Manufacturing a tank by overmolding a composite insert

Abstract

Manufacturing a tank by overmolding a composite insert. The invention relates to a method for manufacturing a pressurized gas tank comprising the following steps: - production of a composite insert (1) comprising a fiber reinforcement embedded in a thermosetting matrix, - placement of said insert (1) in a mold, - overmolding, on at least a portion of the surface of the insert (1) with an overmolding polymer (2), - cooling / curing, further comprising, between the production step and the overmolding step, a step of: - deposition of a bonding polymer, on at least a portion of the surface of the insert (1). Abstract figure: Fig. 3

Description

Title of the invention: Manufacturing a tank by overmolding a composite insert technical field

[0001] The invention relates to a method of manufacturing a tank by overmolding a composite insert and such a tank. Previous technique

[0002] It is known to manufacture a tank or a tank part by overmolding a composite insert.

[0003] Such a process comprises the following steps. In a first step, a composite insert is produced. This insert typically comprises a fiber reinforcement embedded in a thermosetting matrix. Once produced, this insert is placed in a mold. This mold is designed to receive an injection of an overmolding polymer. In an overmolding step, the overmolding polymer is injected into the mold, at least partially, around the insert. The assembly is then cooled to harden the overmolding polymer and obtain the tank component.

[0004] Due to the different materials used, between the overmolding polymer and the composite material of the insert, differential shrinkage may occur between the insert and the overmolding during cooling. This differential shrinkage may create a gap between the insert and the overmolding, causing a lack of material and a lack of adhesion between the insert and the overmolding.

[0005] Therefore, a manufacturing method is sought that corrects this drawback, in order to avoid such a gap appearing and to guarantee adhesion between the insert and the overmolding. Summary of the invention

[0006] The invention aims to correct these drawbacks by preventing the formation of gaps caused by differential shrinkage.

[0007] To this end, the invention relates to a method for manufacturing a reservoir for pressurized gas, such as hydrogen, comprising the following steps: - production of a composite insert comprising a fiber reinforcement embedded in a thermosetting matrix, - placement of said insert in a mold, - overmolding, on at least part of the insert surface with an overmolding polymer, - cooling / hardening, and further including, between the production stage and the overmolding stage, a stage of: - deposition of a bonding polymer, on at least part of the surface of the insert.

[0008] Specific features or embodiments, usable alone or in combination, are: - The bonding polymer is deposited by powdering onto the preheated insert. - the process also includes, between the deposition stage and the overmolding stage, a cooling / curing stage for the bonding polymer, - the bonding polymer is preferentially deposited in at least one area of ​​differential shrinkage, - said at least one differential shrinkage zone, the quantity and distribution of bonding polymer are determined by analysis of the shape of the part / mold or by analysis of a lost part manufactured without bonding polymer, - The bonding polymer is deposited in the concave areas of the insert, - the bonding polymer is a polyethylene-based polymer, - the overmolding polymer is a thermoplastic polymer, - the fiber reinforcement includes glass or carbon fibers and the thermosetting matrix is ​​an epoxy resin.

[0009] According to another aspect, a reservoir for pressurized gas, such as hydrogen, produced by such a process.

[0010] According to another aspect, a pressurized gas reservoir, such as hydrogen, comprising a composite insert, including a fiber reinforcement embedded in a thermosetting matrix, and an overmolding covering at least a part of the surface of the insert with an overmolding polymer, wherein at least a part of the surface of the insert has a deposit of a bonding polymer. Brief description of the drawings

[0011] The invention will be better understood upon reading the following description, given solely by way of example, and with reference to the figures in the appendix in which: [Fig.1] shows, in perspective view, an insert for a gas tank, [Fig.2] shows, in perspective view, an overmolded insert according to the prior art, [Fig.3] shows, in perspective view, an overmolded insert according to the invention. Description of the implementation methods

[0012] The invention relates to a method for manufacturing a tank for pressurized gases, such as hydrogen. This method comprises the following steps, described above.

[0013] In a first step, a composite insert 1 is produced. This insert Insert 1 typically comprises a fiber reinforcement embedded in a thermosetting matrix. Once produced, this insert 1 is placed in a mold. This mold is designed to receive an injection of an overmolding polymer 2. During an overmolding step, the overmolding polymer 2 is injected into the mold, in contact with at least part of the surface of the insert 1. In a final step, the assembly is then cooled to harden it and obtain the part, which is part of a tank.

[0014] According to one feature, the process further comprises a step of depositing a bonding polymer. This deposit is made in contact with at least a portion of the surface of the insert 1. This step takes place between the production step and the overmolding step. This step can be carried out before or after the insert 1 is placed in the mold.

[0015] The purpose of this bonding polymer deposit is twofold. The first purpose of the bonding polymer is to ensure the bonding of the overmolding polymer 2 to the composite insert 1. The second purpose of the bonding polymer is to provide an intermediate material to compensate for the material loss caused by differential shrinkage.

[0016] According to another feature, the bonding polymer is deposited by hot powdering. The bonding polymer is in powder form. This powder is sprinkled onto at least a portion of the surface of the insert 1. To heat the powder, the insert 1 is preheated.

[0017] According to another feature, the process further includes a cooling step. This cooling step allows the bonding polymer to harden. This step is located between the deposition step, where the bonding polymer is introduced, and the overmolding step, where the overmolding polymer is injected.

[0018] The bonding polymer can thus be cooled before overmolding. Overmolding, which injects a hot overmolding polymer 2, leads to further softening of the bonding polymer. This softening helps to improve the adhesion of the overmolding polymer 2 to the bonding polymer and therefore to the composite insert 1 to which the bonding polymer is attached.

[0019] In order to better solve the problem of differential shrinkage, according to another feature, the bonding polymer is deposited, preferentially in at least one differential shrinkage zone 4. Thus, the material supplied by the bonding polymer is disposed where adhesion is most needed and where the lack of material is most present, in order to fill it.

[0020] According to another feature, the determination of said at least one differential shrinkage zone 4 is carried out by analysis of the shape of the part, or which is equivalent to analysis of the shape of the mold.

[0021] A person skilled in the art can predict, by analyzing this shape, the location and dimensions of the shrinkage that will occur. Thus, it is predictable to find a zone of differential shrinkage 4 in the curved areas at the ends. Similarly, the inner face(s), i.e., the concave areas of the insert 1, are candidates. The dimensions of the differential shrinkages also make it possible to determine the quantity and distribution of bonding polymer necessary to compensate for said differential shrinkages.

[0022] Alternatively or complementarily, this determination can be carried out empirically by manufacturing a part without using a bonding polymer, i.e., according to the prior art. This manufacturing process produces a disposable part exhibiting one or more differential shrinkage zones 4. Analysis of these differential shrinkage zones 4 indicates the positions and dimensions of the differential shrinkage zone(s) 4 and therefore makes it possible to determine the quantities and distributions of bonding polymer necessary to compensate for them.

[0023] Generally, differential shrinkage zones 4 appear mainly in the concave parts of the insert 1.

[0024] The exact determination of the quantities and locations of the bonding polymer deposits may require trial and error.

[0025] According to another feature, the bonding polymer is a polyethylene-based polymer. This material has adhesion characteristics that enable bonding between the insert 1 and the overmolding polymer 2. This material also exhibits elongation characteristics compatible with the stresses that appear instead of potential differential shrinkages, so as not to produce them.

[0026] According to another characteristic, the material of the overmolding polymer 2 remains that dictated by the requirements of the part. Thus, it may be a polyamide, such as PA 6, PA 11, or PA 12. Alternatively, it may be a polyethylene, which advantageously offers better cohesion with the bonding polymer. Alternatively still, it may be other thermoplastic polymers.

[0027] According to another feature, the insert 1 is made of composite material. The reinforcement of this composite material is made of fibers. These fibers may be glass or carbon fibers, and preferably carbon fibers. This reinforcement is embedded in a thermosetting matrix. This thermosetting matrix is ​​advantageously made of epoxy resin. Other thermosetting materials may be used.

[0028] The invention further relates to a tank or a tank part made by the process as previously described.

[0029] The invention further relates to a reservoir comprising a composite insert 1 and an overmolding. The insert 1 comprises a fiber reinforcement embedded in a thermosetting matrix. The overmolding covers at least a portion of the insert's surface with an overmolding polymer 2. According to one feature, at least a portion of the insert 1's surface is coated with a bonding polymer deposit.

[0030] The invention has been illustrated and described in detail in the drawings and the preceding description. This description is to be considered illustrative and given by way of example and not as limiting the invention to this single description. Numerous embodiments are possible. List of reference signs

[0031] 1: insert, 2: Overmolding polymer, 4: Differential shrinkage zone.

Claims

Demands

1. A method for manufacturing a pressurized gas tank, such as for hydrogen, comprising the following steps: - production of a composite insert (1) comprising a fiber reinforcement embedded in a thermosetting matrix, - placement of said insert (1) in a mold, - overmolding, on at least a part of the surface of the insert with an overmolding polymer (2), - cooling and curing, characterized in that it further comprises, between the production step and the overmolding step, a step of: - deposition of a bonding polymer, on at least a part of the surface of the insert (1).

2. Method according to claim 1, wherein the deposition of the bonding polymer is carried out by powdering, on the previously heated insert (1).

3. A method according to any one of claims 1 or 2, further comprising, between the deposition step and the overmolding step, a cooling and hardening step of the bonding polymer.

4. A method according to any one of claims 1 to 3, wherein the bonding polymer is preferentially deposited in at least one differential shrinkage zone (4).

5. Method according to claim 4, wherein said at least one differential shrinkage zone (4), the quantity and distribution of bonding polymer are determined by shape analysis of a portion of the tank produced in the mold or of the mold or by analysis of a lost part manufactured without bonding polymer.

6. A method according to any one of claims 1 to 5, wherein the bonding polymer is deposited in the concave areas of the insert.

7. A method according to any one of claims 1 to 5, wherein the bonding polymer is a polyethylene-based polymer.

8. A method according to any one of claims 1 to 6, wherein the overmolding polymer (2) is a thermoplastic polymer.

9. A method according to any one of claims 1 to 7, wherein the fiber reinforcement comprises glass or carbon fibers and wherein the thermosetting matrix is ​​an epoxy resin.

10. A reservoir for pressurized gas, such as hydrogen, made by the process according to any one of the preceding claims.

11. A pressurized gas reservoir, such as hydrogen, comprising a composite insert (1) comprising a fiber reinforcement embedded in a thermosetting matrix, and an overmolding covering at least a part of the surface of the insert with an overmolding polymer (2), characterized in that at least a part of the surface of the insert (1) has a deposit of a bonding polymer.

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