 mm, RI = 1500 mm, and hl = 25 mm; R' 1 = (25 / (25+1.5))x 1500 = 1415 mm; for h2= 5 mm; R'2 = (5 / (5+1.5)) x 1500 = 1150 mm, for h3= 25 mm; R'3= (25 / 25+1.5))x 1500= 1415. The acoustic panel 24 obtained by means of the method and the assembly previously described is also illustrated in [Fig.9].

[0129] In another embodiment not illustrated, the movement between the two tools can be a mixture of the two previous examples.

[0130] In the examples shown, one of the two tools may be rigid and the other tool may be rigid or semi-rigid or flexible.

[0131] Figures 3a, 3b, 6a and 6 illustrate a first variant in which the two tools are rigid. In the example illustrated in Figures 3 for example, the stacking of materials between two tools 2, 16 may be similar to those previously described. The first tool 2 and the second tool 16 may be curved in shape and may be rigid. The first tool 2 may be configured to cover the bottom and the sides of the stack of material. The first tool 2 and the second tool 16 may be arranged so as to leave a clearance between the two tools allowing relative movement between the two tools.

[0132] Figures 4, 5 and 12 illustrate an assembly 20 according to an alternative embodiment in which the first tool 2 can be flexible and the second tool 16 can be rigid. The stack of material (not shown) can be similar to the stacks previously described. In this embodiment, for example, the honeycomb structure element (not visible) can have a decreasing thickness from a first end of the honeycomb structure element to a second end of the honeycomb structure element. This is due to the fact that the honeycomb structure has a decreasing thickness from a first end of the honeycomb core structure to a second end of the honeycomb structure.

[0133] The second tool 16 may be configured to cover the top of the material stack as well as the side of the material stack having the greatest thickness. The end of the honeycomb structure element 6 having the least thickness may have a monolithic return.

[0134] In this example, the second tool 16 can be fixed and the first tool 2 can be mobile relative to the second tool.

[0135] The first and second tools 2, 16 are arranged relative to each other so as to leave a clearance between the two tools, thus allowing them to move closer to each other. The tools 2, 16 are arranged so as to move according to two degrees of freedom. The movements are illustrated by arrows in [Fig.5].

[0136] The first tool 2 and the second tool 16 can be linked together, for example by means of a single spindle 30.

[0137] In a variant illustrated in [Fig. 12], the tools 2, 16 can be linked together, for example by means of at least two pins 30 with radial axes, for example by two pins 30 with radial axes so that over the majority of the part surface, for example the surface of the tool, for example flexible, the movement of the tools relative to each other is locally substantially parallel to the direction of the thickness of the resin layers. This means that the part radii are reduced by the amplitude corresponding to the reduction in thickness, and the angular sector of the molded part increases in return. Thus the assembly can comprise the pins 30 arranged on the side where the honeycomb structure element 6 has the greatest thickness.

[0138] Figures 10 and 11 illustrate an assembly 20 according to an alternative embodiment in which the first tool 2 can be rigid and the second tool 16 can be semi-rigid.

[0139] The assembly 20 may comprise a frame 100. The rigid mold 2 may be fixed to the frame 100.

[0140] The stack of material used may be similar to the stacks previously described. In this embodiment, for example, the honeycomb structure element 6 may have a decreasing thickness from a first end of the honeycomb structure element to a second end of the honeycomb structure element. This is due to the fact that the honeycomb structure has a decreasing thickness from a first end of the honeycomb core structure to a second end of the honeycomb structure. This configuration makes it possible to obtain a panel 24 as illustrated in [Fig. 9].

[0141] In this example, the tools 2, 16 can be linked together, for example by means of a pin 30, for example a single one.

[0142] The first and second tools 2, 16 are arranged relative to each other so as to leave a clearance between the two tools, thus allowing them to move closer to each other. The tools 2, 16 are arranged so as to move according to two degrees of freedom. The movements are illustrated by arrows in [Fig.11].

[0143] Furthermore, the manufacturing method may comprise a step of positioning a U-shaped or Z-shaped edge piece 32 at one of the ends, for example at each of the ends of the honeycomb structure element 6 (Figures 6a, 6b, 7). This step may be carried out so that the lateral legs of the U and the Z extend parallel to the tools and so that the central part of each edge piece is positioned against the end of the honeycomb structure element, for example against the honeycomb structure 8 and locally overlapping a part of the fiber layers 4 and 12. By U-shaped part is meant a part comprising two walls facing each other and being connected, for example connected by a bottom. By Z-shaped part is meant a part comprising two walls facing each other and being connected, for example connected by a third wall connected to opposite ends of the two walls.

[0144] The manufacturing method may include a step of draping a film of intumescent material between the honeycomb structure element and each of the U-shaped or Z-shaped edge pieces. An example is illustrated in Figure 6.

[0145] The [Fig.6a] illustrates an assembly 20 comprising a first tool 2, for example rigid, having for example a curved shape, a first resin layer 4 as previously described which can be positioned, for example directly, on the first tool, a first fiber preform 12 as previously described which can be positioned, for example directly on the first resin layer 4, a honeycomb structure 8 as previously described which can be positioned, for example directly on the first fiber preform 10, a second fiber preform 12 as previously described which can be positioned, for example directly, on the honeycomb structure 8, a second resin layer 14 as previously described which can be positioned, for example directly on the second fiber preform 12, and a second tool 16, for example rigid having for example a curved shape, positioned on the second resin layer.

[0146] The assembly 20 further comprises a first U-shaped edge piece 32 positioned at a first end 6' of the honeycomb structure element 6 and a second U-shaped edge piece 32 positioned at a second end 6” of the honeycomb structure element 6. The lateral legs of each U-shaped edge piece extend parallel to the tools and the central portion of each edge piece is positioned against one of the ends of the honeycomb structure element. The edge pieces are positioned against the honeycomb structure 8 and locally overlap part of the fiber layers 4 and 12, covering the preforms.

[0147] [Fig.6b] the assembly before the vacuum curing step. [Fig.6b] illustrates the assembly after the vacuum curing step. In [Fig.6b], the thickness of the assembly has been reduced by the thickness of the resin layers because the resin has penetrated into the fiber preforms so as to create connecting menisci to the honeycomb structure element. The resin layers are no longer distinguishable in the stack of materials.

[0148] In a variant of the embodiment illustrated in Figures 6a and 6b, at least one of the ends of the honeycomb structure element, for example the other end of the honeycomb structure element 6, can be finished in a sandwich or by a chamfered monolithic return. An example is illustrated in [Fig.7].

[0149] [Fig.7] illustrates an assembly according to one embodiment, the assembly 20 comprises a first tool 2, for example rigid, having for example a curved shape, a first resin layer 4 as previously described which can be positioned, for example directly, on the first tool, a first fiber preform 10 as previously described which can be positioned, for example directly on the first resin layer, a honeycomb structure 8 as previously described which can be positioned, for example directly on the first fiber preform, a second fiber preform 12 as previously described which can be positioned, for example directly, on the honeycomb structure, a second resin layer 14 as previously described which can be positioned, for example directly on the second fiber preform, and a second tool 16, for example rigid having for example a curved shape,positioned on the second layer of resin. In this example, the honeycomb element 6 has a decreasing thickness from a first end 6' of the honeycomb element to a second end 6” of the honeycomb element. This is due to the fact that the honeycomb structure has a decreasing thickness from a first end of the honeycomb structure to a second end of the honeycomb structure.

[0150] The assembly comprises a first U-shaped edge piece 32 positioned at the first end 6' of the honeycomb structure element having the greatest thickness and a second monolithic end 6”, for example a second end terminated by a chamfered monolithic return.

[0151] The manufacturing method may comprise a step, for example prior to the vacuum cooking step, of sealing the volume between the two tools.

[0152] In the example illustrated in [Fig. 1a] and b, the sealing step may comprise the positioning of sealing elements 34, for example between the two tools, for example on either side of the stack of materials, for example connecting the first tool and the second tool. This makes it possible to enclose the stack of materials in a volume formed between the two tools and the, for example, two, sealing elements. These sealing elements are configured to accommodate movement between the two tools, for example during the vacuum cooking step ([Fig. 1a]). The volume in which the depression (vacuum) is exerted is therefore delimited by the two tools 2, 16 and the sealing elements.

[0153] [Fig.8] illustrates an embodiment of the invention in which the sealing elements 34 are two flexible membranes.

[0154] The sealing step may include positioning a first sealing element 340 so as to surround the first ends of the first and second tools and positioning a second sealing element 340 so as to surround the second ends of the first and second tools so as to enclose the stack of materials in the volume between the two tools. These sealing elements are configured to accommodate movement between the two tools, for example during the vacuum cooking step (an example is illustrated in [Fig. 5]).

[0155] In the example illustrated in [Fig.7], the sealing step may comprise positioning a first sealing element 34 on one side of the stack, for example between the first and second tools and positioning a second sealing element 340, for example on the other side of the stack so as to surround the ends of the first and second tools. These sealing elements are configured to accommodate movement between the two tools, for example during the vacuum cooking step.

Claims

Claims

1. A method of manufacturing a composite panel comprising a honeycomb core interposed between two skins, the method comprising the steps of: - positioning a first layer of resin (4) on a first tool (2), - positioning a honeycomb structure element (6) comprising a honeycomb structure (8) arranged between two fiber preforms (10, 12) intended to form the skins, a first of the fiber preforms (10) being positioned on the first layer of resin (4), - positioning a second layer of resin (14) on the second of the fiber preforms (12) or on a second tool (16), - positioning one or the second tool (16), the first tool (2) and the second tool (16) being arranged relative to each other so as to allow relative movement between the two tools (2, 16),- vacuum cooking generating infiltration of the resin into the honeycomb structure element (6) and relative movement between the two tools (2, 16).,

2. Method according to claim 1 in which the relative movement generated between the two tools (2, 16) corresponds to a bringing together of the two tools (2, 16).

3. Method according to any one of claims 1 and 2 in which the two tools (2, 16) are rigid.

4. A method according to any one of claims 1 and 2 wherein one of the tools (2, 16) is rigid and the other tool (2, 16) is flexible.

5. A method according to any preceding claim wherein the resin layers (4, 14) are resin layers in solid form.

6. A method according to any preceding claim comprising a preliminary step in which the thickness of the first resin layer (4) and the second resin layer (14) are selected according to an amount of resin to be used.

7. A method according to any one of the preceding claims wherein the positioning of the honeycomb structure element (6) comprises the steps of: - positioning the first of the fibrous preforms (10) intended to form a first of the skins on the first layer of resin (4), - positioning a first layer of adhesive (26) on the first fibrous preform (10), - positioning the honeycomb structure (8) on the first layer of adhesive (26), - positioning a second layer of adhesive (28) on the honeycomb structure (8), - positioning the second fibrous preform (12) intended to form a second of the skins on the second layer of adhesive (28).

8. A method according to any one of the preceding claims comprising a step of positioning at least one U-shaped or Z-shaped edge piece (32) at one of the ends of the honeycomb structure element (6).

9. Method according to any one of the preceding claims comprising a step of positioning a first sealing element and a second sealing element (34) between the two tools (2, 16) and on either side of a stack formed of at least the element with a honeycomb structure (6) and the resin layers (4, 14).

10. A method according to the preceding claim wherein the first sealing element and the second sealing element (34) are configured to accommodate relative movement between the two tools (2, 16).

11. Assembly (20) for the manufacture of a composite panel comprising a honeycomb core interposed between two skins obtained at the end of the step of positioning one or the second tool of the method according to any one of the preceding claims, the assembly comprising: - the first tool (2), - the first layer of resin (4) positioned on the first tool (2), - the first fiber preform (10) positioned on the first layer of resin (4), - the alveolar structure (8) positioned on the first fibrous preform (10), - the second fibrous preform (12) positioned on the alveolar structure (8), - the second layer of resin (14) positioned on the second fiber preform (12), - the second tool (16) positioned on the second layer of resin (14), the first tool (2) and the second tool (16) being arranged relative to each other so as to allow relative movement between the two tools.

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