System for producing a composite part by automated layup with tape preheating

Abstract

The invention relates to a system (1) for producing a composite part (2) by automated layup, the system (1) comprising a creel (3) comprising at least one reel (80) of a tape (8) of fibres made of composite material, a layup head (5) providing at least one tape (8) of fibres made of composite material, a mould (7) configured to receive the tape (8) and form the composite part (2) by additive manufacturing, and a compacting roller (6) configured to apply the tape (8) to the mould (8) or to already deposited tape. The system (1) further comprises means (10) for preparing the at least one tape (8), these preparation means (10) being mounted upstream of the layup head (5) and comprising at least one heating module (11, 12) for heating the at least one tape (8).

Description

[0001] Description

[0002] Title of the invention: System for manufacturing a composite part by automatic draping with preheating of the ribbon

[0003] Technical Field

[0004] The invention relates to the manufacture of composite material parts from a ribbon of composite material fibers and in particular from a ribbon of thermoplastic material fibers.

[0005] Prior art

[0006] The manufacture of composite parts from a composite fiber ribbon is a form of additive manufacturing. Automated ribbon deposition, more commonly known as "automatic layup," is performed using an automated method that deposits one or more ribbons of material along one or more paths to create a stack of material on a mold.

[0007] Machines have been developed to date mainly for draping fibers pre-impregnated with resin, known as "thermosetting" or dry fibers. Since these materials are sticky at room temperature, these machines are designed so that the material is conveyed, until it leaves the head, in a "cold" environment, i.e. between 6 and 16°C in order to limit friction and jamming of the material due to gluing.

[0008] To cite an example, this is a medium-sized automatic draping machine from the CORIOLIS® brand, ref C1. A CORIOLIS® type machine comprises three main elements for circulating the material: a creel, a sheath, and a head. Note that the automatic draping machine is equipped with a regulated compaction system which contains a roller which ensures the link between the material to be deposited (the ribbon), and the draping mold.

[0009] In this type of machine, there is an air "Vortex" system in the head to generate a flow of cold air and a circulation of air pulsed in the sheath from an air conditioning as well as another in the creel. At the end of the head, in order to allow the cold material coming out of the head to adhere to the lay-up surface (because cold, the material does not adhere or adheres little), an infrared heating medium up to 100°C is used. Unlike thermosetting resins, the fibers impregnated with thermoplastic resin are completely frozen or even rigid and therefore not sticky at room temperature and require a high temperature (between 200 and 400°C) to become sticky.

[0010] When replacing thermosetting resin fibers with thermoplastic resin fibers in a CORIOLIS® type machine, the cold is not or only slightly activated and a very significant heat source is required at the exit of the draping head, most often an expensive and bulky laser source for draping which heats to 450°C, and the mold, on which the material is deposited, is equipped with an expensive heating system.

[0011] The very design of this type of machine is not optimized for this thermoplastic application, in particular for the following reasons.

[0012] The laser source (between 5 and 10kW) at the end of the head is expensive, bulky (thus limiting part access in the concave parts) and presents handling risks (the draping cells equipped with laser are in a partitioned enclosure with optical filters on the windows).

[0013] The draping speed is currently very low, particularly in the context of in situ polymerization (when the part needs to be consolidated at the same time as draping).

[0014] Document EP 3 015 851 discloses a draping system with a roller permeable to the heating laser, the laser locally heating the material at its point of contact with the mold.

[0015] Also known from document EP 3 202 547 is a draping system using a roller coupled to a localized heating system and provided with a means for heating the mold.

[0016] Also known from document EP 3 476 577 is a system for “fine” control of the draping temperature at the point of contact between the material and the draping surface.

[0017] Document EP 3 848 188 discloses a system comprising laser sources on the draping head to better focus the heating at the head outlet at the point of contact between the material and the surface to be draped. Finally, document US 10,843,436 discloses a draping system with a roller that “reflects” the heating laser.

[0018] Statement of the invention

[0019] The invention aims to provide an automatic draping machine suitable for using composite material fibers requiring heating of the material before its deposition and to improve the productivity of such automated deposition. The invention aims in particular to provide an automated draping machine suitable for the deposition of thermoplastic resin ribbons, and thus improve the quality of the material making up the part, particularly in the case of so-called "in situ" draping where the consolidation of the material is carried out at the same time as the draping: the heating must make it possible to bring the material into a crystalline / amorphous state which must allow the result of the draping to have better mechanical strength of the part such as interlaminar shear strength.

[0020] An object of the invention proposes a system for manufacturing a composite part by automatic draping, the system comprising a creel comprising at least one reel of a ribbon of fibers made of composite material, a draping head providing at least one ribbon of fibers made of composite material, a mold configured to receive the ribbon and form said composite part by additive manufacturing, that is to say by successive deposition, and a compacting roller configured to apply the ribbon to the mold or to ribbon already deposited.

[0021] According to a general characteristic of the invention, the system further comprises means for preparing said at least one ribbon, the preparation means being mounted upstream of the draping head and comprising at least one module for heating said at least one ribbon.

[0022] In other words, the preparation means are not mounted on the head, but upstream, i.e. on the creel and / or on any part of the system located upstream of the head of the system, for example on a sheath located between the creel and the head.

[0023] The invention thus makes it possible to preheat the thermoplastic material, in particular so that the fibers are malleable and bring them to the head without damaging them, but also so that the quantity of heat to be supplied at the head for depositing the fibers on the mold is less important. In a first embodiment of the manufacturing system, the preparation means may comprise a first heating module mounted on the creel and configured to heat said at least one reel of fiber ribbon made of composite material.

[0024] Without prior heating, the thermoplastic material is relatively rigid and non-sticky. This poses problems in systems for manufacturing a composite part by automatic draping relying on the tensioning of the thermoplastic fibers between the creel and the draping head. When the material is rigid and not very sticky, in some cases, it can behave like a metallic foil. As a result, it has a spring effect which tends to unwind naturally and therefore generates a pressing action on the belts and tends to push the material to be draped while the draping has not started, thus generating a jam.

[0025] This is what can be observed in particular with a tension limiting system of the fiber application machine described in document EP 1 855 870. The tension limiting system is arranged between fiber storage means and the application head, and it comprises several mutually parallel cylinders on which a plurality of fibers are partially wound, as well as drive means for rotating the cylinders, substantially at the same speed.

[0026] In other words, since thermoplastic material is solid at room temperature, the thermoplastic fiber ribbons tend to be in a straight line in the free state. As a result, the ribbons, even at rest (outside the draping phase), tend to exert contact on the tensioning belts and therefore on the rollers. The carbon then unwinds "by itself" in the creel.

[0027] Heating the material in the creel makes it deformable and can thus eliminate this problem of overfeeding material to the head.

[0028] In addition, heating the material in the creel allows it to be steamed and the water it contains to be eliminated, thus avoiding blistering.

[0029] In a second embodiment of the manufacturing system, the system may comprise at least one conveying sheath disposed between the creel and the lay-up head, said at least one conveying sheath being configured to convey at least one ribbon of fibers made of composite material from the creel to the lay-up head, and the preparation means may comprise a second heating module mounted on the conveying sheath and configured to heat said at least one ribbon of fibers made of composite material circulating in the conveying sheath.

[0030] Preferably, the first heating module is configured to heat said at least one reel of ribbon to a first temperature setpoint less than or equal to a safety temperature threshold for handling the creel, and the second heating module is configured to heat said at least one ribbon to a second temperature setpoint strictly greater than the glass transition temperature of the composite material of the ribbon fibers, the second temperature setpoint being greater than the first temperature setpoint.

[0031] When working with thermoplastic resin fibers, three characteristic temperatures must be considered:

[0032] - The melting temperature (T f): temperature from which the material takes on a sufficiently low-viscosity form so that it is possible to obtain creeping of the molecules and intermingling of the matrix molecules of the deposited ribbon and the ribbons of the substrate and which must be reached at the level of deposition to fuse the layers together;

[0033] - The glass transition temperature (Tg): temperature from which the material experiences a significant drop in rigidity and can “plasticize” under very low mechanical stress;

[0034] - The temperature at which stickiness begins (T peg ) which characterizes the temperature range from which the matrix begins to be “sticky”, which must be avoided during the process up to removal to prevent fouling of the machine components.

[0035] If we look in more detail at the processability of thermoplastic materials, we can consider two temperature objectives:

[0036] An initial temperature target, for example between 50°C and 65°C, to provide an initial supply of calories and to bake the thermoplastic resin. Applying a temperature above ambient temperature but below 65°C to comply with handling safety constraints allows the material to be preheated and an initial supply of calories to be provided while baking the thermoplastic resin to prevent it from containing water (as is done in thermoplastic pellet injection processes. This can prevent blistering by heating a “wet” resin very quickly).

[0037] A second temperature objective to provide a second supply of calories to obtain softening of the material but not too much so as not to flow / col 1st during transfer to the draping head. This second temperature objective must be at least 10 ° C higher than the glass transition temperature (T g ) of the material.

[0038] Advantageously, the preparation means may further comprise a cooling system mounted on the conveying sheath and configured to cool said at least one ribbon located in the sheath if said manufacturing system is stopped, said at least one ribbon stopping circulating in the conveying sheath.

[0039] In a third embodiment of the manufacturing system, the system may comprise a regulation unit of said at least one heating module configured to adapt the heating setpoint according to the draping speed.

[0040] In a fourth embodiment of the manufacturing system, the system may further include an additional heating block mounted on the layup head.

[0041] In a fifth embodiment of the manufacturing system, the system may further comprise a compaction roller heating unit.

[0042] In a sixth embodiment of the manufacturing system, at least one heating module of the preparation means may comprise a conduction heating means.

[0043] In a seventh embodiment of the manufacturing system, at least one heating module of the preparation means may comprise an induction heating means. In an eighth embodiment of the manufacturing system, at least one heating module of the preparation means comprises a microwave heating means.

[0044] In a ninth embodiment of the manufacturing system, at least one ribbon of composite material fibers is a ribbon of thermoplastic fibers.

[0045] Brief description of the drawings

[0046] [Fig. 1] Figure 1 schematically represents a system 1 for manufacturing a composite part 2 by automatic draping according to a first embodiment of the invention.

[0047] [Fig. 2] Figure 2 schematically represents a system 1 for manufacturing a composite part 2 by automatic draping according to a second embodiment of the invention.

[0048] [Fig. 3] Figure 3 schematically represents a system 1 for manufacturing a composite part 2 by automatic draping according to a third embodiment of the invention.

[0049] Description of the embodiments

[0050] Figure 1 schematically shows a system 1 for manufacturing a composite part 2 by automatic draping according to a first embodiment of the invention.

[0051] The manufacturing system 1 comprises a creel 3, a conveying sheath 4, a draping head 5, a compacting roller 6, and a mold 7.

[0052] The creel 3 stores at least one reel 80 of a ribbon 8 of composite material fibers which will be used for draping on the mold 7 of the composite part 2. The composite material fibers are preferably thermoplastic fibers, but they can also be fibers pre-impregnated with an epoxy resin.

[0053] The conveying sheath 4 is configured to transfer the ribbon 8 from the mold 7 and is configured to receive the ribbon 8 supplied by the draping head 5 and form a composite part 2 by additive manufacturing.

[0054] The creel 3 thus feeds the draping head 5 via the conveying sheath 4 with one or more ribbons 8 of composite material fibers. The draping head 3 of the manufacturing system 1 is configured to drape from 1 to 8 ribbons in a single trajectory and can even be adapted to drape 16 or 32 ribbons.

[0055] The compacting roller 5 is configured to apply the tape 8 to the mold 4 or to tape 6 already deposited depending on the progress of the manufacturing of the composite part.

[0056] In the illustrated example, the manufacturing system 1 further comprises three heating modules referenced 11, 12 and 13.

[0057] A first heating module 11 is mounted on the creel 3 and configured to heat the ribbon 8 stored in the frame to a first temperature below 65°C. This is to make the thermoplastic material of the ribbon fibers sticky and more flexible.

[0058] A second heating module 12 is mounted along the routing sheath 4. The second heating module 12 may comprise a plurality of heating units arranged along the sheath to gradually heat the ribbon 6 circulating inside the routing sheath 4 to a temperature higher, preferably at least 10°C, than the glass transition temperature of the composite material of the fibers of the ribbon 8.

[0059] A third heating module 13 is mounted on the draping head 5 and is configured to heat the ribbon at the time of depositing on the mold 7 or on a portion of the part 2 already deposited. The third heating module 13 can be configured to heat the ribbon 8 at its contact with the compacting roller 6 as illustrated, or at the very point of its contact with the mold 7 or the part 2.

[0060] The first heating module 11 and the second heating module 12 form means 10 for preparing the ribbon of fibers made of composite material configured to heat the ribbon upstream of its passage in the draping head 5 and thus reduce the quantity of heat necessary to be provided by the third heating module 13 when depositing the ribbon on the mold 7 or on the part 2. In another configuration the preparation means 10 can comprise a single heating module, such as for example the first heating module 11 or the second heating module 12, or more than two heating modules.

[0061] In the illustrated example, the first heating module 11 and the second heating module 12 may be conduction and ventilation, induction or microwave heating modules, the two heating modules being able to use the same heating technique or different heating techniques.

[0062] Conduction and ventilation heating can be optimized by using the convection phenomenon of air currents generated within the creel 3 or the delivery duct 4.

[0063] An induction heating module can be realized by integrating for example inductive coils in the routing sheath 4 or around it.

[0064] A microwave heating module can be made using a waveguide introducing the microwaves into an enclosure such as that of the creel 3, or an enclosure integrated into the routing duct 4.

[0065] In the example illustrated, the system 1 further comprises a unit 20 for regulating the heating modules 11, 12 and 13 configured to adapt the heating setpoint according to the draping speed.

[0066] In the event of the system 1 being stopped with a portion of ribbon 8 inside the conveying sheath 4, the regulation unit 20 can thus command a preheating phase, when the system 1 is restarted, before the ribbon 8 is put back into circulation to ensure that the ribbon 8 arriving at the draping head 5 to be deposited arrives at the correct temperature.

[0067] Figure 2 schematically shows a system 1 for manufacturing a composite part 2 by automatic draping according to a second embodiment of the invention.

[0068] The second embodiment illustrated in Figure 2 differs from the first embodiment illustrated in Figure 1 only in that the preparation means 10 further comprise a cooling system 14 mounted on the routing sheath 4 and configured to cool the ribbon 8 located in the routing sheath 4 if the system 1 is stopped. In the illustrated example, the cooling system comprises injectors 140 passing through the heating module 12 and configured to inject a cooling gas inside the routing sheath 4 when the system 1 stops. In Figure 3 is schematically represented a system 1 for manufacturing a composite part 2 by automatic draping according to a third embodiment of the invention.

[0069] The third embodiment illustrated in Figure 3 differs from the first embodiment illustrated in Figure 1 only in that the system 1 further comprises a unit 60 for heating the compaction roller 6 controlled by the regulation unit 20.

Claims

Claims

1. System (1) for manufacturing a composite part (2) by automatic draping, the system (1) comprising a creel (3) comprising at least one reel (80) of a ribbon (8) of fibers made of composite material, a draping head (5) providing at least one ribbon (8) of fibers made of composite material, a mold (7) configured to receive the ribbon (8) and form said composite part (2) by additive manufacturing, and a compacting roller (6) configured to apply the ribbon (8) to the mold (8) or to ribbon already deposited, characterized in that the system (1) further comprises means (10) for preparing said at least one ribbon (8), said preparation means (10) being mounted upstream of the draping head (5) and comprising at least one heating module (11, 12) for said at least one ribbon (8).

2. System (1) for manufacturing a composite part by automatic draping according to claim 1, in which the preparation means (10) comprise a first heating module (11) mounted on the creel (3) and configured to heat said at least one reel (80) of ribbon (8) of fibers made of composite material.

3. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 or 2, comprising at least one conveying sheath (4) arranged between the creel (3) and the draping head (5), said at least one conveying sheath (4) being configured to convey at least one ribbon (8) of fibers made of composite material from the creel (3) to the draping head (5), and the preparation means (10) comprising a second heating module (12) mounted on the conveying sheath (4) and configured to heat said at least one ribbon (8) of fibers made of composite material circulating in the conveying sheath (4).

4. System (1) for manufacturing a composite part by automatic draping according to claim 2 in combination with claim 3, in which the first heating module (11) is configured to heat said at least one reel (80) of ribbon (8) to a first temperature setpoint less than or equal to a safety temperature threshold for handling the creel, and the second heating module (12) is configured to heat said at least one ribbon (8) to a second temperature setpoint strictly greater than the glass transition temperature of the composite material of the ribbon fibers, the second temperature setpoint being greater than the first temperature setpoint.

5. System (1) for manufacturing a composite part by automatic draping according to one of claims 3 or 4, wherein the preparation means (10) further comprise a cooling system (14) mounted on the conveying sheath (4) and configured to cool said at least one ribbon (8) located in the conveying sheath (4) if said manufacturing system (1) is stopped, said at least one ribbon (8) stopping circulating in the conveying sheath (4).

6. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 to 5, comprising a regulation unit (20) of said at least one heating module (11, 12) configured to adapt the heating setpoint as a function of the draping speed.

7. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 to 6, further comprising an additional heating block (13) mounted on the draping head (5).

8. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 to 7, further comprising a unit (60) for heating the compaction roller (6).

9. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 to 8, in which at least one heating module (11, 12) of the preparation means (10) comprises a conduction heating means.

10. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 to 9, in which at least one heating module (11, 12) of the preparation means (10) comprises an induction heating means.

11. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 to 10, in which at least one heating module (11, 12) of the preparation means (10) comprises a microwave heating means.

12. System (1) for manufacturing a composite part by automatic draping according to one of claims 1 to 11, in which at least one ribbon (8) of fibers made of composite material is a ribbon of thermoplastic fibers.

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