Manufacturing process for a part made of composite material

Abstract

Method for manufacturing a part from a composite material. Method for manufacturing a part (15) from a thermoplastic polymer matrix composite material comprising: - positioning a profile (1) of a thermoplastic polymer matrix composite material on a substrate (2) having a plurality of plies of a thermoplastic polymer matrix composite material; - heating the assembly (4), at least at the level of the profile (1), to a heating temperature higher than the melting temperature of the thermoplastic polymer material of the matrix of the profile (1) and the melting temperature of the thermoplastic polymer material of the matrix of the substrate (2); - stamping the heated assembly (4) into a predetermined shape in a mold (10) so as to form a part (15) of a composite material having at least one rib (16). Figure for the abbreviation: Fig. 3

Description

Title of the invention: Method for manufacturing a part made of composite material Technical field

[0001] The present invention relates to the field of manufacturing parts made of thermoplastic polymer matrix composite material. In particular, the invention relates to a method for manufacturing such a part. Prior art

[0002] In order to stiffen parts made of composite material without making them too heavy, it is known to have ribs called stiffeners on the part.

[0003] To manufacture these stiffeners on the parts, it is known to carry out overmolding by injection of a thermoplastic comprising short fibers. The mold cavity necessary to overmold the stiffeners generates local deconsolidation during stamping.

[0004] It is also known to make an assembly by thermocompression of composite panels.

[0005] Parts can also be stiffened by assembling stiffeners to the structure by gluing or mechanical fixing.

[0006] However, these methods do not allow parts to be produced at high speed and at low cost while offering high mechanical resistance.

[0007] There are a number of composite material parts and systems that need to be stiffened to support mechanical load. Examples include tank panels, hatches, aircraft doors, vehicle seats, and battery trays. Statement of the invention

[0008] There is a need to stiffen a structure at lower cost in high-speed processes. Summary of the invention

[0009] The present invention meets this need thanks to, according to one of its aspects, a method of manufacturing a part made of composite material with a thermoplastic polymer matrix comprising:

[0010] - the positioning of a profile made of thermo polymer matrix composite material plastic on a substrate comprising a plurality of plies of thermoplastic polymer matrix composite material;

[0011] - heating the assembly at least at the profile level to a temperature of heating above the melting temperature of the thermoplastic polymer material the profile matrix and at the melting temperature of the thermoplastic polymer material of the substrate matrix, in particular at least 10°C, preferably at least 20°C;

[0012] - stamping the assembly thus heated to a predetermined shape in a mold so as to form a part of composite material comprising at least one rib.

[0013] By “profile” is meant a slender piece whose cross-section may or may not be constant.

[0014] The rib preferably forms a stiffener on the resulting part.

[0015] Thus, the method allows the manufacture of a part in stiffened composite material without too much complexity. In addition, it is possible to use prefabricated products for the profile and / or the substrate, which significantly reduces the cost of implementing the process.

[0016] The method also makes it possible to obtain a lighter part than with the aforementioned prior art methods while retaining similar, or even superior, mechanical performance.

[0017] In addition, due to the stamping of the assembly, the material health of the part obtained is good thanks to the compression of the profile on the substrate. Profile

[0018] The method may include a prior step of providing a profile or manufacturing a profile.

[0019] The profile may comprise short, long and / or continuous fibers, preferably long and / or continuous.

[0020] The use of long and / or continuous fibers makes it possible to obtain a part with high mechanical performance. The possibility of having long and / or continuous fibers is made possible in particular by the use of a profile.

[0021] During the positioning step, the profile may be unwound from a coil. In this case, the method may include a step of cutting the profile to a predetermined length.

[0022] During the positioning step, the profile can be positioned so as to extend in a predetermined direction, over a predetermined length and / or at a predetermined position.

[0023] In one embodiment, the profile may extend from one end of the substrate to the other.

[0024] In one embodiment, the profile extends over only a portion of the substrate.

[0025] The method may include positioning several profiles on the substrate.

[0026] During the positioning step, two profiles may cross. In this case, the crossing may be done by superimposing the profiles, with or without the production prior to a cut or notch on one of the profiles.

[0027] The profile may comprise a rod or an assembly of a plurality of rods, in particular be made up of one or more rods.

[0028] Reeds are basic, low-cost products, which are found in particular in the form of reels of several meters. This allows for a reduction in manufacturing costs and facilitates the formation of profiles.

[0029] The assembly of the rods can be carried out in such a way as to obtain a volume of material close to that necessary to form the rib.

[0030] Each rod may have a constant section, in particular circular, semi-cylindrical, ovoid, parallelepiped, triangular, or a combination of these.

[0031] The profile may be of constant section, in particular when it comprises or is made up of the assembly of rods of constant section.

[0032] During the positioning step, the profile can be glued to the substrate.

[0033] Alternatively, the profile can be positioned without additional material.

[0034] At least one rod can be produced by pull-winding.

[0035] Each rod may have a cross-section of between 1 mm and 10 mm.

[0036] The profile can comprise between 1 and 20 rods.

[0037] After the positioning step, the profile can extend over the substrate in a substantially constant direction.

[0038] After the positioning step, the profile can extend over the substrate in a variable direction.

[0039] During the positioning step, the profile can be glued to the substrate.

[0040] The positioning of the profile can, as a variant, be carried out without adding material.

[0041] A plurality of profiles may be positioned on the substrate.

[0042] The volume proportion of the profile matrix may be between 30% and 70%, in particular between 40% and 60%.

[0043] The fibers of the profile can be chosen from the group consisting of carbon fibers, glass fibers, aramid fibers, ceramic fibers, fibers of plant origin, in particular flax fibers, and a combination thereof.

[0044] The fibers of the profile can be assembled together in a form chosen from the group consisting of strands, wicks, braids, and a combination thereof.

[0045] The thermoplastic polymer material of the profile matrix may be chosen from the group consisting of polyamide (PA), in particular PA6, polyethylene (PE), polypropylene (PP), polyetherimide (PEI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyethylene terephthalate (PET), polyurethane (PU) and mixtures thereof.

[0046] The thermoplastic polymer material of the profile matrix may be identical to that of the thermoplastic polymer material of the substrate matrix. Substrate

[0047] The substrate may have at each of its possible curvatures a radius of curvature less than 1 m1, in particular less than 0.5 m1, the shape of the substrate being in particular chosen from the group consisting of planar shapes, non-planar shapes, cylindrical or non-cylindrical shapes, shapes with a circular or non-circular director, preferably planar shapes, with single curvature or double curvature.

[0048] By "possible curvatures" is meant the possible curvatures of the substrate in a plane perpendicular to the direction of extension of the profile after its positioning.

[0049] The fibers of the substrate may be chosen from the group consisting of carbon fibers, glass fibers, aramid fibers, ceramic fibers, fibers of plant origin, in particular flax fibers, and a combination thereof.

[0050] The fibers of the substrate may be assembled together in a form selected from the group consisting of strands, rovings, braids, fabrics, parallel assemblies and a combination thereof.

[0051] The substrate may comprise a plurality of plies with monodirectional fibers.

[0052] The thermoplastic polymer material of the substrate matrix may be selected from the group consisting of polyamide (PA), in particular PA6, polyolefins, in particular polyethylene (PE), polypropylene (PP), polyetherimide (PEI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyethylene terephthalate (PET), polyurethane (PU) and mixtures thereof. Mold

[0053] The mold may have a first and a second part and may take open and closed configurations.

[0054] The heating of the assembly can be carried out outside the mold.

[0055] The mold is preferably heated to a temperature below the temperature of melting of the thermoplastic polymer material of the profile matrix and at the melting temperature of the thermoplastic polymer material of the substrate matrix.

[0056] More preferably, the mold is heated to a temperature lower than the crystallization temperature of the thermoplastic polymer material of the profile matrix and the crystallization temperature of the thermoplastic polymer material of the substrate matrix. Brief description of the drawings

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

[0058] [Fig.l] [Fig.l] illustrates, schematically, in side view, a step of providing an example of a method according to the invention,

[0059] [Fig.2] [Fig.2] illustrates, schematically, in side view, steps of posi operation and heating of an example of a method according to the invention,

[0060] [Fig.3] [Fig.3] illustrates, schematically, in side view, a step of posi operation in a mold of an example of a method according to the invention,

[0061] [Fig.4] [Fig.4] illustrates, schematically, in side view, a step stamping of an example of a method according to the invention,

[0062] [Fig.5] [Fig.5] illustrates, schematically, in side view, a step of demolding of an example of a process according to the invention,

[0063] [Fig.6] [Fig.6] illustrates, schematically, in side view, another example of the process according to the invention,

[0064] [Fig.7] [Fig.7] illustrates, schematically, in side view, another example of the process according to the invention, and

[0065] [Fig.8] [Fig.8] shows two photographs of a comparative test between a part produced according to the method of the invention (figure 8a) and another produced by overmolding stamping (figure 8b). Detailed description

[0066] In the remainder of the description, elements that are identical or have identical functions bear the same reference sign. For the sake of brevity in this description, they are not described with reference to each of the figures, only the differences between the embodiments being 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 method according to the invention.

[0069] In a first step, illustrated in [Fig.l], a profile 1 and a substrate 2 are provided. They are for example purchased from a supplier.

[0070] For example, the profile 1 and the substrate 2 are composite materials comprising a polyamide PA6 matrix and carbon fibers.

[0071] The fibers of the profile 1 are continuous and parallel to each other in the direction of the length of the profile.

[0072] The profile 1 is presented, in this example, in the form of a rod 20 in a half-cylinder of constant section produced by drawing-winding.

[0073] The substrate 2 is for example flat.

[0074] In a second step, illustrated in [Fig.2], the profile 1 is positioned at a predetermined location on an outer surface 3 of the substrate 2.

[0075] Positioning can be done by gluing the profile 1 to the outer surface 3 or without adding material.

[0076] In a third step, still illustrated in [Fig.2], the assembly 4 is heated using a heating means 5, for example by a radiant panel, an oven or even an oven.

[0077] The assembly 4 is heated to a heating temperature 20°C higher than the melting temperature of the thermoplastic polymer material of the matrix of the profile 1, which in this example is identical to that of the thermoplastic polymer material of the matrix of the substrate 2. Heating beyond the melting temperature facilitates the operations of moving and stamping the assembly 4 by keeping the polymer matrices in a molten state.

[0078] After heating, in a fourth step illustrated in [Fig.3], the assembly 4 thus heated is positioned in a mold 10.

[0079] The mold 10 is heated to a temperature lower than the crystallization temperature of the thermoplastic polymer material of the profile matrix, for example between 80°C and 140°C for polypropylene (PP) and polyamide (PA), or between 200°C and 250°C for polyetheretherketone (PEEK). This heating makes it possible to avoid excessively rapid cooling of the assembly 4, in particular of the external surfaces which are in contact with the mold 10, which allows good stamping, as described below.

[0080] The mold 10 comprises a first part 11, on which an outer surface of the substrate 2 opposite the outer surface 3 of the substrate 2 comes into contact. The first part, for example, forms a shape complementary to the assembly 4 that is sought to be obtained.

[0081] The mold 10 also includes a second part 12 not totally complementary with the shape of the assembly 4 at this stage.

[0082] The second part 12 comprises a cavity 13 in which the profile 1 will be stamped. This cavity 13 has the desired shape of the rib to be formed.

[0083] In this example, the cavity 13 has an inverted T shape.

[0084] Once positioned, the mold 10 is closed to stamp the assembly 4, as illustrated in [Fig.4]. During stamping, the closing pressure makes it possible to deform the profile 1 to the shape of the cavity 13.

[0085] Once the assembly 4 has cooled, the part 15 made of composite material can be extracted by opening the mold, as illustrated in [Fig.5].

[0086] This part 15 includes a rib 16 resulting from the stamping of the profile 1.

[0087] The shape of the cavity 13 and of the rib 16 may be different, for example it can be square, triangular, circular or any demouldable shape.

[0088] In a variant illustrated in [Fig.6], two profiles 1 are positioned on the same substrate 2, the mold 10 comprising two corresponding cavities 13.

[0089] As visible in this variant, one of the profiles 1a has a triangular shape and the other profile 1b has a rectangular shape.

[0090] In [Fig.7], a profile 1 and a part 15 of another variant are illustrated.

[0091] As can be seen, the profile 1 comprises an assembly of three rods 20 of constant cylindrical section.

[0092] As regards the part 15, the rib 16 has a general section in the shape of an inverted T and with rounded branches 21.

[0093] Furthermore, the section of the rib 16 is here not constant and comprises, at regular intervals, section widenings 23 extending in a direction normal to the external surface 22 of the part 15. These widenings allow the part to be extracted with ejectors in the mold. Comparative example

[0094] Two photographs of a comparative example are illustrated in [Fig.8].

[0095] In Figure 8a, a section of a part 15 produced according to the method of the invention is presented. The rib 16 was formed using a profile comprising three rods 20, in a similar manner to the variant described above in [Fig.7].

[0096] In Figure 8b, a section of a part made of composite material 30 comprising a rib 31 produced by the injection, onto a substrate 2, of a thermoplastic material with short fibers is shown.

[0097] Part 15 and part 30 were manufactured from a similar substrate 2.

[0098] In order to visualize the penetration of the material of the ribs 16 and 31 into the substrate 2, the profile 1 was white on the part 15 and the injection was carried out in black for the rib 31 of the part 30.

[0099] As can be seen, the penetration of the material of the rib 15 into the substrate is much greater than that of the material of the rib 31 of the part 30. In addition, a portion of the substrate material 2 is present in the rib 16 of the part 15, which is not the case for the part 30.

[0100] Thus, in comparison with the manufacture of a rib by injection, the method according to the invention allows better mutual penetration of the substrate 2 and the rib.

[0101] Furthermore, the mechanical tests carried out show that the method according to the invention allows a gain of 160% for the Young's modulus and a breaking stress increased by 100% compared to the part 30 with the injected rib 31.

[0102] The method according to the invention therefore makes it possible to improve the mechanical properties of the manufactured part.

[0103] The shape of the substrate 2 may be different, for example non-planar, for example half-cylinder.

Claims

Claims

1. Method for manufacturing a part (15) made of thermoplastic polymer matrix composite material comprising: - positioning a profile (1) made of thermoplastic polymer matrix composite material on a substrate (2) comprising a plurality of plies made of thermoplastic polymer matrix composite material; - heating the assembly (4) at least at the profile (1) to a heating temperature higher than the melting temperature of the thermoplastic polymer material of the matrix of the profile (1) and the melting temperature of the thermoplastic polymer material of the matrix of the substrate (2); - stamping the assembly (4) thus heated to a predetermined shape in a mold (10) so as to form a part (15) made of composite material comprising at least one rib (16).

2. Method according to claim 1, wherein the profile (1) comprises short, long and / or continuous fibers, preferably long and / or continuous.

3. Method according to one of claims 1 and 2, in which the profile (1) comprises a rod (20) or an assembly of a plurality of rods (20), in particular is made up of one or more rods (20).

4. Method according to the preceding claim, in which each rod (20) has a constant section, in particular circular, semi-cylindrical, ovoid, parallelepiped, triangular, or a combination of these.

5. Cl. Method according to one of claims 3 and 4, in which at least one rod (20) is produced by pull-winding.

6. A method according to any preceding claim, wherein, after the positioning step, the profile (1) extends over the substrate (2) in a substantially constant direction.

7. Method according to one of claims 1 to 5, in which, after the positioning step, the profile (1) extends on the substrate (2) in a variable direction.

8. A method according to any preceding claim, wherein, during the positioning step, the profile (1) is glued to the substrate (2).

9. Method according to any one of claims 1 to 7, in which the positioning of the profile (1) is carried out without adding material.

10. A method according to any preceding claim, wherein a plurality of profiles (1) are positioned on the substrate (2).

11. A method according to any preceding claim, wherein the thermoplastic polymer material of the matrix of the profile (1) is identical to that of the thermoplastic polymer material of the matrix of the substrate (2).

12. Method according to any one of the preceding claims, in which the substrate has one or more curvatures and each curvature of the substrate (2) has a radius of curvature less than 1 m1, in particular less than 0.5 m1, the shape of the substrate (2) being in particular chosen from the group consisting of planar shapes and half-cylinder shapes.

13. Method according to any one of the preceding claims, in which the heating of the assembly (4) is carried out outside the mold (10).

14. Method according to the preceding claim, in which the mold (10) is heated to a temperature lower than the melting temperature of the thermoplastic polymer material of the matrix of the profile (1) and the melting temperature of the thermoplastic polymer material of the matrix of the substrate (2).

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