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

Abstract

The invention relates to a method for manufacturing an organic matrix composite material part comprising at least one layer of an elastomer, the method comprising the following steps: - producing a fibre preform (100); - consolidating the fibre preform with an organic matrix (110) so as to obtain an organic matrix composite material part; - bonding at least one layer of a vulcanised unsaturated elastomer to the organic matrix composite material part (130), wherein an adhesive film is interposed between the part and a joining surface of the one or more unsaturated elastomer layers. The method comprises, before the bonding step (130), a step of preparing the joining surface (20a) of each unsaturated elastomer layer (120), wherein the preparation step comprises grafting a halogen element onto the joining surface by means of a halogenation reaction.

Description

[0001] Description

[0002] Title of the invention: Method for manufacturing a part made of organic matrix composite material comprising an elastomer layer

[0003] Technical Field

[0004] The present invention relates to the general field of manufacturing parts made of organic matrix composite (OMC) material, i.e. comprising a fibrous reinforcement densified by a matrix of an organic nature.

[0005] Prior art

[0006] These parts are usually made from a fibrous preform impregnated with a resin, typically an epoxy resin, which, upon polymerization, forms an organic matrix within the fibrous preform.

[0007] In the aeronautical field, several types of parts such as 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 loading (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.

[0008] 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 sandblasting, or chemical, such as a deposit of primer or a vulcanizing co-agent, or even surface activation (plasma). 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.

[0009] 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.

[0010] Furthermore, most surface treatments known from the state of the art have limited lifetimes, which requires treatment to be carried out in the days, or even hours, preceding the adhesion phase of the elastomer to the CMO. This causes a significant constraint in the manufacturing process of the CMO part.

[0011] It is therefore desirable to have a solution to improve the adhesion properties of an elastomer to a CMO.

[0012] Statement of the invention

[0013] 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:

[0014] - production of a fiber preform,

[0015] - consolidation of the fiber preform by an organic matrix so as to obtain a part in composite material with an organic matrix,

[0016] - bonding at least one layer of an unsaturated elastomer onto the part made of organic matrix composite material, 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, 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.

[0017] Preparation by halogenation reaction allows unsaturated bonds on the assembly surface of the elastomer to be saturated 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.

[0018] The step of preparing the elastomer assembly surface 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 preparation step of the elastomer assembly phase with the bonding step on the CMO.

[0019] 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.

[0020] 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").

[0021] 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. 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:

[0022] - bringing into contact an assembly surface of at least one layer of an unsaturated elastomer with a fibrous preform impregnated with a resin,

[0023] - transformation of the resin into an organic matrix by heat treatment so as to obtain a part made of organic matrix composite material comprising one or more layers of elastomer,

[0024] - characterized in that it comprises, before the contacting 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.

[0025] Preparation by halogenation reaction allows unsaturated bonds on the assembly surface of the elastomer to be saturated 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.

[0026] The step of preparing the elastomer assembly surface 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 preparation step of the elastomer assembly phase with the contacting step.

[0027] 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.

[0028] 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. 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 halogenation by electrophilic addition with dihalogens or halides.

[0029] 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").

[0030] 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.

[0031] Brief description of the drawings

[0032] 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 limiting in nature.

[0033] [Fig. 1] Figure 1 is a flowchart of the steps of a method for manufacturing a CMO part according to one embodiment of the invention,

[0034] [Fig. 2] Figure 2 is a flowchart of the steps of a method of manufacturing a CMO part according to another embodiment of the invention,

[0035] [Fig. 3] Figure 3 is a flowchart of the steps of a method of manufacturing a CMO part according to another embodiment of the invention,

[0036] [Fig. 4A] Figure 4A shows, schematically and partially, a CMO part equipped with a viscoelastic damping device,

[0037] [Fig. 4B] Figure 4B shows the part of Figure 4A when subjected to vibration. Description of the embodiments

[0038] 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 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.

[0039] As explained in detail below, 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.

[0040] 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.

[0041] Due to the difference in electronegativity between halogen atoms and carbon atoms, the halogenation reaction on an unsaturated elastomer creates polarity. Therefore, saturating the unsaturated bonds of the elastomer with a halogen allows for the creation of very strong polar bonds with the adhesive during a bonding phase of the elastomer to the consolidated CMO part or with the CMO resin during the consolidation phase. The halogen can be chlorine (Cl), fluorine (F), bromine (Br) or iodine (I).

[0042] 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.

[0043] 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.

[0044] 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 resulting solution is applied with a non-metallic brush to the assembly surface of the elastomer until the solvent evaporates. The elastomer can then be dipped into the trichloroisocyanuric acid solution bath.

[0045] 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").

[0046] The preparation of the elastomer assembly surface by addition halogenation, i.e. 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 elastomer assembly phase 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. A method for 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.

[0047] The process 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.

[0048] The fiber 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 fiber 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.

[0049] 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 always being maintained in the molding cavity having a shape corresponding to that of the part to be produced.

[0050] The densification of the fiber preform can be carried out by the well-known transfer molding process called RTM ("Resin Transfer Molding"). According to 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.

[0051] The resin used can 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.

[0052] After injection and polymerization, the CMO part is demolded.

[0053] 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 assembly surface preparation step 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 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.

[0054] Bonding is achieved by interposing a film of adhesive material between the external surface of the CMO part, which has undergone a known surface treatment (e.g. sandblasting), and the assembly surface of the elastomer layer. The adhesive material may, for example, correspond to the EA914 epoxy resin manufactured by Hysol®, the AF191 adhesive film manufactured by 3M®, the FM300 adhesive film manufactured by Cytec®, or the EA9396 epoxy resin manufactured by Hysol®. A thermal cycle is then applied to the assembly to polymerize the adhesive film and finalize the bonding of the elastomer layer to the CMO of the part. By saturating the unsaturated bonds on the assembly surface of the elastomer 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.

[0055] A method of manufacturing a CMO part in accordance with another embodiment of the invention is now described in relation to Figure 2, which differs from the method of Figure 1 in that the adhesion of an elastomer layer is carried out during the consolidation step and not afterwards as for the method of Figure 1.

[0056] 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 in Figure 1. The preform is here made from carbon fibers.

[0057] Once the fiber preform has been produced, a layer of unsaturated elastomer is placed in contact with the preform (step 220).

[0058] 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 assembly surface preparation step is stable for several weeks, it can be carried out before or after step 200 of producing the fiber preform. For example, it can 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.

[0059] A resin is then injected into the fiber preform (step 230) as already explained in detail previously for step 110 of the method of figure 1. 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 tool or RTM. Once the fiber preform is 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 being always held in the molding cavity having a shape corresponding to that of the part to be produced.

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

[0061] By saturating the unsaturated bonds on the elastomer's assembly surface with halogens, highly resistant polar bonds are formed between the elastomer's assembly surface and the resin injected into the preform during its polymerization. This significantly improves the adhesion between the elastomer and the CMO of the part.

[0062] A method of manufacturing a CMO part in accordance with another embodiment of the invention is now described in relation to Figure 3, which differs from the method of Figure 1 in that the adhesion of an elastomer layer is carried out during the consolidation step and not afterwards as for the method of Figure 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 made here 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 to give the preform 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 assembly surface preparation step is stable for several weeks, it can be carried out before or after step 300 of producing the fiber preform. For example, it can 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 always being held against each other, for example in the shaping tool.

[0067] After polymerization, the CMO part with an elastomer layer is demolded.

[0068] By saturating the unsaturated bonds on the elastomer's assembly surface with halogens, highly resistant polar bonds are formed between the elastomer's assembly surface and the resin present in the preform during its polymerization. This significantly improves the adhesion between the elastomer and the CMO of the part.

[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 pre-impregnated CMO draped and 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 step of the part to be damped in the case where the elastomer film as well as the raw prepreg plies 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. 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 damp 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.Preparation of the assembly surface of the elastomer layer by halogenation makes it possible to meet this condition.

[0070] Thanks to the preparation by halogenation reaction of the elastomer assembly surface, 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 elastomer assembly surface) have demonstrated that the preparation by halogenation reaction of the elastomer assembly surface 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).

[0071] 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: - production of a fiber preform (100), - consolidation of the fiber preform by an organic matrix (110) so as to obtain a part made of composite material with an organic matrix, - bonding at least one layer of an unsaturated elastomer onto 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 into contact an assembly surface (20a) of at least one layer of a unsaturated elastomer (20) with a fibrous preform (220, 320), - transformation of a resin present in the fiber 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 electrophilic 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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