FR3075688A1 - METHOD FOR MANUFACTURING A HOLLOW PIECE OF COMPOSITE MATERIALS AND HOLLOW PIECE OBTAINED BY SAID METHOD - Google Patents

Abstract

A method of manufacturing a composite hollow part comprising the following steps: a) placing a fibrous material on a first female mold part and a second female mold part, b) positioning at least one reservation, c) placing a fibrous material, d) depositing at least one first reinforcing element e) setting up a waterproof membrane disposed against each first reinforcing element and each last layer of said fibrous material not covered by the first reinforcing element, f) sealingly, g) compressing each membrane against said fibrous materials, h) demolding the first female mold part and the second female mold part, i) depositing at least one second reinforcing element, j) sealingly joining the first part of the female mold and the second part of the female mold, k) ensuring the hardening of the hollow part.

Description

Technical field and state of the art

The present invention relates to a method for manufacturing a hollow part made of composite materials.

The hollow part in composite materials allows the design of a unique mechanical structure. The production of a composite material part makes it possible to obtain a part with increased qualities such as the strength / weight ratio, longevity under fatigue stresses and very good corrosion resistance.

The applications for manufacturing hollow parts are, for example, wind turbine or tidal turbine blades, aeronautical wing elements, vehicle chassis, structural elements, casings and tanks, or even ship appendages, for example. rudders, daggerboards, keels, foils ...

If a part made of composite materials offers increased performance, its potential is generally limited by the wide dispersion of its properties, particularly in terms of its resistance to rupture. This variability is linked to the manufacturing process which generates differences in microstructure between the parts produced.

A technique for manufacturing hollow parts is described in document FR2992890. This document describes a method of manufacturing a hollow piece of fibrous material comprising a first female mold part on which are arranged a fibrous material, a reinforcing element and a second female mold part on which are also arranged a fibrous material and another reinforcing element.

The parts thus produced make it possible to improve the overall mechanical strength. However, in certain cases, the mechanical resistance is stressed in a complex manner, such as the perpendicular traction and the hollow parts produced in the process described in the document FR2992890 do not allow sufficient resistance to complex stresses.

The object of the present invention is to overcome these drawbacks by proposing a method improving the mechanical characteristics of the hollow part with at least one reinforcing element. It also provides a solution to the delamination problem linked inter alia to the out-of-plane forces encountered during complex stresses, in particular perpendicular traction in structures of the bend type.

Another object of the invention is to obtain a process which is simpler to carry out and more efficient.

Description of the invention The invention provides a method of manufacturing a hollow part made of composite materials comprising the following steps: a) placing a fibrous material consisting of at least one layer on a first part of a female mold and on a second female mold part, so as to spread each layer according to the shape of the female mold, b) positioning at least one reservation forming a half of at least one block on the last layer of said fibrous material of each of the first part of female mold and of the second part of female mold, having previously arranged a separating release film, - c) placing a fibrous material consisting of at least one layer in each half of the block, d) depositing at least a first reinforcing element consisting of at least one layer of fibrous material, - e) putting in place a waterproof membrane disposed against each first reinforcing element and each last layer of said fibrous material not covered by the first reinforcing element, - f) sealingly associating the first female mold part and the second female mold part so that the reinforcing element is in contact with the last layer of said fibrous material corresponding to the other half of the block, - g) compressing each membrane against said fibrous materials, - h) demolding the first female mold part and the second female mold part to extract each block from the female mold and remove each reservation, - i) deposit at least one second reinforcing element on each block consisting of at least one layer of fibrous material, - j) position each block in the first female mold part or the second female mold part and associate sealing the first female mold part and the second female mold part, - k) ensuring the hardening of the hollow part.

Composite material is understood to be a combination of a fibrous reinforcement (such as carbon fiber, glass, aramid, polyethylene, boron, flax, hemp, etc.) and a matrix.

The fibrous reinforcement is associated with a matrix which may be thermosetting, for example, and without being exhaustive, epoxy, phenolic, polyester, vinylester, acrylic, or thermoplastic resins, such as, for example, polyetheretherketone (PEEK), polyetherketone (PEK), polypropylene. (PP), polyamide (PA), polyethylene (PE), polybutylene terephthalate (PBT), polyurethanes (TPU), polymethylmethacrylate (PMMA), polycarbonate (PC), polyether sulfone (PES), polyphenylene (PPS), polyethylenenaphthalate ( PEN) and polybutylenenaphthalate (NEA), cyclic poly (1,4-butylene terephthalate) (TCC) and / or combinations thereof.

The matrix, which acts as a binder, has the advantage of being able to be treated in its pre-polymer state and which can be handled as a liquid, gel, powder or granule. In this way, it can be used for the prepreg of the fibrous material, and thus form a prepreg.

The prepreg is a semi-finished product in the form of either a unidirectional sheet or of fiber fabrics. It does not require the addition of additional resin.

The manufacture of a prepreg is carried out using resin film of a certain thickness in relation to the desired final grammage. This resin film is then applied to a sheet of fibers and / or a fibrous fabric to form the prepreg. In some cases, during the impregnation of the fibers, a heat treatment aims to pre-polymerize the resin in order to slightly increase its viscosity.

It is possible to distinguish two types of hardening: the first for thermosets and the second for thermoplastics.

Thermoplastics are made up of essentially linear polymers. At low temperature, the macromolecules are linked together by multiple weak bonds, which rupture by a heating effect, which allows the sliding of the macromolecules on each other and causes fusion. As this transformation is reversible, these materials retain their properties.

Thermosets are plastics that take on a definitive shape when first cooled. It is understood by hardening for thermosets, the chemical reaction or the process by which molecules of low molecular weight (for example hydrocarbons of 2 to 10 carbon atoms) react with each other to give molecules of molecular weight ten, one hundred or millions of times greater. These plastics have a three-dimensional molecular structure, in which chains cannot slide over each other. The constituents which will form these plastics remain malleable up to a certain temperature. When these thermosets are heated above a certain temperature, they harden irreversibly, so their implementation takes place before they are fully polymerized, the polymerization ending in the mold. The hardening step, also called polymerization, can be accelerated by baking in an autoclave or in an oven, but it can also be linked to the presence of a base and a hardener during impregnation, injection or resin infusion through dry fibrous material.

The reinforcing elements are made of fibrous materials continuous to the neutral fiber of the part. This appreciably improves the characteristics of resumption of shear, of shearing force. In addition, the connection between the fibrous material of the first mold part and one of the lips of the reinforcing element takes place far from the neutral fiber, which improves the recovery of forces by the reinforcing element. This is also applicable between the fibrous material of the second mold part and the other lip of the reinforcing element.

The fact that the first reinforcing element or the second reinforcing element is made of fibrous material made of the same type of material as for the first female mold part and the second female mold part makes it possible to ensure in one step the hardening of the whole with a homogeneity inherent in the common hardening of all the different constituents.

The technique of positioning the waterproof membrane allows the production of parts closed at one or more ends, such as for example on a ship's appendage. This technique also makes it possible to produce parts with strong discontinuities of complex shape and geometry, for example at the foot of a wind turbine blade or a wick of a saffron.

The process also makes it possible to obtain the desired part in one go. It is not necessary to add a core or counter-mold to maintain the reinforcement element in position during the hardening of the part.

The method makes it possible to ensure better transmission of the shear forces between the two tensioned / compressed faces of the part subjected to a bending force.

The method also makes it possible to contain all of these folds in the case of stress of the peeling type and / or perpendicular traction-compression, in particular in singular zones with small radius of curvature inducing significant out-of-plane stresses.

In one embodiment, said method further comprises in step c), the first reinforcing element has a C-shaped section comprising two lips and a bottom, so that a lip of the first reinforcing element either in contact with the last layer of said fibrous material of a half block and a part of the bottom is in abutment against the reservation.

In one embodiment, in step i), the second reinforcing element has a C-shaped section comprising two lips and a bottom, so that part of the bottom of the second reinforcing element is in support with a part of the bottom of the first reinforcing element and that each lip covers part of the block.

In another embodiment, in step i), the second reinforcing element 5 consists of at least one layer of fibrous material which surrounds the entire block.

In another embodiment, in step i), the second reinforcing element 5 has an I-shaped section, so that part of the second reinforcing element 5 is in contact with part of the bottom of the first reinforcing element 4.

In one embodiment, the waterproof membrane of step e) goes back and forth inside the hollow part.

In one embodiment, step a) consists of a fibrous material extending beyond the first part of the female mold or the second part of the female mold so as to constitute a plunge.

Routing is a technique allowing the juxtaposition of adjacent plies of the first mold part and the second mold part.

In one embodiment, the first reinforcing element or the second C-shaped reinforcing element comprises at least two superimposed layers of fibrous material whose orientation of one layer relative to the other is alternated.

In one embodiment, in step c) a separating release film is positioned beforehand. The invention also relates to a hollow part made of composite material implementing the method.

BRIEF DESCRIPTION OF THE FIGURES Other characteristics and advantages of the invention will become apparent in the light of the description which follows, produced on the basis of the appended drawings. These examples are given without limitation. The description should be read in conjunction with the accompanying drawings in which: - Figure 1 shows the step of placing the fibrous material 1 according to a first embodiment of the invention, - Figure 2 shows another step of the process and incorporates certain elements of FIG. 1, - FIG. 3 represents another step of the process and incorporates certain elements of FIG. 1, - FIG. 4 represents another step of the process and incorporates certain elements of FIG. FIG. 5 represents another step of the method and takes up certain elements of FIG. 1, - FIG. 6 represents another step of the method and takes up certain elements of FIG. 1, elements of Figure 1, - Figure 8 shows a variant in Figure 7, - Figure 9 shows another variant in Figure 7, - Figure 10 shows another step of the pr given and uses certain elements of FIG. 1, - FIG. 11 represents a hollow part according to a second embodiment of the invention, - FIG. 12 represents a view of an autoclave cooking cycle.

Description of embodiments of the invention

The process described below makes it possible to obtain a hollow part made of composite materials.

A female mold is used for the production of the hollow part. This mold consists of two parts: a first part and a second part. The first part of the female mold and the second part of the female mold are symmetrical. In a variant, if the part to be produced is asymmetrical, the female mold is necessarily asymmetrical.

Figure 1 shows the step of placing the fibrous material 1, for example a prepreg of carbon fiber or glass associated with an epoxy resin matrix. The fibrous material 1 is deposited on the first part 2a of the female mold. In order to increase the thickness, the fibrous material 1 is deposited in several successive layers which follow the profile of the first part 2a of the female mold.

The concept of layup is used which describes the successive layers of fibrous material 1 deposited one above the other on the female mold.

In order to prepare the assembly between the fibrous material 1 of the first part 2a of the mold and the fibrous material 1 of the second part 2b of the mold, the successive layers extend beyond the first part 2a of the female mold, so as to form a plunge (not shown). That is to say that the fibrous material 1 of the first mold part 2a extends over all or part of the length of the female mold, so as to form a lip adapted to receive the fibrous material 1 of the second part 2b of female mold and allow its connection. This feature makes it possible to obtain a longitudinal hollow part which is closed at one end without adding material and without breaking the shape.

In a variant, the routing is carried out on the second part 2b of the female mold.

According to another variant, not shown, a juxtaposition element is placed at a location in which the angle of the workpiece is less than 20 °. In this way, the juxtaposition element will make it possible to ensure the good connection of the fibrous material 1 of the first part 2a of the female mold and of the second part 2b of the female mold. For example, the juxtaposition element is V-shaped.

According to a variant, the layup is alternated between each successive layer of fibrous material 1 and 1 'which then mix intimately while improving the mechanical strength of the part. Indeed, the external forces will then be better distributed over the whole room. During this step, the different layers of fibrous material 1 and 1 ′ are compacted under vacuum in their position in the female mold to allow better shaping and better resistance, in particular in the case of large thicknesses and / or accidents. of form.

Figure 2 shows some elements of Figure 1. In this figure, it is visible a reservation 3 positioned on the last layer of said fibrous materiall of each female mold part (the first part 2a and the second part 2b).

The role of the reservation is to form a space that will be filled during another stage of the process.

In this figure, the reservation forms three block halves on each part of the female mold (the first part 2a and the second part 2b). When the female mold parts are associated, the reservation makes it possible to create three spaces which form three blocks.

In a variant, the number of blocks depends on the hollow part. Thus, it is possible to have a single block. It is also possible to have a plurality of blocks.

FIG. 3 represents another step of the process and takes up certain elements of the preceding figures. In this figure, the positioning of several successive layers of fibrous material 1 ’is shown, which follow each half of the block formed by the reservation 3. The thickness of the layer of fibrous material 1 ′ depends on the part.

FIG. 4 represents another step of the method and takes up certain elements of the preceding figures. In this figure, a first reinforcing element 4 is shown.

The first reinforcing element 4 is produced using one or more conformers. The conformator is the mold of the reinforcing element 4 which is C-shaped and includes two lips and a bottom. The goal is to create the C-shaped reinforcement element 4 to place it in the female mold inside the reservations. In this exemplary embodiment, the first C-shaped reinforcing element 4 is positioned in each half of the block so that a lip of the first reinforcing element 4 is in contact with the last layer of said fibrous material 1 'd '' a half of a block and part of the bottom rests against the reservation 3.

The former, not shown, will allow the layup of at least one layer of fibrous material. The dimensions of the conformator are a function of the dimensions of the female mold and the sampling of the part.

The fibrous materials have fibers which can be unidirectional, for example fibers oriented at 0 ° along the main longitudinal axis of the hollow part produced, in particular those constituting the bulk of the structure of the wick. According to a variant, the successive layers of the first reinforcing element 4 are produced with fibers oriented in various ways, preferably substantially at +/- 45 ° relative to the transverse axis of the part. In this way, the part thus produced using these fibers has better recovery of the shearing force. In the same way as for draping in the female mold, the different layers of fibrous materials can be compacted under vacuum in their shaping device to allow better shaping and better hold, in particular in the case of large thicknesses and / or d 'accidents of form.

In the example, when two first reinforcing elements 4 are C-shaped, they are arranged so that each lip end of the C-shape is facing the other, so as to form a volume which will be in most cases parallelepiped. The next step of the process consists in putting in place a waterproof membrane disposed against each first reinforcing element and each layer of said fibrous material 1 ’not covered by the reinforcing element.

The waterproof membrane is a bag intended to create a vacuum, for example it is made of plastic film, elastomer or other elastic material; if necessary, it can be coated with a release agent.

FIG. 5 represents another stage of the process and takes up certain elements of the preceding figures. In this figure, the association of the first part 2a of the female mold and the second part 2b of the female mold is shown in a sealed manner so that the other lip of the reinforcing element 4 is in contact with the last layer of said fibrous material 1 'corresponding to the other half of the block. The next step in the process is to compress each membrane against said fibrous material, for example by applying the vacuum between the membrane and the sampling.

FIG. 6 represents another step of the method and takes up certain elements of the preceding figures. In this figure, the various elements are shown without the first part 2a of the female mold or the second part 2b of the female mold. The process step consists of removing from the first part 2a of the female mold and from the second part 2b of the female mold each block of the female mold and removing each reservation 3.

FIG. 7 represents another step of the method and takes up certain elements of the preceding figures. This step consists in depositing at least one second reinforcing element 5 on each block. The second reinforcing element 5 has a C-shaped section comprising two lips and a bottom. The second reinforcing element 5 is made up of at least one layer of fibrous material in the same way as the first reinforcing element. The second reinforcing element 5 is positioned so that a part of the bottom of the second reinforcing element 5 is in contact with a part of the bottom of the first reinforcing element 4 and so that each lip covers part of the block.

FIG. 8 represents a variant in FIG. 7 and takes up certain elements of the preceding figures. This step consists in depositing at least one second reinforcing element 5 between each block. The second reinforcing element 5 has an I-shaped section.

The second reinforcing element 5 is positioned so that part of the second reinforcing element 5 is in contact with part of the bottom of the first reinforcing element 4.

FIG. 9 represents another variant in FIG. 7 and takes up certain elements of the preceding figures. This step consists in depositing at least one second reinforcing element 5 surrounding each block. The second reinforcing element 5 is positioned so that the entire block is covered by at least one layer of fibrous material. The next step in the process consists in positioning each block in the first part 2a of the female mold or the second part 2b of the female mold.

FIG. 10 represents another step of the process and takes up certain elements of FIG. 7. In this figure, it is shown the sealing association of the first part 2a of the female mold with the second part 2b of the female mold. The next step is to harden the hollow part. The autoclave hardening is carried out by controlling the cooking parameters such as temperature, vacuum and surrounding pressure. Their precise control makes it possible to obtain parts made of composite materials which have high properties.

FIG. 11 represents a second embodiment and we find elements of FIG. 10.

In this figure, there are two second secondary reinforcing elements 5 which are supported by the bottom and together form an IPN (I-beam with normal profile). There are two blocks shown and inserted in the hollow part. Inside each block there are four first reinforcing elements, two of which form a substantially parallelepiped volume.

FIG. 12 represents an operating cycle of an autoclave according to the following steps: - apply the complete vacuum (0.9 bar), see curve 6, - apply a pressure of 7 bar autoclave gauge, see curve 7, - reduce the vacuum for a safety value of 0.2 bar when the autoclave pressure reaches approximately 1 bar, see curve 6, - heat at 1 -3 ° C / minute to 120 ° C, see curve 8, - hold at 120 ° C for 60 minutes, see curve 6, - cool to 2-5 ° C / min, see curve 6, - release the pressure from the autoclave when the hollow part reaches 60 ° C.

These parameters can be modified according to the thickness of the constituent materials and their nature.

In another variant, it can be envisaged, without departing from the scope of the invention, to adapt the proportions, the shapes of a hollow part made of composite materials such as those described above by simple constructive arrangements which will appear directly and without excessive effort by a person skilled in the art, so as to be able to use this manufacturing process in order to obtain hollow parts in different fields such as for example, and without being exhaustive, the manufacture of wind turbine blades, tidal turbine, aeronautical wing elements or ship appendages.

Nomenclature 1,1 ’fibrous material 2a first part of female mold 2b second part of female mold 3 reservation 4 first reinforcement element 5 second reinforcement element 6 vacuum curve 7 pressure curve 8 temperature curve

Claims (10)

claims 1. A method of manufacturing a hollow part made of composite materials comprising the following steps: a) placing a fibrous material (1) consisting of at least one layer on a first part (2a) of female mold and on a second part (2b) of female mold, so as to spread each layer according to the shape of the female mold, b) positioning at least one reservation (3) forming a half of at least one block on the last layer of said fibrous material (1) of each of the first part (2a) of female mold and of the second part (2b) of female mold, having previously disposed of a separating release film, c) placing a fibrous material (1 ') consisting of at least a layer in each half of the block, - d) depositing at least one first reinforcement element (4) consisting of at least one layer of fibrous material, - e) putting in place a waterproof membrane disposed against each first reinforcement element and every last re layer of said fibrous material (T) not covered by the first reinforcing element (4), - f) sealingly associating the first part (2a) of female mold and the second part (2b) of female mold so that that the reinforcing element (4) is in contact with the last layer of said fibrous material (1 ') corresponding to the other half of the block, g) compressing each membrane against said fibrous materials, h) demolding the first part (2a ) of female mold and the second part (2b) of female mold to extract each block from the female mold and remove each reservation (3), i) deposit at least one second reinforcing element (5) on each block consisting of at least a layer of fibrous material, j) positioning each block in the first part (2a) of female mold or the second part (2b) of female mold and sealingly associating the first part (2a) of female mold and the second part (2b) female mold, k) assu curing of the hollow part. 2. Method for manufacturing a hollow part made of composite materials according to claim 1, in which in step c), the first reinforcing element (4) has a C-shaped section comprising two lips and a bottom, of so that a lip of the first reinforcing element (4) is in contact with the last layer of said fibrous material (Γ) of a half block and a part of the bottom is in abutment against the reservation (3) . 3. A method of manufacturing a hollow composite material part according to claim 2, wherein in step i), the second reinforcing element (5) has a C-shaped section comprising two lips and a bottom, of so that part of the bottom of the second reinforcing element (5) is in contact with a part of the bottom of the first reinforcing element (4) and so that each lip covers part of the block. 4. A method of manufacturing a hollow composite material according to claim 1, wherein in step i), the second reinforcing element (5) consists of at least one layer of fibrous material which surrounds the whole of the block. 5. A method of manufacturing a hollow composite material according to claim 2, wherein in step i), the second reinforcing element (5) has an I-shaped section, so that a part of the second reinforcement element (5) is in abutment with part of the bottom of the first reinforcement element (4). 6. A method of manufacturing a hollow part made of composite materials according to claim 1, in which the waterproof membrane of step e) performs back-and-forth movements inside the hollow part. 7. A method of manufacturing a hollow part in composite materials according to claim 1, wherein step a) consists of a fibrous material (1) extending beyond the first part (2a) of the mold. female or of the second part (2b) of female mold so as to constitute a plunge. 8. A method of manufacturing a hollow composite material according to claim 3, wherein the first reinforcing element (4) or the second reinforcing element (5) in the form of C comprises at least two superimposed layers of fibrous material whose orientation of one layer relative to the other is alternated. 9. A method of manufacturing a hollow part made of composite materials according to claim 1, in which in step c) a separating release film is positioned beforehand. 10. Hollow part made of composite material obtained by said process according to any one of the preceding claims.