METHOD FOR PRODUCING A PART OF EQUIPMENT OF A MOTOR VEHICLE AND CORRESPONDING PART OF EQUIPMENT

Description

[0001] The present invention relates to a method for manufacturing a piece of motor vehicle equipment, comprising the following steps: forming a stack comprising: a first and a second base sheet; and a spacer arranged between said first and second base sheets; at least the first base sheet comprising first ceramic fibers and at least one first hot-melt polymer; said first base sheet preferably having a surface mass of between 600 g / m 2 and 1000 g / m 2 ; heating and compressing the stack so as to melt the first hot-melt polymer.

[0002] It is known to produce automotive vehicle equipment parts, such as trunk shelves, from a composite material consisting of structural ceramic fibers, generally glass, and a thermoplastic matrix.

[0003] This composite material is obtained by thermoforming, that is to say by heating and then compressing, a textile sheet made up of an intimate mixture of structural fibers and fibers based on a thermoplastic polymer. Such a textile sheet is, for example, marketed under the name Sommold.

[0004] After heating, the thermoplastic fibers fuse, resulting in a pre-formed composite element; which element is transported to a forming mold. The mold is closed, allowing the polymer to cool, which will form the matrix of the composite.

[0005] In order to reduce the weight of the piece of equipment, it is known to stack two textile sheets on either side of a spacer made of lightweight material, such as a cardboard honeycomb. Such a piece of equipment and its manufacturing method are known in particular from document WO2013 / 131917.

[0006] However, when the textile sheet is in direct contact with the spacer, a sagging of said textile sheet occurs at the level of the cells of the honeycomb during compression. This phenomenon, called scalloping, prevents the textile sheet from being compressed sufficiently to provide sufficient mechanical strength to the piece of equipment.

[0007] It is also known, in particular from document FR3014731, to produce motor vehicle equipment parts comprising long fibers, for example made of glass. However, these fibers are not very mobile relative to each other, which causes the edges of the part to be crushed, resulting in an unsatisfactory appearance. US2020230897A1 describes a method for manufacturing a motor vehicle equipment part. The method comprises forming a stack comprising a first and a second base sheet and a spacer arranged between said first and second base sheets. The first base sheet comprises ceramic fibers. In addition, the first base sheet comprises a first hot-melt polymer.

[0008] Furthermore, the adhesion between the composite skins and the spacer is frequently insufficient.

[0009] The present invention aims to propose a piece of equipment which overcomes the above problems, at a moderate production cost.

[0010] To this end, the invention relates to a method for manufacturing a piece of motor vehicle equipment as defined in claim 1.

[0011] According to other advantageous aspects of the invention, the manufacturing method comprises one or more of the following characteristics, taken individually or in all technically possible combinations: the second unidirectional fibers are chosen from ceramic fibers, such as glass fibers, and natural fibers such as flax fibers; the second base sheet comprises third ceramic fibers and at least one third hot-melt polymer; said second base sheet preferably having a surface mass of between 600 g / m 2 and 1000 g / m 2; the stack further comprises a second reinforcing sheet, arranged between the second base sheet and the spacer, said second reinforcing sheet comprising fourth unidirectional fibers substantially parallel to each other and at least one fourth hot-melt polymer; said second reinforcing sheet preferably having a surface mass of between 200 g / m 2 and 500 g / m 2;the stack further comprises at least a first layer of non-woven material arranged between the first reinforcing ply and the spacer, said first layer being formed at least from a fifth hot-melt polymer; the fifth hot-melt polymer has a high melt flow index, preferably greater than 25 g / 10 min, more preferably between 25 and 35 g / 10 min; the step of heating and compressing the stack comprises the following two sub-steps: heating and first compression of the stack against a support, so as to melt at least the first hot-melt polymer and to cause said molten polymer to adhere to the first ceramic fibers to result in a pre-formed composite element; then second compression, in a mold, of the pre-formed composite element. ;

[0012] The invention further relates to a piece of motor vehicle equipment resulting from a manufacturing method as described above, comprising a first and a second composite body; and a spacer sandwiched between the first and second composite bodies; said first composite body comprising: a first main composite layer; and a first reinforcing composite layer, arranged between the main composite layer and the spacer; the first main composite layer comprising a plurality of first ceramic fibers and the first reinforcing composite layer comprising a plurality of second unidirectional fibers.

[0013] According to one embodiment of the invention, each of the first and second hot-melt polymers is a thermoplastic polymer, preferably a polypropylene.

[0014] According to one embodiment of the invention, the third hot-melt polymer is preferably a thermoplastic polymer, more preferably a polypropylene.

[0015] The invention will be better understood on reading the description which follows, given solely as a non-limiting example and made with reference to the drawings in which: [ Fig 1 ] there figure 1 is a detailed view, in section, of a piece of equipment according to one embodiment of the invention; [ Fig 2 ] there figure 2 is a schematic view of a first stage of manufacturing of the piece of equipment of the figure 1 ; And [ Fig 3 ] there figure 3 is a schematic view of a second stage of manufacturing of the piece of equipment of the figure 1 .

[0016] There figure 1 represents a part 10 of motor vehicle equipment according to one embodiment of the invention. The part 10 is advantageously a structural part of the motor vehicle, for example a shelf, such as a rear trunk masking shelf, a false passenger compartment or trunk floor, or a sub-engine.

[0017] The part 10 comprises a first composite body 12, a second composite body 16 and a spacer 18, sandwiched between the first 12 and second 16 composite bodies. Preferably, the part 10 further comprises at least a first facing layer 19 applied to one of the composite bodies 12, 16. In the embodiment shown, the part 10 comprises a first 19 and a second 20 facing layer, respectively applied to the first 12 and to the second 16 composite bodies. Said facing layers 19, 20 form an outer surface of the part 10.

[0018] The previously mentioned elements are superimposed according to an X stacking direction.

[0019] In the embodiment shown, the first 12 and second 16 composite bodies are substantially identical and will be described simultaneously below.

[0020] The composite body 12, 16 comprises: a main composite layer 22; and a reinforcing composite layer 24, disposed between the main composite layer 22 and the spacer 18. Preferably, as in the embodiment shown, the composite body 12, 16 further comprises an adhesive layer 26, disposed between the reinforcing composite layer 24 and the spacer 18.

[0021] The main composite layer 22 comprises a plurality of first ceramic fibers 32 and a first matrix 34 binding the first fibers 32 together.

[0022] The first fibers 32 are preferably glass fibers. Said first fibers 32 are short fibers, having an average length of less than 150 mm. The first fibers 32 have, for example, a diameter of less than 50 micrometers.

[0023] The first matrix 34 comprises at least one first hot-melt polymer 36. Advantageously, said first hot-melt polymer 36 is a thermoplastic polymer, preferably a polypropylene.

[0024] The mass proportion of first matrix 34 in the main composite layer 22 is between 30% and 70% relative to the total mass of said composite layer 22. Similarly, the mass proportion of first fibers 32 in the main composite layer 22 is between 30% and 70% relative to the total mass of said composite layer 22. Preferably, each of the mass proportions of first fibers 32 and first matrix 34 is approximately 50%.

[0025] The composite reinforcing layer 24 comprises a plurality of second unidirectional fibers 40 and a second matrix 42 binding the second fibers 40 together.

[0026] The second fibers 40 are preferably chosen from ceramic fibers, such as glass fibers or filaments, and natural fibers such as linen fibers.

[0027] Said second fibers 40 are long fibers, having an average length greater than the average length of the first ceramic fibers 32. Said second fibers 40 have, for example, an average length greater than 80 cm when they are natural fibers. In the case of glass filaments, their length corresponds, for example, to a width of the part 10.

[0028] The second fibers 40 have, for example, a diameter of 20 micrometers.

[0029] The second unidirectional fibers 40 are substantially parallel to each other and arranged in a direction Y substantially perpendicular to the stacking direction X.

[0030] In the embodiment shown, the direction Y of the second fibers 40 is identical for the first 12 and second 16 composite bodies. Alternatively, the directions of the second fibers 40 of the first 12 and second 16 composite bodies form a non-zero angle in a plane perpendicular to X.

[0031] The second matrix 42 comprises at least one second thermofusible polymer 44. Advantageously, said second polymer 44 is a thermoplastic polymer, preferably a polypropylene. Preferably, the first 36 and second 44 polymers are identical.

[0032] The mass proportion of second matrix 42 in the composite reinforcement layer 24 is between 50% and 70% relative to the total mass of said composite layer 24. Similarly, the mass proportion of the second fibers 40 in the composite reinforcement layer 24 is between 50% and 70% relative to the total mass of said composite layer 24.

[0033] The adhesive layer 26 is formed from at least one third hot-melt polymer 46. Advantageously, said third polymer 46 is a thermoplastic polymer, preferably a polypropylene.

[0034] Preferably, the third hot-melt polymer 46 has a high melt flow index. The melt flow index (MFI), or melt flow index, or in English melt flow index or MFI, characterizes the ability of a polymer to flow under certain temperature and pressure conditions. In particular, the MFI is inversely related to the molar mass of the polymer.

[0035] Preferably, the IFC of the third hot-melt polymer 46 is greater than the IFCs of the first 36 and second 44 polymers. Preferably, the IFC of the third hot-melt polymer 46 is greater than 25 g / 10 min, more preferably between 25 and 35 g / 10 min. Such values ​​of the IFC of the third hot-melt polymer 46 correspond in particular to a temperature of 220°C with a nominal load of 0.325 kg, in accordance with ISO 1133:2005 Method A.

[0036] Advantageously, as will be specified later, the third thermofusible polymer 46 of the adhesive layer 26 is partially impregnated in the spacer 18.

[0037] As an alternative to the above description, the main composite layers 22 of the first 12 and second 16 composite bodies comprise first fibers 32 and / or different first polymers 36; and / or the reinforcing composite layers 24 of the first 12 and second 16 composite bodies comprise second fibers 40 and / or different second polymers 44; and / or the adhesive layers 26 of the first 12 and second 16 composite bodies comprise different third polymers 46.

[0038] The spacer 18 is arranged between the first 12 and second 16 composite bodies. In the example shown, the spacer is in contact with each adhesive layer 26. In a variant not shown, the spacer is in contact with at least one composite reinforcement layer 24.

[0039] The spacer 18 is advantageously formed from a lightweight material, such as paper or cardboard.

[0040] Preferably, the spacer 18 has a honeycomb or alveolar structure. In the embodiment shown, the spacer 18 has a plurality of walls 50 substantially parallel to the stacking direction X. The walls 50 delimit central spaces 52 of closed contour, forming cells.

[0041] The facing layer 19, 20 preferably comprises a layer 54 of non-woven textile, in contact with the main composite layer 22. Said layer 54 is for example made of polyethylene terephthalate (PET) and preferably forms the outer surface of the part 10.

[0042] There figure 2 shows a first step of a manufacturing process of the piece of equipment 10. The figure 2 shows in particular a stack 60 comprising: a first 62 and a second 64 base plies; a spacer 18; a first 66 and a second 68 reinforcing plies; and a first 70 and a second 72 facing plies. Said elements are stacked in the stacking direction X, as will be specified below.

[0043] In the embodiment shown, the stack 60 further comprises a first 74 and a second 76 adhesion sheets.

[0044] Each base sheet 62, 64 comprises a mixture of first ceramic fibers 32 previously described and fibers 78 of thermofusible polymer.

[0045] The fibers 78 comprise at least the first hot-melt polymer 36 previously described. According to one embodiment, all of the fibers 78 are made of the same first hot-melt polymer 36. Alternatively, the fibers 78 include fibers formed from another hot-melt polymer.

[0046] According to one embodiment, the fibers 78 comprise recycled first polymer 36, in particular recycled polypropylene, which reduces the manufacturing cost of the part 10.

[0047] The mass proportion of the first ceramic fibers 32 in the base sheet 62, 64 is between 30% and 70%, and preferably close to 50%, relative to the total mass of said base sheet.

[0048] Each base sheet 62, 64 preferably has a surface mass of between 600 g / m 2 and 1000 g / m 2.

[0049] Each base sheet 62, 64 preferably has a thickness in the X direction of between 6 and 10 mm.

[0050] In a known manner, the base sheet 62, 64 is for example produced using an air dispersion process, or by carding / lapping. The production of said base sheet preferably includes a step of reinforcement by needling.

[0051] Suitable base cloths 62, 64 are, for example, cloths marketed under the name Sommold.

[0052] The spacer 18, described above in the context of part 10, is arranged between the first 62 and second 64 base layers in the stack 60.

[0053] Each of the first 66 and second 68 reinforcing plies is arranged, in the stack 60, between the spacer 18 and respectively the first 62 and the second 64 base plies.

[0054] Each reinforcing sheet 66, 68 comprises second unidirectional fibers 40, arranged substantially parallel to each other, said second fibers 40 being linked by a matrix comprising the second thermoplastic polymer 44, preferably polypropylene.

[0055] Each reinforcing ply 66, 68 preferably has a surface mass of between 200 g / m 2 and 500 g / m 2.

[0056] Each of the first 70 and second 72 facing plies is arranged opposite the spacer 18, relative to the first 62 and second 64 base plies respectively. Each of said facing plies is formed from a porous material, for example a textile of the Dilour ® or jersey type, or even a PET non-woven fabric.

[0057] Each of the first 74 and second 76 adhesion plies is arranged between the spacer 18 and respectively the first 66 and the second 68 reinforcement plies. Each of said adhesion plies 74, 76 is for example formed from a non-woven fabric comprising the third thermofusible polymer 46 described above.

[0058] There figure 2 further shows a pre-forming unit 80. Said pre-forming unit comprises a first 82 and a second 84 heating platen. Said plates are movable relative to each other in the stacking direction X, considering that the stack 60 is arranged on the first heating platen 82. The heating plates 82, 84 are capable of exerting hot compression on the stack 60, so as to lead to a pre-formed composite element 86 ( figure 3 ) as will be described below.

[0059] There figure 3 shows a second step in the manufacturing process of the piece of equipment 10.

[0060] There figure 3 shows in particular a molding unit 90, comprising a mold 92 and a counter-mold 94, movable relative to each other and capable of delimiting between them a molding cavity 96. Said molding cavity 96 has the desired shape for the part 10.

[0061] Optionally, the molding unit 90 further comprises means for regulating the temperature of the mold 92 and the counter-mold 94.

[0062] A method of manufacturing the piece of equipment 10 will now be described.

[0063] The stack 60 is first produced by stacking as described above the base plies 62, 64; the reinforcing plies 66, 68; the spacer 18; the facing plies 70, 72; and the adhesion plies 74, 76. Said elements are previously cut according to the desired contours for the piece of equipment 10.

[0064] Preferably, each layer of the stack 60 has a preferred direction of mechanical strength. For the reinforcing plies 66, 68, this is the Y direction of the second unidirectional fibers 40. A preferred mechanical direction of the base plies 62, 64 corresponds for example to the orientation of the first fibers 32 during a step of manufacturing said base plies by carding / lapping. The spacer 18 preferably has a preferred mechanical direction due to its manufacturing method, namely the direction perpendicular to its stretching.

[0065] Therefore, depending on the specifications, it is possible to combine these different orientations so as to either reinforce the final part 10 in a single preferred direction, or on the contrary to “average” the overall mechanical behavior of said part 10 by distributing the different preferred directions of mechanical resistance in space.

[0066] The stack 60 thus formed is then placed in the pre-forming unit 80, in particular on the first plate 82 at room temperature.

[0067] The first 82 and second 84 trays are then heated and brought together, so as to hot compress the stack 60.

[0068] In particular, the stack 60 is heated to a temperature above the melting temperature of the first hot-melt polymer 36. This temperature is for example above 180°C, and in particular approximately 220°C.

[0069] Preferably, the heating is carried out for a duration greater than 30 seconds, and in particular between 60 seconds and 150 seconds, depending on the thickness of the spacer 18.

[0070] Thus, the fibers 78 of the base sheets 62, 64 melt, to form a fluid resin of first thermofusible polymer 36, in which the first ceramic fibers 32 are embedded.

[0071] Likewise, the second hot-melt polymer 44 of the reinforcing plies 66, 68 and the third hot-melt polymer 46 of the adhesion plies 74, 76 melt at least partially. In particular, said adhesion plies 74, 76 match the shape of the cells 52 of the spacer 18 (scalloping phenomenon), which allows good impregnation of the walls 50 of said cells by the third polymer 46.

[0072] In parallel, the first 82 and second 84 plates exert compression on the stack 60, the pressure exerted being for example of the order of 6 bars. Such compression leads in particular to a reduction in the thickness of the base layers 62, 64.

[0073] Due to the length of the second unidirectional fibers 40, each reinforcing ply 66, 68 provides a flat contact surface, respectively to the first 62 and to the second 64 base ply. Each base ply 62, 64 is in particular isolated from the spacer 18, which eliminates the scalloping phenomena of the base plies. In other words, the presence of the reinforcing ply 66, 68 serves as a flat reference for better compression of the base ply 62, 64 leading to a better composite effect.

[0074] Thus, the main composite layers 22 can be sufficiently compressed during the hot compression step. In addition, the first fibers 32 are oriented in a plane perpendicular to the X direction, for better mechanical strength of the part 10.

[0075] In parallel, during the compression of the stack 60, the fluid resin of the first thermofusible polymer 36 partially impregnates each of the first 70 and second 72 facing layers.

[0076] This first hot compression step thus makes it possible to connect all the layers of the stack 60, leading to a pre-formed composite element 86. The term “pre-formed” is used because the or certain polymers, still in the fluid state, do not yet constitute the matrix of a composite body.

[0077] After this first hot compression step, the first 82 and second 84 plates are separated from each other. The pre-formed composite element 86 obtained can be handled, because the facing plies 70, 72 form an external surface of said pre-formed composite element, confining the fluid polymers in a closed space. Said pre-formed composite element 86 can thus be extracted from the pre-forming unit 80.

[0078] In a next step of the manufacturing process of the piece of equipment 10, the pre-formed composite element 86 is placed in the molding cavity 96 of the molding unit 90 of the figure 3 .

[0079] The mold 92 and the counter-mold 94 are then brought together so as to compress said pre-formed composite element 86.

[0080] During compression, the molding cavity 96 conforms said pre-formed composite element 86 to the desired shape of the part 10.

[0081] The short length of the first fibers 32 gives excellent deformability to the base plies 62, 64. This deformability, as well as the thickness of said base plies 62, 64, allows said plies to effectively drape the edges of the spacer 18 without crushing said edges, to form a clean outline to the part 10.

[0082] According to one embodiment, the temperature of the mold 92 and the counter-mold 94 is controlled during this second compression step to remain close to approximately 15°C.

[0083] The mold 92 and the counter-mold 94 are held close to each other until the first 36, second 44 and third 46 polymers have cooled and hardened. The mold 92 and the counter-mold 94 are then moved apart from each other, revealing the part 10 previously described.

[0084] In addition to the advantages described above during the compression step, the presence of the composite reinforcement layers 24 provides better mechanical resistance to the part 10.

[0085] The possible presence of the adhesive layers 26 makes it possible to improve the adhesion between the spacer 18 and the composite layer 12, 16.

Claims

1. A method for manufacturing a motor vehicle equipment part (10), comprising the following steps: - forming a stack (60) comprising: first (62) and second (64) base plies; and a spacer (18) disposed between said first and second base plies; at least the first base ply comprising first ceramic fibres (32) and at least one first fusible polymer (36); the first fibres (32) having an average length of less than 150 mm; - heating and compressing the stack (60) so as to melt the first fusible polymer (36); wherein the stack further comprises a first reinforcing ply (66), arranged between the first base ply (62) and the spacer (18), said first reinforcing ply comprising unidirectional second fibres (40), substantially parallel to each other, and at least one second fusible polymer (44); said second fibres (40) having an average length greater than the average length of the first ceramic fibres (32); said first reinforcing ply having a weight per unit area of between 200 g / m2 and 500 g / m2.

2. A manufacturing method according to claim 1, wherein the first base ply has a weight per unit area of between 600 g / m2 and 1000 g / m2.

3. The manufacturing method according to claim 1 or 2, wherein the second unidirectional fibres (40) are chosen from ceramic fibres, such as glass fibres, and natural fibres, such as flax fibres.

4. The manufacturing method according to one of the preceding claims, wherein the second base ply (64) comprises third ceramic fibres (32) and at least one third fusible polymer (36); said second base ply preferably having a mass per unit area of between 600 g / m2 and 1000 g / m2.

5. The manufacturing method according to one of the preceding claims, wherein the stack further comprises a second reinforcing ply (68) disposed between the second base ply (64) and the spacer (18), said second reinforcing ply comprising fourth unidirectional fibres (40) substantially parallel to each other and at least one fourth fusible polymer (44); said second reinforcing ply having a mass per unit area of between 200 g / m2 and 500 g / m2.

6. The manufacturing method according to one of the preceding claims, wherein the stack further comprises at least one first layer (74) of non-woven material disposed between the first reinforcing ply (66) and the spacer, said first layer being formed of at least a fifth fusible polymer (46).

7. The manufacturing method according to any of the preceding claims, wherein the step of heating and compressing the stack comprises the following two sub-steps: - heating and first compression of the stack (60) against a support (82, 84), so as to melt at least the first fusible polymer (36) and cause said molten polymer to adhere to the first ceramic fibres (32) to produce a pre-formed composite element (86); then - second compression of the preformed composite element in a mould (92, 94).

8. A motor vehicle equipment part (10) resulting from a manufacturing method according to one of the preceding claims, comprising a first (12) and a second (16) composite body; and a spacer (18) sandwiched between the first and second composite bodies; said first composite body comprising: a first main composite layer (22); and a first reinforcing composite layer (24) disposed between the main composite layer and the spacer; the first main composite layer (22) comprising a plurality of first ceramic fibres (32) and the first reinforcing composite layer comprising a plurality of second unidirectional fibres (40).

9. The motor vehicle equipment part (10) according to claim 8, wherein each of the first (36) and second (44) fusible polymers is a thermoplastic polymer, preferably a polypropylene.

10. The motor vehicle equipment part (10) according to claim 8 or 9, resulting from a manufacturing method according to claim 4, wherein the third fusible polymer (36) is preferably a thermoplastic polymer, more preferably a polypropylene.