METHOD FOR PRODUCING A COMPOSITE MATERIAL PART, STEERING COLUMN SUPPORT AND LOWER SPACE CROSS MEMBER PRODUCED BY SUCH A METHOD

Abstract

A method for producing a part made of a composite material having an organic matrix and a fibrous reinforcement, the method comprising the following steps: a) automatically draping, either in a planar arrangement or shaped over a three-dimensional cavity, at least one lamination (30, 31) comprising at least a first and second different dry plies, at least partially stacked to form a dry, planar or three-dimensional preform, each ply being fibrous and the plies mutually differing in terms of their structure, their positioning on the preform, the fibres composing them and/or the geometry of the ply, wherein at least one ply is laid in a non-woven form and has a plurality of unidirectional fibre layers laid on top of each other with a different angular orientation of the fibres, and/or at least one ply is woven; b) thermoforming the preform, the thermoforming step taking place, when the preform has been draped in a planar arrangement in step a), in a three-dimensional cavity of a first mold to impart a three-dimensional shape thereto; and c) impregnating, with at least one polymer, the preform thus thermoformed inside a mold, the preform being moved, if it is draped in a planar arrangement in step a), from the first thermoforming mold to a second mold for the impregnation step.

Claims

1. A method for producing a part made of composite material having an organic matrix and fiber reinforcement for battery, said method comprising the following steps: a) automatically draping, either flat or shaped on a three-dimensional mold cavity, at least one layered structure comprising at least one first and one second different dry plies, at least partially superposed, so as to form a dry preform, either flat or three-dimensional, each ply being fibrous, the plies differing from one another in structure, positioning on the preform, the fibers of which they are constituted and/or the geometry of the ply, the positioning of the plies relative to one another being defined so as provide at least one zone, having a function, between the plies, b) thermoforming the preform, thermoforming being carried out, when it was draped flat in step a), in a three-dimensional cavity of a first mold in order to give it a three-dimensional shape, c) impregnating, within a mold, the preform thus thermoformed with at least one polymer, the preform being moved, in the case of draping flat in step a), from the first thermoforming mold to a second mold for impregnation.

2. The method as claimed in claim 1, each ply being in the form of a structure selected from the group consisting of a linear structure, a surface structure, or multidirectional.

3. The method as claimed in claim 1, comprising a step consisting of placing at least one core on at least one part of the layered structure, said at least one core, having a total external surface area less than that of at least one of the plies so that only certain predetermined zones of the layered structure are covered.

4. The method as claimed in claim 3, comprising the step of draping a second layered structure comprising at least one ply in order to cover the core and the layered structure at least partially.

5. The method as claimed in claim 1, in which said at least one zone having a function is a cavity for circulation of a fluid within the finished part and/or said at least one zone having a function being a cavity or a projection of suitable geometry, able to receive an element that is to be combined with the final part.

6. The method as claimed in claim 1, in which at least one ply of carbon-fiber fabric is used for supplying a function of conduction or dissipation of heat.

7. The method as claimed in claim 1, in which at least one sensor is inserted in the preform.

8. A battery comprising at least one part made of composite material produced by the method as claimed in claim 1, comprising at least one or projection of suitable geometry, able to receive at least one electric battery.

9. The battery according to claim 8, wherein said at least one zone having a function is a cavity for circulation of a fluid within the finished part in order to allow the cooling of the battery.

10. The battery according to claim 9, comprising at least one ply of carbon-fiber fabric for supplying a function of conduction or dissipation of heat,

11. The battery according to claim 10, wherein the carbon fibers are obtained from PAN (polyacrylonitrile) or from biosourced precursors.

12. The method according to claim 5, wherein said at least one zone having a function is a cavity or a projection of suitable geometry able to receive an element that is to be combined with the final part, wherein the cavity or cavities are sites of the male or female type for receiving batteries.

13. The method according to claim 12, wherein the cavities comprise 30 to 50 cells approximately vertically for a battery with a length of one meter.

14. The battery according to claim 8, wherein said at least one zone having a function is a cavity for circulation of a fluid within the finished part in order to allow the cooling of the battery.

15. The method according to claim 6, wherein the carbon fibers are obtained from PAN (polyacrylonitrile) or from biosourced precursors.

16. The method according to claim 13, wherein at least one ply of precursor fabric that has undergone a carbonization step is used.

Description

FIGURES

[0107] The invention may be better understood on reading the description given hereunder, of nonlimiting embodiment examples of the invention, and on examining the appended drawing, in which:

[0108] FIG. 1 shows, schematically and in perspective, an example of a steering column support according to the invention, pre-assembled,

[0109] FIG. 2 shows, schematically and partially, in perspective, the pre-assembled column support in FIG. 1 with a windshield recess lower crossmember according to the invention,

[0110] FIG. 3 shows, schematically and partially, in perspective, the assembly of column support and windshield recess lower crossmember in FIG. 2 mounted on the front bulkhead of a vehicle,

[0111] FIG. 4 shows in cross section, schematically and partially, an example of column support and windshield recess lower crossmember according to the invention assembled together,

[0112] FIG. 5 shows, schematically and partially, the column support and the windshield recess lower crossmember in FIG. 4 before assembly,

[0113] FIG. 6 shows another example of column support and windshield recess lower crossmember according to the invention after assembly,

[0114] FIG. 7 shows the assembly of column support and windshield recess lower crossmember in FIG. 6 before assembly,

[0115] FIG. 8 shows the assembly in FIG. 4 after a frontal impact,

[0116] FIGS. 9, 10, 11 and 12 show, schematically and partially, the method for producing the column support in FIG. 1,

[0117] FIG. 13 shows the piercing step of the method for producing the part,

[0118] FIG. 14 shows, schematically and in perspective, the preform after the piercing step in FIG. 13,

[0119] FIG. 15 shows, schematically and in perspective, the industrial installation for carrying out the method of FIGS. 9 to 12,

[0120] FIG. 16 is an enlarged view of a part of the installation in FIG. 15,

[0121] FIG. 17 shows in cross section, schematically and in isolation, the windshield recess lower crossmember according to the invention,

[0122] FIGS. 18, 19, 20 and 21 show schematically the various steps of the method for producing the windshield recess lower crossmember in FIG. 17,

[0123] FIG. 22 shows the various steps in the production of the windshield recess lower crossmember, in schematic perspective views,

[0124] FIG. 23 shows, schematically and in perspective, the draping tooling used for making the windshield recess lower crossmember,

[0125] FIG. 24 shows, schematically and in perspective, the installation for carrying out the method in FIGS. 18 to 21,

[0126] FIG. 25 is an enlarged view of a part of the installation in FIG. 24,

[0127] FIG. 26 shows in cross section, schematically and partially, an example of a heat exchanger according to the invention,

[0128] FIG. 27 shows in cross section, schematically and partially, an example of a battery according to the invention,

[0129] FIG. 28 shows in cross section, schematically and partially, an example of insertion of a sensor in a part produced by the method according to the invention.

DETAILED DESCRIPTION

[0130] FIG. 1 shows a steering column support 1 according to an embodiment example of the invention, intended for a motor vehicle, on which the pedal bracket P of the vehicle and the steering column C of the vehicle have been pre-assembled.

[0131] The steering column support 1, in this example, is made of composite material having an organic matrix, according to the method of production described below.

[0132] The column support 1 comprises an upper part 2 made of composite material having an organic matrix, in this example having a sandwich structure at least partially, configured for holding the steering column C at the front 3. As can be seen in FIG. 2, the upper part 2 is also shaped for being fixed at the back 4 on the windshield recess lower crossmember 5 of the vehicle. In this example, the upper part 2 is L-shaped with a relatively flat portion 6 extending from the front 3 to the back 4 and a part 7 extending downwards at the back.

[0133] The support 1 also comprises, in the prolongation of part 7, in this example, a lower part 8 in the approximate shape of a curved cross, arranged for carrying the pedal bracket, as can be seen in FIGS. 1 to 3. The lower part 8 is made of composite material having an organic matrix, not in the form of a sandwich structure but in the form of stacked layers made in one piece with the upper part 2. In this example, this lower part 8 replaces a part of the steel front bulkhead of the vehicle to which it is intended to be fixed and advantageously has stiffness comparable to that of a front bulkhead made of steel.

[0134] The drawing also shows a windshield recess lower crossmember 5 according to an embodiment example, shown in FIGS. 2 and 3, fixed to the support 1. The windshield recess lower crossmember 5 extends transversely over the full width of the vehicle, and has a shape with double curvature matching that of the vehicle's windshield. The support 1 is advantageously fixed to the windshield recess lower crossmember 5 by screwing and/or gluing.

[0135] FIG. 3 shows, arranged in a vehicle V shown very partially, the assembly 10 formed by the support 1, pre-assembled in this example with the pedal bracket P and the steering column C, and the windshield recess lower crossmember 5. The whole is mounted on the bulkhead T. It should be noted that the shape and the mechanical properties of the windshield recess lower crossmember 5, the shape of which is a hollow body, make it possible to dispense with a metal crossmember, which allows new designs of dashboards to be conceived.

[0136] Moreover, compared to assemblies made from metal parts, a smaller number of parts is required to fulfill the same functions.

[0137] The windshield recess lower crossmember 5 is made of a composite material having an organic matrix, in this example partially as a sandwich structure incorporating one or more cores on some or all of its length. As can be seen in FIG. 4, in cross section the windshield recess lower crossmember 5 has a hollow shape, approximately U-shaped, on its whole length.

[0138] As can also be seen in FIG. 4, the column support 1 comprises a strut 12, made at least partially in this example of a metallic material such as steel, fixed in this example on the one hand by an upper end 16, to the upper part 2 of the column support 1 via a fixing system 13 and on the other hand, by a lower end 17, to the lower part 8 of the column support 1.

[0139] For its part, the lower part 8 is fixed to the metal bulkhead T of the vehicle, as shown in particular in FIG. 5.

[0140] In this example, the windshield recess lower crossmember 5 has a fixing part 15 with a sandwich structure matching the shape of the column support 1 at the back 4 of its upper part 2. This fixing part 15 is approximately vertical. The windshield recess lower crossmember 5 further comprises an approximately horizontal upper part 19, in the prolongation of the flat portion 6 of the upper part 2, as well as a reinforced portion with a sandwich structure 22 extending downwards at the back under the vehicle's windshield. The various parts are fixed and assembled according to the arrows in FIG. 5, by gluing and/or mechanical fastening, notably by screwing.

[0141] As illustrated in FIG. 8, the strut 12 is configured so as to buckle in the case of frontal impact, and the lower part 8 of the column support 1 is also designed to deform.

[0142] Another example of a support 1 and a windshield recess lower crossmember 5 is illustrated in FIGS. 6 and 7. In this example, the windshield recess lower crossmember 5 comprises a single sandwich structure zone 25 extending under the support 1, which comprises only an upper part 2 and a strut 12. In this example, the strut 12 is fixed by its upper end 16 to the fixing system 13 and by its lower end 17 to the bulkhead T. Moreover, the windshield recess lower crossmember 5 is fixed to the support 1 and to the bulkhead T, as can be seen in FIG. 7.

[0143] FIGS. 9 to 14 show the different steps of the method for producing a complex part made of composite material having an organic matrix, in this example having a sandwich structure at least partially, a part such as the column support 1 illustrated in FIGS. 1 to 3.

[0144] FIG. 9 shows a step a) of flat draping of a layered structure comprising a first deformable dry ply 30 of rectangular shape with predetermined dimensions.

[0145] Step b), also illustrated in FIG. 9, consists of flat draping of a second deformable dry ply 31 with several pieces with predetermined dimensions and positioning and corresponding to the desired shape. As can be seen, the second ply 31 only partially covers the first ply 30 and the orientation and shape of the pieces are different than the latter. The nature and weight of the second ply 31 may be identical to or different than of the first ply 30, depending for example on the mechanical properties required. The layered structure is, for example, held on the table of the draping machine by vacuum.

[0146] Step c) consists of placement, on a predetermined part of the surface of the layered structure consisting of plies 30 and 31, of a core 32 of foamed polyethylene terephthalate. The core or cores 32 may be glued on the layered structure.

[0147] If the core is not made of foamed PET or if there is no core, this will still be within the scope of the invention. Any other material suitable for the method may be used, including a metal insert, for example made from formed or cast sheets, so as to have a function appropriate to the application: material for damping, strength, sound or heat insulation, conductive or insulating material for example.

[0148] The next step d) consists of flat draping of a second layered structure once again comprising a deformable dry ply 33 corresponding to ply 31, at least in shape.

[0149] In a step e), a deformable dry ply 34, identical at least in shape to ply 30, is draped flat, forming the second layered structure with ply 33. The relative flexibility of the core does not interfere with the draping of these plies 33 and 34. According to a variant embodiment, the plies 33 and 34 making up the second layered structure are stabilized on the preform by thermal activation of a polymer, for example a thermoplastic polymer, dusted on said plies, or by spraying of glue.

[0150] In this step e), it can clearly be seen that one part, in the present case the upper part 2 of the column support 1, is made as a sandwich structure whereas the other part, namely the lower part 8 of the column support 1, is made in one piece with the upper part 2 but without the core and therefore the sandwich structure.

[0151] In this example the plies 30, 31, 33 and 34 are advantageously nonwoven plies of NCF, with a weight selected so as to obtain the desired stiffness without multiplying the number of plies required. For example, a ply in NCF, used for making the column support 1 or for any other part produced by the method according to the invention, comprises a first layer of carbon fibers oriented at +45, a second layer of aramid fibers oriented at 0, and a third layer of carbon fibers oriented at 45, without this example being limiting or exhaustive. Thus, the nature of the fibers that are draped is adapted to meet the needs of mechanical durability with respect to stresses during use of the part made and the requirements in an exceptional stress situation, such as in the case of an impact or penetration of a foreign body. If the preform comprises for example glass fibers, carbon fibers, kevlar fibers or natural fibers, among others, this will still be within the scope of the invention.

[0152] In a step f), at least one seam 35 of the plies is produced, so as to keep the two layers together. The seam 35, preferably in zigzag, may follow the contour of the core or cores so as to allow separation of the layers on either side of the core or cores, reinforcing this separation zone against peeling. As a variant or additionally, the seam 35 may constitute one or more lines of folding of the preform. The location of the seam 35 is determined for example by experience or by simulation. The seam may be produced by a seaming system bonding the plies together to fix their position. Such a system may have two needles or one curved needle. In both cases, a buffer zone is provided under the preform for receiving the needles. The speed of producing the seam may be about 1400 stitches/min, or about 10 cm/s.

[0153] In a variant embodiment that is not shown, the seam or seams under most stress are covered with bands of unidirectional fibers, for example of carbon fibers, in order to reinforce them. The fibers of said bands are oriented approximately parallel to the general direction of progression of the seams that they cover.

[0154] A flat dry preform 36 is then obtained. As illustrated in FIG. 10, the flat dry preform 36 obtained in step f) is moved into a three-dimensional cavity E of a mold and a radiant panel R heats it to a temperature of about 100 C., in such a way that, as illustrated in FIG. 11, the preform matches the shape of the cavity E.

[0155] The thermoformed preform 37 thus obtained is then moved into a second mold, not visible in the figures, in which it is impregnated with at least one polymer in order to produce the part, shown in FIG. 12, in this example constituting the support 1 described above. In a manner known per se, the impregnation step may consist of a step of injection molding of material, of the resin transfer molding type RTM, light resin transfer molding (called RTM light), at high-pressure HP-RTM, thermoplastic resin transfer T-RTM or others. Molding may also be of the compression transfer type, for example employing one or more thermoplastic polymers in sheet or powder form, or some other type, comprising for example an infusion step.

[0156] The polymer used for impregnation may be a thermosetting or thermoplastic resin.

[0157] According to an embodiment example that is not illustrated, the second mold comprises two parts and sealing means so that, when the mold is closed, said two parts define a sealed cavity in which the dry preform is located. The mold comprises means for vacuuming said cavity, and according to one embodiment example, means for heating each part of the mold. According to various embodiment examples, the two parts of the mold are heated by circulation of a fluid, by electric resistances or by induction. When the preform is under vacuum in the mold cavity, channels allow a polymer to be injected into the preform, so as to impregnate it. This injection is carried out at a temperature appropriate to the polymer used. Injection may be carried out at high pressure, for example of about 30 bar, and at high temperature, notably between 120 C. and 180 C. The mold may be made of metal, notably steel. According to one embodiment example, polymers of different nature are injected into the upper part and into the lower part of the mold and/or in specific zones of the upper and/or lower parts, in order to confer suitable properties on the part as a function of the stressing to which it is subjected.

[0158] After consolidating the part 1 by solidification of the polymer when it is a thermoplastic polymer or by baking the polymer when it is a thermosetting polymer, the part 1 is removed from the mold. Simple deburring, not machining, may be carried out to finish the part 1.

[0159] With such a method, the rate for production of one part may be less, in cumulative time, than 200 s, the steps of draping and of impregnation, notably injection, each requiring 90 s.

[0160] FIGS. 13 and 14 show a step of piercing the preform, which may take place during production of the latter. The mold M comprises a moving needle A, which is inserted through the plies 30 and 34 and optionally the core 32 as can be seen. During injection of material, the impregnating polymer forming the matrix 41 of part 1 will also create a shaft 40 surrounding the pierced hole. FIG. 14 shows the locations for piercing 42 provided in part 1, which, in another embodiment, may be produced by placement of metal inserts, pre-existing in the material of the core or cores.

[0161] An installation D for carrying out the method in FIGS. 9 to 14 is illustrated in FIGS. 15 and 16. FIG. 15 shows a first flat draping zone 45, a second preforming or thermoforming zone 46, and finally a third zone for impregnation 47 with a polymer, for example by injection. The flat draping zone 45 is more visible in FIG. 16, notably illustrating the fact that four preforms may be produced, notably draped, simultaneously with this installation D, by using a 300t injection press in this example.

[0162] A robot R1 performs the flat draping automatically. A second robot R2, visible in FIG. 15, allows the flat preforms to be moved to the second zone 46, for example by a gripping effector, with needles or with vacuum, preferably with needles.

[0163] In the third zone 47, besides a robot R3 arranged for moving the thermoformed preforms to the third zone 47, tooling O including the mold for impregnation, notably by injection, of polymer into the preform is shown. In this example the tooling is an injection device such as a press.

[0164] FIG. 17 shows in isolation the windshield recess lower crossmember 5, in cross section. It is of a hollow shape, with an open section. The sandwich structure makes it possible to endow the part with stiffness, by selecting carbon fibers for the most heavily stressed parts or pieces and glass fibers for the parts or pieces under less stress.

[0165] The method for producing the latter is illustrated in FIGS. 18 to 23. FIG. 18 shows a step l) of mold draping on a cavity E having a three-dimensional surface. Draping is carried out automatically using small rollers S draping a little at a time, forming a layered structure comprising in this example a first deformable dry ply 51 of NCF.

[0166] In step m), second plies 52, constituting reinforcement, are positioned on certain zones of the first ply 51. These plies 52 are for example made of carbon fiber cloth.

[0167] Then, in step n), cores 53, numbering two in this example, are positioned on a part of the first layered structure 51, in the present case on plies 52.

[0168] In step o), a second layered structure 54, comprising in this example a deformable dry ply of NCF, is produced automatically using the rollers S. It should be noted that plies 52 were also deposited beforehand above the cores 53, as can be seen in this step o).

[0169] A preforming step, or thermoforming step, at low pressure, of the order of 1 bar, and at low temperature, below 100 C., is carried out after step o), in a simple mold, for example of aluminum or of composite material having an organic matrix, or of resin, or some other.

[0170] The three-dimensional preform 55 obtained is shown in perspective in FIG. 19. The preform 1 is moved to another mold where, as can be seen in FIG. 20, a countermold M is arranged on the preform 55.

[0171] In the step illustrated in FIG. 21, a thermosetting resin is injected into the mold so as to impregnate the preform 55 with a polymer. After consolidation, in this example by baking the resin, the part can be removed from the mold.

[0172] It should be noted that the features described above for the preform, the materials used, the steps of the method as well as the tooling, with respect to FIGS. 9 to 12, even if not included in the description, may be identical, at least for some of them, to those of the preform, materials, tooling, and steps of the method in FIGS. 18 to 21.

[0173] FIG. 22 illustrates the same steps as those illustrated in FIG. 18, except that the part is shown in perspective. It shows the draping tools and then the step of mold draping of the first ply 51 and placement of the second plies 52 and then adding the cores 53 and finally mold draping of a second layered structure with the plies 52 and 54.

[0174] An example of tooling that may be used for mold draping is shown in FIG. 23. For draping this complex shape, preferably automatic draping is used by indexing the lateral displacement of the fabric rollers in a groove of the tooling, of suitable profile, rather than by programming the robot. This simplifies the programming of the means and the process of changing the part reference.

[0175] With the complete installation illustrated in FIG. 24 it is possible to produce two preforms of windshield recess lower crossmember simultaneously. The draping zone 60 is juxtaposed with an injection zone 61, and a robot R5 makes it possible to move, with a gripping effector, the preforms produced using the tooling D.

[0176] The method, the steps of which are illustrated in FIGS. 9 to 12 and 18 to 21, may be used for making parts other than a steering column support or a windshield recess lower crossmember.

[0177] In particular, such a method may allow high-rate production of any complex parts made of composite material having an organic matrix that may comprise at least one part having a sandwich structure, whether intended for the automotive sector, aeronautical sector or other industrial sectors.

[0178] Other parts produced using the method of the invention are illustrated in FIGS. 26 and 27.

[0179] FIG. 26 shows, partially, a heat exchanger 70 comprising at least one, in this example two cavities 71 for circulation of a fluid within the finished part, made between the plies 72 and 73.

[0180] FIG. 27 shows, partially, a battery 75 comprising at least one cavity 76 of suitable geometry, made from two plies 77 and 78, able to receive at least one electric battery B. In an example not illustrated, at least one projection could be made.

[0181] FIG. 28 illustrates the possibility of incorporating a sensor G between two plies 80 and 81 in a part produced by the method according to the invention.

[0182] It should be noted that the steps of the method according to the invention for producing the preform or preforms may be carried out independently of the final step of impregnation with a polymer in order to produce the part. The dry preforms may be stored in a stack to save storage space. The final step of the method may be carried out subsequently after a time lapse that may be for example from 1 h up to a year. As a variant, all the steps of the method may be carried out successively, without delay, i.e. in less than about 1 h, notably of the order of some minutes at most.