Method for manufacturing a gas tank

Abstract

A method for manufacturing a high-pressure tank (40) for gas, in particular hydrogen, comprising the following steps: a) laying at least one outer layer (1) of fibres on a gas-tight liner (2) impervious to said gas, having at least two opposite main walls (5, 6) spaced apart by through-wells (10), so as to externally cover at least the opposite main walls (5, 6) of the liner (2); b) engaging rovings (20) of dry fibres in at least a portion of the through-wells (10) of the liner (2); c) after steps a) and b), using injection to impregnate the outer layer (1) and the rovings (20) with a resin; d) during or after the impregnation step, consolidating the resin in the outer layer (1) and the rovings (20).

Description

[0001] Description

[0002] Title: Manufacturing process of a gas tank

[0003] Technical field

[0004] The present invention relates to the storage of high-pressure gas, in particular hydrogen, and more specifically but not exclusively for the transport sectors, including the automotive and aeronautical sectors. In particular, the invention relates to a high-pressure gas tank, in particular hydrogen, and a method for manufacturing such a tank.

[0005] Prior art

[0006] To store hydrogen at high pressure, especially at pressures above 500 bars, it is known to use a cylindrical tank.

[0007] However, in a motor vehicle, the space available to accommodate a large diameter cylindrical tank is limited, unless it encroaches on the volumes available for the passenger compartment or the trunk, which is not desirable.

[0008] It was proposed to make the hydrogen tank with a general parallelepiped shape to facilitate its integration into the vehicle under the passenger compartment floor.

[0009] However, such a reservoir shape produces mechanical constraints which tend to limit the storage pressure.

[0010] WO 2021 / 255041 proposes a pressurized hydrogen tank made of composite material of generally parallelepiped shape, comprising a liner having opposite main walls connected by wells into which are inserted reinforcing elements based on continuous fibers, such as resin-impregnated carbon fibers whose ends are deployed and fixed on the outer surface of the main walls. A jacket of composite material covers the deployed ends, this jacket being put in place and crosslinked after the insertion of the reinforcing elements into the wells. An insert is arranged in the center of the deployed part. A locking disc covers the insert. An intermediate reinforcing layer can be applied to the liner before the deployment of the reinforcing element. The manufacturing process of such a tank involves a large number of parts and steps, which makes it relatively complex and expensive.

[0011] WO20 16 / 057024 proposes a liner, made of a previously manufactured polymer material, coated with pre-impregnated fibers. The whole is then polymerized in a mold, the liner being pressurized during this step. In application FR 2764 671 a wall of unconsolidated composite material comprising fibers and a polymer resin is positioned around a bladder and shafts are positioned in wells of the bladder. The shafts are made of consolidated composite material. Tanks manufactured using one of these methods, however, do not offer the high mechanical strength required to store a gas at a pressure greater than 500 bars.

[0012] Statement of the invention

[0013] There is a need to improve gas tanks of generally parallelepiped shape in order to allow high pressure storage and to offer good mechanical resistance.

[0014] Summary of the invention

[0015] The present invention meets this need thanks to, according to one of its aspects, a method for manufacturing a gas tank having a liner sealed against said gas with at least two opposite main walls spaced apart by through-wells, said gas being in particular hydrogen, high pressure, in particular a pressure greater than or equal to 350 bars, comprising the following steps: a) depositing at least one outer layer of fibers on the liner, so as to externally cover at least the opposite main walls of the liner; b) engaging fiber strands in at least part of the through-wells of the liner; c) after steps a) and b), impregnating by injection the outer layer and the strands with a resin; d) during or after the impregnation step c), consolidating, in particular polymerizing, the resin in the outer layer and the strands.

[0016] The consolidation, in particular the polymerization, of the same resin in the outer layer and the wicks makes it possible to obtain good cohesion of the polymer structure, in particular at the junction between the wicks and the outer layer.

[0017] Wicks

[0018] Preferably, the wicks are of slender shape extending along a longitudinal axis.

[0019] The fibers of the strands may be dry. Preferably, all the strands are dry. By "dry fibers" is meant fibers not impregnated with a polymer that will melt or polymerize during steps a) to d) above.

[0020] By "dry wicks" we mean unimpregnated wicks, similarly to what is stated above.

[0021] The use of dry fiber strands, in combination with injection impregnation, allows for a high fiber density at the through-wells, in particular a fiber volume proportion greater than 50%. Such a proportion is difficult, if not impossible, to obtain with pre-impregnated fiber strands, because when such a strand is engaged, part of its volume is occupied by the resin. In other words, for a given volume, a dry fiber strand can contain more fibers than a strand with pre-impregnated fibers.

[0022] The fibers of the outer layer and / or at least part of said strands, in particular all the strands, may be long and / or continuous fibers.

[0023] By “long fibers” we mean fibers with a length greater than or equal to 3 cm, preferably greater than or equal to 5 cm.

[0024] In particular, the fibers of the strands may extend from one end of the strand to another, in particular between the two longitudinal ends of the strand, when the strands are slender in shape.

[0025] After step d) of consolidation, in particular polymerization, the volume proportion of fibers at the level of the wicks can be greater than 50%. Such a fiber proposal makes it possible to obtain good recovery of pressure forces.

[0026] During step d) of consolidation, in particular polymerization, the resin in the outer layer can be consolidated, in particular polymerized, simultaneously with the resin in the wicks. Such simultaneous consolidation, in particular polymerization, makes it possible to obtain good cohesion of the polymer matrix of the reservoir obtained, in particular at the level of the through-wells.

[0027] At least one wick, in particular each wick, may comprise at least one bundle of fibres formed of a core, comprising long fibres parallel to each other, and a coating, comprising at least one long fibre wound around the core. The use of such a bundle makes it possible to obtain a tightening of the fibres, which makes it possible to increase the proportion of fibres engaged in the well and to maintain the fibres of the core in a predetermined direction, during and after the engagement of the wicks. The core may comprise between 70,000 and 20,000,000 fibres for a through well of 13 mm in diameter.

[0028] The ratio between the number of fibers in the core and the diameter of the through-well can be between 5,000 and 1,600,000 fibers / mm.

[0029] The coating can contain between 1 and 100 threads.

[0030] Preferably, when the coating comprises at least two fibers, at least two fibers are wound around the core in two different directions, for example by braiding.

[0031] The core may comprise at least 80, better at least 99% of the fibers of the bundle.

[0032] The core fibers may be identical to the coating fibers.

[0033] Alternatively, the core fibers may be different from the coating fibers, for example of different diameter and / or different material.

[0034] Each fiber can have a diameter between 1 and 20 microns.

[0035] Each strand can contain between 1,000 and 50,000 fibers.

[0036] In one embodiment, each strand is comprised of one or more bundles.

[0037] The wicks may have, before engagement in the wells, a larger section of between 0.8 and 1.1, in particular between 0.95 and 1 times the section of the wells in order to have a force-fitting of the wicks in the wells.

[0038] Before engagement step b), each wick may have a cross-section between 1 and 5 mm.

[0039] The fibers of the wicks can be selected 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.

[0040] In engagement step b), the wicks may be caused to extend from one end of the through-wells to another.

[0041] After engagement step b), the wicks may protrude from at least one side, in particular from both sides, of the outer layer, preferably a protrusion of at least 10 mm, better still at least 50 mm.

[0042] After step b), the fibers of the wicks can form blossoms covering the outer layer and / or the liner.

[0043] After step b), the method may comprise a step of depositing at least a second outer layer of fibers on a liner so as to cover the expansions. Outer layer

[0044] During deposition step a), the outer layer fibers may be deposited by draping and / or winding.

[0045] During deposition step a), several layers of fibers can be deposited to form the outer layer, in particular between 2 and 50 layers.

[0046] Before step b) of engaging the wicks, the outer layer can be cut so as to form openings at the level of the through wells of the liner.

[0047] The fibers of the outer layer may be dry.

[0048] The outer layer may comprise fibers assembled together in the form of a textile, in particular a fabric, a knit or a non-woven NFC (in English “Non-Crimp-Fabrics”).

[0049] During step a), the fibers of the outer layer may be laid down to extend parallel to the main walls of the liner at the level of the latter.

[0050] Injection and consolidation

[0051] Step c) of impregnation and step d) of consolidation can be carried out in a mold, in particular a single mold, in particular a heated or preheated mold.

[0052] The mold may comprise a first part and a second part and may take an open or closed configuration. The first part and the second part form between them, in the closed configuration, a cavity configured to receive the assembly.

[0053] Each part can be configured to receive one of the main walls.

[0054] The first part may have one or more holes for injecting the resin.

[0055] The first part may comprise at least one orifice configured to be opposite a through well during injection.

[0056] In particular, the first part may comprise for each through-well an orifice configured to be opposite this through-well.

[0057] The second part may include at least one vent allowing the evacuation of air and possibly excess resin during the impregnation stage.

[0058] In particular, the second part may comprise for each through-well a vent configured to be opposite this through-well. Before and / or during the impregnation step d), the mold cavity may be put at a negative relative pressure. In other words, a vacuum, at least partial, may be created in the mold cavity.

[0059] During step c) and / or d), an internal cavity of the liner may be pressurized, in particular a pressure higher than the injection pressure, in particular higher than 5 bars. This pressurization makes it possible to maintain the shape of the assembly during the impregnation step.

[0060] During d) injection, the polymer resin can be injected at a pressure between 0.1 bar and 30 bar.

[0061] The resin can be a thermosetting resin or a thermoplastic resin.

[0062] The thermosetting resin can be a polyepoxide.

[0063] The thermoplastic resin may be chosen from the group consisting of polyolefins, in particular polypropylene, polyamides, in particular aliphatic polyamides, such as polycaprolactam PA 6, polyhexamethylene adipamide PA 6.6, polycarbonates, PAEK (Polyaryletherketone) which includes PEEK (polyetheretherketone) and PEKK (polyetherketoneketone), acrylic-based materials such as PMMA (in particular the resin known as ELIUM®), PEI (Polyetherimide also known as ULTEM), PPS (Polyphenylene sulfide), TABS (acrylonitrile butadiene styrene), PLA (polylactic acid), TPU (thermoplastic polyurethane) and PET (polyethylene), and mixtures thereof.

[0064] Liner

[0065] The liner can be made of thermoplastic polymer material.

[0066] The liner can form a single cavity.

[0067] The liner can form a cavity with a volume between 1 1 and 5 0001.

[0068] The liner may include a peripheral wall connecting the opposite main walls at their periphery.

[0069] The opposing walls of the liner can have a thickness between 0.1 mm and 500 mm.

[0070] The outer layer may be deposited so as to cover the peripheral wall, in particular completely covering the peripheral wall.

[0071] The opposing main walls of the liner may be substantially parallel to each other. The surface density of wells on the opposing main walls may be between 1 well / dm 2 (for wicks with a diameter of 25 mm for example) and 43 wells / dm 2 (for 4 mm diameter drill bits for example).

[0072] The peripheral wall of the liner may have a curved shape in section, in particular an outwardly convex shape, for example substantially hemicircular in section. Such a shape improves the mechanical resistance to pressure stresses.

[0073] The liner can be made of a thermoplastic polymer material, in particular polyamide (PA), for example PA6, PAI 1 or PA12, or polyethylene (PE).

[0074] The opposing main walls of the liner may be spaced apart from each other by a maximum distance of between 20 mm and 300 mm, in particular between 120 mm and 200 mm.

[0075] The spacing between the two main walls can be constant.

[0076] Alternatively, the spacing between the main walls can be variable. In this case, the length of the wells is also variable, depending on the spacing between the walls. The length of each wick can also be variable to adapt to the length of the corresponding well.

[0077] The opposing main walls of the liner can have a length of between 1 m and 3 m, in particular between 1.20 m and 2 m.

[0078] The main opposing walls of the liner can have a width of between 50 cm and 2 m, in particular between 1 m and 1.50 m.

[0079] The wells can have a circular section with a smaller diameter of between 4 and 25 mm.

[0080] The liner can be produced by any suitable process for forming a polymer material, in particular by injection molding.

[0081] The liner can be made in one or more parts assembled after manufacture.

[0082] Reservoir

[0083] The invention also relates, according to another of its aspects, independently or in combination with the above, to a gas reservoir, in particular hydrogen, at high pressure, in particular obtained according to the method as defined above, comprising:

[0084] - a liner impervious to said gas, in particular to hydrogen, having at least two opposite main walls spaced apart by through-wells connecting these main walls, - an envelope made of polymer matrix composite material externally covering at least the main walls and extending into at least part of the through-wells, the volume proportion of fibers of the envelope in the through-wells being between 50% and 90%, preferably between 55% and 65%.

[0085] The composite material envelope is preferably a single piece.

[0086] The tank can be configured to store gas at a pressure greater than or equal to 350 bars, in particular greater than or equal to 700 bars.

[0087] The tank can contain hydrogen at a pressure between 350 and 1000 bars, including 700 bars.

[0088] Brief description of the drawings

[0089] 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

[0090] [Fig 1] illustrates, in cross-section, schematically, a step of depositing a layer of fibers of an example of a method according to the invention,

[0091] [Fig 2] illustrates, in cross-section, schematically, a cutting step according to an example of the method according to the invention,

[0092] [Fig 3] illustrates, in cross-section, schematically, a step of engaging wicks of an example of a method according to the invention,

[0093] [Fig 4] illustrates, in side view, schematically, an example of a wick according to the invention,

[0094] [Fig 5] illustrates, in cross-section, schematically, a step of spreading the wicks of an example of the method according to the invention,

[0095] [Fig 6] illustrates, in cross-section, schematically, injection and consolidation steps of an example of the method according to the invention, and

[0096] [Fig 7] illustrates, in perspective, an example of a reservoir according to the invention.

[0097] Detailed description

[0098] 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.

[0099] In the figures, the actual proportions have not always been respected, for the sake of clarity.

[0100] Figures 1 to 6 illustrate an example of a method according to the invention.

[0101] In a first step, illustrated in Figure 1, an outer layer 1 of fibers is deposited around a liner 2 by unwinding a reel 3 of fibers.

[0102] The fibers of the outer layer 1 are, for example, long, dry carbon fibers assembled together in the form of a fabric.

[0103] Winding is carried out by unwinding the coil 3 around the liner 2 in a direction X so as to form several layers of fibers.

[0104] The winding is carried out so as to cover a first main wall 5 of the liner 2, a second main wall 6 of the liner 2, opposite the first wall 5, and at least part of a peripheral wall 7 connecting the first wall 5 and the second wall 6.

[0105] For example, the peripheral wall 7 has a curved shape, in particular convex towards the outside, for example substantially hemicircular in section. This shape allows good absorption of pressure forces at the level of the peripheral wall 7.

[0106] The first wall 5 is spaced from the second wall 6 by through wells 10, in this example of substantially circular section.

[0107] Each through well 10 has an opening 11 at the level of the first wall 5 and at the level of the second wall 6.

[0108] The liner 2 forms a single closed cavity 12.

[0109] Liner 2, for example, is made of polyamide, particularly PAU.

[0110] Then, in a step illustrated in Figure 2, cutouts 15 are made in the outer layer 1 at each opening 11 of each through-well 10.

[0111] The cutouts 15 have, for example, a section substantially the same as that of the openings 11.

[0112] The cutouts 15 are for example made using a cutting tool.

[0113] In a further step, illustrated in FIGS. 3 and 4, strands 20 of dry carbon fibers are engaged in the through-wells 10 through the cutouts 15. As illustrated in FIG. 4, each strand 20 can be slender along an elongation axis L and have a circular section.

[0114] At least one wick 20, preferably each wick 20, comprises a bundle 21 of fibers, in particular a single bundle, formed of a core 22, comprising long fibers parallel to each other, and a coating 23, comprising a long fiber wound around the core 22.

[0115] The wicks 20 are caused to extend from one opening 11 to another of the through-wells 10, the openings 11 constituting the ends of the through-wells 10.

[0116] The wicks 20 can be parallel to each other.

[0117] The wicks 20 protrude on each side of the outer layer 1 over a distance S of at least 5 mm, for example 50 mm.

[0118] After engagement, in a step illustrated in FIG. 5, the projecting parts of the wicks 20 are deployed, for example manually, to form expansions 25 covering, in this example, the outer layer 1 externally and to come to bear on it.

[0119] The blossoms 25 form widened ends of the wicks 20.

[0120] At the level of the expansions 25, the fibers of the wicks 20 diverge away from the elongation axis L of the wick 20.

[0121] The assembly 30 thus formed is then placed in a mold 31, as illustrated in Figure 6.

[0122] The mold 31 comprises a first part 32, receiving the first wall 5, and a second part 33, receiving the second wall 6.

[0123] The first part 32 and the second part 33 can be separated to position the mold 31 in an open insertion or extraction configuration.

[0124] The first part 32 and the second part 33 can be assembled to position the mold 31 in a closed configuration, illustrated in FIG. 6. In the closed configuration, the mold 31 forms a cavity 35 receiving the assembly 30.

[0125] Once the assembly 30 is in the mold 31, the cavity 12 of the liner 2 is put under pressure, for example hydraulic or pneumatic pressure, to a pressure of 5 bars.

[0126] Then an at least partial vacuum is created in the cavity 35 of the mold 31 through vents 36 present in the first part 32. In this example, the first part 32 comprises a vent 36 opposite an opening 11 of each through-well 10.

[0127] A thermosetting resin is injected in parallel into the cavity 35 through orifices 37 in the second part 33. In this example, the second part 33 comprises an orifice 36 opposite an opening 11 of each through-well 10.

[0128] Thus, in alignment with each through-well 10, the mold 31 comprises a vent 36 and an orifice 37. This facilitates the penetration and therefore the impregnation of the fibers in the wicks 20, even with a high fiber density in the through-wells 10.

[0129] The injection also allows the impregnation of the fibers of the outer layer 1.

[0130] During injection, the resin present in the wicks 20 and in the outer layer 1 is consolidated by heating the mold 31.

[0131] Once the resin has consolidated, the assembly 30 can be extracted from the mold 31, which then forms a high-pressure reservoir 40.

[0132] An example of such a parallelepiped-shaped reservoir 40 is illustrated in Figure 7.

[0133] The tank 40 comprises a liner 2 which is gas-tight, in particular hydrogen-tight, and has two opposite main walls 5 and 6 spaced apart by through-wells 10.

[0134] The tank 40 comprises an envelope 41 made of thermosetting polymer matrix composite material externally covering the liner 2 and extending entirely into all the through-wells 10, the volume proportion of fibers of the envelope 41 in the through-wells 10 being greater than or equal to 50%.

[0135] The tank 40 can be configured to store gas at a pressure greater than or equal to 350 bars, in particular greater than or equal to 700 bars.

[0136] The tank 40 has a single cavity formed by the liner 2.

[0137] As illustrated, the reservoir 40 may comprise cones 45 open towards the outside resulting from the use of the wicks 20. Each cone 45 is thus above a through well 10.

[0138] It is possible to have identical through-wells 10 throughout the reservoir 40 and to use identical wicks 20. It is also possible to have through-wells 10 whose cross-section varies depending on the location on the reservoir 40 and to use wicks 20 of varied cross-sections, depending on those of the corresponding through-wells 10. In particular, the cross-section of the through-wells 10 may be larger in the center of the reservoir 10 than on the periphery.

[0139] It is also possible to have a variable spacing between the through wells 10. In particular, the density of through wells 10 may be higher in the center of the reservoir 40 than at the periphery.

[0140] As illustrated, the through wells 10 and therefore the wicks 20 can be positioned in longitudinal and transverse rows on the reservoir 40.

[0141] The tank 40 also includes a valve 46 allowing the supply of gas, in particular hydrogen, and the extraction thereof. The invention is not limited to the examples which have just been described.

[0142] The section of the wicks 20 may be different, for example non-constant and / or oval, rectangular, semi-circular, half-moon or even parallelepiped.

[0143] The tank 40 can be given a shape other than generally parallelepiped, for example a shape substantially matching the profile of an airplane wing, or a partitioned shape with one or more interior cavities.

[0144] The resin can be a thermoplastic resin.

Claims

Claims 1. Method for manufacturing a gas tank (40) having a liner sealed against said gas with at least two main walls (5, 6) opposite each other spaced apart by through-wells (10), said gas being in particular high-pressure hydrogen, comprising the following steps: a) depositing at least one outer layer (1) of fibers on the liner (2), so as to externally cover at least the main walls (5, 6) opposite each other of the liner (2); b) engaging wicks (20) of dry fibers in at least part of the through-wells (10) of the liner (2); c) after steps a) and b), impregnate by injection the outer layer (1) and the wicks (20) of a resin; d) during or after the impregnation step c), consolidating the resin in the outer layer (1) and the wicks (20).

2. Method according to claim 1, wherein the fibers of the outer layer (1) and / or at least part of said strands (20) are long and / or continuous fibers.

3. Method according to any one of the preceding claims, in which, during the consolidation step d), the resin in the outer layer (1) is consolidated simultaneously with the resin in the wicks (20).

4. Method according to any one of the preceding claims, in which at least one wick (20), in particular each wick (20), comprises at least one bundle (21) of fibers formed from a core (22), comprising long fibers parallel to each other, and a coating (23), comprising at least one long fiber wound around the core (21).

5. Method according to any one of the preceding claims, in which, during the engagement step b), the wicks (20) are caused to extend from one end (11) to another of the through wells (10).

6. Method according to any one of the preceding claims, in which, after step b) of engagement, the wicks (20) protrude from at least one side, in particular from both sides, of the outer layer (1), preferably a protrusion of at least 10 mm, better still of at least 50 mm.

7. Method according to the preceding claim, in which, after step b), the fibers of the wicks (20) form expansions (25) covering the outer layer (1) and / or the liner (2).

8. Method according to any one of the preceding claims, in which, during the deposition step a), the fibers of the outer layer (1) are deposited by draping and / or winding.

9. Method according to any one of the preceding claims, in which, before step b) of engaging the wicks (20), the outer layer (1) is cut so as to form openings (15) at the level of the through wells (10) of the liner (2).

10. Method according to any one of the preceding claims, in which the outer layer (1) comprises fibers assembled together in the form of a textile, in particular a fabric, a knit or a non-woven NCF (in English “Non-Crimp-Fabrics”).

11. Method according to any one of the preceding claims, in which step c) of impregnation and step d) of consolidation are carried out in a mold (31), in particular a single mold, in particular a heated or preheated mold.

12. Method according to any one of the preceding claims, in which, during step c) and / or d), an interior cavity (12) of the liner (2) is put under pressure, in particular a pressure greater than 5 bars.

13. Method according to any one of the preceding claims, in which, during d) injection, the polymer resin is injected at a pressure of between 0.1 bar and 30 bar.

14. Tank (40) of gas, in particular hydrogen, at high pressure, obtained according to the method as defined in any one of the preceding claims, comprising: - a liner (2) sealed against said gas, in particular against hydrogen, having at least two opposite main walls (5, 6) spaced apart by through wells (10) connecting these main walls (5, 6); - an envelope (41) made of polymer matrix composite material externally covering at least the main walls (5, 6) and extending in at least part, in particular in all, of the through-wells (10), the volume proportion of fibers of the envelope (41) in the through-wells (10) being between 50% and 90%.

15. Reservoir (40) according to the preceding claim, in which the volume proportion of fibers of the envelope (41) in the through wells (10) is between 55% and 65%.

16. Tank (40) according to any one of claims 14 and 15, configured to store gas at a pressure greater than or equal to 350 bars, in particular greater than or equal to 700 bars.

17. Tank (40) according to any one of claims 14 to 16, in which the liner (2) forms a single cavity (12).

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