Device for heating a resin for an apparatus for manufacturing a composite part

Abstract

The invention relates to a device (140) for heating a resin for an apparatus for manufacturing a composite part, said heating device being characterized in that it comprises: – a metal block (142) comprising a resin transport pipe (144), the pipe extending in a first direction (X), – a conduction heating system (150) configured to heat the resin transport pipe by conduction, and – a dielectric heating system (160) configured to heat the resin inside the transport pipe.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: DEVICE FOR HEATING A RESIN FOR A PLANT FOR MANUFACTURING A COMPOSITE PART

[0003] TECHNICAL FIELD

[0004] The technical field of the invention is that of the manufacture of aircraft turbomachine parts made of composite material, in particular by resin injection molding of a part made of composite material.

[0005] The present invention relates to a resin heating device and a composite parts manufacturing plant equipped with such a heating device. The present invention also relates to a method for manufacturing a composite part, in particular for an aircraft engine, using such a plant.

[0006] PRIOR ART

[0007] The technical background includes in particular document FR 3 130 679 A1.

[0008] The use of composite materials is advantageous in the aeronautics industry in particular because these materials have interesting mechanical performances for relatively low masses.

[0009] A method for manufacturing a composite part for the aeronautical industry from resin-impregnated fibers, which is well known to those skilled in the art, is the RTM molding process, according to the English acronym for "Resin Transfer Molding". Such a method is, for example, used to manufacture fan blades or casings and involves several successive steps.

[0010] First, a three-dimensional preform blank is made by weaving fibers. Then this blank is generally cut to obtain a preform having substantially the shape of the part to be obtained, for example a blade. This preform is then placed in a mold which is closed. Then, resin is injected in the liquid state into the mold while maintaining pressure on the injected resin while the part is polymerized by heating.

[0011] The resins used are very fluid resins that are able to penetrate the fibers of the preform well, even when injected under reduced pressure. During polymerization, under the effect of heat, the injected resin successively passes from the liquid state to the gel state and finally to the solid state. The continuous supply of resin to the mold under pressure is a primary requirement which aims to guarantee quality parts, without defects and without porosity. Indeed, since the resin tends to degas during polymerization, it is necessary to maintain the pressure of the resin until the complete polymerization of the part in order to avoid gas releases compromising the integrity of the resin.

[0012] Figure 1 illustrates an installation 10 for manufacturing a composite material part according to the state of the art. Such an installation generally comprises a means for distributing and pressurizing the resin, such as a piston 12 configured to distribute and pressurize the resin. An outlet 12b of the piston 12 is connected to an inlet 14a of a mold 14.

[0013] Heating the resin before its injection into the mold 14 is also very important. It is indeed important that one of the components of the resin, a hardener, is completely dissolved in the resin before its contact with the preform because this component would risk being filtered into the preform, and the mechanical properties of the resin during curing would not be respected. In the current technique, the resin is heated to at least 150°C (or even at least 154°C). This corresponds to resins containing "CAF" as a hardener (9,9-Bis(4-amino-3-chlorophenyl) fluorene).

[0014] The heating of the resin is generally carried out by means of a conduction heating device 16, one inlet 16a of which is connected to the outlet 12b, and one outlet 16b of which is connected to the inlet 14a of the mold 14. This heating device 16 comprises a stack of plates 16c. The plates 16c define serpentine-shaped circulation paths for the resin. The plates and the resin are heated by heat conduction with electric heating, for example by heating cartridges.

[0015] The arrows in Figure 1 show the path of the resin when filling the mold.

[0016] At the end of the manufacturing process of a part, the resin remaining in the piston 12, the heating device 16, is lost because it has completely polymerized and is not reusable.

[0017] Furthermore, in order for the resin to be heated in the device 16 to the desired temperature before being injected into the mold 14, a significant cumulative length (several meters) of resin circulation paths is required. It is then necessary in the current technique to use a stack of a significant number of plates 16c. However, the greater this length, the greater the quantity of resin lost at the end of the manufacturing process. Since resin is a relatively expensive raw material, this quantity of lost resin represents a significant financial loss.

[0018] There is therefore a need for a solution that can significantly reduce the amount of resin lost in each manufacturing process.

[0019] Furthermore, such a method of heating by heat conduction using electric heating by heating cartridges has the disadvantage of having poor efficiency for high flow rates greater than 500 cc / min.

[0020] Thus, an increase in the resin flow rate no longer allows the minimum temperature to be reached to dissolve the hardener contained in the resin. This limitation constrains the optimization of the manufacturing process, in particular the injection times, because the injection flow rate cannot be increased.

[0021] The objective of the present invention is to overcome at least some of the aforementioned drawbacks by proposing a heating device allowing rapid heating of the resin in order to enable injection of the resin at high flow rates.

[0022] SUMMARY OF THE INVENTION

[0023] To this end, the invention relates to a device for heating a resin for an installation for manufacturing a composite part, the heating device being characterized in that it comprises:

[0024] - a metal block comprising a resin transport pipe, the pipe extending in a first direction,

[0025] - a conduction heating system configured to conductively heat the resin transport pipeline, and

[0026] - a dielectric heating system configured to heat the resin inside the transport pipeline.

[0027] The invention thus offers a solution to the problems mentioned above by proposing a hybrid heating device making it possible to heat up more quickly a resin whose characteristic is low thermal conductivity, in particular for an RTM molding manufacturing process.

[0028] This hybrid heating device combines a conduction heating system to heat the resin on the surface, i.e. at the interface of the pipe, and a dielectric heater to heat the core of the resin. The coupling of these two heating modes makes it possible to diffuse the temperature in the thickness of the resin in order to minimize the useful length of the resin transport pipe in the heating device and thus the volume of resin required to reach the temperature necessary for the manufacturing process of a composite part.

[0029] Such a heating device advantageously makes it possible to heat the resin evenly, even at high flow rates, while minimizing the volume of resin and the pressure required for the resin to pass through the heating device.

[0030] The heating device 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 in any technically possible combination:

[0031] - the conduction heating system comprises at least one pair of resistors arranged in the metal block near the resin transport pipe and a source of electric current supplying the at least one pair of resistors;

[0032] - the or each resistor extends in a second direction perpendicular to the first direction;

[0033] - the dielectric heating system comprises at least one pair of dielectric elements arranged in the metal block near the resin transport pipeline and an alternating current source supplying the electrical elements of the at least one pair of dielectric elements;

[0034] - preferably, the alternating current source is a high frequency alternating current source;

[0035] - the dielectric elements of the at least one pair of dielectric elements are closer to the resin transport pipe than the resistors of the at least one pair of resistors of the conduction heating system;

[0036] - the alternating current source is configured to generate an alternating current having a frequency between 100 MHz and 300 GHz;

[0037] - the alternating current source is configured to generate an alternating current having a voltage between 10 and 20 kV;

[0038] - the resin is transported in the transport pipeline with a flow rate between 100 and 2000 cc / min and preferably greater than or equal to 500 cc / min;

[0039] - the heating device is configured to heat the resin to a temperature greater than or equal to 150°C, preferably equal to 165°C. The invention also relates to an installation for manufacturing a composite part, in particular for an aircraft engine, the installation comprising at least:

[0040] - a piston for storing and dispensing a polymerizable resin comprising a resin outlet,

[0041] - a resin heating device according to the invention and as described previously, this heating device comprising a resin outlet and a resin inlet connected to the resin outlet of the piston, and

[0042] - a mold for receiving a fiber preform and injecting the resin for impregnating this preform, this mold comprising a resin inlet connected to the resin outlet of the heating device.

[0043] Preferably, the resin contained in the piston comprises a hardener comprising at least 9,9-Bis(4-amino-3-chlorophenyl) fluorene.

[0044] The invention also relates to a method for manufacturing a composite part, in particular for an aircraft engine, by means of an installation according to the invention and as described previously, the manufacturing method comprising at least one step of heating the resin by conduction and one step of heating the resin by dielectric heating, the steps of dielectric heating and induction heating are simultaneous and implemented before injection of the resin into the mold.

[0045] BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which:

[0047] - figure 1, already described, is a schematic view of a manufacturing installation by molding a part made of composite material according to the state of the art;

[0048] - figure 2 is a three-dimensional schematic view in partial section of a heating device according to the invention;

[0049] - Figure 3 is a sectional view of the heating device according to the invention; and

[0050] - figure 4 is a schematic view of an installation according to the invention for manufacturing by molding a part in composite material equipped with the heating device of figure 2. The elements having the same functions in the different implementations have the same references in the figures.

[0051] DESCRIPTION OF EMBODIMENTS

[0052] Figure 2 schematically illustrates a three-dimensional and partially sectional view of a heating device 140 for a resin for a manufacturing installation by molding composite material parts. Such an installation will be described later. The heating device 140 according to the invention comprises:

[0053] - a metal block 142 comprising a resin transport pipe 144,

[0054] - a 150 resin conduction heating system, and

[0055] - a 160 dielectric resin heating system.

[0056] The materials of the metal block 142 must provide good mechanical strength and good thermal conductivity. The metal block 142 is, for example, an alloy of the Toolox® 33 / 23CrMnNiMo4 type.

[0057] The block 142 is parallelepipedal in shape and symmetrical with respect to two mutually perpendicular planes. A first plane P1 extends in a first direction X and a second direction Y, the second plane P2 extending in the first direction X and a third direction Z. The directions X, Y and Z are mutually perpendicular. In Figure 2, only one half of this block is partially illustrated. In particular, only the so-called “lower” half is shown, this half is a portion of the block 142 symmetrical along the plane P2.

[0058] In addition, a section view in a plane P3 perpendicular to the first direction X is shown.

[0059] Figure 3 illustrates a sectional view in plane P1 of block 142 of heating device 140.

[0060] The transport pipeline 144 is cylindrical and has a main axis C extending in the first direction X. In the illustrated example, the pipeline has a rectangular cross-section (in a plane perpendicular to the first direction). However, this cross-section may be circular or square or of any shape.

[0061] The resin conduction heating system 150 is configured to conductively heat the resin transport pipe 144. For this purpose, the conduction heating system 150 comprises at least one pair of resistors 152 arranged in the metal block 142 near the resin transport pipe 144 and an electrical source 154 supplying the pair or pairs of resistors. The two resistors of each pair are arranged symmetrically to each other with respect to the main axis C of the pipe and therefore with respect to the plane P2 in order to ensure uniformity of the thermal field. The resistors 152 are arranged at the shortest possible distance from the resin transport pipe 144 in order to diffuse the heat into the resin.The order of magnitude of this distance is a few centimeters, for example between 5 cm and 50 cm depending on the power of the resistors in order to have a uniform temperature field at the level of the surface in contact with the resin.

[0062] When there is more than one pair of resistors, all the resistors 152 are preferably arranged at the same distance from the transport pipeline 144 in the second direction Y.

[0063] In the example illustrated in Figures 2 and 3, the or each resistor 152 extends in the third direction Z.

[0064] Preferably, the resistors and / or pairs of resistors are regularly spaced from each other along the first direction X.

[0065] Each resistor 152 is electrically connected to the electrical source 154 configured to power them. The electrical source 154 is an alternating current or direct current source. The resistors 152 are thermal resistors of the heating cartridge type.

[0066] When the resistors are powered by the electric current source 154, heat dissipates by the Joule effect and propagates to the transport pipe 144. In operation, the resin located inside the pipe is heated at least peripherally, that is to say the portion of the resin in contact with the transport pipe, more precisely with an internal surface of the transport pipe. Typically, the heat propagates over a distance of the order of a few millimeters. The intensity of the electric current generated by the source 154 makes it possible to adjust the temperature of the resin at the outlet of the heating device.

[0067] The dielectric resin heating system 160 is configured to heat the resin inside the transport pipe. In fact, unlike the conduction heating system, the dielectric heating system 160 is configured to heat the “core” of the resin, that is to say a portion of the resin contained in the transport pipe located closer to the main axis of the pipe 144 than the peripheral portion located near the internal surface of the transport pipe.

[0068] For this purpose, the dielectric heating system 160 comprises at least one pair of dielectric elements 162 arranged in the metal block near the resin transport pipe and a source 164 of high-frequency alternating current supplying the pair or pairs of dielectric elements. The two dielectric elements of each pair are arranged symmetrically to each other with respect to the main axis C of the pipe and therefore with respect to the plane P2 in order to ensure uniformity of the thermal field.

[0069] The dielectric elements 162 are positioned as close as possible to the resin transport pipe 144 in order to diffuse the heat into the resin. This distance is between 0 and a few millimeters from the resin. Thus, the dielectric elements can be in contact with the resin or a few millimeters from the surface in contact with the resin, for example between 5 cm and 50 cm depending on the power of the resistors in order to have a uniform temperature field at the surface in contact with the resin.

[0070] Preferably, the dielectric elements 162 or pairs of dielectric elements are regularly spaced from one another along the first direction X.

[0071] Each dielectric element 162 is electrically connected to the high frequency alternating current source 164 configured to power them.

[0072] The permittivity of the resin is between 3 and 6 depending on the temperature. The two dielectric elements of the same pair form two electrodes shaped to be traversed by an alternating current so as to excite the polarization of the molecules contained in the resin.

[0073] The alternating current source 164 is configured to generate an alternating current having high frequencies between 100 MHz and 300 GHz and a voltage between 10 and 20 kV in order to thermally stress the resin. The frequency and the voltage make it possible to adjust the temperature of the resin at the output of the heating device. The heat dissipation is directly proportional to the square of the stress voltage of the dielectrics and the frequency.

[0074] Advantageously, the dielectric elements 162 are closer to the resin transport pipe 144 than the resistors 152 of the conduction heating system 150. The heating device is adapted to heat the resin to a temperature greater than or equal to 150°C, and preferably equal to 165°C.

[0075] Furthermore, the heating device is suitable for heating a resin circulating in the transport pipeline with a flow rate of between 100 and 2000 cc / min and preferably greater than or equal to 500 cc / min.

[0076] Such a heating device 140 according to the invention makes it possible to couple a conduction heating mode particularly suitable for heating the resin close to the internal surface of the transport pipe and a dielectric heating mode particularly suitable for heating the resin in the center of the transport pipe. The coupling of these two modes makes it possible to diffuse the temperature in the thickness of the resin, the latter is then heated homogeneously, advantageously making it possible to minimize the useful length of the heating device, and in particular of the transport pipe, and thus the volume of resin necessary to reach the temperature necessary for a manufacturing process by resin injection molding.

[0077] We refer to figure 4 which illustrates an example of an installation 200 for manufacturing a part made of composite material according to the invention, in particular a part for an aircraft engine.

[0078] The installation 200 comprises at least one piston for storing and distributing a resin 212, a heating device 140 and a mold 214.

[0079] The resin storage and dispensing piston 212 has an outlet 212b in fluid communication with an inlet 140a of the heater 140, and the heater 140 includes an outlet 140b in fluid communication with an inlet 214a of the mold 214, preferably via a resin supply valve 222.

[0080] The mold 214 further comprises a purge valve 224 or outlet valve.

[0081] Advantageously, the installation may further comprise a pressure sensor (not shown) for measuring the pressure of the resin in the mold 214.

[0082] The piston 212, the heating device 140 and the mold 214 are fluidically connected respectively via pipes 230 and 240 in which the resin can circulate.

[0083] The installation 200 may comprise other elements, shown or not in the drawings. The mold 214 may for example comprise a vent to create a partial vacuum in the cavity of the mold 214 and thus facilitate the injection of the resin into the mold. The installation may comprise a bypass pipe extending between the resin inlet and outlet of the heating device allowing pressure transmission from the piston 10.

[0084] The various elements of the installation can be connected to remote control and command means, such as computerized means for example.

[0085] For example, the piston 212 can be controlled to maintain a predetermined pressure and / or flow rate in the fluid circuit of the installation.

[0086] The piston 212 has the function of storing the polymerizable resin and pressurizing it to circulate it in the installation 200.

[0087] Preferably, the resin contained in the piston comprises a hardener comprising at least 9,9-Bis(4-amino-3-chlorophenyl) fluorene known as CAF.

[0088] In the example illustrated in Figure 4, the mold 214 comprises two parts 214c and 214d forming a mold and a counter-mold defining a closed cavity into which a fiber preform 250 is introduced in order to form a matrix. In the example illustrated here, the fiber preform 250 is a fiber preform of an aeronautical turbomachine fan blade. However, the installation is suitable for manufacturing any part made of composite material, in particular for an aircraft engine, such as casings.

[0089] The mold 214 generally comprises means for regulating the temperature of the cavity, for example by circulating a heated liquid in channels inside the parts 214c and 214d of the mold. The mold may also be equipped with a pressure sensor for measuring and controlling the pressure of the resin inside the mold 214, in order to allow regulation of the latter by the piston 212.

[0090] Such an installation is particularly suitable for implementing a method according to the invention for manufacturing a composite part, in particular for an aircraft engine. Such a method notably comprises a step of heating the resin by conduction and a step of heating the resin by dielectric heating. The dielectric heating and induction heating steps are simultaneous and implemented before injecting the resin into the mold.

[0091] The resin is heated to a temperature greater than or equal to 150°C, and preferably equal to 165°C.

[0092] In addition, the resin circulates in the various elements constituting the installation with a flow rate between 100 and 2000 cc / min and preferably greater than or equal to 500 cc / min.

Claims

CLAIMS 1. Heating device (140) for a resin for an installation for manufacturing a composite part, the heating device being characterized in that it comprises: - a metal block (142) comprising a resin transport pipe (144), the pipe extending in a first direction (X), - a conduction heating system (150) configured to conductively heat the resin transport pipeline, and - a dielectric heating system (160) configured to heat the resin inside the transport pipeline.

2. Heating device (140) according to claim 1, wherein the conduction heating system (150) comprises at least one pair of resistors (152) arranged in the metal block near the resin transport pipe and a source (154) of electric current supplying the at least one pair of resistors.

3. A heating device (140) according to claim 2, wherein the or each resistor (152) extends in a second direction perpendicular to the first direction.

4. Heating device (140) according to one of claims 1 to 3, in which the dielectric heating system (160) comprises at least one pair of dielectric elements (162) arranged in the metal block near the resin transport pipe and a source (164) of alternating current supplying the electrical elements of the at least one pair of dielectric elements.

5. A heating device (140) according to claim 4 in combination with one of claims 2 and 3, wherein the dielectric elements (162) of the at least one pair of dielectric elements are closer to the resin transport pipe than the resistors (152) of the at least one pair of resistors of the conduction heating system.

6. Heating device (140) according to one of the preceding claims, wherein the resin is transported in the transport pipe with a flow rate of between 100 and 2000 cc / min and preferably greater than or equal to 500 cc / min.

7. Heating device (140) according to one of the preceding claims, configured to heat the resin to a temperature greater than or equal to 150°C, preferably equal to 165°C.

8. Installation (200) for manufacturing a composite part, in particular for an aircraft engine, the installation comprising at least: - a piston (212) for storing and dispensing a polymerizable resin comprising a resin outlet, - a heating device (140) for the resin according to one of the preceding claims, this heating device (140) comprising a resin outlet and a resin inlet connected to the resin outlet of the piston, and - a mold (214) for receiving a fiber preform and injecting the resin for impregnating this preform, this mold comprising a resin inlet connected to the resin outlet of the heating device.

9. Installation (200) according to the preceding claim, in which the resin contained in the piston comprises a hardener comprising at least 9,9-Bis(4-amino-3-chlorophenyl) fluorene.

10. Method for manufacturing a composite part, in particular for an aircraft engine, by means of an installation (200) according to one of claims 8 or 9, the manufacturing method comprising at least one step of heating the resin by conduction and one step of heating the resin by dielectric heating, the steps of dielectric heating and induction heating are simultaneous and implemented before injection of the resin into the mold.

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