RU2774914C2 - Method and tool for production of part by injecting resin into billet of woven fibers - Google Patents

Abstract

FIELD: casting.

SUBSTANCE: invention relates to a method for the manufacture of a part by injecting resin into a billet of woven fibers. The method includes stages of: c) giving a shape to the billet, d) molding the billet, and e) injecting resin into the billet, and casting. In this case, the stage e) is implemented using a tool containing a mold, a counter-mold, and a means for injecting resin. At the same time, the stage e) contains following substages: e1) partial opening of the tool by separation the mold from the counter-mold or vice versa, e2) injection of resin to the tool, e3) closing of the tool by approach of the mold to the counter-mold or vice versa, and e4) increase in the pressure, and heating of the impregnated billet between the mold and the counter-mold.

EFFECT: simplification of the manufacture of a part, time saving and reduction in the risk of damage to the part, when it is moved from one tool to another.

11 cl, 9 dwg

Description

Technical field

The present invention relates to a method and tool for producing a part by injecting resin into a preform of woven fibers.

State of the art

A part, in particular a turbomachine, such as a fan blade, can be made by injecting resin into a woven fiber preform. This molding method, referred to as RTM (an acronym for Resin Transfer Molding), is a manufacturing method well known in the art, consisting of placing a fibrous preform containing at least one outer wall of dry fabric into an impermeable tool cavity and filling this cavity impregnating resin, usually epoxy resin.

The outer wall of the workpiece or the workpiece as a whole is usually obtained by interweaving composite fibers such as carbon fibers.

Figure 1a shows the various steps in the method of manufacturing a part of the above type in accordance with modern technology. The method essentially consists of the following six steps:

1) obtaining a workpiece by three-dimensional (3D) weaving, and the fibrous workpiece emerging from the loom is flat and voluminous,

2) cutting the workpiece to the desired dimensions, in particular by cutting off the weft threads,

3) shaping the workpiece by positioning the workpiece on the shaping support, this support forms the first tool 10,

4) shaping the blank by moistening the blank and molding the second tool 10' in the mold, and

5) Injection molding third tool 10".

In modern technology, steps 3-5 of the actual RTM process are implemented using three different tools, which makes the production of the part by the RTM method difficult and time consuming. Such a configuration is described or mentioned in US-2015/343717-A1 and FR-3002477-A1.

The casting step 5 is carried out as follows (see FIG. 1b). The forming tool contains a mold defining a first internal cavity and a counter-form defining a second internal cavity, wherein the mold and counter-form are designed to fit one inside the other so that their internal cavities define the aforementioned cavity to accommodate the workpiece and resin injection. The workpiece is placed in the inner mold cavity (step 5a). The tool is closed with a press to seal the blank in the cavity (step 5b). Pipelines are attached to the resin injection tool and piston (step 5c). A vacuum is created in the cavity (step 5d) and the resin is introduced into the piston and then forced by the piston into the tool cavity (step 5e). The press is heated and allows the preform to be kept under pressure during resin polymerization (step 5f). After cooling, the tool is opened, the part is removed from the mold, and the tool and equipment can be cleaned (step 6).

However, the current method has several disadvantages.

Resin injection into the cavity is carried out using external equipment (piston or pressurized vessel, resin heater, pipes, etc.). All of them are complex means, since the injection must be carried out with precise control of pressure, temperature, flow rate, etc. In addition, there is also an increased risk of breakdowns or anomalies. The worst case scenario is dangerous: if the resin is heated for too long or too much, the exothermic effect can cause the piston to explode. Equipment must be cleaned for each injection, which is a lengthy operation that exposes workers to tar and acetone fumes. Pipes are connected and disconnected and then discarded for each piece to be made. The installation time of all equipment is very long. To avoid pinching when closing the instrument, preferred paths are created when filling the cavity, which complicates the injection strategy. The loss of material leads to significant additional costs, and part of the resin is not distributed into the part, but remains in the equipment (in the piston, in the heater, in pipes, etc.). The external piston, which allows injection pressure, has great difficulty in controlling the pressure inside the cavity, in particular, at the moment when the resin begins to harden. If the resin polymerizes faster in the tube connecting the piston to the cavity, it may form a plug inside the tube and result in insufficient resin injection.

The present invention provides a solution to at least some of the above problems, which solution is simple, effective and economical.

The essence of the invention

The invention provides a method for manufacturing a part by injecting resin into a woven fiber preform, comprising the following steps:

c) shaping the blank,

d) shaping the blank and

e) resin injection into the billet and casting,

wherein step e) is carried out with a tool containing a mould, a counter-mould and a resin injection means,

and characterized in that step e) contains the following sub-steps:

e1) partial opening of the tool by moving the mold away from the counter-mould or vice versa,

e2) resin injection into the tool,

e3) closing the tool, bringing the mold closer to the counter mold or vice versa, and

e4) pressurizing and heating the impregnated blank between the mold and the counter-mould.

The partial opening of the tool allows for easier injection and distribution of resin between mold and counter mold. In this way, enough resin can be added to the tool without excess to impregnate the workpiece and fill the cavity formed between the mold and the counter-mould, in accordance with the final geometry of the part.

Preferably, said steps c), d) and e) are carried out with said tool, which is thus the only tool used in the process. Said shape defines the internal shape of the cavity calculated for performing step c), and, in addition, the tool contains means for air suction and resin injection.

The invention is particularly advantageous because it simplifies the RTM manufacturing process by limiting the number of tools required to do so to one. Indeed, a single tool is used to carry out the above three steps, which results in significant time savings and reduces the risk of damage to the part when it is moved from one tool to another.

The method according to the invention may have one or more of the following characteristics or the following steps, taken alone or in combination with each other:

- before step c), the method includes the following steps:

a) obtaining a preform by interlacing fibers and

b) finishing the workpiece in size;

- step c) includes the sub-steps of wetting the preform and positioning the preform in the inner cavity of the mold;

- step d) includes the sub-steps of closing the tool and heating and evacuating the workpiece between the mold and the counter-mould;

- the sub-step of at least partially opening the tool is realized by removing the counter-form from the mold by a predetermined distance, the mold and the counter-form remaining essentially pushed into each other;

- the resin is injected through one channel of the tool, and the vacuum is created by suction of air through the other channel of the tool;

- these stages are carried out using a single tool.

The present invention also relates to a tool for carrying out the method according to one of the preceding claims, characterized in that it contains

- two heating plates, respectively upper and lower, wherein the lower heating plate is rigidly connected to a mold containing an internal cavity for shaping the workpiece, and the upper heating plate is rigidly connected to a counter-mold having another internal cavity,

- powered means for moving the plates, preferably in a substantially vertical direction, from a remote position to a position in which the mold and the counter-mold are inserted one into the other, and wherein the powered means is able to apply a compressive force to the plates to pressurize the workpiece between the internal cavities.

Preferably, both plates are part of a press, the bottom of which forms the base and the top plate is slidable in a substantially vertical direction along guide posts.

The tool may include a means for laser projecting the contours of the workpiece on the internal mold cavity.

Description of figures

The invention will become more understandable and other details, characteristics and advantages of the invention will appear on reading the following description, given as a non-limiting example, with reference to the accompanying drawings, in which:

- figure 1a shows a block diagram illustrating the steps of a method corresponding to the prior art for manufacturing a part from a composite material,

- figure 1b shows a block diagram illustrating the steps of a prior art method for casting a part by injecting resin into a preform of woven fibers,

- figure 2a shows a block diagram illustrating the steps of the method according to the invention for manufacturing a part from a composite material,

- figure 2b shows a block diagram illustrating the steps of the method according to the invention for casting a part by injecting resin into a preform of woven fibers,

- figure 3 schematically shows a tool for carrying out the method according to figures 2a and 2b,

- figure 4 is a schematic perspective view of the shape and countershape of the tool from figure 3, and

- figures 5-7 are other schematic views of the tool shown in fig. 3 and illustrate the steps of the method.

Detailed description

Figures 1a and 1b have been described above, they illustrate the method according to the prior art.

Figures 2a and 2b illustrate the process according to the invention for producing a composite material part, these steps being preferably carried out with the tool 100 shown in Figure 3 et seq.

Tool 100 generally comprises a mold 102 rigidly connected to a bottom plate 104, preferably a heating plate, and a counter-mold 106 rigidly connected to an upper plate 108, also preferably a heating one. Sealing means are preferably provided between the mold and the counter mold. In the example shown, the bottom plate 104 forms a tool support base that can, for example, rest on a floor in a manufacturing facility.

Mold 102 is located on the top side of platen 104 and has an internal cavity 110, which is best seen in Figure 4. In the example shown, internal cavity 110 corresponds to the surface of a fan blade, such as its back. In this case, the inner cavity 110 is oriented upwards and is opposite the inner cavity 112 of the counter-mould, which is also better seen in figure 4, with the counter-mould 106 being above and opposite the mold. In this case, the inner cavity 112 corresponds to the other side of the fan blade, such as, for example, its lower surface.

Plate 108 is slidably mounted on guide posts 114, in this case two of them, which extend from their lower ends connected to plate 104 to their upper ends connected to cross member 116. Plate 108 and counterform 106 can translate substantially along vertically by means of a jack 118 or the like, the cylinder of which is attached to the cross member 116, and the piston is connected to the plate 108.

The platen 108 and counterform 106 can move from the top position shown in Figure 3, in which the tool is open and the mold 102 and counterform 106 are spaced apart, to a nested or closely spaced position, in which the tool is closed and the mold and counterform interlocked with each other, as shown in figure 5. Intermediate positions are possible, such as the position shown in figure 6, where the tool is open, and the mold and the counter-mold are partially extended from one another, and the counter-mold is retracted by a predetermined distance from the mold. Tool 100 is also used to pressurize workpiece 200 in a cavity defined by internal cavities 110, 112 by means of a predetermined force applied by jack 118 against plate 108 (arrow 120).

In addition, tool 100 includes means for heating plates 104, 108 (not shown), as well as means for vacuuming and feeding into the cavity defined by internal cavities 110, 112.

The vacuum means includes a first channel 122, for example in a mold, one end of which opens into the inner cavity 110. The other end of this channel 122 is intended to be connected to a suction means such as a pump (not shown).

The supply means comprises a second channel 124 located, for example, in a mold, one end of which opens into the inner cavity 110. The other end of this channel 124 is intended to be connected to a resin injection means (not shown).

In addition, the tool may include means 126 for projecting, in particular, the contour of the workpiece 200 onto the inner cavity 110 of the mold to facilitate its positioning at the beginning of the process.

Referring now to figures 2a, 2b, 3, 5 et seq., the various steps of one embodiment of the method according to the invention will be described.

The first step a) of the method is to obtain the workpiece 200 by three-dimensional weaving with a weaving machine, for example, a type of jacquard machine. At the exit of the loom, the workpiece is coarse, generally flat in shape, and loose.

The next step b) of the method consists in finishing the dimensions of the blank 200, for example by cutting off the weft threads.

Steps a) and b) are similar to steps 1) and 2) of the prior art method described above.

Step c) as well as subsequent steps differ from prior art step 3) and subsequent steps in that they are carried out using the tool 100 shown in figures 3 and 5-7.

Figure 3 illustrates step c) which consists in shaping the preform 200. To do this, the preform is preferably pre-moistened to make it more pliable. It is placed in the inner cavity 110 of the mold 102 by means of a laser projection means 126. This projection means makes it possible, for example, to well position the markers to be inserted into the blank 200 at predetermined positions.

Figure 5 illustrates step d) which consists in shaping the blank. To do this, the tool is closed and the pressure is increased to, for example, 5-10 bar, then heated, for example, to 100°C, using heating plates 104, 108 and a jack 118. A residual vacuum is applied to the cavity containing the workpiece by means of a suction means , which allows moisture to be removed (arrow 128). At this stage, the workpiece is pressed to the desired final geometry and dried by heating. The preform 200 is then ready for injection.

Figures 6 and 7 illustrate step e), which consists of injecting resin 202 into the cavity of tool 100. To do this, the tool is partially opened (step e1), while the counter-mold is removed from the mold by a predetermined distance, as explained above. This makes it possible to deliver to it the volume of resin strictly necessary for wetting the workpiece and filling the final geometry of the part (taking into account the fiber content). During this resin injection operation (arrow 130, step e2), the mold and counter mold as well as the resin are preferably heated.

The tool is then closed (FIG. 7, step e3) and a pressure, for example 3-10 bar, is applied to the workpiece 200 by means of a jack. The temperature can be maintained at 150°C during injection and raised to 180°C to polymerize the resin. As shown by arrows in the drawing, during the polymerization step (step e4), the pressure is preferably kept constant over the entire length of the part.

The resin used is, for example, an epoxy resin known under the name CYCOM PR520®, commercially available from CYTEC.

After polymerization, the tool 100 is opened, the part 200 is removed and the tool can be cleaned for a new manufacturing operation.

In this example, the prior art piston for injecting resin into the tool is replaced by an upper counter-mold that applies pressure and allows resin to be impregnated into the workpiece. In this way, the resin remains under constant pressure during the entire polymerization process, which avoids the formation of pores in the part.

The invention provides several advantages. Only the required amount of resin can be used, which is economical. When using pipes (eg copper) according to the prior art, they are all discarded after injection because the resin solidifies inside them. Thanks to the present invention, pipes can be dispensed with or they can be significantly shortened. A part is obtained from a composite material with the expected dimensions (shape versus shape technology) and with smooth surfaces (aerodynamics). No liquid such as water or oil is used to apply pressure. Even more difficult to inject resins with higher viscosities can be used. If necessary, the pressure in the pressurization phase can be varied (particularly in the case of PR520® resin, which is compressible or shrinks during polymerization).

Claims (24)

1. A method for manufacturing a part by injecting resin (202) into a blank (200) of woven fibers, including the steps: c) shaping the blank, d) shaping the blank, and e) resin injection into the billet and casting, wherein step e) is implemented using a tool (100) containing a mold (102), a counter-mold (106) and a means (124) for resin injection, characterized in that step e) contains the following sub-steps: e1) partial opening of the tool (100) by moving the mold away from the counter-mould or vice versa, e2) injection of resin (202) into the tool, e3) closing the instrument by bringing the mold closer to the counter-mould or vice versa, and e4) pressurizing and heating the impregnated blank (200) between the mold (102) and the counter-mold (106). 2. The method according to the previous paragraph, in which the specified steps c), d) and e) are implemented using the specified tool (100), the specified shape defines the cavity intended for the implementation of step c), and the tool further comprises an air suction means (122) and resin injection. 3. The method according to claim 1 or 2, comprising before step c) the steps: a) obtaining a blank (200) by interlacing fibers, and b) finishing the workpiece in size. 4. The method according to one of paragraphs. 1-3, in which step c) includes the sub-steps of wetting the blank (200) and positioning the blank in the cavity (110) of the mold (102). 5. The method according to one of the preceding claims, wherein step d) includes the sub-steps of closing the tool (100) and heating and vacuuming the blank (200) between the mold (102) and the counter-mold (106). 6. The method according to one of the preceding claims, wherein the sub-step of partially opening the tool (100) is implemented by retracting the counter-mold (106) from the mold (102) by a predetermined distance, while the mold and the counter-mold remain substantially pushed into each other. 7. A method according to one of the preceding claims, wherein resin (202) is forced through one channel (124) in the tool and vacuum is created by suction through another channel (122) in the tool. 8. The method according to one of the previous paragraphs, and these steps are carried out using a single tool (100). 9. Tool (100) for implementing the method according to one of the previous paragraphs, characterized in that it contains: - two heating plates (104, 108), respectively, upper and lower, wherein the lower heating plate (104) is rigidly connected to the mold (102) containing a cavity (110) for shaping the workpiece (200), and the upper heating plate (108) rigidly connected to the counterform (106) having another cavity (112), - powered means (118) for moving the plates, preferably in a substantially vertical direction, from a remote position to a position in which the mold and counter-mold are inserted one into the other, the powered means being able to apply a compressive force (120) to the plates to pressurize the workpiece (200) between cavities. 10. The tool (100) according to the previous paragraph, both said plates (104, 108) forming part of the press, with the lower plate (104) forming the base and the upper plate (108) being able to slide in a substantially vertical direction along the guide posts ( 114). 11. Tool (100) according to claim 9 or 10, containing means (126) for laser projection of the contours of the workpiece (200) onto the cavity (110) of the mold (102).

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