EP4347226A1

EP4347226A1 - Effector for dynamic welding of parts made of composite material

Info

Publication number: EP4347226A1
Application number: EP22728637.4A
Authority: EP
Inventors: Damien SIREUDE
Original assignee: Institut de Recherche Technologique Jules Verne
Current assignee: Institut de Recherche Technologique Jules Verne
Priority date: 2021-05-25
Filing date: 2022-05-24
Publication date: 2024-04-10
Also published as: FR3123248B1; FR3123248A1; WO2022248430A1

Abstract

The invention relates to an effector for dynamic welding of at least two parts made of composite material comprising a thermoplastic polymer matrix, the effector comprising: - at least one welding device, for heating at least one zone of at least one of the parts to a temperature greater than or equal to the melting temperature of said thermoplastic polymer matrix in order to weld said at least two parts together at said at least one zone; and - at least one post-heating device configured to heat said at least one zone in order to supply heat to said zone without the temperature thereof exceeding the crystallisation onset temperature of said thermoplastic polymer matrix.

Description

Title: Dynamic welding effector for composite material parts Technical field

The present invention relates to the field of welding two parts made of composite material with a thermoplastic polymer matrix, in particular without adding material. In particular, the invention proposes a dynamic welding effector of at least two parts made of composite material with a thermoplastic polymer matrix. The invention also relates to a process for the dynamic welding of two parts made of composite material with a thermoplastic polymer matrix using such an effector.

Prior technique

To weld two parts made of composite material with a thermoplastic polymer matrix, it is known to heat the two parts in contact with each other so that the polymer material of the parts softens or melts, which makes it possible to weld the parts between them at their interface. During this heating, deconsolidation of the matrix of the parts occurs before melting and results in local swelling. It is thus known to apply, in addition to heating, pressure to the heated zone in order to ensure good contact at the interface between the two parts and to limit deformations during subsequent cooling and consolidation to reduce the risk of parts separating after pressing.

For small parts, the welding can be done under a vacuum bag or a press, which makes it possible to limit deformations due to swelling. However, such techniques are difficult to apply to large parts.

For large parts, it is known to use a mobile assembly 1, as seen in Figure 1, combining a heating device 2, for example induction, and a pressing element 3. Such a mobile assembly 1 allows carry out the welding of the parts P gradually during its displacement. The pressing element 3 is configured to exert pressure on the parts P after heating by the heating device 2.

In the state of the art of dynamic welding, the welded parts cool freely after the moving assembly has passed. However, it is found experimentally that in this case, the cooling rate is very fast, of the order of 200 to 300° C./min. The heat applied to the interface between the parts to raise the temperature of the thermoplastic polymer matrix above the melting temperature, is very quickly dissipated by conduction in composite parts, and in parts in contact, such as tools, for example. This cooling rate is not compatible with the crystallization kinetics of the polymer so that the crystallinity of the polymer after welding is affected and remains lower than the initial crystallinity rate (of the order of 50% compared to the state initial).

JP2005028784 describes a laser welding method using several laser beams.

There is still a need to improve the quality of the weld between two parts made by a dynamic welding effector of two parts made of composite material with a thermoplastic polymer matrix.

Disclosure of Invention

Dynamic welding effector

The present invention achieves this in whole or in part thanks to, according to one of its aspects, an effector for dynamic welding of at least two parts made of composite material comprising a thermoplastic polymer matrix, the effector comprising: at least one device for welding, so as to heat at least one zone of at least one of the parts to a temperature greater than or equal to the melting temperature of the said thermoplastic polymer matrix in order to weld the said at least two parts together at the level of the said at least one zone, at least one post-heating device configured to heat said at least one zone to provide heat to said zone without the temperature thereof exceeding the crystallization onset temperature of said thermoplastic polymer matrix.

By “dynamic welding”, we mean that the welding is carried out progressively during the movement of the effector relative to the parts. The welding is preferably carried out without addition of material.

By “crystallization onset temperature”, is meant the temperature from which a growth of the crystalline structure of the thermoplastic polymer occurs in said thermoplastic polymer matrix during its cooling from the molten state. The determination of this temperature for a given material is carried out by analyzing the enthalpy of crystallization by anisothermal differential scanning calorimetry. During the cooling phase from the molten state, the crystallization onset temperature corresponds to the onset of the peak of the enthalpy of crystallization. This crystallization onset temperature is between the melting temperature Tf and the crystallization temperature Ts, generally between 30° C. below the melting temperature Tf and 15° C. above the crystallization temperature Ts. This crystallization temperature Ts is characterized by a maximum rate of growth of the crystalline structure of the thermoplastic polymer. The crystallization temperature Ts is lower than the melting temperature Tf, generally between 60°C below the melting temperature Tf and 20°C below the melting temperature Tf.

Thanks to the invention, it is possible to obtain controlled cooling of the part or parts, independently of the characteristics of said parts, in particular of their material and/or their dimensions, independently of the support on which the welding is carried out or even independently ambient conditions such as humidity, temperature or air pressure, for example.

The heating of said at least one zone, with said at least one welding device, to a temperature greater than or equal to the melting temperature of said thermoplastic polymer matrix allows the latter to pass into a state of melting. Thus, an interpenetration of the polymer chains of said at least two parts can occur, allowing welding at said zone.

Said at least one post-heating device can be configured to heat said at least one of the parts to a temperature below the crystallization start temperature and above the temperature of the ambient air which is for example 25° C., such a temperature possibly being for example between 230° C. and 260° C. for a part with a PEKK matrix.

Said at least one post-heating device is preferably arranged downstream of said at least one welding device relative to the direction of movement of the effector.

Said at least one post-heating device is preferably disposed at a distance between approximately 3 and 30 mm from said at least one welding device within the effector. The distance is preferably determined as a function of the speed of movement of the effector, of the thermoplastic polymer matrix of said at least two parts and of the speed of cooling in the open air of said parts. This speed of cooling in the open air depends on the heat exchange conditions at the interfaces between said parts.

Said at least one post-heating device is preferably configured to slow down the cooling rate of said at least one part.

By “cooling rate of said at least one part”, is meant the temporal variation of the temperature of said at least one part heated with said at least one welding device.

By “slowing down the cooling rate”, it is meant that the cooling rate of said at least one part heated with said at least one welding device is lower than the cooling rate in the open air. This slowing down can lead to an increase, or not, transient, of the temperature of said at least one part heated with said at least one welding device.

Said at least one post-heating device can make it possible to heat said at least one zone to a temperature T comprised within a range of predetermined temperature values extending, for example between approximately 90° C. below the crystallization temperature and the crystallization start temperature is Ts-90°C<T<Tc, better between approximately 75°C below the crystallization temperature and the crystallization start temperature is Ts-75°C<T<Tc, even better between approximately 40° C. below the crystallization temperature and the crystallization start temperature, ie Ts-40° C.<T<Tc.

For example, for at least two parts made of composite material comprising a polyetherketoneketone (PEKK) with a melting temperature of approximately 340° C., the post-heating device can make it possible to maintain the outer surface of at least one of the parts in a range of temperature values comprised between approximately 230° C. and approximately 260° C.

Said at least one welding device and/or said at least one post-heating device can be configured and/or be controlled, in particular by an effector control system, to heat the two or more parts if there is has more than two parts by heating each zone successively passing under the welding device and the post-heating device. Said at least one welding device and/or said at least one post-heating device can be configured and/or controlled to make it possible to heat all the parts to be welded. Said at least one welding device and said at least one post-heating device can heat at least the welding interface of the part or parts concerned by this heating, not necessarily the entire part or parts.

Preferably, said at least two parts comprise a semi-crystalline thermoplastic polymer matrix.

By “semi-crystalline thermoplastic material”, is meant a thermoplastic polymer having crystalline zones and amorphous zones. Such a polymer can comprise lamellae consisting of cubic, orthorhombic or hexagonal meshes. The degree of crystallinity can vary between 20% to 30% approximately. Semi-crystalline thermoplastic polymer materials are high performance materials with high stiffness and good creep resistance.

The thermoplastic material of said at least two parts can alternatively be amorphous.

The effector advantageously comprises at least one pressing device. This pressure device allows the application of pressure on the previously heated area. The application of pressure to the area previously heated by the welding device makes it possible to limit deformations during subsequent cooling and consolidation and to reduce the risk of separation of the parts after pressing.

In this case, said at least one pressing device is advantageously arranged between said at least one welding device and said at least one post-heating device. Said at least one post-heating device can also be part of such a pressing device, then ensuring the two functions of post-heating and pressing.

Said at least one pressing device can also be a fixed tool relative to said at least two parts, as for example in application NL1030304.

Preferably, said at least one welding device comprises a heating system by induction, by ultrasound, by thermal conduction and/or by infrared, preferably by induction. It is possible, for example, to use a welding device comprising an induction heating system associated with the use of a sucker. The succeptor is a magnetic and electrically conductive element located at the interface between said at least two parts, making it possible to inject more power into the interface. The post-heating device advantageously comprises a heating system by induction or by infrared radiation.

The post-heating device may comprise at least one temperature sensor, in particular a pyrometer, so as to measure the temperature of the outer surface of at least one of the parts.

The post-heating device preferably comprises a servo system for maintaining the outer surface of at least one of the parts within a range of predetermined temperature values for a predetermined duration, for example substantially 30 s. The post-heating device can thus adapt its heating power according to the characteristics of said parts, in particular their material and/or their dimensions, the support on which the weld is made or even ambient conditions such as the rate of humidity, temperature or air pressure for example.

Such a servo system can, for example, adapt its heating power as a function of the difference between at least one temperature from the range of predetermined temperature values and at least one temperature measured by said at least one temperature sensor and/or or an average of temperatures measured by said at least one temperature sensor.

The post-heating device can operate between a minimum heating power, or even zero, and a maximum heating power. The post-heating device can also operate at at least one intermediate heating power between the minimum heating power and the maximum heating power.

The effector is preferably mobile while the parts to be welded are fixed. Alternatively, the parts are moved under the effector, which remains fixed or is also movable.

Dynamic welding process

Another subject of the invention, according to another of its aspects, in combination with the foregoing, is a process for dynamically welding at least two parts made of composite material comprising a thermoplastic polymer matrix, using an effector dynamic welding as described above, comprising the following steps: i) at least partially superimposing said at least two parts to be welded together, ii) positioning the effector on the side of at least one outer surface of at least one of said parts, iii) moving the effector relative to the parts, in a direction of movement, such that said at least one device post-heating device is arranged downstream of said at least one welding device, iv) heating with the welding device at least one zone of at least one of the two parts passing under the welding device, v) heating said at least one zone with the post-heating device when the latter passes under the post-heating device, to provide heat to said zone without the temperature thereof exceeding the crystallization start temperature Te of said thermoplastic polymer matrix of said parts P.

Thanks to this method, the cooling of said zone previously heated by the welding device and passing under the post-heating device can be controlled, independently of the characteristics of said parts, in particular of their material and/or their dimensions, of the support on which the welding is carried out or ambient conditions such as humidity, temperature or air pressure for example.

Controlling the cooling rate can make it possible to obtain the desired properties of the weld, for example by promoting the crystallization of the thermoplastic polymer matrix if necessary, and thus improving the quality of the weld.

The post-heating of at least one zone of said at least one part during the displacement of the effector is preferably carried out after the heating of said at least one zone after a time comprised between approximately 5 and 10 seconds.

The post-heating of at least one zone of said at least one part during the movement of the effector lasts preferably between 20 and 30 seconds approximately.

The heating of said parts can result in local deconsolidation of said parts, which produces local swelling. Preferably, the method comprises a step consisting in bringing at least one presser device of the effector into contact with said outer surface of at least one of the parts in the zone passing under the pressing device. This makes it possible to constrain the constituent material of the parts after heating to improve consolidation during cooling and to limit the deformations induced by local swelling.

In this case, between steps iv) and v), simultaneously with step v) or after step v), preferably between steps iv) and v), the method may comprise a step consisting in exerting pressure on the outer surface of said zone with said at least one presser device. The pressing device can promote adhesion between the parts by ensuring contact between them and allowing the interpenetration of the polymer chains. The risk of separation of the parts after the passage of the effector is thus limited.

Step v) is advantageously implemented so that said at least one post-heating device maintains in said zone a temperature comprised within a range of predetermined temperature values, for example between 90° C. below the crystallization temperature and the crystallization start temperature, better still between 75°C below the crystallization temperature and the crystallization start temperature, even better between 40°C below the crystallization temperature and the crystallization start temperature crystallization.

This post-heating temperature can make it possible to promote the transformation kinetics of the thermoplastic polymer matrix of said parts. In particular, for semi-crystalline thermoplastic polymer materials, maintaining a temperature of approximately 80° C. below the melting temperature can allow rapid formation of crystalline zones.

For example, for the welding together of at least two parts made of composite material comprising a polyetherketoneketone (PEKK) with a melting temperature of substantially 340° C., step v) of post-heating advantageously makes it possible to maintain a temperature of 250° C. approximately in said zone.

The post-heating step v) advantageously makes it possible to obtain a cooling rate in said zone which is less than 50° C./min. Such a cooling rate, which is slower than the cooling rate in the open air, can contribute to favoring the transformation kinetics of the thermoplastic polymer matrix of said parts.

Advantageously, during steps iv) and v), the effector moves at a speed of between 3 and 30 mm/s approximately, preferably equal to 5 mm/s approximately. When said at least two composite material parts comprise a semi-crystalline thermoplastic polymer matrix, step v) is preferably implemented so that the crystallinity rate in said zone, after passage of said at least one device post-heating, is substantially the same as the degree of crystallinity in said zone, before the passage of said at least one welding device, in particular by adapting the post-heating temperature range and the post-heating time.

Thus, the mechanical characteristics of said at least one part after cooling are substantially homogeneous throughout said at least one part. In this way, the weld at the weld interface does not constitute an area of weakness in the final part.

Preferably, the welding takes place without adding an additional material to the interface between the effector and at least one of said parts, nor between the parts, nor between said at least one pressing device and at least one of said parts if applicable. Said at least one welding device in fact advantageously makes it possible to heat each zone of at least one of said at least two parts which passes under the welding device to a temperature greater than or equal to the melting temperature of said parts, which then allows an interpenetration between the parts at their interface, thus creating the weld between them.

Said at least two parts advantageously comprise a fibrous reinforcement consisting of carbon fibers.

Said at least two parts comprise a thermoplastic polymer matrix chosen from the group consisting of polyaryletherketones (PAEK), in particular polyetheretherketone (PEEK) or polyetherketoneketone (PEKK).

The thermoplastic polymer matrices of said at least two parts can comprise the same thermoplastic polymer matrix or different thermoplastic polymer matrices.

Post-welding device

Another subject of the invention, according to another of its aspects, in combination with the foregoing, is a post-heating device intended to equip a dynamic welding effector with at least two parts made of composite material comprising a thermoplastic polymer matrix , in particular an effector as defined above, configured for, after heating at least one zone of the weld interface of said at least two parts to a temperature above the melting temperature, supplying heat to said zone without the temperature thereof exceeding the temperature of start of crystallization of said thermoplastic polymer matrix.

Thanks to this post-heating device, it is possible to control the cooling of said at least two parts during welding, independently of the effector used and of the characteristics of said parts, in particular of their material and/or their dimensions, of the support on which the weld is made or ambient conditions such as humidity, temperature or air pressure for example. The post-heating device can be as defined above.

Brief description of the drawings

The invention may be better understood on reading the detailed description which follows, non-limiting examples of implementation thereof, and on examining the appended drawing, on which

[Fig 1] Figure 1 schematically shows, in side view, a dynamic welding effector according to the prior art comprising a pressing element,

[Fig 2] Figure 2 shows, schematically, in side view, a dynamic welding effector according to the invention,

[Fig 3] figure 3 represents, in the form of a block diagram, the steps of an example of a dynamic welding process according to the invention,

[Fig 4] figure 4 illustrates, using a schematic graph, the evolution of the temperature as a function of time during the displacement of the effector of figure 3,

[Fig 5] figure 5 illustrates using a schematic graph the evolution of the temperature as a function of time during the displacement of the effector of figure 1, and [Fig 6] figure 6 represents in isolation , schematically, in side view, a post-heating device according to the invention.

detailed description

In the remainder of the description, identical elements or identical functions bear the same reference sign. For the purpose of conciseness of the present description, they are not described with regard to each of the figures, only the differences between the embodiments being described. In the figures, the actual proportions have not been respected, for the sake of clarity.

There is illustrated in Figure 2 a dynamic welding effector 10 according to the invention. The effector 10 is provided for carrying out the welding, in this example of two parts P, superimposed at least partially on each other, without adding material. Parts P, numbered PI and P2, are made of composite material comprising a semi-crystalline thermoplastic polymer matrix, in this example PEKK, and a fibrous reinforcement, in this example carbon fibers. The effector 10 is able to move relative to the parts according to a direction of movement illustrated by the arrow 13 in order to form a final part Pf, formed by the welding of the parts PI and P2.

The effector 10 is positioned on the side of an outer surface S of at least one of the parts P, in this example the outer surface of the part P1.

As visible, the effector 10 comprises a welding device 11, in this example comprises an induction heating system. The welding device 11 makes it possible, in this example, to heat the parts P, or at least one of them, in particular the part P1, in a zone 12 passing under the welding device 11 to a temperature greater than or equal to at the melting temperature Tm of said thermoplastic polymer matrix and thus perform the welding between the two parts P1 and P2 at the interface between them without adding material.

The effector 10 also comprises a post-heating device 15 configured to heat said zone 12 of the parts P, when it passes under the post-heating device 15, to provide heat to the zone 12 without the temperature T of this does not exceed the crystallization onset temperature Te of said thermoplastic polymer matrix. The fact of heating the zone 12 again after heating and welding makes it possible to slow down the cooling rate of the parts P compared to the speed of cooling in the open air, which is faster.

The post-heating device 15 is, in this example, placed at a distance di of approximately 15 mm from said at least one welding device within the effector.

In this example, the effector 10 also comprises two pressing devices 20 placed upstream (pressing device 20a) and downstream (pressing device 20b) of the welding device 11 relative to the direction of movement 13, allowing the application of a pressure on zone 12 heated. Zone 12 is the zone of the parts P which passes under the various components of the effector 10 at a given moment, during the movement of the effector. Zone 12 comprises at least part of the weld interface between the parts, which corresponds to the contact zone between the parts which is to be welded. It passes first under the welding device 11, then, in this example, under the pressing device 20b, then under the post-heating device 15. All the zones to be welded of the parts P thus pass under the effector 10 .

To use an effector 10 as described previously, the steps illustrated in FIG. 3 can be implemented.

In a first step 30, the parts P1 and P2 of composite material are superimposed at least partially.

In a second step 31, the effector 10 is positioned on the side of the outer surface S of the part P1.

In a third step 32, the effector 10 is set in motion in a direction of movement 13, such that the post-heating device 15 is downstream of the welding device 11.

In a step 33, the effector 10 being still in motion, the welding device 11 heats, by an induction phenomenon, the zone 12 of the parts P passing under the welding device 11.

In a step 34, the post-heating device 15 makes it possible to heat, for example by induction, the zone 12 of the parts P which passes under the post-heating device 15, to provide heat to the zone 12 without the temperature thereof does not exceed the crystallization onset temperature Te of said thermoplastic polymer matrix of the parts P.

In this example, the pressing device 20a is brought into contact with the outer surface S of the part P1 so as to constrain the constituent material of the parts P before passing under the welding device 11.

In this example, the method also includes a step, not illustrated, consisting in exerting pressure on the outer surface S of said zone 12, implemented between steps 33 and 34 using the pressing device 20b.

In this example, during steps 32 to 34, the effector 10 moves at a speed of the order of 5 mm/s. There is shown in Figure 4 the evolution of the temperature of the zone 12 as a function of time, during the implementation of the method according to the invention with the effector 10 illustrated in Figure 2, for parts PI and P2 featuring PEKK and carbon fibers.

As visible in this figure, in a first phase A, the temperature of zone 12 increases, when it is under the welding device 11, up to a temperature T1, in this example equal to 350° C., greater than the melting point Tm of the thermoplastic polymer matrix of the parts P, in this example equal to 330°C.

In a second phase B, zone 12 cools freely at a free air cooling rate of 250°C/min.

In a third phase C, the zone 12 is heated again by the post-heating device 15. This makes it possible to maintain a temperature T of between approximately 40° C. below the crystallization temperature Ts, Ts being in this example equal at approximately 235° C., and the crystallization onset temperature Te, Te being in this example equal to approximately 250° C., and to reduce the cooling rate to a cooling rate equal to 50° C./min.

In this way, the crystallinity rate in zone 12, after the passage of the post-heating device 15, is the same as the crystallinity rate in zone 12 before the passage of the welding device 11, namely between 25 % and 30% approximately.

In this example, the welding takes place without adding any additional material to the interface between the effector 10 and the part P1 or between the parts P1 and P2.

In a fourth phase D, zone 12 cools freely in air at a rapid cooling rate of 250°C/min.

The evolution of the temperature as a function of time during the welding of two parts with the welding effector of the prior art illustrated in FIG. 1 without a post-heating device is visible in FIG. 5. As visible, the heated zone 5 cools freely in contact with the ambient air and by conduction in the parts P. The heat supplied during the heating step 6, to obtain a temperature in the parts P higher than the melting temperature Tf of the thermoplastic polymer matrix of the parts P, is very rapidly dissipated during cooling 7, for example with a cooling rate of approximately 250° C./min.

This rapid cooling of the welded area affects the quality of the final part at the weld level. Is shown in isolation in Figure 6, the post-heating device 15 can equip the effector 10 of Figure 2. The post-heating device 15 comprises a system 39 of induction heating.

In this example, the post-heating device 15 comprises two pyrometers 40 making it possible to measure the temperature of the outer surface S of at least one of the parts P upstream and downstream of the post-heating device 15 with respect to the direction displacement 13. The pyrometers 40 measure, in this example, the temperature of the outer surface S of at least one of the parts P continuously.

The heating power of the heating system 39 of the post-heating device 15 is controlled to maintain the outer surface S of at least one of the parts P passing under the post-heating device 15 within a range of predetermined temperature values. , in this example between 230° C. and 260° C., and for a predetermined time, in this example 30 s.

In this example, the control is achieved by comparing a predetermined target temperature, in this example 250°C, and the temperatures measured by the pyrometers.

In this example, the post-heating device 15 can operate between a minimum heating power, or even zero, a maximum heating power and at least one intermediate heating power comprised between the minimum and maximum power.

The operation of the post-heating device can be adapted according to the composite material of the parts PI and P2, in particular by adapting the heating power of the heating system 39 and/or by modifying the parameters of the servo-control, in particular the target temperature .

The invention is not limited to the examples which have just been described.

The post-heating device 15 can equip other types of dynamic welding effector with at least two parts P made of composite material comprising a thermoplastic polymer matrix without departing from the scope of the invention.

The parts can be moved if the effector is fixed or mobile relative to them.

The post-heating device 15 may comprise another type of heating system, in particular an infrared heating system. The pyrometers 40 may not measure the temperature of the outer surface S of at least one of the parts P continuously. For example, the pyrometers 40 can measure the temperature of the outer surface S of at least one of the parts P at a predetermined frequency, for example a frequency of 10 Hz or 100 Hz. The post-heating device 15 can comprise another sensor, in particular another temperature sensor.

The post-heating device 15 can operate in all or nothing.

The post-heating device can be arranged before the downstream pressing device, or be part of such a pressing device, thus ensuring the two functions of post-heating and pressing.

Claims

1. Effector (10) for dynamic welding of at least two parts (P) made of composite material comprising a thermoplastic polymer matrix the effector (10) comprising: at least one welding device (11), so as to heat at least a zone (12) of at least one of the parts (P) at a temperature (Tl) greater than or equal to the melting temperature (Tf) of said thermoplastic polymer matrix in order to weld said at least two parts (P) together at said at least one zone (12), at least one post-heating device (15) configured to heat said at least one zone (12) to provide heat to said zone (12) without the temperature of this does not exceed the crystallization onset temperature (Te) of said thermoplastic polymer matrix.

2. Effector (10) according to claim 1, wherein said at least one post-heating device (15) is disposed downstream of said at least one welding device (11) relative to the direction of movement of the effector (10 ).

3. Effector (10) according to claim 1 or 2, wherein the post-heating device (15) comprises a heating system (39) by induction or by infrared radiation.

4. Effector (10) according to any one of the preceding claims, wherein the post-heating device (15) comprises at least one temperature sensor, in particular a pyrometer (40), so as to measure the temperature of the outer surface ( S) of at least one of the pieces (P).

5. Effector (10) according to any one of the preceding claims, in which the post-heating device comprises a servo system for maintaining the outer surface (S) of at least one of the parts (P) at a temperature comprised in a range of predetermined temperature values for a predetermined duration.

6. Effector (10) according to any one of the preceding claims, comprising at least one pressing device (20).

7. Effector according to any one of the preceding claims, in which said at least one welding device (11) comprises a heating system by induction, by ultrasound, by thermal conduction and/or by infrared, preferably by induction.

8. Process for dynamic welding of at least two parts (P) of composite material, comprising a thermoplastic polymer matrix, using a dynamic welding effector (10) according to any one of the preceding claims, the process comprising the following steps: i. at least partially overlapping said at least two parts (P) to be welded together, ii. positioning the effector (10) on the side of at least one outer surface (S) of at least one of said parts (P), iii. moving the effector (10) relative to the parts (P), in a direction of movement (13), such that said at least one post-heating device (15) is arranged downstream of said at least one welding device (11), iv. heating with the welding device (11) at least one zone (12) of at least one of the two parts (P) passing under the welding device (11), v. heating said at least one zone (12) with the at least one post-heating device (15) when the latter passes under the post-heating device (15), to provide heat to said zone ( 12) without its temperature exceeding the crystallization onset temperature (Te) of said thermoplastic polymer matrix of said parts (P).

9. Method according to claim 8, step v) being implemented so that said at least one post-heating device (15) maintains in said zone (12) a temperature (T) comprised in a range of predetermined temperature values, in particular between 90° C. below the crystallization temperature and the crystallization start temperature, better still between 75° C. below the crystallization temperature and the crystallization start temperature, even better between 40 °C below the crystallization temperature and the crystallization start temperature.

10. Process according to claim 8 or 9, post-heating step v) making it possible to obtain a cooling rate in said zone (12) which is less than 50° C./min.

11. Method according to any one of claims 8 to 10, in which, during steps iv) and v), the effector (10) moves at a speed of between 3 and 30 mm/s approximately, in particular equal at around 5 mm/s.

12. Method according to any one of claims 8 to 11, step v) being implemented so that the level of crystallinity in said zone (12), after the passage of said at least one post- heating (15), is substantially the same as the degree of crystallinity in said zone (12), before the passage of said at least one welding device (11).

13. Method according to any one of claims 8 to 12, comprising a step consisting in bringing at least one pressing device (20; 20a, 20b) of the effector (10) into contact with the outer surface (S) of at least one of the pieces (P).

14. Method according to the preceding claim, comprising, between steps iv) and v), simultaneously with step v) or after step v), a step consisting in exerting pressure on the outer surface (S) of said area (12) with said at least one pressing device (20b).

15. Post-heating device (15) intended to equip an effector (10) for dynamic welding of at least two parts (P) made of composite material comprising a thermoplastic polymer matrix, in particular an effector (10) as defined in any one of claims 1 to 7, configured for, after heating at least one zone (12) of the weld interface of said at least two parts (P) to a temperature (Tl) above the melting temperature ( Tf), supplying heat to said zone (12) without the temperature (T) thereof exceeding the crystallization onset temperature (Te) of said thermoplastic polymer matrix.