Method for manufacturing a part made of organic matrix composite material comprising an elastomer layer

Abstract

Method for manufacturing a part made of organic matrix composite material comprising a layer of elastomer A method for manufacturing a part made of organic matrix composite material comprising at least one layer of an elastomer comprises the following steps: - producing a fiber preform (100), - consolidating the fiber preform with an organic matrix (110) so as to obtain a part made of organic matrix composite material, - bonding at least one layer of a vulcanized unsaturated elastomer to the part made of organic matrix composite material (130), an adhesive film being interposed between the part and an assembly surface of the layer(s) of unsaturated elastomer. The method comprises, before the bonding step (130), a step of preparing the assembly surface (20a) of each layer of unsaturated elastomer (120), the preparation step comprising grafting a halogenated element onto said assembly surface by halogenation reaction.Figure for abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing a part made of organic matrix composite material comprising an elastomer layer Technical field

[0001] The present invention relates to the general field of the manufacture of parts made of organic matrix composite (OMC) material, i.e. comprising a fibrous reinforcement densified by a matrix of an organic nature. Prior art

[0002] These parts are usually manufactured from a fibrous preform impregnated with a resin, typically an epoxy resin, which, upon polymerization, forms an organic matrix within the fibrous preform.

[0003] In the aeronautical field, several types of parts such as, for example, fan blades or fan casings are made of CMO. These parts are subjected to high vibration levels which can lead to the appearance of vibration instabilities (of the flutter type) and / or to a reduction in fatigue life under forced stress (crosswind, ground effect, etc.). In order to reduce the vibration level, it is known to provide the CMO part with vibration damping properties by adding one or more layers of elastomer. Document US 2009 / 074586 discloses the use of an elastomer on a CMO fan blade to introduce a mechanical damping function into the blade.

[0004] The adhesion strength of the elastomer to the CMO of the part is important to ensure the dedicated functions of the elastomer such as vibration damping. For this purpose, there are surface treatments to increase the adhesion of an elastomer to a CMO (already consolidated or not). These treatments can be mechanical (abrasive), such as sanding or blasting, or chemical, such as a deposit of primer or a vulcanizing co-agent, or even surface activation (plasma).

[0005] Mechanical treatments such as sanding or even sandblasting are complex to carry out on thin elastomer films because they deform the film during treatment and can even damage it in the most extreme cases.

[0006] Even with such treatments, adhesive failures at the interface between the elastomer layer and the CMO have been observed during adhesion tests (out-of-plane traction, peeling, etc.). These adhesive failures are not acceptable from a certification point of view for critical parts such as a propeller or a fan blade.

[0007] Furthermore, most surface treatments known from the state of the art have limited lifetimes, which requires the treatment to be carried out in the days, or even hours, preceding the adhesion phase of the elastomer to the CMO. This results in a significant constraint in the manufacturing process of the CMO part.

[0008] It is therefore desirable to have a solution making it possible to improve the adhesion properties of an elastomer to a CMO. Statement of the invention

[0009] To this end, the invention proposes a method for manufacturing a part made of organic matrix composite (OMC) material comprising at least one layer of an elastomer comprising the following steps:

[0010] - production of a fiber preform,

[0011] - consolidation of the fibrous preform by an organic matrix so as to obtain a part in organic matrix composite material,

[0012] - bonding of at least one layer of an unsaturated elastomer on the material part organic matrix composite, an adhesive film being interposed between the part and an assembly surface of the layer(s) of unsaturated elastomer,

[0013] characterized in that it comprises, before the bonding step, a step of preparing the assembly surface of each layer of unsaturated elastomer, the preparation step comprising grafting a halogenated element onto said assembly surface by halogenation reaction.

[0014] Preparation by halogenation reaction makes it possible to saturate unsaturated bonds on the assembly surface of the elastomer with a halogen which will create polar bonds with the adhesive during bonding and thus strengthen the adhesion of the elastomer to the CMO of the part. It is thus possible to obtain cohesive ruptures in the elastomer compatible with the certification requirements for aeronautical parts while having particularly high peel strength values.

[0015] The step of preparing the assembly surface of the elastomer by halogenation also has the advantage of remaining stable for several weeks. This greatly simplifies the manufacturing process because it is no longer necessary to link the step of preparing the assembly phase of the elastomer with the step of bonding to the CMO.

[0016] According to a particular characteristic of the process of the invention, the step of preparing the assembly surface of the layer(s) of unsaturated elastomer comprises halogenation by electrophilic addition with dihalogens or halides.

[0017] According to another particular characteristic of the method of the invention, the step of preparing the assembly surface of the layer(s) of unsaturated elastomer includes the application to at least the assembly surface of a solution of trichloroisocyanuric acid (symclosene). Trichloroisocyanuric acid has the advantage of not being identified as a hazardous chemical substance by the European Union regulation "Registration, Evaluation and Authorisation of Chemicals" also known by the acronym "REACh" (for "registration, evaluation and authorisation of Chemicals").

[0018] According to another particular characteristic of the method of the invention, the elastomer layer(s) have a thickness greater than or equal to 0.2 mm.

[0019] The invention also proposes a method for manufacturing a part made of organic matrix composite material comprising at least one layer of an elastomer comprising the following steps:

[0020] - bringing into contact an assembly surface of at least one layer of a unsaturated elastomer with a fibrous preform impregnated with a resin,

[0021] - transformation of the resin into an organic matrix by heat treatment of so as to obtain a part made of organic matrix composite material comprising one or more layers of elastomer,

[0022] - characterized in that it comprises, before the contacting step, a pre- preparation of the assembly surface of each layer of unsaturated elastomer, the preparation step comprising grafting a halogen element onto said assembly surface by halogenation reaction.

[0023] Preparation by halogenation reaction makes it possible to saturate unsaturated bonds on the assembly surface of the elastomer with a halogen which will create polar bonds with the resin during its transformation into an organic matrix. It is thus possible to obtain cohesive ruptures in the elastomer compatible with the certification requirements for aeronautical parts while having particularly high peel strength values.

[0024] The step of preparing the assembly surface of the elastomer by halogenation also has the advantage of remaining stable for several weeks. This greatly simplifies the manufacturing process because it is no longer necessary to chain the step of preparing the assembly phase of the elastomer with the contacting step.

[0025] According to a particular characteristic of the method of the invention, the latter comprises, before the contacting step, the production of a fiber preform and, after the contacting step, the injection of a resin into the fiber preform.

[0026] According to another particular characteristic of the method of the invention, the latter comprises, before the contacting step, the production of a fibrous preform by draping fibrous plies pre-impregnated with a resin.

[0027] According to another particular characteristic of the method of the invention, the step of preparing the assembly surface of the layer(s) of unsaturated elastomer includes electrophilic addition halogenation with dihalogens or halides.

[0028] According to another particular characteristic of the method of the invention, the step of preparing the assembly surface of the layer(s) of unsaturated elastomer comprises the application to at least the assembly surface of a solution of trichloroisocyanuric acid (symclosene). Trichloroisocyanuric acid has the advantage of not being identified as a dangerous chemical substance by the European Union regulation "Registration, Evaluation and Authorisation of Chemicals" also known by the acronym "REACh" (for "registration, evaluation and authorisation of Chemicals").

[0029] According to another particular characteristic of the method of the invention, the elastomer layer(s) have a thickness greater than or equal to 0.2 mm. Brief description of the drawings

[0030] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate exemplary embodiments thereof which are not in any limiting nature.

[0031] [Fig.l] [Fig.l] is a flowchart of the steps of a method for manufacturing a CMO part according to an embodiment of the invention,

[0032] [Fig.2] [Fig.2] is a flowchart of the steps of a method for manufacturing a CMO part according to another embodiment of the invention,

[0033] [Fig.3] [Fig.3] is a flowchart of the steps of a method for manufacturing a CMO part according to another embodiment of the invention,

[0034] [Fig.4A] [Fig.4A] schematically and partially represents a CMO part equipped with a viscoelastic damping device,

[0035] [Fig.4B] [Fig.4B] represents the part of [Fig.4A] when it is subjected to vibrations. Description of the embodiments

[0036] The invention applies to the manufacture of any part made of organic matrix composite (OMC) material comprising one or more layers of elastomer. By "layer" is meant here an elastomer having a thickness greater than or equal to 0.2 mm and which may have various geometries. The OMC part according to the invention may in particular be entirely coated with a layer of elastomer or else comprise one or more layers or pieces of elastomer arranged at determined locations on the part. The elastomer used in the present invention is an unsaturated elastomer such as for example Polyisoprene (IR), Polybutadiene (BR), Styrene-butadiene (SBR), Butadiene-acrylonitrile (NBR), Butadiene-propylene-diene (EPDM) and isobutylene-isoprene (IIR). The elastomer used is preferably vulcanized.

[0037] As explained below in detail, the adhesion of the elastomer layer(s) can be achieved on a CMO part already consolidated by bonding using an adhesive or during a consolidation phase of the CMO of the part, the elastomer adhering in this case directly with the resin.

[0038] According to the invention, the manufacturing method comprises a step of preparing the assembly surface of each layer of unsaturated elastomer. This step of preparing the assembly surface is carried out by means of a halogenation reaction called addition halogenation. The halogenation reaction allows halogen atoms to react with the double bonds present in the structure of the elastomer. Halogenation is an addition reaction in which the halogen atoms are added to the double bonds of the unsaturated elastomer. The preparation of the assembly surface therefore comprises grafting a halogen element onto the assembly surface.

[0039] Due to the difference in electronegativity between halogen atoms and carbon atoms, the halogenation reaction on an unsaturated elastomer creates polarity. Therefore, the saturation of the unsaturated bonds of the elastomer with a halogen makes it possible to create very strong polar bonds with the adhesive during a bonding phase of the elastomer on the consolidated CMO part or with the CMO resin during the consolidation phase. The halogen can be in particular chlorine (Cl), fluorine (F), bromine (Br) or iodine (I).

[0040] The step of preparing the assembly surface of the unsaturated elastomer can be carried out by halogenation by electrophilic addition, in particular with dihalogens such as dichlorine Cl2, difluorine F2, diiodine I2, dibromine Br2 or corresponding hydrogen halides (HCl, HF, HI, HBr), the reaction mainly by gaseous means being able to be carried out at room temperature and at atmospheric pressure.

[0041] According to a particular characteristic of the method of the invention, the step of preparing the assembly surface of the layer(s) of unsaturated elastomer comprises the application to at least the assembly surface of a solution of trichloroisocyanuric or symclosene acid.

[0042] As a non-limiting example, a solution is made by diluting 20 grams of trichloroisocyanuric acid powder in 1 liter of solvent, here ethyl acetate. The solution obtained is applied with a non-metallic brush to the assembly surface of the elastomer until the solvent evaporates. The elastomer can then be dipped in the bath of trichloroisocyanuric acid solution.

[0043] Trichloroisocyanuric acid has the advantage of not being identified as a hazardous chemical substance by the European Union regulation "Registration, Evaluation and Authorisation of Chemicals" also known by the acronym "REACh" (for "registration, evaluation and authorisation of Chemicals”).

[0044] The preparation of the assembly surface of the elastomer by addition halogenation, that is to say the creation of polarities by grafting a halogen element onto the assembly surface, remains stable for several weeks. This greatly simplifies the manufacturing process because it is no longer necessary to chain the preparation step of the assembly phase of the elastomer with the bonding step on the CMO or the consolidation step of the CMO. The elastomer thus prepared can be stored for several weeks before its use with the CMO.

[0045] A method of manufacturing a CMO part is now described in relation to [Fig. 1] in which an elastomer is bonded to the consolidated part in accordance with one embodiment of the invention.

[0046] The method begins with the production of a dry fiber preform (step 100). The fiber preform is intended to form the fiber reinforcement of the CMO part to be manufactured. It can be obtained by any known textile construction technique or combination of techniques. The preform can be produced in particular by stacking unidirectional (UD) or two-dimensional (2D) plies or layers. It can also be produced directly in a single piece by three-dimensional weaving. By "two-dimensional weaving" is meant here a conventional weaving method by which each weft thread passes from one side to the other of threads of a single warp layer or vice versa. By "three-dimensional weaving" is meant here a weaving by which warp threads pass through several layers of weft threads, or weft threads pass through several layers of warp threads. The preform is here made from carbon fibers.

[0047] The fibrous preform is then consolidated or densified (step 110), which is generally held in shape in a molding cavity of an injection tool. The consolidation of the fibrous preform consists of filling its porosity with the material constituting the matrix. This densification is carried out in a manner known per se using the liquid process (LC). The liquid process consists of impregnating the preform with a liquid composition containing a precursor of the matrix material. The precursor is usually in the form of a polymer, such as a high-performance epoxy resin, possibly diluted in a solvent.

[0048] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the injection tool, after elimination of any solvent and crosslinking of the polymer, the preform still being maintained in the molding cavity having a shape corresponding to that of the part to be produced.

[0049] The densification of the fiber preform can be carried out by the well-known method transfer molding called RTM ("Resin Transfer Molding"). In accordance with the RTM process, the fiber preform is placed in a mold having the external shape of the part to be produced. A thermosetting resin is injected into the internal space of the mold which contains the fiber preform. A pressure gradient is generally established in this internal space between the place where the resin is injected and the resin discharge orifices in order to control and optimize the impregnation of the preform by the resin.

[0050] The resin used may be, for example, an epoxy resin with a temperature class of 180°C (maximum temperature supported without loss of characteristics). Resins suitable for RTM processes are well known. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of temperature class and / or the chemical nature of the resin is determined according to the thermomechanical stresses to which the part must be subjected. Once the resin has been injected throughout the reinforcement, it is polymerized by heat treatment in accordance with the RTM process.

[0051] After injection and polymerization, the CMO part is demolded.

[0052] A layer of unsaturated elastomer is then bonded to the CMO part (step 130). Before this bonding step, the assembly surface of the unsaturated elastomer layer has been prepared by addition halogenation as explained above in detail (step 120). Since the step of preparing the assembly surface is stable for several weeks, it can be carried out before or after steps 100 and 110 corresponding respectively to the production of the fiber preform and to its consolidation. It can, for example, be carried out well in advance of the first step 100, the elastomer thus prepared being stored until it is bonded to the CMO part.

[0053] The bonding is carried out by interposing a film of adhesive material between the external surface of the CMO part which has undergone a surface treatment in a known manner (for example sandblasting) and the assembly surface of the elastomer layer. The adhesive material may for example correspond to the EA914 epoxy resin manufactured by the company Hysol®, to the AF191 adhesive film manufactured by the company 3M®, to the FM300 adhesive film manufactured by the company Cytec®, or to the EA9396 epoxy resin manufactured by the company Hysol®. A thermal cycle is then applied to the assembly to polymerize the adhesive film and to finalize the bonding of the elastomer layer on the CMO of the part. By saturating the unsaturated bonds on the elastomer assembly surface with halogens, very strong polar bonds are formed with the adhesive, thus significantly improving the adhesion between the elastomer and the CMO of the part.

[0054] A method of manufacturing a CMO part according to another embodiment of the invention which differs from the method of [Fig.l] in that the adhesion of an elastomer layer is carried out during the consolidation step and not after as for the method of [Fig.l].

[0055] The process begins with the production of a dry fiber preform (step 200). The fiber preform is intended to form the fiber reinforcement of the CMO part to be manufactured. It can be obtained using one of the techniques already described for step 100 of the process of [Fig.l]. The preform is here produced from carbon fibers.

[0056] Once the fiber preform has been produced, a layer of unsaturated elastomer is placed in contact with the preform (step 220).

[0057] Before this contacting step, the assembly surface of the unsaturated elastomer layer was prepared by addition halogenation as explained above in detail (step 210). Since the step of preparing the assembly surface is stable for several weeks, it can be carried out before or after step 200 of producing the fiber preform. It can, for example, be carried out well in advance of this first step 200, the elastomer thus prepared being stored until it is bonded to the CMO part.

[0058] A resin is then injected into the fiber preform (step 230) as already explained in detail previously for step 110 of the method of [Fig.l]. The fiber preform with the elastomer layer can in particular be held in shape and against each other in a molding cavity of an injection or RTM tool.

[0059] Once the fiber preform has been impregnated with the resin, it is transformed into a matrix, namely its polymerization (step 240), by heat treatment, generally by heating the injection tool, after elimination of any solvent and crosslinking of the polymer, the preform and the elastomer layer still being maintained in the molding cavity having a shape corresponding to that of the part to be produced.

[0060] After injection and polymerization, the CMO part provided with a layer of elastomer is demolded.

[0061] By saturating the unsaturated bonds at the elastomer assembly surface with halogens, highly resistant polar bonds are formed between the elastomer assembly surface and the resin injected into the preform during its polymerization. The adhesion between the elastomer and the CMO of the part is thus significantly improved.

[0062] A method of manufacturing a CMO part in accordance with another embodiment of the invention is now described in relation to [Fig. 3] which differs from the method of [Fig. 1] in that the adhesion of an elastomer layer is carried out during the consolidation step and not afterwards as for the method of [Fig. 1].

[0063] The process begins with the production of a pre-impregnated fiber preform made by draping or stacking UD or 2D plies pre-impregnated with a resin (step 300). The fiber preform is intended to form the fiber reinforcement of the CMO part to be manufactured. The preform is here made from carbon fibers.

[0064] Once the pre-impregnated fiber preform has been produced, a layer of unsaturated elastomer is brought into contact with the preform (step 320). The elastomer layer can be held on the pre-impregnated preform in a shaping tool that allows the preform to be given the shape of the final part.

[0065] Before this contacting step, the assembly surface of the unsaturated elastomer layer was prepared by addition halogenation as explained above in detail (step 310). Since the step of preparing the assembly surface is stable for several weeks, it can be carried out before or after step 300 of producing the fiber preform. It can, for example, be carried out well in advance of this first step 300, the elastomer thus prepared being stored until it is bonded to the CMO part.

[0066] Once the contact has been made, the resin is transformed into a matrix, namely its polymerization (step 340), by heat treatment, generally by heating, the preform and the elastomer layer still being held against each other, for example in the shaping tool.

[0067] After polymerization, the CMO part provided with a layer of elastomer is demolded.

[0068] By saturating the unsaturated bonds at the elastomer assembly surface with halogens, highly resistant polar bonds are formed between the elastomer assembly surface and the resin present in the preform during its polymerization. The adhesion between the elastomer and the CMO of the part is thus significantly improved.

[0069] Figures 4A and 4B illustrate an example of application of the invention to a CMO part provided with a damping system. In the example described here, a CMO part 10, for example a turbomachine fan blade, is equipped with a viscoelastic damping device consisting of a stack of an elastomer layer 20 and a counter-layer of rigid material 30, for example a metallic material. The counter-layer of rigid material 30 can also advantageously consist of a CMO of the pre-impregnated type draped then polymerized on the previously halogenated elastomer film. The step of polymerizing the pre-impregnated composite counter-layer can be carried out prior to the step of bonding the elastomer film to the CMO part to be damped. The polymerization step can also be carried out at the same time as the RTM injection polymerization of the part to be damped in the case where the elastomer film as well as the prepreg plies raw materials are draped in the mold with the dry fiber preform. The assembly surface 20a of the elastomer layer 20 has been prepared by addition halogenation as described above and therefore adheres strongly to the surface 10b of the CMO of the part 10.

[0070] As illustrated in [Fig.4B], the vibration of the CMO part 10 causes the deformation of the elastomer 20 interposed between the part 10 and the counter-layer of rigid material 30 and whose viscoelastic nature makes it possible to dissipate the mechanical energy of the vibrations and thus dampen them. Good adhesion of the elastomer layer 20 to the CMO part 10 and to the counter-layer 30 is necessary for the good performance of the damping technology and its durability. The preparation of the assembly surface of the elastomer layer by halogenation makes it possible to meet this condition.

[0071] Thanks to the preparation by halogenation reaction of the assembly surface of the elastomer, it is possible to obtain cohesive ruptures in the elastomer compatible with the certification requirements for aeronautical parts while having particularly high peel strength values. Comparative tests (with and without preparation by halogenation reaction of the assembly surface of the elastomer) have demonstrated that the preparation by halogenation reaction of the assembly surface of the elastomer before bonding allows at least a fourfold increase in peel strength which reaches at least 4N / mm (peel force per unit width of the peeled strip).

[0072] The expression “between ... and ...” must be understood as including the limits.

Claims

Claims

1. Method for manufacturing a part made of organic matrix composite material (10) comprising at least one layer of an elastomer (20) comprising the following steps: - producing a fiber preform (100), - consolidating the fiber preform with an organic matrix (110) so as to obtain a part made of organic matrix composite material, - bonding at least one layer of an unsaturated elastomer to the part made of organic matrix composite material (130), an adhesive film being interposed between the part and an assembly surface of the layer(s) of unsaturated elastomer, characterized in that it comprises, before the bonding step (130), a step of preparing the assembly surface (20a) of each layer of unsaturated elastomer (120), the preparation step comprising grafting a halogenated element onto said assembly surface by halogenation reaction.

2. The method of claim 1, wherein the step of preparing the assembly surface of the one or more layers of unsaturated elastomer comprises applying to at least the assembly surface a solution of trichloroisocyanuric acid.

3. The method of claim 1, wherein the step of preparing the assembly surface of the unsaturated elastomer layer(s) comprises electrophilic addition halogenation with dihalogens or halides.

4. Method according to any one of claims 1 to 3, wherein said at least one layer of elastomer (20) has a thickness greater than or equal to 0.2 mm.

5. Method for manufacturing a part made of organic matrix composite material (10) comprising at least one layer of an elastomer (20) comprising the following steps: - bringing an assembly surface (20a) of at least one layer of an unsaturated elastomer (20) into contact with a fibrous preform (220, 320), - transforming a resin present in the fibrous preform into an organic matrix (240, 330) by heat treatment so as to obtain a part made of organic matrix composite material (10) comprising one or more layers of elastomer (20), - characterized in that it comprises, before the contacting step, a step of preparing the assembly surface (20a) of each layer of unsaturated elastomer (20) (210, 310), the preparation step comprising grafting a halogenated element onto said assembly surface by halogenation reaction.

6. Method according to claim 5, comprising, before the contacting step (220), producing a fiber preform (200) and, after the contacting step, injecting the resin into the fiber preform (230).

7. Method according to claim 5, comprising, before the contacting step (320), producing a fibrous preform by draping fibrous plies pre-impregnated with the resin (300).

8. A method according to any one of claims 5 to 7, wherein the step of preparing the assembly surface of the layer(s) of unsaturated elastomer comprises applying to at least the assembly surface a solution of trichloroisocyanuric acid.

9. A method according to any one of claims 5 to 7, wherein the step of preparing the assembly surface of the unsaturated elastomer layer(s) comprises halogenation by electrotrophic addition with dihalogens or halides.

10. A method according to any one of claims 5 to 9, wherein said at least one layer of elastomer (20) has a thickness greater than or equal to 0.2 mm.

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