METHOD AND DEVICE FOR PRODUCEING A PART BY INJECTING RESIN INTO A FIBER PREFORM

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and tooling for manufacturing a part by injecting resin into a preform made of woven fibers. STATE OF THE ART

[0002] A part, particularly a turbomachine component such as a fan blade, can be manufactured by injecting resin into a woven fiber preform. This molding process is called RTM, an acronym for the Anglo-Saxon term Resin Transfer Molding is a well-known prior art manufacturing process consisting of placing a fibrous preform having at least one outer wall of dry fabric in a sealed cavity of a tool, and filling this cavity with an impregnation resin, usually an epoxy resin.

[0003] The outer wall of the preform, or the preform as a whole, is usually made by weaving composite fibers such as carbon fibers.

[0004] There figure 1a represents the different stages of a manufacturing process for a part of the aforementioned type using current technology. The process essentially comprises six stages, which are: 1) the production of the preform by three-dimensional (3D) weaving, the preform of fibers coming off a loom being flat and loose, 2) the sizing of the preform, by cutting in particular the floats, 3) the shaping of the preform, by positioning the preform on a shaping support, this support forming a first tool 10, 4) the forming of the preform, by moistening the preform and forming in a mold of a second tool 10', and 5) the injection molding in a mold of a third tool 10".

[0005] In current techniques, steps 3 through 5 specific to the RTM process are therefore performed using three separate tooling sets, which makes manufacturing a part by the RTM process complex and time-consuming. Such a configuration is described or discussed in documents US-2015 / 343.717-A1 and FR-3.002.477-A1.

[0006] Step 5 of the molding process is carried out as follows (see figure 1b The molding tooling comprises a mold defining a first cavity and a counter-mold defining a second cavity. The molds and counter-mold are designed to be nested one inside the other so that their cavities define the aforementioned cavity for receiving the preform and injecting the resin. The preform is positioned in the mold cavity (step 5a). The tooling is closed using a press to compact the preform in the cavity (step 5b). Pipes are connected to the tooling and to a resin injection piston (step 5c). A vacuum is created in the cavity (step 5d), and the resin is introduced into the piston and then injected through the piston into the tooling cavity (step 5e). The press is heated to maintain pressure on the preform during resin polymerization (step 5f).After cooling, the tooling is opened, the part is removed from the mold, and the tooling and equipment can be cleaned (step 6).

[0007] Furthermore, the current technique has many drawbacks.

[0008] The resin is injected into the cavity using external equipment (piston or pressure pot, resin heater, piping, etc.). This is a complex process, requiring precise injection control over pressure, temperature, and flow rate. Furthermore, there is a high risk of malfunctions or anomalies. The worst-case scenario is dangerous: if the resin is heated for too long or at too high a temperature, exothermic heat can cause the piston to explode. After each injection, the equipment must be cleaned, a lengthy process that exposes operators to resin and acetone fumes. The piping is connected and disconnected, then discarded for each part manufactured. Setting up all the tooling takes a considerable amount of time. To prevent pinching when closing the tooling, preferential flow paths are used during cavity filling, which complicates the injection strategies.Material loss results in significant additional costs, and some of the resin remains in the equipment (piston, heater, piping, etc.) rather than being distributed within the part. The external piston, which generates the injection pressure, struggles to control the pressure inside the cavity, especially as the resin begins to harden. If the resin were to polymerize too quickly in the piping connecting the piston to the cavity, it could form a blockage inside the piping, leading to insufficient resin injection.

[0009] The present invention offers a solution to at least some of the above problems, which is simple, effective and economical. DESCRIPTION OF THE INVENTION

[0010] The invention proposes a method for manufacturing a part by injecting resin into a woven fiber preform, comprising the steps of: c) shaping of the preform, d) forming of the preform, and e) injection of resin into the preform and molding, step e) being carried out by means of tooling comprising a mold, a counter-mold and means for injecting resin, characterized in that step e) comprises the substeps of: e1) partial opening of the tooling, by moving the mold away from the counter-mold or vice versa, e2) injection of resin into the tooling, e3) closing of the tooling, by moving the mold closer to the counter-mold or vice versa, and e4) pressurizing and heating the impregnated preform between the mold and the counter-mold.

[0011] The partial opening of the tooling facilitates the injection and distribution of resin between the mold and the counter-mold. A sufficient, but not excessive, quantity of resin can thus be injected into the tooling to impregnate the preform and fill the cavity defined between the mold and the counter-mold, according to the final geometry of the part.

[0012] Advantageously, which of the said steps c), d) and e) are carried out using said tooling, which is therefore the only tooling used in the process. Said mold defines a cavity configured to carry out step c), and the tooling further includes means for air extraction and resin injection.

[0013] The invention is particularly advantageous because it simplifies the RTM manufacturing process for a part by reducing the number of tooling pieces required to just one. A single tooling piece is used to perform the three aforementioned steps, resulting in significant time savings and a reduction in the risk of damage to the part during transfers between tooling pieces.

[0014] The process according to the invention may comprise one or more of the following features or steps, taken individually or in combination with each other: The process includes, before step c), the steps of: a) making the preform by weaving fibers, and b) sizing the preform, step c) includes the substeps of humidifying the preform and positioning the preform in the mold cavity, step d) includes the substeps of closing the tooling and heating and vacuuming the preform between the mold and the counter-mold, the substep of at least partially opening the tooling is carried out by moving the counter-mold away from the mold by a predetermined distance, the mold and the counter-mold remaining substantially nested within each other, the resin is injected through one port of the tooling, and the vacuum is created by drawing air through another port of the tooling, said steps are carried out using a single tooling.

[0015] The present invention also relates to tooling for implementing the process according to one of the preceding claims, characterized in that it comprises: two heating plates respectively upper and lower, the lower heating plate being attached to a mold having a cavity for shaping a preform and the upper heating plate being attached to a counter-mold having another cavity, motorized means for moving the plates, preferably in a substantially vertical direction, from a distant position to a position in which the mold and the counter-mold are nested one inside the other, the motorized means being capable of applying a compressive force to the plates for the purpose of pressurizing the preform between the cavities.

[0016] Advantageously, the two platens are part of a press in which the lower platen forms a base and the upper platen is mounted to slide in a substantially vertical direction on guide columns.

[0017] The tooling may include means for laser projection of the preform contours onto the mold cavity. DESCRIPTION OF THE FIGURES

[0018] The invention will be better understood and other details, features and advantages of the invention will become apparent upon reading the following description, given by way of non-limiting example with reference to the accompanying drawings, in which: there figure 1a is a block diagram representing steps in a process according to the previous technique for manufacturing a part from composite material, the figure 1b is a block diagram representing steps in a process according to the earlier technique of molding a part by injecting resin into a woven fiber preform, the figure 2a is a block diagram representing steps in a process according to the invention for manufacturing a part made of composite material, the figure 2b is a block diagram representing steps in a process according to the invention for molding a part by injecting resin into a woven fiber preform, the figure 3 is a schematic view of a tool for implementing the process of figures 2a et 2b , there figure 4 is a schematic perspective view of the mold and counter-mold of the tooling of the figure 3 , and the figures 5 à 7 are other schematic views of the tooling of the figure 3 and illustrate steps in the process. DETAILED DESCRIPTION

[0019] THE figures 1a et 1b have been described above and represent a process according to prior art.

[0020] THE figures 2a et 2b illustrate a process according to the invention for producing a part made of composite material, these steps preferably being carried out using the tooling 100 shown in figures 3 and following.

[0021] The tooling 100 essentially comprises a mold 102 attached to a lower plate 104, preferably heated, and a counter-mold 106 attached to an upper plate 108, also preferably heated. Sealing means are preferably provided between the mold and the counter-mold. In the example shown, the lower plate 104 forms a support base for the tooling, which can, for example, rest on the floor of a manufacturing workshop.

[0022] Mold 102 is located on one upper face of tray 104 and includes an imprint 110, best seen at the figure 4 In the example shown, the imprint 110 is that of a face of a fan blade, such as its upper surface. The imprint 110 is oriented upwards here and faces an imprint 112 of the inner mold, also more clearly visible in the figure 4 The counter-mold 106 is located above and opposite the mold. The impression 112 here is that of another face of a blower blade, such as its intrados for example.

[0023] The plate 108 is mounted to slide on guide columns 114, here two in number, which extend between their lower ends connected to the plate 104 and their upper ends connected to a mast 116. The plate 108 and the counter-mold 106 are moved in substantially vertical translation by means of a jack 118 or similar, the cylinder of which is fixed to the mast 116 and the piston of which is connected to the plate 108.

[0024] The plate 108 and the counter-mold 106 are movable from a superior position, shown in the figure 3 , in which the tooling is open and the mold 102 and the counter-mold 106 are spaced apart, and a nested or close-coupled position in which the tooling is closed and the mold and the counter-mold are engaged with each other, shown in the figure 5 . Intermediate positions are conceivable, such as the position of the figure 6 in which the tooling is open and the mold and counter-mold are partially disassembled from each other, the counter-mold being moved a predetermined distance away from the mold. The tooling 100 is also used to pressurize the preform 200 in the cavity defined by the cavities 110, 112, by a predetermined force applied by the cylinder 118 on the plate 108 (arrow 120).

[0025] Tooling 100 also includes means for heating the plates 104, 108, not shown, as well as means for vacuuming and feeding the cavity defined by the impressions 110, 112.

[0026] The vacuum means include a first port 122 located for example in the mold and one end of which opens into the cavity 110. The other end of this port 122 is intended to be connected to suction means such as a pump, not shown.

[0027] The feeding means include a second port 124 located for example in the mold and one end of which opens into the cavity 110. The other end of this port 124 is intended to be connected to resin injection means, not shown.

[0028] The tooling may also include means 126 for laser projection in particular of the contour of the preform 200 onto the cavity 110 of the mold, in order to facilitate its positioning at the beginning of the process.

[0029] We will now describe the different steps of an embodiment of the process according to the invention, starting from the figures 2a, 2b , 3 , 5 and following.

[0030] The first step a) of the process consists of creating a preform 200 by weaving in three dimensions using a loom, for example of the Jacquard type. As it comes off the loom, the preform is rough and has a generally flat shape and is loose.

[0031] A subsequent step b) of the process consists of bringing the preform 200 to the correct dimensions, for example by cutting out its floats.

[0032] Steps a) and b) are similar to steps 1) and 2) of the prior art process, described above.

[0033] Step c), and the following steps, differ from steps 3) and following of the prior art in that they are carried out using tooling 100 shown in figures 3 And 5 à 7 .

[0034] There figure 3 This illustrates step c), which consists of shaping the preform 200. For this, the preform is preferably moistened beforehand to make it more malleable. It is placed in the cavity 110 of the mold 102 using laser projection means 126. These projection means allow, for example, the precise positioning of tracers that would be integrated into the preform 200 in predefined positions.

[0035] There figure 5 Figure 1 illustrates step d), which involves shaping the preform. For this, the tooling is closed and pressurized, for example, to between 5 and 10 bar, then heated, for example, to 100°C, using the heated platens 104 and 108 and the cylinder 118. A residual vacuum is applied to the cavity receiving the preform using suction devices, which removes moisture (arrow 128). During this step, the preform is compacted to the desired final geometry and dried by heating. The preform 200 is then ready for injection molding.

[0036] THE figures 6 And 7These figures illustrate step e), which consists of injecting resin 202 into the cavity of tooling 100. For this, the tooling is partially opened (step e1), with the counter-mold positioned a predetermined distance from the mold, as explained above. This allows for the introduction of only the volume of resin strictly necessary to wet the preform and fill the final geometry of the part (maintaining the required fiber content). During this resin injection operation (arrow 130 - step e2), the mold and counter-mold are preferably heated, as is the resin.

[0037] The tooling is then closed ( figure 7- step e3) and a pressure of 3 to 10 bar, for example, is applied by the cylinder to the preform 200. The temperature can be maintained at 150°C during injection and raised to 180°C for resin polymerization. As shown in the drawing by means of the arrows, the pressure is preferably kept constant over the entire surface of the part during polymerization (step e4).

[0038] The resin used is for example an epoxy resin such as that known under the reference CYCOM PR520 ®< , marketed by the company CYTEC.

[0039] After polymerization, tooling 100 is opened, part 200 is removed and the tooling can be cleaned in preparation for a new manufacturing operation.

[0040] The piston used in the previous technique for injecting resin into the tooling is replaced here by the upper counter-mold, which applies pressure and allows the preform to be impregnated with the resin. The resin thus remains under constant and continuous pressure during polymerization, preventing any porosity in the part.

[0041] The invention offers several advantages. A precise amount of resin can be used, resulting in cost savings. When using pipes (e.g., copper) with the prior art, the entire assembly is discarded after injection because the resin hardens inside. With the invention, the pipes can be eliminated or even significantly shortened. A composite part is obtained with the desired dimensions (mold-to-mold) and smooth (aerodynamic) surfaces. No pressurizing fluid, such as water or oil, is required. Even more difficult-to-inject resins with high viscosities can be used. The pressure can potentially change during the holding phase (particularly in the case of PR520® resin, which can be compressible or have its volume decrease as it polymerizes).

Claims

1. Method for producing a part by injecting resin (202) into a woven fibre preform (200), comprising the steps of: c) shaping the preform, d) forming the preform, and e) injecting resin into the preform and moulding, step e) being carried out by means of an item of equipment (100) comprising a mould (102), a countermould (106), and means (124) for injecting resin, wherein step e) comprises the substeps of: e1) partially opening the item of equipment (100), by moving the mould away from the countermould or vice versa, e2) injecting resin (202) into the equipment, e3) closing the equipment, by bringing the mould closer to the countermould or vice versa, and e4) pressurising and heating the impregnated preform (200) between the mould (102) and the countermould (106).

2. Method according to the preceding claim, wherein said steps c), d) and e) are carried out by means of said equipment (100), said mould defining a cavity configured to implement the step c), and the equipment further comprising means (122) for suctioning air and injecting resin.

3. Method according to claim 1 or 2, wherein it comprises, before the step c), the steps of: a) producing the preform (200) by weaving fibres, and b) sizing the preform.

4. Method according to one of claims 1 to 3, wherein the step c) comprises the substeps of humidifying the preform (200) and positioning the preform in the cavity (110) of the mould (102).

5. Method according to one of the preceding claims, wherein the step d) comprises the substeps of closing the equipment (100) and heating and putting the preform (200) under vacuum between the mould (102) and the countermould (106).

6. Method according to one of the preceding claims, wherein the substep of partially opening the equipment (100) is carried out by extending the countermould (106) by a predetermined distance from the mould (102), the mould and the countermould remaining substantially interlocked with one another.

7. Method according to one of the preceding claims, wherein the resin (202) is injected through a port (124) of the equipment, and the vacuum is produced by suctioning air through another port (122) of the equipment.

8. Method according to one of the preceding claims, wherein said steps are carried out by means of a single item of equipment (100).

9. Equipment (100) for implementing the method according to one of the preceding claims, the equipment comprising: - two heating plates (104, 108), respectively upper and lower, the lower heating plate (104) being integral with a mould (102) comprising a cavity (110) for shaping a preform (200) and the upper heating plate (108) being integral with a countermould (106) comprising another cavity (112), - motorised means (118) for moving plates, preferably in a substantially vertical direction, from an extended position to a position wherein the mould and the countermould are interlocked with one another, the motorised means being capable of applying a compression force (120) to the plates in view of pressurising the preform (200) between the cavities.

10. Equipment (100) according to the preceding claim, wherein the two plates (104, 108) form part of a press of which the lower plate (104) forms a base and the upper plate (108) is mounted sliding in a substantially vertical direction on the guiding columns (114).

11. Equipment (100) according to claim 9 or 10, wherein it comprises means for laser projection (126) of the contours of the preform (200) on the cavity (110) of the mould (102).