Method for manufacturing a part made of thermoplastic composite material
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ARIANEGRP SAS
- Filing Date
- 2026-01-05
- Publication Date
- 2026-07-30
Smart Images
Figure FR2026050002_30072026_PF_FP_ABST
Abstract
Description
Description Title of the invention: Method for manufacturing a part made of thermoplastic composite material Technical Field
[0001] The present presentation relates to a manufacturing process for a part made of thermoplastic matrix composite material using an automated fiber placement draping technique (“Automated Fiber Placement”; “AFP”). Previous technique
[0002] Composite materials offer a weight saving compared to metallic materials, which is of particular interest in aerospace and aeronautical applications with a view to improving performance.
[0003] The use of a thermoplastic composite can be considered for forming large components intended for integration into a space launch vehicle, such as a shell or a tank. Automated fiber placement techniques are advantageous for reducing the production cost of composite parts. However, inventors have observed that the automated fiber placement process, using a mold at room temperature, of pre-impregnated fibrous layers of thermoplastic resin can lead to deformation of the stack as the thickness increases. This deformation is more pronounced the thicker the part. These deformations are linked to the stresses created in the preform by the thermal gradient through the thickness during the draping process. These stresses tend to curve the part as the draping progresses and can lead to its detachment from the draping mold.
[0004] To counter this phenomenon, one could consider integrating a heating element into the draping mold to relieve stress in the preform during draping through continuous heating. However, this solution presents other problems, particularly for large parts, in terms of maintaining the part's geometry due to the expansion of the heated mold, energy consumption, and operator safety, as they may have to work in an overheated environment. All these aspects limit the use of thermoplastic technology.
[0005] Another difficulty concerns the availability of a heating device, such as an oven or autoclave, capable of reaching the temperatures required to consolidate large thermoplastic parts. Investing in such a device is extremely expensive, and the energy and maintenance costs are also very high.
[0006] In addition, several difficulties are encountered concerning the molding tools on which the parts are draped and which also serve to consolidate these parts.
[0007] First, these tools require a material resistant to repeated cycles at high temperatures, for example, 350°C to 400°C, and with a coefficient of thermal expansion close to that of the thermoplastic composite part to avoid any problems with differential expansion during heating and cooling. Steel tools can withstand the temperatures but expand too much relative to the composite and can induce high stresses or deformations. The use of Invar tools, which have a thermal expansion close to that of the composite, overcomes this problem, but their high cost can limit their use for large parts.
[0008] Furthermore, when these molding tools incorporate a heating system, the problems previously described for draping arise, but these heating systems also generally cannot withstand the consolidation temperatures required by the oven or autoclave. This may necessitate having tooling with an integrated heating system for draping parts, and tooling for consolidation without an integrated heating system. Such a solution is associated with very high costs in terms of tooling, cycle time, and part quality, with an increased risk of scrap. All of this prevents the application of thermoplastic technology for large parts.
[0009] Finally, much research is focused on developing the in-situ consolidation process, which involves performing draping and consolidation in a single step. This process would be ideal for manufacturing large parts. Compared to the traditional two-step process—draping the part followed by hot consolidation—the in-situ process modifies the AFP draping parameters to apply the appropriate temperature, roller pressure, and draping speed to achieve consolidation simultaneously with draping. Generally, the temperatures reached with the in-situ process are higher, the roller pressure is greater, and the draping speed is reduced. However, this process has not yet reached a level of maturity for industrial application, and numerous difficulties are encountered. First, this process does not eliminate the creation of internal stresses during draping.This necessitates integrating a heating system into the molding tooling, capable of reaching high temperatures close to 250°C, to minimize these constraints. The integration of this heating system therefore presents the same difficulties as those detailed above. Furthermore, due to a generally slower draping speed, the draping time may be increased. Finally, the material health of a part produced using the in-situ process is still inferior to that obtained with the two-step process, making it unsuitable for primary structures in the aerospace sector. Thus, despite all the work carried out, this process faces numerous challenges and is not yet applicable for the production of high-performance, large-scale thermoplastic parts.
[0010] It is therefore desirable to have a manufacturing process for a part made of thermoplastic composite material that addresses all or some of the aforementioned disadvantages. Description of the invention
[0011] This presentation concerns a manufacturing process for a part made of thermoplastic composite material, the process comprising: - the deposition onto a support of a first set of stacked fibrous layers by automatic fiber placement, the fibrous layers being made of thermoplastic prepreg fibrous material, - the interruption of the deposition of the fibrous layers and the carrying out, while this deposition is interrupted, of a first consolidation under vacuum, the first assembly being subjected, during the first consolidation, to a first heat treatment comprising a sweep of a surface of the first assembly, opposite the support, by a first local heating, of limited extent to a fraction of this surface, in relative movement with respect to this surface, the first local heating allowing to selectively melt or soften the thermoplastic resin in the heated zone, - the resumption, after the first consolidation, of the deposition of the fibrous layers and the deposition, on at least part of the first consolidated set, of a second set of stacked fibrous layers by automatic fiber placement, and - the interruption of the deposition of the fibrous layers and the carrying out, while this deposition is interrupted, of a second vacuum consolidation during which the second assembly is consolidated, the second assembly being subjected, during the second consolidation, to a second heat treatment comprising a sweep of a surface of the second assembly, opposite to the support, by a second local heating, of limited extent to a fraction of this surface, in relative motion with respect to this surface, the second local heating allowing to selectively melt or soften the thermoplastic resin(s) in the heated area, the second assembly being welded to the first consolidated assembly following the second consolidation.
[0012] The invention makes it possible to reduce, or even eliminate, the stresses (stress relaxation) and deformations of the stacked layers as they are deposited, particularly for thick parts. The invention thus reduces the curvature of the part as the draping progresses and prevents it from detaching from the substrate. This reduction in deformation simplifies, or even eliminates, the need for means of holding the part during draping, thereby simplifying its implementation.
[0013] The invention implements a so-called dynamic consolidation, in which the heated zone is displaced relative to the deposited fibrous layers. Furthermore, the consolidation is sequential, with first consolidation of a first fraction of the stack, corresponding to the first set of layers, followed by consolidation of a second fraction of the stack, corresponding to the second set of layers. The process can optionally be continued in this manner with the deposition of additional fibrous layers and subsequent consolidation until the complete structure is obtained.
[0014] Generally, the thermoplastic resin in the first set may be the same as, or different from, that in the second set. Within a given set, the thermoplastic resin may consist of a single thermoplastic polymer or a mixture of thermoplastic polymers. Various examples of usable polymers will be provided later.
[0015] Furthermore, as described above, during the second consolidation, the second assembly is welded to the first consolidated assembly to ensure a strong bond between them. This welding requires a sufficient temperature at the interface between the first and second assemblies to soften or melt the thermoplastic resin(s) present, thus creating a weld after cooling, due to the interpenetration of the polymer chains on either side of the interface.
[0016] Dynamic consolidation makes the invention particularly well-suited to the hot forming of large thermoplastic composites, offering an "out-of-oven" solution. This eliminates the need for a sufficiently large heating vessel to accommodate the structure being processed and reduces energy consumption by avoiding heating a large volume within the heating vessel containing the structure. Furthermore, the localized heating system prevents the differential expansion problems encountered with global heating of the structure. Therefore, Invar tooling is no longer required, and conventional steel molding tools, for example, can be used instead.
[0017] The implementation of sequential dynamic consolidation can make it possible to avoid the integration of a heating element into the support or at least to greatly reduce its stress, thus overcoming the disadvantages encountered with the in-situ consolidation mentioned above which requires maintaining the tooling at a high temperature, typically around 250°C, and imposing a slower draping speed.
[0018] In one embodiment example, the thermoplastic resin present on one face, located on the side of the support, of the first consolidated assembly is subjected, during the second consolidation, to a temperature at least equal to its glass transition temperature.
[0019] The glass transition temperature, denoted "Tg" hereafter, can be determined by Differential Scanning Calorimetry ("DSC").
[0020] This characteristic helps avoid introducing new stresses within the stack thickness by minimizing the temperature gradient through the thickness during the second consolidation, thus further improving the quality of the resulting part. The thermoplastic resin of the first consolidated assembly is therefore subjected, during the second consolidation, to a temperature at least equal to its Tg throughout the entire thickness of the first consolidated assembly (the temperature increases along the thickness of the first consolidated assembly as one moves towards the second assembly), with a sufficient temperature at the interface with the second assembly to produce the weld as described above. As will be described later, various solutions can be implemented to minimize this gradient.
[0021] In one example embodiment, the second local heating defines at least a first heating zone imposing a first temperature allowing to selectively melt or soften the thermoplastic resin(s), and a second heating zone imposing a second temperature, lower than the first temperature, between the glass transition temperature of the thermoplastic resin of the second assembly and its crystallization temperature, the heated zone being swept successively by the first heating zone and then by the second heating zone.
[0022] The crystallization temperature, denoted "Te" hereafter, corresponds to the temperature at which the material begins to stiffen. The crystallization temperature can be determined by differential scanning calorimetry during the cooling phase.
[0023] This characteristic helps control the temperature gradient through the stack thickness during the cooling of the zone heated to the consolidation temperature by allowing stress relaxation through the successive sweep provided by the second heating zone. In a specific case where the thermoplastic resins differ between the first and second sets, the second temperature can also be between the Tg of the thermoplastic resin in the first set and its Te.
[0024] In one embodiment example, after completion of the deposition of the sets of layers and consolidation of the last set of deposited layers, an additional heat treatment of relaxation is carried out comprising a sweep of a surface of the consolidated stack obtained, opposite the support, by an additional local heating, of limited extent to a fraction of this surface, in relative motion with respect to this surface, and imposing a temperature between the glass transition temperature of the thermoplastic resin of the last set deposited and the crystallization temperature of this resin.
[0025] This characteristic also contributes to stress relaxation through dynamic relaxation after the final consolidation. The relaxation is performed at a temperature lower than that imposed during consolidation, which is between Tg and Te. It does not result in the melting or softening of the resin. Those skilled in the art will recognize that other variations are possible, such as performing dynamic relaxation in the event of observed incipient deformation or after consolidation of one assembly before initiating the deposition of the next.
[0026] In one embodiment example, the first assembly is placed on at least one structure made of thermoplastic composite material that has already been consolidated and positioned beforehand on or in the support, and the structure is welded to the first assembly during the first consolidation.
[0027] This characteristic advantageously allows for further functionalization of the resulting part by leveraging the initial consolidation. The weld produced after cooling results from the interpenetration of polymer chains that occurred during localized heating on either side of the welded interfaces.
[0028] In particular, the structure may include at least one of a stiffening element, a reinforcing element, an element configured to form an end or a bottom of the part to be obtained, or configured to compartmentalize an internal volume of the part to be obtained.
[0029] In particular, the first assembly can be placed on two structures made of thermoplastic composite material that have already been consolidated and positioned beforehand on or in the support so as to connect them, and there can be welding of the structures with the first assembly during the first consolidation.
[0030] In one embodiment, at least part of the deposited fibrous layers has at least locally a dome shape, the extent of the associated local heating covering an area between two meridians of the dome and corresponding to a fraction of the dome's surface, and the associated local heating being in rotation around an axis of the dome relative to the latter.
[0031] Such a feature corresponds to the application of the invention to a type of curved part, which can be open or closed. As will be further described below, it should be noted that the invention is not limited to a particular geometry for the manufactured part.
[0032] In particular, the manufactured part may be a tank, and at least part of the deposited fibrous layers may define a structure comprising a cylinder, intended to form at least part of a body of the tank, and at least two domes located at a respective end of the cylinder, the extent of the associated local heating being able to cover an area between two meridians of this structure and being able to correspond to a fraction of the area of this structure, and the associated local heating being able to rotate about an axis of this structure.
[0033] In one embodiment, each set of fibrous layers is deposited on a support having an evolving shape along a first direction, and each local heating takes up the evolution of the shape of the support along the first direction and carries out the sweeping of the surface of the corresponding set along a second transverse direction, for example perpendicular, to the first direction.
[0034] This case corresponds to the application of the invention to a situation where the local heating adapts to the shape of the room by following its evolving profile.
[0035] In one exemplary embodiment, each set of fibrous layers comprises carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers.
[0036] In one embodiment, the thermoplastic resins of the fibrous layer assemblies are identical or different and each comprise: a polyaryletherketone polymer (PAEK), a polyetheretherketone polymer (PEEK), a polyetherketoneketone polymer (PEKK), a polyethersulfone polymer (PES), a poly(phenylene sulfide) polymer (PPS), a polyetherimide polymer (PEI), or a mixture of these polymers.
[0037] The aforementioned features and advantages, as well as others, will become apparent upon reading the detailed description that follows. This detailed description refers to the attached drawings. Brief description of the drawings
[0038] The attached drawings are schematic and primarily intended to illustrate the principles of the presentation. In these drawings, identical elements (or parts of elements) are identified by the same reference symbols from one figure to another. [Fig. 1] Figure 1 represents, schematically and partially, the deposition of a first set of fibrous layers by AFP in the context of an example of a process according to the invention. [Fig. 2] Figure 2 represents, schematically and partially, the first vacuum consolidation to consolidate the first deposited assembly. [Fig. 3] Figure 3 represents, schematically and partially, a detail of a heating wall that can be implemented to achieve local heating. [Fig.4] Figure 4 represents, schematically and partially, the deposition of a second set of fibrous layers by AFP on the first consolidated set. [Fig. 5] Figure 5 schematically and partially represents the second vacuum consolidation to consolidate the second deposited assembly, as well as a possible evolution of the temperature within the thickness of the stack. [Fig. 6] Figure 6 schematically and partially represents another example of a process according to the invention in which, during the second consolidation, a sweep is carried out with heating zones having different temperatures in order to control the cooling of the zone which has been heated to the consolidation temperature. [Fig. 7] Figure 7 schematically and partially represents another example of a process according to the invention in which the first set of deposited layers is welded to a stiffening element during the first consolidation. [Fig. 8] Figure 8 schematically and partially represents another example of a process according to the invention in which the first set of deposited layers is welded, during the first consolidation, to an element configured to form a bottom within the internal volume of the part to be obtained. [Fig. 9] Figure 9 represents, schematically and partially, another example of a process according to the invention in which the first set of deposited layers is welded to two structures so as to ensure their joining during the first consolidation. [Fig. 10] Figure 10 schematically and partially represents the realization of a tank made of thermoplastic composite material in the context of an example according to the invention. [Fig. 11] Figure 11 represents, schematically and partially, the realization of a dome in thermoplastic composite material in the context of another example according to the invention. [Fig. 12] Figure 12 represents, schematically and partially, the realization of a panel in thermoplastic composite material in the context of another example according to the invention. [Fig. 13] Figure 13 schematically and partially illustrates the construction of a room with an evolving shape and localized heating that follows the room's profile. [Fig. 14] Figure 14 schematically illustrates the implementation of several localized heating systems. [Fig. 15] Figure 15 schematically represents the implementation of a local heating device whose size corresponds to the largest dimension of the assembly to be consolidated. Description of the implementation methods
[0039] Figure 1 schematically and partially illustrates the deposition by AFP, on a support 10, of a first set El of stacked fibrous layers 3-1 in the context of an example of a process according to the invention.
[0040] Figure 1 illustrates part of the structure of a dispensing head of a device for implementing an AFP technique. The structure of the illustrated dispensing head is known per se. The dispensing head is fed by a fibrous tape 3 composed of one or more fibrous strands impregnated with a thermoplastic resin, which is draped over the support 10 to deposit each of the layers 3-1. The tape 3 is conveyed by a conveying element (not shown) to a pressure application element 7 located on the side of the support 10, in the direction indicated by the arrow Fl.
[0041] The pressure application element 7 applies pressure to the impregnated strip 3 to deposit it onto the substrate 10. The pressure application element 7 may be in the form of a roller. The dispensing head also includes a heating element 9 capable of heating the strip 3 and the last deposited layer in the vicinity of, or directly on, the pressure application element 7. This heating element 9 heats the impregnated strip 3 during its deposition and also cools the last deposited layer to liquefy the thermoplastic resin and thus impart the desired adhesion to the deposited strip. In the illustrated case, the heating element 9 is a laser, but those skilled in the art will readily recognize that other heating methods can be used.
[0042] During application, the dispensing head is mobile in order to apply the impregnated strip 3 to the desired area of the substrate 10 (the movement of the head is indicated by arrow F2) and thus deposit each of the layers 3-1 of the assembly El. Elements ensuring good adhesion of the first layer deposited on the substrate 10 and forming a thermal barrier with the substrate 10 are part of the state of the art known to those skilled in the art and are not shown. Similarly, elements ensuring good demolding of the final part from the substrate 10, such as the application of release agents if necessary, are also part of the state of the art known to those skilled in the art and are not detailed here.
[0043] Once all the layers 3-1 of the first assembly El have been deposited, the deposition of the layers is stopped to allow for initial consolidation, as illustrated in Figure 2. Thus, no additional fibrous layers are deposited during this initial consolidation. In the illustrated example, the support 10 is a molding tool, and a vacuum bag 20 has been attached, in a sealed manner, to cover the first assembly El. The bag 20 is positioned on the side of a surface SI of the first assembly El that is opposite the support 10. The bag 20 may be, but is not limited to, made of polyimide or elastomeric material, reinforced or unreinforced, and is a known element in itself.
[0044] The first assembly El is inserted between the support 10 and the tarpaulin 20. The initial consolidation is then carried out by creating a vacuum in an internal volume between the support 10 and the tarpaulin 20. This vacuuming causes the tarpaulin 20 to press against the first assembly El, thus conforming it between the support 10 and the tarpaulin 20 by applying a conforming pressure PC. During the initial consolidation, the first assembly El undergoes a first heat treatment involving a sweep of its surface SI by localized heating produced by a local heating device 30 to selectively melt or soften the thermoplastic resin in the heated area. This sweep is indicated by arrow F3. Following the application of the pressure PC and the first heat treatment, the thickness el of the first assembly El can be reduced by at least 5%, for example, by at least 10%, in particular by 5% to 15% or by 10% to 15%.The vacuum is maintained during the first heat treatment, during the sweeping of the SI surface by the first local heating, as well as during the cooling of the heated area after this local heating.
[0045] Generally, a skilled person will be able to calibrate the heating power and the movement speed of the device 30 to achieve the melting or softening of the resin(s) present and thus allow for consolidation, taking into account, in particular, the distance of the device 30 from the surface of the last deposited assembly, the target temperature (at least equal to the consolidation temperature for the last deposited assembly and at the interface with the previous assembly), and the minimum time required at that temperature. The area heated by the local heating system is brought, during each consolidation, to a temperature greater than or equal to the consolidation temperature, for example, to a temperature greater than or equal to 250°C, for example, greater than or equal to 300°C, or even between 300°C and 450°C or between 350°C and 450°C.The duration for which the thermoplastic resin or resins are subjected to a temperature at least equal to the consolidation temperature in a heated area may be greater than or equal to 1 second, for example between 1 second and 1 hour.
[0046] In general, the local heating is in relative motion with respect to the SI surface of the last deposited set El; that is, only the local heating can be mobile, only the SI surface can be mobile, or both the local heating and the surface can be mobile with relative motion between them. The local heating can be moved continuously with respect to the SI surface of the last deposited set El, or alternatively, a stepwise movement can be performed in which the local heating is stationary to process one area and then moved to process another in a static manner (sequential processing). During the first consolidation, the first local heating can sweep at least 80%, for example at least 90%, or even substantially all, of the SI surface of the first set El.The invention is not limited to a complete scanning of the surface of the fibrous layers, in particular when part of the stack is intended to be eliminated, for example by trimming, at the end of the manufacture of the part.
[0047] As will be described later, the local heating device can have various shapes, adapted to the geometry of the part to be manufactured, and its trajectory to sweep the surface to be treated can vary to a large extent.
[0048] The heating device 30 may include at least one heating wall 32 positioned opposite the tarpaulin 20 and the surface SI. The wall 32 is outside the internal volume defined by the support 10 and the tarpaulin 20. The wall 32 has an extent limited to a fraction of the surface SI, or to a fraction of the surface of the support 10. Figure 3 schematically illustrates an example of a usable wall 32 comprising a plurality of infrared lamps 323 attached to a frame 321. Those skilled in the art will recognize that other means are available to produce the desired local heating. For example, the shape of the infrared lamps 323 can be varied by using curved lamps, or alternatively, pulsed flash lamps (lasers) or induction heating can be used.The wall 32 can be mounted on a robotic arm for scanning; in particular, the wall 32 can be permanently mounted on the robotic arm used during draping, or simply positioned there for consolidation. Other variations are possible, such as guiding the heated wall on a gantry or rails to traverse the surface to be treated.
[0049] Once the initial consolidation is complete and the tarpaulin 20 is removed, the deposition of the fibrous layers by AFP resumes. Figure 4 shows the deposition of a second set E2 of 3-2 fiber layers stacked on top of the first consolidated set E1C. The second set E2 can, as illustrated, cover the entire first consolidated set E1C, or only a portion of it. The deposition of the 3-2 layers is carried out similarly to that described above for the 3-1 layers using the AFP deposition head. The 3-2 layers of the second set are made of thermoplastic pre-impregnated fibrous material. The second set E2 can, as illustrated, be deposited in contact with the first consolidated set E1C.
[0050] Once all the layers 3-2 of the second assembly E2 have been deposited, the layer deposition is stopped to proceed with a second consolidation as illustrated in Figure 5. Thus, no additional fibrous layers are deposited during this second consolidation. The tarpaulin 20 is repositioned in a watertight manner so as to cover the overlap of the first consolidated assembly E1C and the second assembly E2. A vacuum is drawn as described above to conform the stack formed by the assemblies E1C and E2, between the support 10 and the tarpaulin 20, by applying the pressure PC. In cases where the second assembly E2 does not cover the entire surface of the first consolidated assembly E1C, a vacuum environment can be created that does not fully cover the first assembly E1C but only the portion covered by the second assembly E2. This can be particularly advantageous in the case of a large structure.During the second consolidation, the second assembly E2 undergoes a second heat treatment involving a second localized heating of its surface S2 by device 30 to selectively melt or soften the thermoplastic resin(s) in the heated area. Following the application of PC pressure and the second heat treatment, the thickness e2 of the second assembly E2 can be reduced by at least 5%, for example, by at least 10%, specifically by 5% to 15% or by 10% to 15%. Vacuum is maintained during the second heat treatment, both during the second localized heating of the surface S2 and during the cooling of the heated area after this localized heating. After the second consolidation, the second consolidated assembly is welded to the first consolidated assembly.
[0051] Figure 5 also illustrates the imposed temperature as a function of the position within the stack thickness. During the example of the second consolidation considered here, a temperature greater than or equal to the consolidation temperature is imposed on the second assembly E2 while maintaining, in the first consolidated assembly E1C, a temperature between the Tg of the thermoplastic resin and its consolidation temperature.More specifically, the FAI face of the first consolidated assembly E1C, located on the side of support 10 or on the opposite side to the second assembly E2, is subjected, during the second consolidation, to a temperature at least equal to the Tg of the thermoplastic resin present, and the FA2 face of the first consolidated assembly E1C, located on the opposite side to support 10 or on the side of the second assembly E2, is subjected, during the second consolidation, to a temperature Tconso sufficient to produce the bond between assemblies E1C and E2 by interpenetration of the polymer chains on either side of the FA2 face. As illustrated in Figure 5, the temperature through the thickness of the first consolidated assembly E1C increases as one moves from the FAI face to the FA2 face.In the example considered here, the temperature gradient is controlled throughout the thickness by maintaining a temperature at least equal to the Tg of the thermoplastic resin(s) present across the entire thickness of the stack formed by the deposited E1C, E2 assemblies. Several solutions can be implemented to achieve this control of the thermal gradient. One solution is to integrate a heating element into the support 10, activated at a moderate temperature, only during consolidations following the initial consolidation, in order to avoid the drawback of continuous mold heating encountered in the case of in-situ consolidation. Another solution, which can be used as an alternative or in combination with the first, is to control the sweep speed of the local heating element, specifically to slow it down in order to achieve deep heat diffusion within the stack.
[0052] Figure 6 provides another example in which the second local heating defines two distinct heating zones to control the cooling of the thermoplastic resin(s) after heating to a temperature above the consolidation temperature. In this case, the heating device 30-1 defines a first heating zone Z1 at a temperature above the consolidation temperature (resulting in melting or softening of the resin(s) in the heated zone), and a second heating zone Z2 at a temperature lower than the first, between the Tg of the thermoplastic resin in the second assembly and its consolidation temperature, for example, closer to this Tg than to the consolidation temperature, for example, approximately equal to this Tg, within 10°C.
[0053] A given area of the S2 surface is first swept by the first zone Z1 and then by the second zone Z2 in order to control the cooling gradient. Initially, the cooling rate is less than or equal to 10°C per minute until the crystallization temperature (generally between 250 and 300°C) is reached, thus controlling the degree of crystallinity. Subsequently, after the passage of the second zone Z2, the temperature is homogenized around the Tg throughout the entire thickness of the stack, as illustrated in the temperature evolution graph. This minimizes the temperature gradient at the periphery of the heating device 30-1. This management of peripheral gradients may be preferable for heating devices that are small relative to the structure being consolidated.Of course, we do not depart from the scope of the invention if we use a heating device having more than two heating zones at distinct temperatures.
[0054] As described above for the first consolidation, the second local heating can sweep at least 80%, for example at least 90%, or even substantially all, of the surface S2 of the second set E2 during the second consolidation.
[0055] Generally, the number of 3-1, 3-2 layers deposited for each El, E2 assembly will be determined by a skilled professional based on the application and the heating and vacuum capabilities used, in order to ensure high-quality consolidation. For example, each El, E2 assembly may contain at least 10 3-1, 3-2 layers, for instance, between 10 and 30 3-1, 3-2 layers, or even between 10 and 20 3-1, 3-2 layers. An assembly may, of course, contain fewer than 10 layers, resulting in longer manufacturing time and therefore higher manufacturing costs for the final part. Naturally, the number of 3-1, 3-2 layers deposited for each El, E2 assembly may be the same or different, and each deposited assembly may include areas of reduced number of layers. In other words, each set can have a variable number of layers depending on the area considered.The skilled technician will naturally take care to limit the temperature applied during each heat treatment so as not to degrade the material, for example by working at least 50°C below the material's degradation temperature during each consolidation. Depending on the local heating system, the surface area of certain deposited assemblies, and the total number of assemblies, it is also possible that some assemblies may undergo several heat consolidation cycles, either partially or completely, provided that these cycles do not degrade the material of the assemblies in question.
[0056] The choice of reinforcing material and resin depends on the intended application. For example, the 3-1, 3-2 layers deposited include carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers. For example, the thermoplastic resins of the fiber layer assemblies may be identical or different and each may include: a polyaryletherketone (PAEK) polymer, a polyetheretherketone (PEEK) polymer, a polyetherketoneketone (PEKK) polymer, a polyethersulfone (PES) polymer, a poly(phenylene sulfide) (PPS) polymer, a polyetherimide (PEI) polymer, or a mixture of these polymers. In a particular case, the thermoplastic resin of the first assembly may be PEI and the thermoplastic resin of the second assembly may be PEAK, PEEK, or PEKK. According to another special case, the thermoplastic resin of the first set can be a mixture of PEI and PEAK, or PEEK, or PEKK.
[0057] The examples just described concern the manufacture of a part by implementing two sequences of AFP deposition and subsequent consolidation. It is naturally not beyond the scope of the invention if the deposition is continued with at least a third AFP deposition / consolidation sequence, and the characteristics described for the first and second sequences also apply to subsequent sequences.
[0058] As an example, an additional heat treatment for relaxation by localized heating can be performed once the consolidated stack is achieved (after completion of the final AFP deposition and consolidation sequence). This heat treatment can be carried out similarly to that described above for dynamic consolidation, but by imposing a lower temperature, between the Tg of the resin of the last deposited assembly (e.g., the second or third assembly) and its crystallization temperature. For example, a temperature between 150°C and 250°C can be imposed during relaxation.
[0059] The following section describes, in connection with figures 7 to 9, process variants according to the invention allowing for further functionalization of the part obtained by welding, during the first consolidation, the layers of the first assembly deposited to one or more third structures.
[0060] In the example in Figure 7, the support 10-1 defines a housing in which a stiffening element 40-1 made of already consolidated thermoplastic composite material has been positioned, prior to the initiation of the deposition of the first assembly El. As illustrated, part of the element 40-1 may be located inside the support, and a surface S40-1 of the element 40-1 may extend outside the support 10-1. The first assembly El is deposited in contact with the surface S40-1 by implementing an AFP technique as described above, and then the first consolidation is carried out in a manner similar to that just described to bond the first assembly El to the element 40-1 by interpenetration of the polymer chains on either side of the surface S40-1.
[0061] In the example of Figure 8, the support 10-2 defines a housing in which an axisymmetric element 40-2 made of already consolidated thermoplastic composite material has been positioned before the deposition of the first assembly El begins. The element 40-2 is configured to be positioned at one end of the part to be obtained or to compartmentalize an internal volume of the part. The element 40-2 can correspond to a tank bottom or to a common bottom separating the internal volume of the part into two adjacent compartments. A surface S40-2 of the element 40-2 can open outside the support 10-2. The first assembly El is deposited in contact with the surface S40-2 using an AFP technique as described above, and then the first consolidation is carried out in a manner similar to that described above to bond the first assembly El to the element 40-2 by interpenetration of the polymer chains on either side of the surface S40-2.In the illustrated example, the scanning is carried out along a longitudinal X axis of the first set, but other trajectories are possible such as a circumferential scanning as described below in relation to figure 10.
[0062] The example in Figure 9 illustrates another application in which the first assembly El enables the joining between two structures 40-3 made of thermoplastic composite material already consolidated and previously positioned on the support 10. In this case, there is welding of the structures 40-3 with the first assembly El during the first consolidation, in a manner similar to what has been described above.
[0063] In all the examples described above, simplified representations of the scanning path and the part geometry have been used. The following section describes various possibilities for these aspects in more detail.
[0064] Figure 10 illustrates the fabrication of a tank by implementing an example of a process according to the invention, in which deposited layers define a cylinder 50 and two end domes 52 intended to form the tank bottoms. Figure 10 illustrates a consolidation by sweeping of the local heating device 30-2. The structure being fabricated extends along a longitudinal axis X, which can correspond to an axis of revolution of the structure. The local heating covers an area between two meridians of this structure and corresponds to a fraction of the surface area of this structure. Thus, the local heating corresponds to a longitudinal sector of this structure and rotates about the X-axis. Alternatively, the deposited structure could be rotated about the X-axis with the local heating device either moving or stationary.Of course, the heating system implemented can contain different heating zones according to the principle described above. In particular, a common base can be bonded as shown in Figure 8, and, for example, differentiated heating zones can be used between the central part, intended to be directly connected to the common base, and the domes 52. It is also possible to have a greater number of assemblies to be placed in the end dome zones, which may have a final thickness greater than the thickness of the main body of the tank, and therefore differentiated heating zones for the consolidation of these additional assemblies.
[0065] Figure 11 illustrates the fabrication of a dome 60 by implementing an example of a process according to the invention. Similar to what has been described previously, the local heating device 30-3 covers an area between two meridians of the dome, corresponding to a fraction of the dome's surface area, and is animated by a relative rotational movement around its X axis.
[0066] Figure 12 represents, for its part, the application of an example of a process according to the invention to the manufacture of a panel 70, by sweeping a local heating device 30-5 along a broken line trajectory, for example so as to cover the entire surface of the last set of layers deposited (movement along the entire width and length of the last set deposited).
[0067] In general, it should be noted that the invention applies to the manufacture of parts with various geometries. The manufactured parts may be closed or open, for example, cylinders closed or not at their ends, domes or ferrules, for example for integration into a space launcher, or panels, for example aircraft fuselage panels, wing panels, or center box panels. The parts may be flat or curved. They may or may not have a changing cross-section, that is, a change in their local curvature. The following description, in conjunction with Figures 13 to 15, provides further details on the heating process that can be implemented.
[0068] Figure 13 illustrates the case where the local heating device 30-4 adapts to the shape of the room by following an evolving profile. The support 10-3 exhibits an evolving shape along a first direction Dl, for example with alternating protruding and recessed portions as illustrated. The recently deposited set of layers El conforms to the shape of the support 10-3. The local heating device 30-4 conforms to the shape of the support 10-3 and the assembly El. In the illustrated example, the device 30-4 consists of several heated walls 30-41 ... 30-4n which are offset along the first direction Dl and which have different inclinations so as to adapt to the profile of the assembly El. Each wall 30-41 ... 30-4n is connected to a frame 31 by means of respective positioning and inclination adjustment means 33-1 ... 33-n, known per se.The device 30-4 scans the surface of the corresponding assembly along a second transverse direction D2, for example, perpendicular to the first direction D1. It should be noted that as the scan progresses, walls 30-41 ... 30-4n may become deactivated, or conversely, activated, for example, depending on changes in the dimension of the assembly El measured along the first direction. The position and / or inclination of the walls 30-41 ... 30-4n may also be modified during the scan to adapt to any changes in the shape of the support.
[0069] Figure 14 illustrates the simultaneous use of several 30-5 local heating devices, for example, to cover different areas (respective zones) of the surface of the last set of deposited layers. The movement of one of the 30-5 devices can be linked to the movement of the other 30-5 devices, or alternatively, be independent of the latter.
[0070] Figure 15 shows a local heating device 30-6 covering the entire length of the last layer set deposited (largest dimension). In this case, the device 30-6 moves along the width of this set, for example to cover its entire surface.
[0071] A person in the trade will recognize that other variations are possible, such as a device covering the entire width of the last set deposited, or transverse to the length and width of this set, or even a plurality of devices having a joint movement, with for example a staggered distribution.
[0072] In general, the shape of the heating device can correspond closely to the shape of the surface of the last set of layers deposited, being flat or curved.
[0073] Generally speaking, and even though it depends on the shape and dimensions of the room in question, the extent of local heating can cover a fraction of the surface of the last set deposited, between 1% and 50%, in particular between 3% and 15%, or between 5% and 10%.
[0074] Although the present invention has been described with reference to specific embodiments, modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.
[0075] The expression "between ... and ..." should be understood as including the boundaries.
Claims
Demands
1. A method for manufacturing a part made of thermoplastic composite material, the method comprising: - the deposition on a support (10; 10-1; 10-2; 10-3) of a first set (El) of stacked fibrous layers (3-1) by automatic fiber placement, the fibrous layers being made of pre-impregnated thermoplastic fibrous material, - the interruption of the deposition of the fibrous layers and the carrying out, while this deposition is interrupted, of a first consolidation under vacuum, the first assembly being subjected, during the first consolidation, to a first heat treatment comprising a sweep (F3) of a surface (SI) of the first assembly, opposite the support, by a first local heating, of limited extent to a fraction of this surface, in relative movement with respect to this surface, the first local heating allowing to selectively melt or soften the thermoplastic resin in the heated zone, - the resumption, after the first consolidation, of the deposition of the fibrous layers and the deposition, on at least part of the first consolidated set (E1C), of a second set (E2) of stacked fibrous layers (3-2) by automatic fiber placement, and - the interruption of the deposition of the fibrous layers and the carrying out, while this deposition is interrupted, of a second vacuum consolidation during which the second assembly is consolidated, the second assembly being subjected, during the second consolidation, to a second heat treatment comprising a sweep of a surface (S2) of the second assembly, opposite the support, by a second local heating, of limited extent to a fraction of this surface, in relative motion with respect to this surface, the second local heating allowing to selectively melt or soften the thermoplastic resin(s) in the heated zone, the second assembly being welded to the first consolidated assembly following the second consolidation.
2. A method according to claim 1, wherein the thermoplastic resin present on one face (FAI), located on the side of the support (10), of the first consolidated assembly (E1C) is subjected, during the second consolidation, to a temperature at least equal to its glass transition temperature.
3. A method according to claim 1 or 2, wherein the second local heating defines at least a first heating zone (Z1) imposing a first temperature enabling the thermoplastic resin(s) to be selectively melted or softened, and a second heating zone (Z2) imposing a second temperature, lower than the first temperature, between the glass transition temperature of the thermoplastic resin of the second assembly and its crystallization temperature, the heated zone being swept successively by the first heating zone and then by the second heating zone.
4. A method according to any one of claims 1 to 3, wherein, after completion of the deposition of the sets (E1; E2) of layers and consolidation of the last set of deposited layers, an additional heat relaxation treatment is carried out comprising sweeping a surface of the consolidated stack obtained, opposite the support, by additional local heating, of limited extent to a fraction of this surface, in relative motion with respect to this surface, and imposing a temperature between the glass transition temperature of the thermoplastic resin of the last set deposited and the crystallization temperature of this resin.
5. A method according to any one of claims 1 to 4, wherein the first assembly (El) is deposited on at least one structure (40-1; 40-2; 40-3) of thermoplastic composite material already consolidated and positioned beforehand on or in the support, and wherein the structure is welded with the first assembly during the first consolidation.
6. A method according to claim 5, wherein the structure (40-1; 40-2; 40-3) comprises at least one of a stiffening element, a reinforcing element, an element configured to form an end or a bottom of the part to be obtained, or configured to compartmentalize an internal volume of the part to be obtained.
7. Method according to claim 5 or 6, wherein the first assembly (El) is deposited on two structures (40-3) of thermoplastic composite material already consolidated and positioned beforehand on or in the support so as to connect them, and wherein the structures are welded with the first assembly during the first consolidation.
8. A method according to any one of claims 1 to 7, wherein at least a portion of the deposited fibrous layers has at least locally a dome shape (52; 60), the extent of the associated local heating (30-2; 30-3) covering an area between two meridians of the dome and corresponding to a fraction of the dome's surface, and the associated local heating being in rotation about an axis (X) of the dome relative to the latter.
9. A method according to claim 8, wherein the manufactured part is a tank, and wherein at least a portion of the deposited fibrous layers defines a structure comprising a cylinder (50), intended to form at least a portion of a body of the tank, and at least two domes (52) located at a respective end of the cylinder, the extent of the associated local heating (30-2) covering an area between two meridians of this structure and corresponding to a fraction of the area of this structure, and the associated local heating being in rotation about an axis (X) of this structure.
10. A method according to any one of claims 1 to 9, wherein each set (El; E2) of fibrous layers is deposited on a support (10-3) having an evolving shape along a first direction (Dl), and wherein each local heating (30-4) takes up the evolution of the shape of the support along the first direction and carries out the sweeping of the surface (SI; S2) of the corresponding set along a second direction (D2) transverse to the first direction.
11. A method according to any one of claims 1 to 10, wherein each set (E1; E2) of fibrous layers comprises carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers.
12. A method according to any one of claims 1 to 11, wherein the thermoplastic resins of the (E1; E2) assemblies of fibrous layers are identical or different and each comprise: a polyaryletherketone polymer, a polyetheretherketone polymer, a polyetherketoneketone polymer, a polyethersulfone polymer, a poly(phenylene sulfide) polymer, a polyetherimide polymer, or a mixture of these polymers.