Static welding installation

Abstract

The invention relates to a static welding installation (1) for welding together parts (P1; P2) made of composite material, the static welding installation (1) comprising a welding tool (10) comprising a heat-conducting surface (11) configured to be in contact with a part (PI) made of composite material during a welding operation so as to heat the part (PI) by conduction, a heat source configured to heat the conducting surface (11), and a rigid frame (15) comprising a main face (16) and lateral faces (17), the rigid frame (15) being configured, during an operation of welding together a first and a second part (P1; P2) made of thermoplastic-matrix composite material, to be in contact with the first part (P1) via the main face (16) and to cover the edges (18) of the second part (P2) via the lateral faces (17).

Description

[0001] Description

[0002] Title: Static Welding Installation

[0003] technical field

[0004] The present invention relates to the field of thermoplastic matrix composite parts. In particular, the invention relates to a static welding installation for thermoplastic matrix composite parts, as well as a static welding method for thermoplastic matrix composite parts.

[0005] Previous technique

[0006] There are several solutions for welding parts made of thermoplastic polymer matrix composite material.

[0007] When welding is performed statically, i.e. when the parts and the welding tool are stationary relative to each other, the parts are generally brought into contact between two tools, at least one of the tools being configured to bring heat to the parts and allow the polymer to melt at the interface.

[0008] In some cases, heat is supplied by conduction between heated tools and the parts to be assembled.

[0009] When parts are not perfectly aligned, particularly when one part is smaller than the other, they can undergo deformation or damage during welding. Specifically, the edges of one part may warp during heating. Furthermore, a surface of one part adjacent to the contact interface may experience debonding or structural changes in the matrix arrangement, such as the crystal lattice or fibrous reinforcement. These unintended deformations and damage compromise the quality of the welded joint.

[0010] Description of the invention

[0011] The present invention addresses this need by means of, according to one of its aspects, a static welding installation for welding together parts made of thermoplastic polymer matrix composite material, comprising:

[0012] - a conduction welding tool comprising a heat-conducting surface, configured to be in contact with at least one part of thermoplastic polymer matrix composite material during a welding operation, so as to heat it by conduction, and a heat source, configured to heat the conductive surface; - at least one rigid frame comprising a main face and side faces, said at least one rigid frame being configured, during a welding operation between a first and a second part of thermoplastic polymer matrix composite material, to be in contact by the main face on the first part, and to cover, at least partially, by the side faces, the edges of the second part.

[0013] The use of the rigid frame in the present invention provides protection against deformation and damage to the first and second parts during the welding operation. In particular, by its contact of the main face with the first part, said at least one rigid frame limits the deconstruction and structural changes of the first part near the contact interface between the parts to be welded. Furthermore, the contact of said at least one rigid frame with the edges of the second part protects these edges, notably from creep.

[0014] By "edge of a piece" we mean the lateral surface or edge of a piece, which may extend obliquely from a main face.

[0015] Furthermore, depending on the materials used, said at least one rigid frame can influence the thermal fields on the parts during welding.

[0016] Said at least one rigid frame may include a frame heating device.

[0017] Said at least one rigid frame may include a frame cooling device.

[0018] In one embodiment, said at least one rigid frame includes a frame heating device and a frame cooling device. Said at least one rigid frame is thus adapted to provide variable thermal performance depending on the requirements.

[0019] This at least one rigid frame may also be made of a thermally insulating material, in particular insulating ceramic or mica. This at least one rigid frame may be formed by an insulating material encapsulated in a casing of steel, stainless steel, or a metal alloy with a low coefficient of expansion.

[0020] Said at least one rigid frame may be metallic, ceramic, or composite. The installation may include at least two rigid frames, each rigid frame comprising a main face and side faces, each rigid frame being configured so that, during a welding operation between a first and a second piece of thermoplastic matrix composite material, it is in contact by the main face on the first piece, and to cover, at least partially, by the side faces, the edges of the second piece.

[0021] The at least one rigid frame can be independent of the welding tool. In this configuration, the at least one rigid frame can be positioned, manually or automatically, on the parts to be welded before the welding tool. The at least one rigid frame can thus serve as a guide for positioning the parts relative to each other. This configuration is also advantageous when the geometry of one of the parts does not allow, by movement in a single direction, the positioning of the at least one rigid frame and the welding tool.

[0022] Alternatively, said at least one rigid frame may be attached to the welding tool.

[0023] The installation may include a chassis on which the welding tool and said at least one rigid frame are mounted.

[0024] Said at least one rigid frame can be elastically stressed in a predefined position relative to the welding tool.

[0025] In particular, at least one rigid frame may be mounted on the chassis using at least one elastically deformable connecting element. The elastically deformable connecting element may be a spring.

[0026] The installation may include an actuator, in particular a cylinder, configured to apply pressure to a portion of said at least one rigid frame opposite the main face.

[0027] The installation may include an actuator, in particular a cylinder, configured to apply pressure to a portion of the welding tool opposite the heat-conducting surface.

[0028] Preferably, the actuator, in particular the cylinder, configured to apply pressure to a portion of said at least one rigid frame opposite the main face, is also configured to apply pressure to a portion of the welding tool opposite the heat-conducting surface.

[0029] The installation may also include a support configured to receive at least one of the parts made of thermoplastic polymer matrix composite material. The invention further relates, according to another aspect, in combination with the foregoing, to a static welding method for a first and a second part made of thermoplastic polymer matrix composite material, particularly using an installation as defined above.

[0030] The process includes the following steps:

[0031] a) bring a first face of the second piece into contact with a first face of the first piece in such a way that the first face of the first piece is partially covered by the first face of the second piece;

[0032] b) position at least one rigid frame on the first piece so as to bring a main face of said at least one rigid frame into contact with the first face of the first piece and to bring lateral faces of said at least one rigid frame into contact with edges of the second piece;

[0033] c) position a heat-conducting surface of a conduction welding tool on a second face of the second piece opposite the first piece and / or on a second face of the first piece opposite the second piece;

[0034] d) heat the heat-conducting surface so as to heat the matrix of the first part and / or the matrix of the second part at least at the interface between the first part and the second part to a temperature above the melting or glass transition temperature of said matrix;

[0035] e) cool the die of the first part and / or the die of the second part so as to weld the first part and the second part together.

[0036] During step d), said at least one rigid frame can apply, by the main face, pressure on the first face of the first piece.

[0037] During step d), said at least one rigid frame may be heated so as to heat the first and / or second piece.

[0038] During step d), said at least one rigid frame can be cooled so as to cool the first and / or second part.

[0039] After step b), the shape of each side face of said at least one rigid frame can conform to the shape of the edge of the second piece with which it is in contact.

[0040] During step b), at least two rigid frames can be positioned on the first piece. After step b), each rigid frame can include a main face in contact with the first face of the first piece and side faces in contact with the edges of the second piece.

[0041] Steps b) and c) can be carried out simultaneously.

[0042] Steps b) and c) can be carried out separately.

[0043] Step a) can be carried out before step b). Alternatively, step b) can be carried out before step a).

[0044] During step d), the heat-conducting surface can apply pressure to the second face of the second piece or to the second face of the first piece.

[0045] During step d), the heating of the first part's die and / or the second part's die may include:

[0046] - an initial phase of temperature increase up to a conformation temperature strictly higher than the glass transition temperature of said matrix,

[0047] - a shaping phase in which the temperature of said matrix is ​​maintained within a range of ± 30°C around the shaping temperature, preferably within a range of ± 20°C around the shaping temperature, for a predetermined duration, the pressure applied by the heat-conducting surface on the second face of the second part or on the second face of the first part allowing the first part and / or the second part to be deformed in such a way as to compensate for any gaps between the parts,

[0048] - a welding phase in which said matrix is ​​maintained at a welding temperature strictly higher than the forming temperature, preferably for a period of between 30 seconds and 30 minutes, better between 3 min and 15 min.

[0049] The said conforming temperature is preferably at least 15°C higher, better at least 20°C higher than the glass transition temperature.

[0050] When the matrix of the first part and / or the matrix of the second part comprises a semi-crystalline polymer, the forming temperature is preferably strictly lower than the melting temperature of said matrix.

[0051] The said forming temperature is preferably at least 15°C lower, and better at least 20°C lower, than the melting temperature of said matrix. When the matrix of the first part and / or the matrix of the second part comprises a semi-crystalline polymer, the welding temperature is preferably strictly higher than the melting temperature of said matrix.

[0052] During the shaping phase, the temperature of said matrix can be substantially constant.

[0053] Alternatively, during the shaping phase, the temperature of said matrix can be variable.

[0054] According to one embodiment, during the shaping phase, the temporal variation of the temperature of said matrix may be less, in particular at least twice as less, than the temporal variation of the temperature of said matrix during the initial heating phase. In this case, the heating of said matrix can be described as slowed down.

[0055] According to one embodiment, during the shaping phase, the temperature of said matrix may include at least one period of increase and at least one period of decrease. In this case, the heating of said matrix can be described as oscillating, for example with a sinusoidal shape.

[0056] Brief description of the drawings

[0057] The invention will be better understood by reading the detailed description that follows, by examining the non-limiting examples of its implementation, and by examining the attached drawing, in which

[0058] [Fig 1] represents, in perspective, an example of an installation according to the invention, [Fig 2] is an enlargement of figure 1 according to II,

[0059] [Fig 3] represents, in perspective from below, the head of an arm of the installation in figure 1,

[0060] [Fig 4] schematically represents, in perspective, the positioning of a first part, a second part and a rigid frame according to the invention,

[0061] [Fig 5] schematically represents, from the side, a welding process according to the invention,

[0062] [Fig 6] is a view similar to Figure 4 in which a second frame is positioned, [Fig 7] represents, in perspective, a variant of the arm head of an installation according to the invention,

[0063] [Fig 8] illustrates, in perspective, schematically, the positioning of a first part, a second part, and variants of frames according to the invention, and

[0064] [Fig 9] is a graph illustrating the evolution of the temperature of the heated matrix during the implementation of the process according to the invention.

[0065] Detailed description

[0066] In the following description, identical elements or elements with identical functions are designated by the same reference numeral. For the sake of brevity, they are not described alongside each figure; only the differences between the embodiments are described.

[0067] In the figures, the actual proportions have not always been respected, for the sake of clarity.

[0068] Figures 1 to 5 illustrate an example of a static welding installation 1 for welding together parts made of thermoplastic polymer matrix composite material, in this example a first part PI, which can be a skin, and a second part P2, which can be a stiffener having a base S, which rests on the first part PI, and an apron T extending substantially perpendicularly to the base S.

[0069] Installation 1 comprises a table 2 supporting a gantry 3. A support 4 is mounted on the lower part of the gantry 3. The support 4 accommodates the first part PI and the second part P2. In this example, the support 4 conforms to the shape of the first part PL.

[0070] Installation 1 also includes several arms 5, each comprising a head 6, which forms a chassis, movable between an extended position and a retracted position.

[0071] As illustrated in Figures 2 and 3, each head 6 carries a conduction heating device 10 which includes a heat-conducting surface 11, configured to be in contact with at least one of the parts PI and P2 during a welding operation so as to heat it by conduction, as will be described later.

[0072] The heat-conducting surface 11 can be made of metal, in particular steel, a copper alloy, an Fe-Ni36% alloy or stainless steel. The heating device 10 also includes a heat source for heating the heat-conducting surface 11, for example a resistive heating system, an induction heating system for the heat-conducting surface 11 or a thermofluid heating system.

[0073] The conductive surface li has for example a shape configured to fit the shape of a second face 32 of the sole S of the second part P2 which will be in contact with the conductive surface 11.

[0074] Each head 6 also carries a rigid frame 15 comprising a main face 16 and side faces 17, in this example three side faces 17. As will be detailed later, the rigid frame 15 is configured so that, during a welding operation between parts PI and P2, it is in contact by the main face 15 on the first part PI, and to cover, at least partially, by the side faces 17 the edges 18 of the second part P2.

[0075] In this example, the rigid frame 15 is metallic and has a thickness el substantially equal to the thickness e of the base S of the second part P2. In this way, the edges 18 of the second part P2 in contact with the lateral faces 17 during the welding operation are covered over substantially their entire thickness.

[0076] The rigid frame 15 includes, for example, two openings 22 to allow its attachment to the head 6 by screwing.

[0077] As illustrated in Figure 3 in particular, a shoulder 23 is formed at the junction between the conductive surface 11 and the main face 16 so that the conductive surface 11 is not in continuity with the main face 16. This allows, during welding, the partial encapsulation of the sole S between the heat-conducting surface 11 and the rigid frame 15.

[0078] Each arm 5 may also include a jack 20 for applying pressure to an upper portion 21 of the rigid frame 15 opposite the main face 16 and to an upper portion 50 of the heating device 10 opposite the conductive surface 11.

[0079] The rigid frame 15 may include a frame heating device 25 and / or frame cooling device 26, depending on the thermal requirements required or desired during the welding operation. To weld the parts PI and P2 together using the installation 1, a first step consists of positioning the first part PI on the support 4 and then bringing into contact a first face 30 of the second part P2 with a first face 31 of the first part PI so that the first face 31 of the first part PI is partially covered by the first face 30 of the second part P2.

[0080] Next, in a second step illustrated in Figure 5, the cylinder 20 of each arm 5 is actuated so as to move the head 6 to position the rigid frame 15 on the first part PI, in order to bring the main face 16 into contact with the first face 31 of the first part PI and to bring the side faces 17 into contact with the edges 18 of the second part P2.

[0081] Since the conductive surface 11 and the rigid frame 15 are integral with the head 6, the conductive surface 11 is simultaneously positioned on the second face 32 of the second piece P2 opposite the first piece PI.

[0082] By the action of the jack 20, the conductive surface 11 and the rigid frame 15 are then pressed respectively onto the second face 32 of the second part P2 and the first face 31 of the first part P1.

[0083] Once in place, the shape of each lateral face 17 conforms to the shape of the edge 18 of the second piece P2 with which it is in contact.

[0084] The conductive surface 11 is then heated so as to bring the matrix of the first part PI and / or the matrix of the second part P2, at least at the level of the interface 33 between the first part PI and the second part P2, to a temperature higher than the melting or glass transition temperature of said matrix.

[0085] More specifically, as illustrated in the curve in Figure 9, the heating is carried out in several phases.

[0086] In an initial phase Phi, the temperature of the heated matrix is ​​increased to a conformation temperature Te strictly higher than the glass transition temperature Tg of said matrix. Assuming that the matrix of the first part PI and / or the matrix of the second part P2 comprises a semi-crystalline polymer, the conformation temperature Te is strictly lower than the melting temperature Tf of said matrix.

[0087] Once the forming temperature Te is reached, in a forming phase Ph2, the temperature of the mold is maintained at the forming temperature Tc for a predetermined duration t. At this temperature, the elasticity of the first part PI and / or the second part P2 is significantly increased. In other words, the first part PI and / or the second part P2 is more flexible. Thus, during this phase Ph2, the pressure applied by the heat-conducting surface 11 on the second face 32 of the second part P2 or on the second face of the first part PI, thanks to the increased elasticity of the first part PI and / or the second part P2, deforms the first part PI and / or the second part P2 to compensate for any gaps between the parts. This holding period at the forming temperature ensures proper alignment between the first part PI and the second part P2 before they are welded.

[0088] This plateau at the forming temperature Tc also allows for the relaxation of a large portion of the stresses related to deformation. This results in a relaxed plastic deformation of parts PI and P2 in their formed state.

[0089] The pressure applied by the heat-conducting surface 11 on the second face 32 of the second part P2 or on the second face of the first part PI is preferably between 0.5 bar and 15 bar, in particular between 1 bar and 3 bar.

[0090] After this plateau, in a new phase Ph3, the temperature of the heated matrix is ​​increased to a welding temperature strictly above the melting temperature Tf.

[0091] The temperature is then maintained in a steady state, in a Ph4 welding phase, in order to carry out the welding between parts PI and P2.

[0092] The rigid frame 15, during heating, can limit the creep of the thermoplastic polymer matrix of the second part P2 at the edges 18 covered by the lateral faces 17 of the rigid frame 15, limit the deconsolidation or deformation of the first part PI around the interface 33 and / or guide or maintain the second part P2 in a desired position relative to the first part PL. Depending on the requirements, the rigid frame 15 can be cooled or heated using the frame cooling device 26 or the frame heating device 25, depending on the desired temperature gradient around the interface 33.

[0093] Furthermore, support 4 can also be heated if necessary.

[0094] Alternatively, only the support 4 is heated using a heat-conducting surface during welding, so as to heat the matrix of the first part PI and the matrix of the second part P2 at least at the interface 33 between the first part PI and the second part P2 to a temperature above the melting or glass transition temperature of said matrix. In this case, the head 6 may lack a conductive surface 11.

[0095] After a predetermined time, the die of the first part PI and the die of the second part P2 are cooled in phases Ph5, Ph6, and Ph7, at least at the interface 33, so as to weld the first part PI and the second part P2 together. The arm 5 can then move the head 6 to release the assembly of the first part PI and the second part P2.

[0096] The cooling rate can be slightly slowed, in a Ph5 phase, to a temperature between the melting temperature Tf and the glass transition temperature Tg in order to promote the crystallization of the polymer matrix.

[0097] In one variant, the cooling rate can be substantially zero, in the Ph5 phase, at a temperature between the melting temperature Tf and the glass transition temperature Tg in order to promote the crystallization of the polymer matrix.

[0098] In a variant illustrated in figure 6, at least one of the heads 6 includes a second rigid frame 15b so as to completely frame the sole S of the second piece P2.

[0099] This second rigid frame 15b can have a thickness e2 similar to the thickness el of the rigid frame 15. The second frame 15b can also include openings 22 to allow its attachment to the head 6 by screwing.

[0100] In the embodiments described above, the rigid frame(s) 15 are securely mounted on the head 6. However, it may be otherwise.

[0101] For example, in an embodiment illustrated in Figure 7, the rigid frame 15 is mounted on the head 6 by means of springs 40 so that the rigid frame 15 is elastically returned to a predefined position relative to the welding tool 10 during welding. This can compensate for any play between the rigid frame 15 and parts P1 and P2 during the welding operation.

[0102] In another variant, illustrated in the view of figure 8, the second part P2 has, in cross section, an S shape, and the base S has at least one recess 4L. This particular shape does not allow the rigid frame 15 to be positioned by a linear movement from bottom to top as previously described.

[0103] In this variant, two rigid frames 15 are used and are not attached to the welding tool 10. The rigid frames 15 are, for example, during the welding process, positioned manually or with the help of an actuator different from that used for moving the welding tool 10.

[0104] In this example, the thickness e3 of the frames 15 is significantly greater than the thickness e of the edges 18. This allows the use of a thick shim to fill gaps between the parts to be welded while protecting the edges 18 from creep. In this case, the shim covers the base S.

[0105] The frame 15 also allows the welding tool 10 to be guided towards the base S of the second part P2.

[0106] Furthermore, one of the rigid frames 15 includes a side face 17 with a concave portion in a lower part 42, to best fit the shape of one of the edges 18 having a rounded corner 43.

[0107] In this variant, during the welding operation, the rigid frames 15 can simply be placed on the first piece PI, without applying additional pressure to the rigid frames 15.

[0108] The invention is not limited to the examples just described.

[0109] In particular, installation 1 does not necessarily include an arm 5. It may include any means such as a chassis, mobile or not, allowing the attachment of the rigid frame 15 and / or the welding tool 10.

Claims

Demands 1. Static welding installation (1) for welding together parts (PI; P2) made of thermoplastic polymer matrix composite material, comprising: - a conduction welding tool (10) comprising a heat-conducting surface (11), configured to be in contact with at least one part (P1; P2) of thermoplastic polymer matrix composite material during a welding operation, so as to heat it by conduction, and a heat source, configured to heat the conductive surface (11); - a rigid frame (15) comprising a main face (16) and lateral faces (17), the rigid frame (15) being configured so that, during a welding operation between a first and a second piece (P1; P2) made of thermoplastic polymer matrix composite material, it is in contact by the main face (16) on the first piece (P1), and to cover, at least partially, by the lateral faces (17) the edges (18) of the second piece (P2).

2. Installation (1) according to claim 1, wherein said at least one rigid frame (15) includes a frame heating device (25).

3. Installation (1) according to claim 1 or 2, wherein said at least one rigid frame (15) includes a frame cooling device (26).

4. Installation (1) according to any one of the preceding claims, wherein said at least one rigid frame (15) is integral with the welding tool (10).

5. Installation (1) according to the preceding claim, said at least one rigid frame (15) being elastically stressed in a predefined position relative to the welding tool (10).

6. Installation (1) according to any one of the preceding claims, comprising an actuator (20), in particular a cylinder, configured to apply pressure to a portion (21) of said at least one rigid frame (15) opposite the main face (16).

7. Installation (1) according to any one of the preceding claims, wherein said at least one frame is metallic, ceramic, or composite.

8. A method for statically welding a first and a second part (PI; P2) made of thermoplastic polymer matrix composite material, in particular using an installation (1) according to any one of the preceding claims, the method comprising the following steps: a) bringing a first face (30) of the second part (P2) into contact with a first face (31) of the first part (PI) so that the first face (31) of the first part (PI) is partially covered by the first face (30) of the second part (P2); b) positioning at least one rigid frame (15) on the first part (PI) so as to bring a main face (16) of said at least one rigid frame (15) into contact with the first face (31) of the first part (PI) and to bring lateral faces (17) of said at least one rigid frame (15) into contact with edges (18) of the second part (P2); (c) position a heat-conducting surface (11) of a conduction welding tool (10) on a second face (32) of the second part (PI) opposite the first part (PI) and / or on a second face of the first part (PI) opposite the second part (P2); (d) heat the heat-conducting surface (11) so as to heat the matrix of the first part (PI) and / or the matrix of the second part (P2) at least at the interface between the first part (PI) and the second part (P2) to a temperature above the melting or glass transition temperature of said matrix; e) cool the matrix of the first part (PI) and / or the matrix of the second part (P2) so as to weld together the first part (PI) and the second part (P2).

9. Method according to the preceding claim, wherein, during step d), said at least one rigid frame (15) applies, by the main face (16), pressure on the first face (31) of the first part (PI).

10. A method according to any one of claims 8 and 9, wherein, during step d), said at least one rigid frame (15) is heated so as to heat the first and / or second piece (P1; P2).

11. A method according to any one of claims 8 and 9, wherein, during step d), said at least one rigid frame (15) is cooled so as to cool the first and / or second part (P1; P2).

12. A method according to any one of claims 8 to 11, wherein, after step b), the shape of each side face (17) of said at least one rigid frame (15) conforms to the shape of the edge (18) of the second piece (P2) with which it is in contact.

13. A method according to any one of claims 8 to 12, wherein, during step b), at least two rigid frames (15) are positioned on the first part (PI), and wherein, after step b) each rigid frame (15) comprises a main face (16) in contact with the first face (31) of the first part (PI) and lateral faces (17) in contact with edges (18) of the second part (P2).

14. A method according to any one of claims 8 to 13, wherein steps b) and c) are carried out simultaneously.

15. A method according to any one of claims 8 to 13, wherein steps b) and c) are carried out separately.

16. A method according to any one of claims 8 to 15, wherein, during step d), the heat-conducting surface (11) applies pressure to the second face (32) of the second part (PI) or to the second face of the first part (PI).

17. A method according to the preceding claim, wherein, during step d), the heating of the die of the first part (PI) and / or the die of the second part (P2) comprises: - an initial phase of temperature increase up to a conformation temperature strictly higher than the glass transition temperature of said matrix, - a shaping phase in which the temperature of said matrix is ​​maintained within a range of ± 30°C around the shaping temperature, preferably within a range of ± 20°C around the shaping temperature, for a predetermined duration, the pressure applied by the heat-conducting surface (11) on the second face (32) of the second part (PI) or on the second face of the first part (PI) allowing the first part (PI) and / or the second part (P2) to be deformed in such a way as to compensate for any gaps between the parts, - a welding phase in which said matrix is ​​maintained at a welding temperature strictly higher than the forming temperature.

18. A method according to the preceding claim, wherein the matrix of the first part (PI) and / or the matrix of the second part (P2) comprises a semi-crystalline polymer, the forming temperature being strictly lower than the melting temperature of said matrix, the welding temperature being strictly higher than the melting temperature of said matrix.

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