FR3156365A1 - SOLUBLE CORE FOR THE MANUFACTURE OF HOLLOW PARTS MADE OF ORGANIC MATRIX COMPOSITE MATERIAL - Google Patents

Abstract

Forming core comprising a body soluble in a liquid and a polymerized resin skin coating the soluble body. Method for obtaining the forming core. Assembly of a forming core and a hollow part (62) made of organic matrix composite material. Hollow part (62) made of organic matrix composite material comprising a cavity (80), the cavity (80) being covered with a polymerized resin skin (54). Method for manufacturing the hollow part (62). Figure for abstract: Fig. 14

Description

SOLUBLE CORE FOR THE MANUFACTURE OF HOLLOW PARTS MADE OF ORGANIC MATRIX COMPOSITE MATERIAL

This disclosure relates to the manufacture of hollow parts made of organic matrix composite material, in particular turbomachinery, in particular hollow parts made of organic matrix composite (OMC). More specifically, this disclosure relates to a molding core used in the manufacture of OMC parts, a method for manufacturing such a molding core, a method for manufacturing such a hollow OMC part, for example a hollow OMC part, and the part thus obtained.

CMO parts are commonly used in aeronautical engines such as aircraft turbomachines in order to reduce their mass, while guaranteeing the desired mechanical properties, in particular, their stiffness.

These CMO parts are particularly commonly used in the production of fan module parts, for example fan blades or outlet guide vanes (OGVs).

These CMO parts can be obtained by using a fibrous reinforcement made from a three-dimensional weave in which the threads intertwine in a three-dimensional manner (so-called “3D interlock” weave) and which is impregnated in an organic matrix.

The organic matrix can be injected by liquid means using the LCM process (Liquid Composite Molding), for example using the VARTM process (Vacuum Assisted Resin Transfer Molding).

Processes such as stamping, thermocompression or additive manufacturing can also be used.

CMOs withstand temperatures ranging from 100°C to 250°C. These materials replace metallic parts in certain parts of turbomachines, particularly for fan blades and/or outlet guide vanes.

Furthermore, their use contributes to optimizing the performance of turbomachines or turbomachine equipment, in particular by reducing the overall mass of the turbomachine, thus reducing fuel consumption which in turn leads to a reduction in harmful emissions (CO, _CO2 , _NOx, etc.).

Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new aircraft types and those already in operation, requiring the implementation of technological solutions to ensure their compliance with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

Technological research efforts have already led to significant improvements in the environmental performance of aircraft. Factors impacting all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products, whose integration and use in civil aviation have moderate environmental consequences, are taken into account with the aim of improving the energy efficiency of aircraft.

Consequently, reducing negative climate impact is a permanent subject of improvement through the use of methods and the exploitation of virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible to reduce the environmental footprint.

This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as an essential complement to technological progress, aeronautical biofuels.

In order to lighten the fan blades and/or the CMO outlet guide vanes, it is known to manufacture hollow blades.

Manufacturing processes that allow parts to be directly produced in the desired shape are particularly advantageous from an industrial point of view. Indeed, they generally allow for a better production rate. Such parts are obtained using molds having the desired shape.

However, not all parts are suitable for such processes. While casting processes have been widely developed and can be used for a wide variety of different materials, the desired part geometry is still often limited.

For example, if the final geometry includes cavities, it is not possible to obtain the part directly by molding.

However, solutions exist for the preparation of parts with cavities, such as the placement of cores in the mold, which are removed or eliminated once the part is obtained.

FR3125238 discloses a core comprising a material that decomposes upon contact with water or humid air. This material is present at the grain boundaries, which allows the core to fragment and therefore be eliminated when the core is exposed to water or humid air.

However, removing the core once the part is finished complicates the molding process or requires the use of special tools. Also, for core removal, it is necessary to create large openings between the cavity and the outside of the part, and some part geometries are not accessible using this technology.

In the case of a soluble core, the core can be dissolved once the desired part is obtained. Cores have thus been proposed and the geometry of the accessible parts is then limited by the constraints in the manufacture of the core.

For the manufacture of cores, the solutions proposed in the prior art all have shortcomings, for example, on the minimum size of the cores that can be obtained or the complexity of the core manufacturing process. Also, the processes for dissolving the core can be complex and/or involve toxic compounds.

There remains a need for improvement in the manufacturing processes of hollow parts using casting processes.

This presentation aims to remedy at least in part these drawbacks, in particular to significantly improve the performance of aircraft and, in this sense, contribute to reducing the environmental impact of aircraft.

To this end, the present disclosure relates to a forming core comprising a soluble body and a polymerized resin skin coating the soluble body.

Thanks to the polymerized resin skin that encases the entire soluble body, the forming core is not exposed to liquids and/or moisture during storage, handling, insertion of the molding core into a fiber preform and/or the preform shaping step. Similarly, the forming core can be used to form an external surface of the fiber preform, the forming core then being arranged between a mold surface and an external surface of the fiber preform.

Thus, the forming core does not undergo any degradation before its removal from the part.

Furthermore, when injecting resin into the fiber preform, a forming core that has been exposed to liquids and/or moisture may begin to dissolve in the fiber preform and contaminate the impregnation resin of the fiber preform, which could result in altering the mechanical properties of the resin and therefore of the final part.

It is understood that the soluble body may comprise a material which dissolves upon contact with a liquid, either by complete dissolution of the soluble body or by dissolution of the grain boundaries of the soluble body and fragmentation of the soluble body. The fragments can be easily removed from the cavity formed by the dissolution of the grain boundaries and fragmentation of the soluble body.

It is understood that the melting temperature of the polymerized resin skin is lower than the melting temperature of the soluble body.

In some embodiments, the polymerized resin skin may be a thermosetting resin.

In some embodiments, the polymerized resin skin may be a thermoplastic resin.

In some embodiments, the soluble body may be soluble in a liquid.

By way of non-limiting example, the liquid may be an aqueous solution or water.

The choice of a soluble body which can be dissolved by water makes it possible to have parts whose extraction openings, which allow the elimination of the soluble body, are smaller than for solutions of the prior art, in particular less than 5 millimeters or even less than 4 millimeters.

Furthermore, from an environmental and safety point of view, water is less harmful and reduces risks for operators compared to other liquids, for example a non-aqueous solvent.

In some embodiments, the soluble body may comprise a soluble thermoplastic polymer.

By way of non-limiting example, the soluble thermoplastic polymer is soluble in a non-aqueous solvent, for example in acetone, ethanol, methanol or isopropanol.

In some embodiments, the soluble body may comprise a material that decomposes upon contact with a liquid.

By way of non-limiting example, the soluble body may decompose upon contact with a liquid, for example an aqueous solution or water.

From an environmental and safety perspective, water is less harmful and reduces risks for operators.

By way of non-limiting example, the soluble body may comprise a composite material comprising on the one hand a first phase of formula M _n+1 AlC _n , where n = 1 to 3, and M being a transition metal chosen from the group consisting of titanium, niobium, chromium or zirconium, the composite material comprising on the other hand a second phase of formula Al ₄ C ₃ .

By way of non-limiting example, the first phase is of one of the formulas Ti ₃ AlC ₂ , Ti ₂ AlC, Cr ₂ AlC, Zr ₂ AlC, Zr ₃ AlC ₂ , Nb ₄ AlC ₃ , or Nb ₂ AlC.

The combination of this first phase with a second phase of formula Al ₄ C ₃ is particularly advantageous. Indeed, aluminum carbide (Al ₄ C ₃ ) is an inorganic compound with a very high melting point (2200°C) and which can easily hydrolyze at room temperature in the presence of a water-rich atmosphere. Thus, the composite material used for the molding core of the present disclosure incorporates this second phase of aluminum carbide into the grain boundaries of the first phase. This makes the composite material particularly reactive to atmospheres containing water. The degradation of the aluminum carbide is accompanied by a variation in volume and a release of gas, capable of fragmenting the grain boundary and propagating cracks in the first initial phase. It is thus possible to propagate the hydrolysis phenomenon over relatively large distances, and thus facilitate fragmentation and debonding of the core. In other words, the composite material forming the core can be initially dense and massive, and be reduced to powder by hydrolysis.

The present disclosure also relates to an assembly of a forming core as defined previously and a hollow part made of organic matrix composite material, the polymerized resin having a glass transition temperature greater than or equal to a glass transition temperature of the organic matrix of the hollow part made of organic matrix composite material.

Since the polymerized resin has a glass transition temperature greater than or equal to the glass transition temperature of the organic matrix, the polymerized skin resin will not degrade during the polymerization step of the impregnation resin to form the organic matrix of the hollow part made of organic matrix composite material.

In some embodiments, the polymerized resin may be different from the organic matrix.

In some embodiments, the polymerized resin and the organic matrix may be of the same nature, for example they may be the same.

The present disclosure also relates to a method for obtaining a forming core as defined previously comprising the following steps:
- a step of manufacturing the soluble body;
- a step of coating the soluble body with a coating resin;
- a step of transforming the coating resin to obtain the skin in polymerized resin coating the soluble body.

It is understood that the coating step can be carried out in several removal steps and using the appropriate tools in order to cover all the surfaces of the core, including those in contact with the holding or quenching supports, for example.

In some embodiments, the step of manufacturing the soluble body may comprise a step of mixing powders, a step of at least partially liquefying the powder mixture, for example by heating the powder mixture, a step of forming the soluble body by casting the at least partially liquefied powder mixture into a mold, a step of solidifying in the mold and a step of demolding the soluble body.

The soluble body once solidified is soluble in a liquid, for example in water.

By way of non-limiting example, the powder mixture may be a mixture of sodium nitrate, potassium nitrate and zirconium silicate.

By way of non-limiting example, the powder mixture may comprise 13.3% by mass of sodium nitrate (NaNO ₃ ), 33.3% by mass of zirconium silicate (SiO ₄ Zr) and 53.4% by mass of potassium nitrate (KNO ₃ ).

In some embodiments, the coating step may be performed by dipping the soluble body into a bath of coating resin.

In some embodiments, the coating step may be performed by applying the coating resin to the soluble body, for example by brush or spray.

In some embodiments, the coating resin may be a thermosetting resin.

When the coating resin is a thermosetting resin, the processing step includes a step of polymerization of the coating resin is carried out by heat treatment of the coating resin to form the polymerized resin skin.

By way of non-limiting example, the coating resin may be an epoxy resin, for example an epoxy resin marketed under the reference PR520 or RTM6.

In some embodiments, the coating resin may be a thermoplastic resin.

When the coating resin is a thermoplastic resin, the resin is heated before the coating step to obtain a sufficiently fluid resin to coat the soluble body. When the soluble body is coated, the forming step includes a step of cooling the coating resin to form the polymerized resin skin.

It is understood that the thermoplastic resin is polymerized before the coating step.

By way of non-limiting examples, the coating resin may be a polyamide resin (polyamide 6 or polyamide 6,6) or polycarbonate, or polyethylene terephthalate or a copolymer such as glycated polyethylene terephthalate.

This disclosure also relates to a method for manufacturing a hollow part made of organic matrix composite material comprising the following steps:
- a step of obtaining the forming core as defined previously;
- a step of assembling the forming core as defined previously and a fibrous preform forming a precursor of the hollow part made of ceramic matrix composite material;
- a step of draping the fiber preform and the forming core in a mold;
- a mold closing step;
- a step of impregnating the fiber preform with an impregnation resin;
- a step of polymerization of the impregnation resin in the mold to form the organic matrix;
- a step of demolding the hollow part made of organic matrix composite material and the forming core; and
- a step of elimination of the soluble body;
the coating resin having a glass transition temperature greater than or equal to a glass transition temperature of the impregnating resin.

By way of non-limiting examples, the fibrous preform may comprise glass, carbon, aramid fibers, and/or a mixture of these fibers.

As non-limiting examples, the fibrous preform may also include a metal insert, such as a leading edge shield and/or a screw insert.

The coating resin having a glass transition temperature greater than or equal to the glass transition temperature of the impregnation resin, the coating resin, once polymerized to form the polymerized resin skin, will not degrade during the polymerization step of the impregnation resin to form the organic matrix of the hollow part made of organic matrix composite material.

In some embodiments, the coating resin may be different from the impregnation resin.

In some embodiments, the coating resin and the impregnation resin may be of the same nature, for example they may be the same.

In some embodiments, between the assembly step and the draping step, the fiber preform may be shaped.

Shaping improves the positioning of the fibers in the fiber preform and limits the forces and movements of closing the mold, particularly during the draping stage and the mold closing stage.

In some embodiments, the shaping may be performed on the wet fibrous preform and the shaped fibrous preform is dried prior to the draping step.

By way of non-limiting example, the drying is carried out at a temperature greater than or equal to 100°C and less than or equal to 130°C, for example 120°C.

It is understood that the shaping of the wet fiber preform is made possible thanks to the polymerized resin skin of the forming core which protects the soluble body from any deterioration.

In some embodiments, during the assembly step, the core may be flush with an outer surface of the fiber preform.

When the hollow part made of organic matrix composite material is demolded, the forming core is accessible on the external face where the forming core is flush. It is possible to tear the polymerized resin skin coating the soluble body and dissolve the soluble body.

In some embodiments, the step of removing the soluble body may comprise a step of drilling a soluble body removal channel in the hollow part of organic matrix composite material to reach the soluble body.

In some embodiments, the forming core may include a channel core configured to form a soluble body removal channel in the hollow organic matrix composite material part.

It is understood that, once the part of the soluble body forming the channel core is dissolved, a channel for eliminating the soluble body is formed in the hollow part made of organic matrix composite material.

The soluble body elimination channel allows the soluble body to be dissolved or fragmented by projecting a liquid onto the soluble body.

By way of non-limiting example, the channel may have a diameter greater than or equal to 5 mm and less than or equal to a maximum thickness of the soluble body to be eliminated.

In some embodiments, the step of removing the soluble body may comprise dissolving the soluble body or fragmenting the soluble body with a pressurized jet of liquid, for example, water.

Liquid pressure is a compromise between core extraction time and the risk of damage to the composite part. The higher the liquid pressure, the faster the core extraction will be.

In some embodiments, the water may be heated to a temperature greater than or equal to 40°C and less than or equal to 95°C.

Water heated to a temperature greater than or equal to 40°C and less than or equal to 95°C can allow for faster dissolution of the soluble body.

The present disclosure also relates to a hollow part made of organic matrix composite material comprising a cavity, the cavity being covered with a skin made of polymerized resin.

By way of non-limiting example, the hollow part made of organic matrix composite material may be a fan guide vane called OGV in accordance with the English acronym for “Outlet Guide Vane”, a propeller or a FAN blade.

Other characteristics and advantages of the subject of the present disclosure will emerge from the following description of embodiments, given as non-limiting examples, with reference to the appended figures.

FIG. 1 There FIG. 1 is a schematic longitudinal sectional view of a turbomachine.

FIG. 2 There FIG. 2 is a schematic representation of a step of coating a soluble body with a coating resin according to one embodiment.

FIG. 3 There FIG. 3 is a schematic representation of a step of coating a soluble body with a coating resin according to a second embodiment.

FIG. 4 There FIG. 4 is a schematic representation of a step of coating a soluble body with a coating resin according to a third embodiment.

FIG. 5 There FIG. 5 is a flowchart representing the steps of a method for obtaining a forming core according to one embodiment.

FIG. 6 There FIG. 6 is a flowchart representing the steps of a method for manufacturing a hollow part made of organic matrix composite material according to one embodiment.

FIG. 7 There FIG. 7 is a schematic representation of a step of assembling the forming core and a fiber preform according to one embodiment.

FIG. 8 There FIG. 8 is a schematic representation of a step of shaping the fiber preform according to one embodiment.

FIG. 9 There FIG. 9 is a schematic representation of the fibrous preform shaped with the soluble core in a mold according to one embodiment.

FIG. 10 There FIG. 10 is a schematic representation of a step of impregnation of the fiber preform according to one embodiment.

FIG. 11 There FIG. 11 is a schematic view of the hollow part made of organic matrix composite material and the soluble core after demolding according to one embodiment.

FIG. 12 There FIG. 12 is a schematic representation of a step of removing the soluble body according to one embodiment.

FIG. 13 There FIG. 13 is a schematic view of the hollow part made of organic matrix composite material according to one embodiment.

FIG. 14 There FIG. 14 is a schematic view of the hollow part made of organic matrix composite material and of the soluble core after demolding according to a second embodiment.

FIG. 15 There FIG. 15 is a schematic view of the hollow part made of organic matrix composite material and of the soluble core after demolding according to a third embodiment.

Detailed description

There FIG. 1 represents in section along a vertical plane passing through its main axis A, a double-flow turbojet 10 which is an example of a turbomachine. The double-flow turbojet 10 comprises, from upstream to downstream according to the circulation of the air flow F, a fan 12, a low-pressure compressor 14, a high-pressure compressor 16, a combustion chamber 18, a high-pressure turbine 20, and a low-pressure turbine 22.

The terms “upstream” and “downstream” are defined in relation to the direction of air circulation in the turbomachine, in this case, according to the circulation of the air flow F in the turbojet 10.

The turbojet 10 comprises a fan casing 24 extended towards the rear, that is to say towards the downstream, by an intermediate casing 26, comprising an external shell 28 as well as an internal shell 30 parallel and arranged, in a radial direction R, internally with respect to the external shell 28. The radial direction R is perpendicular to the main axis A.

The terms "external" and "internal" are defined with respect to the radial direction R so that the internal part of an element is, in the radial direction, closer to the principal axis A than the external part of the same element.

The intermediate casing 26 further comprises structural arms 32 distributed circumferentially and extending radially between the inner shell 30 and the outer shell 28. For example, the structural arms 32 are bolted to the outer shell 28 and to the inner shell 30. The structural arms 32 make it possible to stiffen the structure of the intermediate casing 26.

The main axis A is the axis of rotation of the turbojet 10 and the low pressure turbine 22. This main axis A is therefore parallel to the axial direction.

The low pressure turbine 22 comprises a plurality of impellers which form the rotor of the low pressure turbine 22.

In the following, the elements common to the different embodiments are identified by the same numerical references.

There FIG. 2 represents a forming core 50 according to one embodiment. The forming core 50 comprises a soluble body 52 coated with a polymerized resin skin 54.

In the following, the elements common to the different embodiments are identified by the same numerical references.

The method 100 for obtaining the forming core 50 comprises a first step 102 of manufacturing the soluble body 52.

As non-limiting examples, the soluble body 52 may be soluble in a liquid; the soluble body 52 may comprise a material that decomposes upon contact with a liquid. The liquid may be an aqueous liquid, for example, water, or a non-aqueous solvent.

The obtaining method 100 then comprises a step 104 of coating the soluble body 52 with a coating resin 56.

As shown in the FIG. 2 , the coating step 104 can be carried out by dipping the soluble body 52 in a bath of a coating resin 56.

As shown in the FIG. 3 , the coating step 104 can be carried out by applying the coating resin 56 with a brush to the soluble body 52.

As shown in the FIG. 4 , the coating step 104 can be carried out by applying the coating resin 56 by spray on the soluble body 52.

When the soluble body 52 is coated with the coating resin 56, the obtaining method 100 comprises a transformation step 106 of the coating resin 56 to obtain the polymerized resin skin 54, as shown in the FIG. 2 .

By way of non-limiting example, when the coating resin 56 is a thermosetting resin, the transformation step 106 may comprise a step of polymerization of the coating resin 56.

By way of non-limiting example, when the coating resin 56 is a thermoplastic resin, the transformation step 106 may comprise a step of cooling the coating resin 56.

By way of non-limiting example, the coating resin may be a thermosetting resin, for example an epoxy resin, for example an epoxy resin marketed under the reference PR520N®.

The manufacturing method 200 of a hollow part 62 made of organic matrix composite material will be described on the basis of figures 6 to 13.

As shown in Figures 6 and 7, the manufacturing method 200 comprises a first step 100 of obtaining the forming core 50 followed by a step 202 of assembling the forming core 50 and a fiber preform 60. The fiber preform 60 forms a precursor of the hollow part 62 made of organic matrix composite material.

As shown in Figures 6 and 8, the manufacturing method 200 may then comprise a shaping step 204 of the fiber preform 60. The shaping step 204 is an optional step.

When the fiber preform 60 is wet during the shaping step 204, the shaping step 204 may include a step of drying the fiber preform 60.

The manufacturing method 200 then comprises a step 206 of draping the fiber preform 60 and the forming core 50 in a mold 70.

As shown in the FIG. 6 , the manufacturing method 200 then comprises a step 208 of closing the mold 70. On the FIG. 9 , the mold 70 is shown closed, that is to say once the closing step 208 is completed. The mold 70 may comprise inlet and outlet openings for the impregnation resin.

As shown in the FIG. 6 , the manufacturing method 200 then comprises a step 210 of impregnation of the fiber preform 60 with an impregnation resin 58. On the FIG. 10 , the fiber preform 60 is entirely impregnated with the impregnation resin 58.

The coating resin 56 has a glass transition temperature greater than or equal to the glass transition temperature of the impregnation resin 58.

By way of non-limiting example, the impregnation resin 58 and the coating resin 56 may be a thermosetting resin, for example an epoxy resin, for example an epoxy resin marketed under the reference PR520N®.

As shown in the FIG. 6 , the manufacturing method 200 then comprises a step 212 of polymerization of the impregnation resin 58 in the mold 70 to form the organic matrix 64 of the hollow part 62 made of organic matrix composite material.

The polymerized resin skin 54 has a glass transition temperature greater than or equal to the glass transition temperature of the organic matrix 64.

Indeed, after the transformation step 106 of the method 100 for obtaining the forming core 50, the coating resin 56 forms the skin in polymerized resin 54 and, after the polymerization step 212 of the method 200 for manufacturing the hollow body 62 in organic matrix composite material, the impregnation resin 58 forms the organic matrix 64.

As shown in the FIG. 6 , the manufacturing method 200 then comprises a step 214 of demolding the hollow part 62 made of organic matrix composite material, the forming core 50 being present in the hollow part 62 made of organic matrix composite material.

There FIG. 11 is a schematic view of the hollow part 62 made of organic matrix composite material and the soluble core 50 after the demolding step 214.

As shown in the FIG. 6 , the manufacturing method 200 then comprises a step 216 of removing the soluble body 52.

There FIG. 12 is a schematic representation of the step 216 of removing the soluble body 52 comprising a step of piercing an elimination channel 68 (shown in the FIG. 13 ) using a 72 drill bit.

The elimination channel 68 allows access, from outside the hollow body 62 made of organic matrix composite material, to the soluble body 52.

By way of non-limiting example, the elimination step 216 comprises a step of injecting heated water, for example between 40°C and 95°C, preferably under pressure, in order to dissolve or decompose/fragment the soluble body 52 and evacuate it via the elimination channel 68.

There FIG. 13 is a schematic view of the hollow part 62 made of organic matrix composite material obtained after the step of removing the soluble body 52. The hollow part 62 made of organic matrix composite material comprises a cavity 80, the cavity 80 being covered with the polymerized resin skin 54.

There FIG. 14 is a schematic view of the hollow part 62 made of organic matrix composite material and of the soluble core 50 after the demolding step 214 according to a second embodiment.

In the embodiment of the FIG. 14 , the forming core 50 includes a channel core 74 configured to form the removal channel 68. The channel core 74 is flush with the outer surface 66 of the hollow part 62 made of organic matrix composite material.

There FIG. 15 is a schematic view of the hollow part 62 made of organic matrix composite material and of the soluble core 50 after the demolding step 214 according to a third embodiment.

In the embodiment of the FIG. 15 , the forming core 50 is flush with the outer surface 66 of the hollow part 62 made of organic matrix composite material.

In the embodiments of Figures 14 and 15, the step 216 of removing the soluble body comprises a step where the polymerized resin skin 54 flush with the outer surface 66 of the hollow part 62 made of organic matrix composite material is torn in order to have access to the soluble body 52 from the outside of the hollow part 62 made of organic matrix composite material.

The removal step 216 of the soluble body 52 is similar to the removal step 216 described above.

Although the present disclosure has been described with reference to a specific exemplary embodiment, it is obvious that various modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments recited may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated/mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims (11)

Forming core (50) comprising a soluble body (52) in a liquid and a polymerized resin skin (54) coating the soluble body (52). The forming core (50) of claim 1, wherein the soluble body (52) comprises a soluble thermoplastic polymer. The forming core (50) of claim 1, wherein the soluble body (52) comprises a material that decomposes upon contact with a liquid. A forming core (50) according to any one of claims 1 to 3, wherein the liquid is water. Assembly of a forming core (50) according to any one of claims 1 to 4 and a hollow part (62) made of organic matrix composite material, the polymerized resin having a glass transition temperature greater than or equal to a glass transition temperature of the organic matrix (64) of the hollow part (62) made of organic matrix composite material. Method for obtaining (100) a forming core (50) according to any one of claims 1 to 4 comprising the following steps:
- a manufacturing step (102) of the soluble body (52);
- a step of coating (104) the soluble body (52) with a coating resin (56);
- a step of transformation (106) of the coating resin (56) to obtain the skin in polymerized resin (54) coating the soluble body (52). Method for manufacturing (200) a hollow part (62) made of organic matrix composite material comprising the following steps:
- a step of obtaining (100) the forming core (50) according to claim 6;
- a step of assembling (202) the forming core (50) according to any one of claims 1 to 4 and a fibrous preform (60) forming a precursor of the hollow part made of ceramic matrix composite material;
- a draping step (206) of the fibrous preform (60) and the forming core (50) in a mold (70);
- a step of closing (208) the mold (70);
- a step of impregnation (210) of the fibrous preform (60) with an impregnation resin (58);
- a polymerization step (212) of the impregnation resin (58) in the mold (70) to form the organic matrix (64);
- a step of demolding (214) the hollow part (62) made of organic matrix composite material and the forming core (50); and
- a step of eliminating (216) the soluble body (52);
the coating resin (56) having a glass transition temperature greater than or equal to a glass transition temperature of the impregnation resin (58). Manufacturing method (200) according to claim 7, wherein the step of removing (216) the soluble body (52) comprises a step of drilling a channel (68) for removing the soluble body (52) in the hollow part (62) made of organic matrix composite material to reach the soluble body (52). The manufacturing method (200) of claim 7, the forming core (50) comprises a channel core (74) configured to form a soluble body removal channel (68) in the hollow part (62) of organic matrix composite material. The manufacturing method (200) of any one of claims 7 to 9, wherein the step of removing (216) the soluble body (52) comprises dissolving the soluble body (52) or fragmenting the soluble body (52) by a jet of pressurized liquid. Hollow part (62) made of organic matrix composite material comprising a cavity (80), the cavity (80) being covered with a skin made of polymerized resin (54).