Method for manufacturing a part made from composite material, in particular for an aircraft turbine engine, and associated facility

Abstract

The invention relates to a method for manufacturing a part (2) made from composite material, in particular for an aircraft turbine engine, the method comprising the following steps: (a) producing a fibrous blank (30) intended to form said part (2) made from composite material, (b) pre-heating a polymerisable mixture (7) comprising a resin and a hardener in order to dissolve the hardener in the resin, (c) injecting the polymerisable mixture (7) into at least one mould (6) comprising the fibrous blank (30), (d) heating and densifying the fibrous blank (30) so as to polymerise the polymerisable mixture (7) and impregnate the fibrous blank (30), and (e) demoulding the part made from composite material obtained in this way, wherein step (b) comprises a sub-step (b2) of using microwaves to dissolve the hardener in the resin.

Description

[0001]DESCRIPTION TITLE: METHOD FOR MANUFACTURING A COMPOSITE MATERIAL PART, IN PARTICULAR FOR AN AIRCRAFT TURBOMACHINE, AND AN ASSOCIATED FACILITY Technical field of the invention The present invention relates to a method for manufacturing a composite material part, in particular for an aircraft turbomachine, as well as an installation for implementing such a method. Technical background The state of the art includes in particular document US-A1-2004 / 0089975. The use of composite materials is advantageous in the aeronautical industry in particular because these materials have interesting mechanical performances for relatively low masses. A method for manufacturing a composite material part, in particular for the aeronautical industry, which is well known to those skilled in the art, is the LCM (Liquid Composite Molding) method. The LCM manufacturing method can be of the liquid molding type.RTM resin injection (acronym for "Resin Transfer Molding") or flexible injection (known by the English term "Polyflex"). This is a process for producing a composite material part based on fibers impregnated with a so-called polymerizable resin-based mixture. Such a process is used, for example, to manufacture a so-called aeronautical part, in particular for an aircraft turbomachine. Such composite material parts can be a blade part, a casing or a turbomachine shim. An LCM process, which can be of the RTM or Polyflex type, involves several successive stages. First, the fibers are woven to obtain a three-dimensional fiber preform blank, then the fiber blank is cut to substantially the shape of the final part to be produced. This fiber blank is then placed in a mold, which is closed. Then, a resin-based mixture is injected in the liquid state while maintaining apressure on the injected mixture while the assembly is polymerized by heating. The resulting part is demolded and possible machining steps and / or bonding operations can be carried out. The current injection line consists of: - an injection cylinder where a resin-based mixture is heated to a temperature between 80°C and 120°C, after a vacuum degassing phase; - a heater in which a hardener in the solid state in the resin-based mixture is dissolved and the mixture reaches the optimum injection temperature (between 155°C and 170°C for a PR520N type resin), i.e. the temperature at which the viscosity is minimal (less than 100 centipoise (cP)); - a press mold (or a self-heating mold or an oven), when the resin-based mixture has filled the cavity and the fiber preform placed in the mold is completely impregnated, the assembly is heated to the temperature ofcuring (between 170°C and 200°C for a PR520N type resin); or in a variant called co-injection cycle, the resin-based mixture, particularly in the case of AF191 type resin, can be injected into a so-called colder mold (generally at a temperature between 80°C and 120°C) containing the fiber preform; - a system for creating a vacuum so as to prevent air from remaining inside the mold cavity and forming porosities and / or dry areas. The vacuum is also an aid for the infusion of the resin into the fibers constituting the reinforcement. Before the injection step, the resin-based mixture is preheated in a known manner to make it as less viscous as possible. Heating the mixture before its injection into the mold is very important. It is indeed important that one of the components of the mixture, in particular the hardener, has completely dissolved in the mixture (for example with a dissolution rategreater than 85%) before its contact with the fiber blank because this component would risk being filtered into the fiber blank, and the mechanical properties of the resin during curing would not be respected. In current technology, the preheating of the resin-based mixture to dissolve the hardener is carried out in the heater in which the resin is heated between approximately 90°C and 170°C throughout the heater. There are different types of heaters. This can be, for example, a thin-film heater. The resin circulates between two hot walls of the thin layer (approximately 0.2 mm). The heat exchange is optimized by the low thickness of resin which is exposed to the heat flow. The flow of resin that can be heated is however limited, which leads to a limitation of the maximum size of the part to be injected. For example, the resin injection time can be limited to approximately 30minutes for PR520N resin. It can also be a heater consisting of a series of superimposed hot plates in which at least one serpentine-shaped channel is dug. The number of plates and the dimensions of the channel(s) determine the volume treated. The duration of the resin within it is directly linked to the flow rate and its volume. The regulation of the temperature and the time of passage of the resin in the heater can be complex to control, which can lead to a risk of poor dissolution of the hardener or early crosslinking (or in other words, polymerization) of the resin leading to obstruction of the conduits. It can also be a heat exchanger with a heat transfer fluid. This solution requires the presence of a secondary system for pumping and heating the heat transfer fluid. This system can therefore be longer, more expensive and more difficult to implement than the previous solutions because it requires sealing athigh-performance hot water heater. Thus, these known heaters are dynamic heat exchange systems, with many parameters to keep under control: the temperature of the plates, the inlet temperature of the resin, the time spent inside the system, the flow rates of the resin, the state of progress of the resin at the inlet of the system (which can strongly influence its viscosity), etc. The risk of error can be significant, especially when the temperature and time setpoints deviate from the nominal value for an unforeseen reason (such as a failure of an injection piston, a pipe leak, etc.). Thus, the dissolution of the hardener remains difficult to control. For example, in the case of the co-injection cycle, the hardener may have difficulty dissolving in a so-called colder mold, especially at a temperature between 80°C and 120°C. Therefore, it may be necessary to control the proper dissolution of the hardener. Furthermore, theThe sizing of a heater, whatever its type, can restrict certain parameters, such as the injection flow rate. In the case of an injection flow rate of the resin-containing mixture which is blocked by the sizing of the heater, the injection time of the resin can be longer. In addition, a certain quantity of the resin-containing mixture can be lost at the end of an injection depending on the type of heater. This loss is generally taken into account during the manufacturing process. In these different contexts, it is interesting to propose a solution making it possible to optimize and simplify the production of a composite material part, in particular for an aircraft turbomachine. Summary of the invention The present invention proposes a solution to at least some of the aforementioned problems which is simple, effective and economical. To this end, the invention relates to a method for manufacturing a composite material part, in particular for an aircraft turbomachine.aircraft turbomachine, the method comprising the following steps: (a) producing a fiber blank intended to form said composite material part, (b) preheating a polymerizable mixture comprising a resin and a hardener, to dissolve the hardener in the resin, (c) injecting the polymerizable mixture into at least one mold comprising the fiber blank, (d) heating and densifying the fiber blank so as to cause the polymerization of the polymerizable mixture and impregnation in said fiber blank, and (e) demolding the composite material part thus obtained. According to the invention, step (b) comprises a sub-step (b2) of dissolving the hardener in the resin by microwaves. Thus, this solution makes it possible to achieve the aforementioned objective. In general, the method according to the invention makes it possible to simplify and optimize the production of a composite material part, in particular by molding LCM liquid (such as RTM orpolyflex). For this, the dissolution of the hardener is carried out by microwaves. It has thus been observed that microwaves make it possible to provide the specific energy necessary for the dissolution of the solid particles of the hardener contained in the polymerizable mixture. Indeed, the typical polarization of the polymerizable mixture (in particular of the epoxy resin) is used advantageously in the present invention since the microwaves can stress the molecular structure and the resulting molecular vibrations generate heat allowing the dissolution of the hardener (in particular of the solid particles composing the hardener) within the polymerizable mixture. The energy provided by the microwaves is consumed in the phase change (for example from a solid phase to a liquid phase) of the hardener, but it remains insufficient to initiate crosslinking reactions (or in other words polymerization) of the resin. The process according tothe invention makes it possible to simplify the production of the part and also of the systems implemented. Indeed, it is no longer necessary to use a heater as described above which limits the flow rate of the mixture and consequently the size of the composite part to be manufactured. The method according to the invention also makes it possible to limit the quantity of resin lost at the end of the part manufacturing process. It is thus possible to increase the injection flow rate, which allows the manufacture of large parts. According to the invention, step (b) further comprises a sub-step (b3) of cooling the polymerizable mixture, for example to room temperature, and / or a sub-step (b4) of stabilizing the temperature of the polymerizable mixture. The cooling sub-step (b3) can be carried out after the hardener dissolution sub-step (b2) and the sub-step (b4) can be carried out after the sub-step (b2) or the sub-step (b3). This makes it possible to stop (or even notnot initiate) any polymerization reaction of the resin, before injecting the polymerizable mixture into the mold and / or any other packaging container. The manufacturing method according to the invention may comprise one or more of the following features, taken in isolation from each other or in combination with each other: - in sub-step (b2), the microwaves are emitted by at least one fixed or mobile source; - in sub-step (b2), the polymerizable mixture is contained in a container that is fixed or mobile, for example rotating, relative to the microwaves; - the resin is in liquid form and the hardener is in solid form before carrying out step (b); -- the hardener is dispersed, in particular beforehand, in the resin in liquid form; - the polymerizable mixture is static or mobile relative to the container; - the polymerizable mixture is mobile relative to the fixed container; - the method further comprises a step (i) ofconditioning of the polymerizable mixture, this step (i) being carried out before or simultaneously with step (c); - the container is at least one conduit for transferring the polymerizable mixture obtained at the end of step (b) to the at least one mold and / or at least one conditioning container; -- the method further comprises a heating step (ii) of the polymerizable mixture which is carried out before step (i) and / or before step (c); -- the polymerizable mixture obtained in sub-step (b2) is heated with a temperature gradient, for example in step (ii); this makes it possible to promote the viscosity of the polymerizable mixture to be injected in step (c); -- the heating of the polymerizable mixture obtained in sub-step (b2) is carried out by a heat source which is preferably remote and different from a microwave source used in sub-step (b2); -- the microwaves are applied directly to the at least one transfer conduit; -- sub-step (b4) is carried out by isolatingthe polymerizable mixture obtained in sub-step (b2) or sub-step (b3), for example via an insulated (or remote) pipe; - the microwaves generate a power of between 100 Watt and 3000 Watt, preferably this power is between 100 Watt and 1500 Watt; - the microwaves are applied for a maximum duration of approximately 5 minutes, this duration is for example between 1 second and 90 seconds, preferably this duration is approximately 30 seconds; - step (b) comprises a sub-step (b1) of pre-heating the resin of the polymerizable mixture to a pre-heating temperature, this sub-step (b1) being carried out before the sub-step (b2) of dissolving the hardener; -- the polymerizable mixture obtained in sub-step (b2) is placed in the cooling zone, for example via the transfer conduit or any other element, and configured to maintain the temperature without triggering or accelerating the polymerization of the resin of saidpolymerizable mixture; -- the polymerizable mixture is cooled by at least 1°C below a predetermined outlet temperature of said polymerizable mixture at the end of sub-step (b2); -- the dissolution of the hardener is complete or partial; - complete dissolution means the dissolution of the hardener with a dissolution rate which may be greater than 80% or 85%; -- the complete dissolution rate of the hardener is between 85% and 100%; - the partial dissolution of the hardener comprises a dissolution rate of between 50% and 85%; -- sub-step (b2) has a dissolution rate greater than 80% or 85%; - the preheating temperature of the resin, in particular in step (b1), is between 80°C and 120°C; -- the heating temperature in the mold, in particular in step (d), is between 80°C and 200°C, preferably this heating temperature is between 160°C and 200°C, in particular when the polymerizable mixture comprises apolyepoxide resin (such as PR520N resin); -- the resin of the polymerizable mixture is a thermosetting material; -- the resin of the polymerizable mixture is free of thermoplastic material; -- the resin comprises polyepoxides (or epoxides), polyimides or polybismaleimides; -- the polymerizable mixture comprises a PR520N resin marketed by Solvay, a 2896 resin marketed by 3M, or an RTM250ST resin marketed by Hexcel; - the polyepoxide resin is based on DiGlycidyl Ether of Bisphenol F (having the acronym DGEBF) in particular when the polymerizable mixture comprises the PR520N resin or DiGlycidyl Ether of Bisphenol A (having the acronym DGEBA) in particular when the polymerizable mixture comprises the 2896 resin; -- the hardener of the polymerizable mixture is a crosslinking agent which triggers the polymerization and the hardening is irreversible of the resin under the effect of heat; -- the hardener is chosen from the9,9-Bis(4-amino-3chlorophenyl)fluorene having the acronym CAF, 1,12-dodecanedioic acid having the acronym DDA, 4,4'-diamino-diphenylsulfone having the acronym DDS and hexamethylenediamine having the acronym HDMA; -- the composite material part is an aeronautical composite part, for example a turbomachine blade part (such as a rotor blade for example of a fan or a stator blade for example of a turbomachine rectifier), a casing (such as a fan casing) or a shim (such as a fan shim). The present invention also relates to an installation for implementing a method of manufacturing the composite material part according to one of the particularities of the invention, the installation comprising: - a zone for producing the fiber blank to implement step (a), - a zone for pre-treating the polymerizable mixture configured to dissolve the hardener in the resin of step (b), and - theless mold for receiving the fiber blank and injecting the polymerizable mixture to carry out steps (c) and (d). According to the invention, the pre-treatment zone comprises at least one microwave source configured to carry out sub-step (b2) of dissolving the hardener in the resin. According to the invention, the pre-treatment zone comprises a cooling zone to carry out sub-step (b3) of cooling the polymerizable mixture. The installation according to the invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another: - the microwave source is a microwave oven; - the pre-treatment zone comprises a pre-heating device, for example an oven or an autoclave, configured to carry out sub-step (b1) of pre-heating the resin of the polymerizable mixture; - the cooling zone comprises a cooling device chosen from a water bath,a cooling chamber, an air cooling tunnel, a heat exchanger, an annealing furnace and a liquid nitrogen system; -- the transfer conduit or any other element comprising the polymerizable mixture obtained in sub-step (b2) is arranged in the cooling zone and configured to maintain the temperature without triggering or accelerating the polymerization of the resin of said polymerizable mixture; -- the installation comprises a conditioning zone for the polymerizable mixture configured to store the polymerizable mixture obtained at the end of step (b) for its subsequent use, for example for injection into the at least one mold and / or the at least one conditioning container; -- the conditioning zone comprises at least one conditioning container, such as a drum or an injector. The installation may comprise any element making it possible to carry out the steps of the method mentioned above. Brief description of the figures Otherscharacteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which: Figure 1 is a block diagram representing the steps of carrying out a method of manufacturing a part made of composite material according to the invention; Figure 2 is a very schematic view of a first example of an installation according to the invention for implementing the manufacturing method of Figure 1, in which a polymerizable mixture is injected into a mold; Figure 3 is a very schematic view representing a part of the installation of Figure 2; Figure 4 schematically represents an example of arrangement of a microwave source in the installation of Figure 2 or Figure 3; Figure 5 represents another example of arrangement of a microwave source in the installation of Figure 2; Figure 6 is a very schematic view of a second example of the installation implementingimplements the manufacturing method of Figure 1, in which the polymerizable mixture is transferred into one or more packaging containers; Figure 7 is a very schematic view of an alternative embodiment of the installation of Figure 6; Figure 8 is a very schematic view of a third example of the installation implementing the manufacturing method of Figure 1, in which the polymerizable mixture is injected into the mold and also transferred into the packaging container. The elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention The present invention relates to a method for manufacturing a part 2 made of composite material, in particular for an aircraft turbomachine, comprising several successive steps: (a) production of a fiber blank 30 intended to form the part 2, (b) preheating a polymerizable mixture 7 comprising a resin(preferably in liquid form) and a hardener (preferably in solid form), to dissolve the hardener in the resin, (c) injecting the polymerizable mixture 7 into at least one mold 6 comprising the fiber blank 30, (d) heating and densifying the fiber blank 30 so as to cause the polymerization of the polymerizable mixture 7 and the impregnation in said fiber blank 30, and (e) demolding the part 2 made of composite material thus obtained. The method may further comprise a step (i) of conditioning the polymerizable mixture 7. This step (i) may be carried out before or simultaneously with step (c). The polymerizable mixture 7 conditioned in step (i) may form a semi-finished product. Figure 1 summarizes the steps of the method for manufacturing the part 2, in which the optional steps are shown in dotted lines. A non-limiting example of an installation 1 making it possible to implement such a method is illustrated in Figures 2 to 8.The composite material part 2 may be an aeronautical composite part, for example a bladed part of the turbomachine (such as a rotor blade for example of a fan or a stator blade for example of a rectifier of the turbomachine), a casing of the turbomachine (such as a fan casing), a wedge of the turbomachine (such as a fan wedge for keeping a fan blade in position when the turbomachine is stopped) or any other part of the turbomachine or of an aircraft. The composite material part 2 may comprise a polymer matrix (or resin) and the fiber blank 30 (or fiber reinforcement) embedded and densified in this matrix to form a fiber preform. In other words, the fiber preform may be embedded in the resin. By "fiber preform", is meant an intermediate component of production in particular between the fiber blank 30 and the final part 2. The composite material can be organic matrix (OMC).CMO materials replace parts made of metallic material, in particular in certain parts of turbomachines (such as the aforementioned parts with blades, casing, etc.). Furthermore, their use contributes to optimizing the performance of the turbomachine and aircraft in general, in particular by improving the efficiency of the turbomachine and reducing the overall mass of the turbomachine, significantly reducing harmful emissions to the environment (CO, CO2, NOx, etc.). In step (a), the fiber blank 30 can be produced by three-dimensional fiber weaving or by superimposing several layers or plies of fibers. For example, the three-dimensional fiber weaving can be an “interlock” weave. By interlock weave, we mean here a weave in which each layer of weft threads binds several layers of warp threads with all the threads of the same weft column having the same movement.in the plane of the armor. Step (a) may also comprise cutting the fiber blank 30, for example with a pressurized water jet, to obtain the final geometry of the part 2 to be obtained. The fiber blank 30 obtained in step (a) may be placed in a cavity of the mold 6. The fiber blank 30 may be made from carbon, glass, aramid, ceramic, Kevlar fibers ®, a mixture of at least two of these fibers or any other fibers. Before carrying out step (b), the polymerizable mixture 7 may be provided beforehand by mixing the resin (preferably in liquid form) and the hardener (preferably in solid form). The hardener may be dispersed, preferably prior to carrying out step (b), in the resin in liquid form. The resin (or the matrix, once the resin has been densified) of the polymerizable mixture 7 may be a thermosetting material. Preferably, the resin may comprise polyepoxides (or epoxides), polyimides or polybismaleimides. The resin of the polymerizable mixture 7 may be free of thermoplastic material. The polymerizable mixture 7 may comprise a PR520N resin marketed by Solvay, a 2896 resin marketed by 3M, or an RTM250ST resin marketed by Hexcel.Advantageously, the resin may be a polyepoxide resin, for example the PR520N resin marketed by Solvay which may be based on DiGlycidyl Ether of Bisphenol F (having the acronym DGEBF), or the 2896 resin marketed by 3M which may be based on DiGlycidyl Ether of Bisphenol A (having the acronym DGEBA). The hardener of the polymerizable mixture 7 may be a crosslinking agent which triggers the polymerization and the hardening is in particular irreversible of the resin under the effect of heat. Preferably, the hardener may be selected from 9,9-Bis(4-amino-3chlorophenyl)fluorene having the acronym CAF, 1,12-dodecanedioic acid having the acronym DDA, 4,4'-diamino-diphenylsulfone having the acronym DDS and hexamethylenediamine having the acronym HDMA. The polymerizable mixture 7 may further comprise at least one or more other components, such as at least one additional filler.Preferably, this filler may represent less than 30% by mass of the polymeric mixture, 10% maximum for elastomeric fillers. Its objective is to improve certain physicochemical and / or mechanical characteristics of the part 2. For example, the additional filler of the polymerizable mixture 7 may be, without limitation, of the elastomer, mineral, ceramic or metallic type. For an optimal result, in particular in terms of the mechanical properties of the resin after curing, the hardener must be dissolved in the resin before injection into the mold 6. Thus, one of the particularities of the invention is that step (b) of preheating the polymerizable mixture 7 comprises a sub-step (b2) of dissolving the hardener in the resin by microwaves. This optimizes and simplifies the dissolution of the hardener without initiating the crosslinking of the resin and while avoiding the use of complex, expensive and time-consuming heating systems.The dissolution of the hardener in the resin may be complete or partial. The complete dissolution of the hardener may comprise a dissolution rate which may be greater than 80% or 85%. Preferably, the complete dissolution rate of the hardener is between 85% and 100%. The partial dissolution of the hardener may comprise a dissolution rate of between 50% and 85%. The method may further comprise a heating step (ii) of the polymerizable mixture 7 which is carried out before step (i) and / or before step (c). This makes it possible to condition and preserve or inject the polymerizable mixture at a temperature appropriate to step (i) or step (c). The polymerizable mixture 7 obtained in sub-step (b2) may be heated with a temperature gradient, for example in step (ii). This makes it possible to promote the viscosity of the polymerizable mixture 7 to be injected in step (c).The heating of this polymerizable mixture 7 after sub-step (b2) can be carried out by a heat source which is preferably remote and different from a microwave source used in sub-step (b2). Another of the particularities of the invention is that the method further comprises a sub-step (b3) of cooling the polymerizable mixture 7, and / or a sub-step (b4) of stabilizing the temperature of the polymerizable mixture 7. The sub-step (b3) of cooling can be carried out after the sub-step (b2) of dissolving the hardener and the sub-step (b4) can be carried out after the sub-step (b2) or the sub-step (b3). The cooling and / or the stabilizing the temperature of the polymerizable mixture makes it possible not to start or stop the polymerization of the resin, while having the dissolved hardener contained in the polymerizable mixture.In particular, temperature stabilization may be an alternative for gradually cooling or maintaining the temperature of the polymerizable mixture at the outlet of sub-step (b2). Sub-step (b4) may be carried out by isolating the polymerizable mixture 7 obtained in sub-step (b2) or sub-step (b3), for example via an insulated (or remote) pipe. The polymerizable mixture 7 obtained at the end of step (b), preferably at the end of sub-step (b2), may subsequently be directly injected into the mold(s) 6 according to step (c), in particular without passing through any other pre-heating element such as the heaters described in the technical background above. Alternatively, the polymerizable mixture 7 obtained at the end of step (b), preferably at the end of sub-step (b2), may be directly packaged (or pre-packaged) according to step (i). This may be carried out in at least one packaging container 72.The container(s) 72 may be a drum 720 and / or an injector 722. The conditioned polymerizable mixture 7 may be reused later, for example for injection into the mold(s) 6. According to another variant, the polymerizable mixture 7 obtained at the end of step (b), preferably at the end of sub-step (b2), may be injected into the mold(s) 6, and also conditioned in the conditioning container(s) 72. This may be carried out simultaneously or non-simultaneously in time. The microwaves may be produced and applied by at least one source 44 (or otherwise said a generator), such as a microwave oven, magnetron or any other device for generating and applying / emitting microwaves. The microwave source 44 may be fixed or mobile, in particular relative to the installation 1 and / or the polymerizable mixture 7.The microwaves can generate a power of between 100 Watts and 3000 Watts, in particular depending on the type of microwave source 44. For example, the microwaves can generate a power of between 100 Watts and 1500 Watts. Preferably, this power is approximately 800 Watts. The microwaves can be applied for a maximum duration of approximately 5 minutes. For example, the microwaves can be applied for a duration of between 1 second and 90 seconds, preferably this duration is approximately 30 seconds. The microwaves can be emitted by the at least one fixed or mobile source 44 in sub-step (b2). For example, the microwaves can be emitted by the fixed or mobile microwave source 44, in particular in the installation 1 (described above). The term "mobile" means microwaves in dynamic motion, for example in a rotary, linear, or helical manner.The polymerizable mixture 7 may be contained in a container 70 that is fixed or mobile, for example rotating, relative to the microwaves in sub-step (b2). The container 70 may be a glass jar or any other container capable of being heated by microwaves. Preferably, the container 70 may be at least one transfer conduit located, for example, in a system of conduits 5 (described below) of the installation 1. The microwaves may thus be applied directly to this transfer conduit, which in particular allows the continuous transfer of the polymerizable mixture 7 containing the dissolved hardener to the mold 6 and / or the container 72. The polymerizable mixture 7 may be static or mobile relative to the container. For example, the container 70 may be placed on a support capable of making the polymerizable mixture mobile. Advantageously, the polymerizable mixture 7 may be mobile and the container 70 is fixed (Figures 3 to 5).The polymerizable mixture 7 can thus be in motion in the container 70, for example in the form of a transfer conduit. The movement of the polymerizable mixture can be controlled by adjusting the flow rate and / or the pressure within the container. The present application will now describe, in a non-limiting manner, an example of an operating mode of sub-step (b2) of the method of the invention. Firstly, a sample of the polymerizable mixture comprising the PR520N resin and of approximately 20 grams (g) is placed in a glass jar. Then, the sample and the glass jar are placed in a microwave oven, in particular a commercial one, to dissolve the hardener contained in this sample. For this, a power of 800 Watts is applied for a period of approximately 30 seconds. At the end of this dissolution (or heating) cycle, the so-called dissolved sample is left to cool to room temperature (such as approximately 25°C).At the end of sub-step (b2), the physical state of the dissolved sample is characterized by measuring the vitreous temperature and enthalpy parameters (or in other words the specific heat capacity) to characterize the dissolution of the hardener. For this, a DSC test (English acronym for "Differential Scanning Calorimetry" was carried out on the dissolved and in particular cooled sample. Thus, the vitreous temperature Tg (known under the English designation "Glass Temperature") of the dissolved sample (i.e. after microwave exposure) is higher than that measured on the undissolved sample (i.e. in a totally undissolved and uncrosslinked initial state). Indeed, the vitreous temperature of the initial undissolved sample is approximately -23°C and the vitreous temperature of the dissolved sample is approximately +11°C. Furthermore, the residual enthalpy of dissolution of the dissolved sample is measured at a value lower than 5 Jg -1(Joule per unit mass in grams), while the enthalpy of a crosslinking reaction of the sample has an initial standard value between 280 and 300 Jg -1. Thus, the enthalpy of the dissolved sample being lower than the enthalpy of the crosslinking reaction, the sample after microwave exposure is dissolved without initiating crosslinking of the resin. It is thus possible to determine the dissolution rate of the sample after microwave exposure which is greater than 80%, while avoiding initiating the crosslinking reaction of the resin. The dissolution rate can be measured and obtained by calorimetry, for example by modulated differential scanning calorimetry (mDSC). For this, the energy required to dissolve the hardener in an unheated resin of the initial undissolved sample is compared with that in a microwave-heated resin of the dissolved sample. Step (b) of preheating the polymer mixture may comprise a sub-step (b1) of preheating the resin of the polymerizable mixture 7 to a preheating temperature.This sub-step (b1) is carried out before the sub-step (b2) of dissolving the hardener. The preheating temperature of the resin may be between 80°C and 120°C. As mentioned above, step (b) may comprise the sub-step (b3) of cooling the polymerizable mixture 7, for example to room temperature (such as between 18 and 25°C). The cooling sub-step (b3) is carried out after the sub-step (b2) of dissolving the hardener. The sub-step (b3) may be carried out before step (c) and / or step (i) and / or sub-step (b4). The polymerizable mixture 7 obtained at the end of sub-step (b3) can subsequently be directly injected into the mold(s) 6 according to step (c), as illustrated in a non-limiting manner in Figure 3. As a variant, the polymerizable mixture 7 obtained at the end of sub-step (b3) can be directly conditioned (or pre-conditioned) according to step (i), as illustrated in a non-limiting manner in Figures 6 and 7.This can be carried out in the packaging container(s) 72, as described above in a non-limiting manner. The packaged polymerizable mixture 7 can be reused later, for example, for injection into the mold(s) 6. In this case, the polymerizable mixture 7 containing the dissolved hardener can be injected directly into the mold(s) 6 without undergoing a new dissolution (i.e., step (b)) of the hardener for each mold 6. The polymerizable mixture 7 packaged according to step (i) can be stored at a predetermined temperature (for example, at room temperature) which makes it possible to store the hardener dissolved in the resin, the polymerization reaction of which is stopped. The room temperature can be between 18 and 25°C.The polymerizable mixture 7 obtained in sub-step (b2) can be placed in a cooling zone 8 of the installation 1 (described below) and configured to maintain the temperature without triggering or accelerating the polymerization of the resin of this polymerizable mixture 7. For example, this polymerizable mixture 7 can be placed via the transfer conduit or any other element making it possible to maintain the temperature of the polymerizable mixture. Advantageously, the polymerizable mixture 7 can be cooled by at least 1°C below a predetermined outlet temperature of the polymerizable mixture at the end of sub-step (b2). This can be carried out at room temperature. According to another variant, the polymerizable mixture 7 obtained at the end of sub-step (b3) can be injected into the mold(s) 6, and also packaged in the packaging container(s) 72, as illustrated in a non-limiting manner in FIG. 8.This can be carried out simultaneously or non-simultaneously over time. In step (d), the heating temperature in the mold 6 can be between 80°C and 200°C. Preferably, the heating temperature can be between 160°C and 200°C, in particular when the polymerizable mixture comprises the PR520N resin. Advantageously, steps (b), (c) and / or (d) of the method can be carried out under vacuum, such as by a vacuum system (not illustrated in the figures). The present application will now describe the installation 1 for implementing the method as described above.With reference to Figure 2, the installation 1 comprises: - a production zone 3 for the fiber blank 30 to implement step (a) of production of this fiber blank 30, - a pre-treatment zone 4 for the polymerizable mixture configured to carry out step (b) of dissolving the hardener in the resin, and - the at least one mold 6 for receiving the fiber blank 30 and injecting the polymerizable mixture to carry out step (c) of injecting the polymerizable mixture (in particular with the hardener dissolved completely or partially in the resin) into the mold 6 and step (d) of heating and densifying the fiber blank 30. The installation 1 may comprise a system of conduits 5 for conveying the polymerizable mixture 7 from one element of the installation 1 to another.For example, this conduit system 5 may comprise at least one conduit for transferring the polymerizable mixture 7 with the hardener dissolved completely or partially in the resin from the pre-treatment zone 4 (in particular from the source 44) to the mold(s) 6 and / or the packaging container(s) 72. As described above, the polymerizable mixture 7 may be contained in the container 70, in particular to carry out step (b). This container 70 may be the conduit, called the transfer conduit, of the conduit system 5, as illustrated in FIGS. 6 to 8. One of the particularities of the invention is that the pre-treatment zone 4 comprises at least one microwave source 44 configured to carry out the sub-step (b2) of dissolving (for example completely or partially) the hardener in the resin. The microwave source 44 may be a microwave oven, for example of the commercial type.The microwave source 44 can be applied directly to the transfer conduit containing the polymerizable mixture 7, as illustrated in Figures 6 to 8. In the example of Figure 3, the pre-treatment zone 4 can comprise an injection device 40 (or otherwise known as an injector) intended to contain and inject (for example by a piston) the polymerizable mixture 7. As illustrated in a non-limiting manner in Figures 3 to 8, the polymerizable mixture 7 can be injected from the injection device 40 to the container 70 (such as a pipe or transfer conduit) to dissolve the hardeners by microwaves. The polymerizable mixture 7 is thus mobile, in particular in the fixed container 70, and circulates in a direction indicated by the dotted arrows.The polymerizable mixture 7 comprising the hardener dissolved completely by the microwaves can then be brought to the mold(s) 6 and / or to the packaging container(s) 72 by the conduit(s) of the conduit system 5. The source 44 can extend around the container 70 containing the polymerizable mixture 7 with reference to FIGS. 3, 4 and 6 to 8. The polymerizable mixture 7 can be mobile in the container 70 with a flow rate of, for example, 20 and 2000 cubic centimeters per minute (cm. 3 / min). In another variant, the source 44 can be directly connected to the container 70 to dissolve the hardener with reference to FIG. 5. The pre-treatment zone 4 can comprise a pre-heating device 42 configured to carry out the sub-step (b1) of pre-heating the resin of the polymerizable mixture. For example, the pre-heating device 42 can be an oven or an autoclave. The pre-treatment zone 4 can comprise a cooling zone 46 to carry out the sub-step (b3) of cooling the polymerizable mixture. The cooling zone 4 can comprise a cooling device chosen from a water bath, a cooling chamber, an air cooling tunnel, a heat exchanger, an annealing furnace and a liquid nitrogen system.The transfer conduit or any other element comprising the polymerizable mixture 7 of sub-step (b2) may be arranged in the cooling zone 4 and configured to maintain the temperature without triggering or accelerating the polymerization of the resin of the polymerizable mixture 7. The installation 1 may comprise a conditioning zone 8 of the polymerizable mixture 7 configured to store the polymerizable mixture 7 obtained at the end of step (b) for its subsequent use, for example for injection into the mold(s) 6 and / or the conditioning container(s) 72. The conditioning zone 8 may comprise the conditioning container(s) 72, such as a drum 720 or an injector 722 (Figures 6 to 8). The installation 1 may comprise or be connected to remote control and command means, such as computerized means for example.The installation 1 may include the vacuum system making it possible to create a vacuum in the installation 1, in particular at the level of the elements requiring vacuum.

Claims

CLAIMS 1. A method of manufacturing a composite material part (2), in particular for an aircraft turbomachine, the method comprising the following steps: (a) producing a fiber blank (30) intended to form said composite material part (2), (b) preheating a polymerizable mixture (7) comprising a resin and a hardener to dissolve the hardener in the resin, (c) injecting the polymerizable mixture (7) into at least one mold (6) comprising the fiber blank (30), (d) heating and densifying the fiber blank (30) so as to cause polymerization of the polymerizable mixture (7) and impregnation in said fiber blank (30), and (e) demolding the composite material part thus obtained, characterized in that step (b) comprises a sub-step (b2) of dissolving the hardener in the resin by microwaves, and in that step (b) further comprises a sub-step (b3) of cooling the polymerizable mixture (7),for example at room temperature, and / or a sub-step (b4) of stabilizing the temperature of the polymerizable mixture (7), the sub-step (b3) of cooling being carried out after the sub-step (b2) of dissolving the hardener and the sub-step (b4) being carried out after the sub-step (b2) or the sub-step (b3).

2. Manufacturing method according to claim 1, characterized in that in sub-step (b2), the microwaves are emitted by at least one fixed or mobile source.

3. Manufacturing method according to claim 1 or 2, characterized in that the resin is in liquid form and the hardener is in solid form before carrying out step (b).

4. Manufacturing method according to any one of claims 1 to 3, characterized in that in sub-step (b2), the polymerizable mixture (7) is, contained in a container (70) which is fixed or mobile, for example rotating, relative to the microwaves.

5. Manufacturing method according to the preceding claim, characterized in that the polymerizable mixture (7) is mobile relative to the fixed container (70).

6. Manufacturing method according to one of the preceding claims, characterized in that it further comprises a step (i) of conditioning the polymerizable mixture (7), this step (i) being carried out before or simultaneously with step (c).

7. Manufacturing method according to claims 5 and 6, characterized in that the container (70) is a conduit for transferring the polymerizable mixture (7) obtained at the end of step (b) to the at least one mold (6) and / or a packaging container (72).

8. Manufacturing method according to one of claims 5 to 7, characterized in that there is also a heating step (ii) of the polymerizable mixture (7) which is carried out before step (i) and / or before step (c). 9.Manufacturing method according to any one of the preceding claims, characterized in that the microwaves generate a power of between 100 Watt and 3000 Watt, preferably this power is between 100 Watt and 1500 Watt.

10. Manufacturing method according to any one of the preceding claims, characterized in that the microwaves are applied for a maximum duration of approximately 5 minutes, this duration is for example between 1 second and 90 seconds, preferably this duration is approximately 30 seconds.

11. Manufacturing method according to any one of the preceding claims, characterized in that step (b) comprises a sub-step (b1) of preheating the resin of the polymerizable mixture (7) to a preheating temperature, this sub-step (b1) being carried out before the sub-step (b2) of dissolving the hardener.

12. Manufacturing method according to claim 11, characterized in that the preheating temperature of the resin, in particular in step (b1), is between 80°C and 120°C.

13. Manufacturing method according to any one of the preceding claims, the dissolution in sub-step (b2) is partial with a dissolution rate of between 50% and 85%. 14.Installation (1) for implementing a method for manufacturing the composite material part (2) according to any one of the preceding claims, the installation (1) comprising: - a production zone (3) for the fibrous blank (30) to implement step (a), - a pre-treatment zone (4) for the polymerizable mixture (7) configured to dissolve the hardener in the resin of step (b), and - the at least one mold (6) for receiving the fibrous blank (30) and for injecting the polymerizable mixture (7) to carry out steps (c) and (d), characterized in that the pre-treatment zone (4) comprises at least one microwave source (44) configured to carry out the sub-step (b2) of dissolving the hardener in the resin, and in that the pre-treatment zone (4) comprises a cooling zone (46) to carry out the sub-step (b3) of cooling the polymerizable mixture. 15.Installation according to the preceding claim in combination with claim 10, characterized in that the pre-treatment zone (4) comprises a pre-heating device (42), for example an oven or an autoclave, configured to carry out the sub-step (b1) of pre-heating the resin of the polymerizable mixture.

Images