High-pressure hydrogen tank

Abstract

High-pressure hydrogen tank. Method for manufacturing a high-pressure gas tank (10), in particular a hydrogen tank, comprising the following steps: a) depositing, in particular by draping, at least one first layer (5) of thermoplastic matrix composite material onto a liner (1) that is leak-proof for said gas, in particular hydrogen, having at least two opposing main walls (2) connected by through-wells (4), so as to externally cover at least the opposing main walls (2); b) engaging rivets (15) of thermoplastic matrix composite material in through-wells (14) of the liner (1) through the first layer (5), before consolidation thereof; c) widening by thermoforming at least one end (21) of the rivets (15) emerging from the through-wells (4), preferably both ends (21).so as to form enlarged ends (16) capable of absorbing at least part of the pressure forces exerted on the opposite main walls (2) of the liner (1). Figure for the abbreviation: Fig. 1,

Description

Title of the invention: High pressure hydrogen tank Technical field

[0001] The present invention relates to the storage of high-pressure gas, in particular hydrogen, in particular for the transport sectors, including the automotive and aeronautical sectors. In particular, the present invention relates to a high-pressure gas tank, in particular hydrogen, and a method for manufacturing such a tank. Prior art

[0002] To store hydrogen at high pressure, in particular at pressures greater than 500 bar, it is known to use a cylindrical tank.

[0003] 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.

[0004] It has been proposed to make the hydrogen tank with a generally parallelepiped shape to facilitate its integration into the vehicle under the floor of the passenger compartment.

[0005] However, such a reservoir shape produces mechanical stresses which tend to limit the storage pressure.

[0006] WO 2021 / 255041 describes 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, the ends of which are deployed and fixed to the outer surface of the main walls. A jacket made 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 disk covers the insert. An intermediate reinforcing layer may be applied to the liner before the deployment of the reinforcing element.

[0007] The manufacturing process of such a tank involves a large number of parts and steps, which makes it relatively complex and expensive. Statement of the invention

[0008] There thus remains a need to improve hydrogen tanks made of composite materials, in particular those suitable for automotive applications, as well as their manufacturing process. Summary of the invention

[0009] The present invention aims to meet this need and achieves this by means of, according to a first of its aspects, a method for manufacturing a high-pressure gas tank, in particular hydrogen. Manufacturing method

[0010] This method according to the first aspect of the invention comprises the following steps: a) depositing, in particular by draping, at least a first envelope made of thermoplastic matrix composite material on a liner impermeable to said gas, in particular to hydrogen, having at least two opposite main walls connected by through-wells, so as to externally cover at least the opposite main walls, b) engaging rivets made of thermoplastic matrix composite material in the through-wells of the liner through the first envelope, before consolidating the latter, c) widening by thermoforming at least one end of the rivets emerging from the through-wells, preferably both ends, so as to form widened ends capable of absorbing at least part of the pressure forces exerted on the opposite main walls of the liner.

[0011] Such a method makes it relatively easy to manufacture a hydrogen tank allowing storage at high pressure, in particular at 350 bar or more. Indeed, the rivets make it possible to take up a significant part of the mechanical pressure constraints which are exerted on the opposing main walls.

[0012] Since the formation of the widened ends of the rivets is carried out by thermoforming, the industrialization of the process is facilitated, and the operation can easily be automated. In addition, since the insertion of the rivets is carried out through the first envelope before consolidation thereof, the installation of this first envelope on the liner is facilitated, because it is not hindered by the presence of the rivets. The fibers of the first envelope move apart by themselves under the effect of the installation of the rivets through the first envelope.

[0013] During the process, in particular by draping, at least one second envelope made of composite material can be deposited, externally covering at least one peripheral wall connecting the opposite main walls at their periphery and overlapping at least partially the first envelope and a plurality of through-wells of the liner.

[0014] The rivets can thus be engaged in the wells by penetrating the first casing and, where appropriate, the second casing. This allows the rivets to perform an additional function of mechanically connecting the first and second casings to each other.

[0015] The method may include a step of manufacturing and / or supplying the rivets.

[0016] The rivets may be manufactured by pultrusion of long fibers impregnated with a thermoplastic polymer material. Pultrusion manufacturing facilitates the industrialization of rivets. In addition, this process ensures that the rivet fibers are properly tensioned and parallel to each other, giving the rivets good mechanical strength.

[0017] The manufactured rivets may have, over at least 50% of their length, a circular section.

[0018] The rivets may have, before thermoforming, a larger section with a circumscribed circle diameter of between 4 and 25 mm, in particular between 10 and 15 mm.

[0019] The rivets may also include portions of non-circular section.

[0020] The rivets may have, before engagement in the wells, a greater section between 1 and 1.1, in particular between 1 and 1.05 times the section of the wells in order to have a force-fitting of the rivets in the wells.

[0021] Preferably, the end of the rivets by which they are inserted into the through-wells has a tapered shape, in particular a beveled or pointed shape. Such a shape facilitates the penetration of the rivet through the first casing and, where appropriate, through the aforementioned second casing.

[0022] The thermoforming step can be carried out using a tool, in particular a sonotrode, allowing pressure to be applied to the end of a rivet simultaneously with the heating of this end.

[0023] The sonotrode may have a head with a central tip. Such a head may allow, during thermoforming, the fibres of the rivet to be spread apart and thus the end of the rivet to be widened more easily.

[0024] Each rivet has a length greater than the length of the well in which it is engaged before thermoforming.

[0025] After thermoforming, the enlarged ends of the rivets may have a shape substantially matching that of the outer surface of the liner in the area bordering the through-well.

[0026] The method may comprise a step of impregnating with a polymer material, preferably thermoplastic, in particular in a mold, the assembly formed by the liner, the rivets, the first envelope and, where appropriate, the second envelope. This step may make it possible to consolidate all of the elements so as to form the tank. Hydrogen tank with overlapping jackets

[0027] The invention also relates, according to a second 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 defined above, comprising: - a liner impervious to said gas, in particular to hydrogen, having at least two opposite main walls, through wells connecting these main walls and a peripheral wall connecting the opposite main walls at their periphery, - at least a first envelope made of composite material externally covering at least the opposite main walls of the liner, - at least one second envelope made of composite material externally covering at least the peripheral wall and overlapping at least partially the first envelope and a plurality of through-wells of the liner, - rivets made of composite material each engaged in a corresponding well of said plurality and through the first and second casings and having widened ends.

[0028] The second envelope makes it possible to absorb the mechanical forces at the junctions between the peripheral wall and the opposite main walls, areas where the mechanical stresses are particularly high. Hydrogen tank reinforced with rivets

[0029] The invention also relates, according to a third 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 defined above, comprising - a liner impervious to said gas, in particular to hydrogen, having at least two opposite main walls and through wells connecting these main walls, - at least a first envelope made of thermoplastic matrix composite material externally covering at least the opposite main walls of the liner, - rivets made of thermoplastic matrix composite material, each engaged in a corresponding well of the liner and having at least one thermoformed widened end after passing through at least the first envelope, so as to take up at least part of the pressure forces exerted on the opposite main walls of the liner.

[0030] As explained above, the rivets which have at least one thermoformed widened end allow significant absorption of the pressure stresses exerted on the two opposite main walls.

[0031] In addition, thermoforming the ends of the rivets ensures the absorption of mechanical stress, which allows high pressure storage, in particular at pressures above 350 bar, in particular 700 bar, while resisting pressures 2.5 times higher than the storage pressure, i.e. 1750 bar, in order to comply with current safety standards.

[0032] The reservoir according to the second or third aspect of the invention may have all or part of the characteristics set out above in connection with the method and ca- following characteristics. Envelopes

[0033] The liner may comprise, as mentioned above, a peripheral wall connecting the opposite main walls at their periphery, the first envelope in particular completely covering the peripheral wall.

[0034] Preferably, the tank comprises at least one second envelope made of composite material externally covering at least the peripheral wall of the liner and overlapping at least partially the first envelope and a plurality of through-wells of the liner. The second envelope can thus partially cover the opposite main walls. The second envelope can in particular externally cover the first envelope. The second envelope makes it possible to absorb the mechanical stresses at the junctions between the peripheral wall and the opposite main walls, areas where the mechanical stresses are particularly high.

[0035] The first envelope may have a thickness of between 3 and 30 mm, in particular between 5 and 15 mm.

[0036] The second envelope may have a thickness of between 2 and 40 mm, in particular between 3 and 30 mm.

[0037] The first and / or the second envelope may comprise long fibers.

[0038] The first and / or the second envelope may comprise fibers spaced apart at rivet level, the spacing of the fibers of an envelope resulting from the insertion of the rivet through the envelope.

[0039] The first and / or the second envelope may comprise fibers chosen from the group consisting of carbon fibers, Kevlar® fibers, glass fibers, ceramic fibers, fibers of polymer material, for example thermoplastic, in particular aramid or polyester fibers, fibers of plant origin, in particular flax fibers, metal fibers, the fibers preferably being carbon fibers, or a mixture of such fibers.

[0040] The thermoplastic matrix of the first and / or second envelope may be made from at least one thermoplastic polymer 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 (polymethyl methacrylate) (in particular the resin known under the name ELIUM®), PEI (Polyetherimide also known under the name ULTEM®), PPS (Polyphenylene sulfide), ABS (acrylonitrile butadiene styrene), PLA (polylactic acid), TPU (thermoplastic polyurethane) and PET (polyethylene), and their blends.

[0041] Preferably, the matrix of the envelope(s) is chosen to be compatible with the matrix of the rivets, being for example of the same chemical family or identical.

[0042] The first and / or the second envelope can be produced with a plurality of superimposed layers, in particular between 2 and 50 layers. Liner

[0043] The opposite main walls of the liner may be substantially parallel to each other.

[0044] The surface density of wells on the opposite main walls can be between 1 well / dm2 (for rivets with a diameter of 25mm for example) and 43 wells / dm2 (for rivets with a diameter of 4mm for example).

[0045] The peripheral wall of the liner may have a curved shape in section, in particular a shape that is convex towards the outside, for example substantially hemicircular in section. Such a shape promotes mechanical resistance to pressure stresses.

[0046] The liner can be made of a thermoplastic polymer material, in particular PA6, PA11, PA12, PE.

[0047] The opposite main walls of the liner may be separated from each other by a maximum distance of between 20 mm and 300 mm, in particular between 120 mm and 200 mm.

[0048] The spacing between the two main walls can be constant.

[0049] Alternatively, the spacing between the main walls may be variable. In this case, the length of the wells is also variable, depending on the spacing between the walls. The length of each rivet may also be variable to adapt to the length of the corresponding well.

[0050] The opposite main walls of the liner may have a length of between 1 m and 3 m, in particular between 1.20 m and 2 m.

[0051] The opposite main walls of the liner may have a width of between 50 cm and 2 m, in particular between 1 m and 1.50 m.

[0052] The wells may have a circular section with a smaller diameter of between 4 and 25 mm.

[0053] The liner can be produced by any suitable process for forming a polymer material, in particular by injection molding.

[0054] The liner can be made in one or more parts assembled after manufacture.

[0055] The cavity formed by the liner may have a lower thickness at the periphery of the main walls, in particular at the level of the second envelope. The reduction in the thickness of the cavity makes it possible to compensate for the excess thickness induced by the superposition of the two envelopes. Rivets

[0056] Rivets can also be called rushes.

[0057] The part engaged in the rivet wells can be mounted with a tight fit.

[0058] The rivets can transverse the first casing and / or, where appropriate, the second casing. The enlarged end of the rivets in this case bears axially on the outermost casing.

[0059] In particular, the rivets closest to the peripheral wall advantageously pass through the first envelope and the second envelope. Thus, the rivets located on the periphery also contribute to the absorption of mechanical stresses at the junctions between the opposite peripheral and main walls.

[0060] The section of the rivets may be substantially identical. Alternatively, the section of the rivets may increase with the distance from the peripheral wall, to take into account the fact that the absorption of forces provided by the periphery of the tank decreases with increasing distance from the latter.

[0061] The rivets may each comprise a bundle of long fibers oriented over part of their length substantially parallel to the wells.

[0062] At least one rivet, preferably each rivet, may have two ends with an enlarged end formed by thermoforming.

[0063] The thermoplastic polymer matrix of the rivets can be made from at least one thermoplastic polymer 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), ABS (acrylonitrile butadiene styrene), PLA (polylactic acid), TPU (thermoplastic polyurethane) and PET (polyethylene), and mixtures thereof.

[0064] The fibres of the rivets are preferably glass, carbon or aramid fibres.

[0065] The rivets may have, before thermoforming, a larger section with a circumscribed circle diameter of between 5 and 20 mm, in particular between 10 and 15 mm.

[0066] The rivets may have, before thermoforming, a length of between 20 mm and 400 mm.

[0067] Preferably, at least one end of the rivets has, before thermoforming, a tapered shape, in particular a beveled or pointed shape.

[0068] Rivets may be manufactured by pultrusion of long fibers impregnated with a thermoplastic polymer material.

[0069] The manufactured rivets may have, over at least 50% of their length, a circular section.

[0070] The rivets may have, before engagement in the wells, a larger section of between 1 and 1.1 times, better still between 1 and 1.05 times the internal section of the wells.

[0071] Thermoforming can be carried out using a tool, in particular a sonotrode, allowing pressure to be applied to the end of a rivet simultaneously with heating this end.

[0072] The sonotrode may have a head with a central tip. Such a head may allow, during thermoforming, the fibres of the rivet to be spread apart and thus the end of the rivet to be widened more easily.

[0073] Each rivet has a length greater than the length of the well in which it is engaged before thermoforming. In particular, the rivets may protrude from the wells before thermoforming by a length of between 2 mm and 100 mm.

[0074] The widened ends of the rivets may include a cup, which may correspond to the trace left by the head of the sonotrode used for thermoforming.

[0075] The widened ends formed by thermoforming may have a substantially circular or elliptical outline, eccentric relative to the axis of the well, in particular when the thermoforming is carried out on a beveled end, or centered on the axis of the well, when the thermoforming is carried out on a flat or pointed end. Miscellaneous

[0076] The tank may include a valve for supplying and extracting gas, in particular hydrogen.

[0077] The tank may have a generally parallelepiped shape, particularly suitable for positioning the tank under the floor of a motor vehicle.

[0078] The tank can contain hydrogen at a pressure of between 350 and 1000 bar, in particular at 700 bar. Brief description of the drawings

[0079] 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

[0080] [Fig.l] [Fig.l] illustrates, in perspective, in a schematic manner, an example of a hydrogen tank according to the invention,

[0081] [Fig.2] [Fig.2] is a schematic and partial cross-section of the reservoir of [Fig.l],

[0082] [Fig.3] [Fig.3] is another view, in perspective and partial, of the reservoir of the [Fig.l],

[0083] [Fig.4] [Fig.4] illustrates, in partial cross-section and schematically, the tank after the deposition by draping the envelopes around the liner,

[0084] [Fig.5] [Fig.5] shows in elevation different forms of rivets,

[0085] [Fig.6] [Fig.6] illustrates the engagement of a rivet in the well of a liner with crossing of the first envelope, before thermoforming its end,

[0086] [Fig.7] [Fig.7] is a view similar to [Fig.6] after thermoforming of the end of the rivet, and

[0087] [Fig.8] [Fig.8] is a top and schematic view of enlarged ends after ther rivet molding. Detailed description

[0088] In the remainder of the description, elements that are identical or similar or have similar or identical functions bear the same reference sign. For the sake of brevity of the present description, they are not described with regard to each of the figures, only the main differences between the embodiments being described.

[0089] In the figures, the actual proportions have not always been respected, for the sake of clarity.

[0090] Figures 1 to 3 illustrate an example of a high-pressure hydrogen tank 10.

[0091] The tank 10 has, as illustrated in [Fig.l], a generally parallelepiped shape. It has a thickness E of the order of 150 mm for example, a length Lo of the order of 1.60 m for example, and a width La of the order of 1.20 m for example.

[0092] The tank 10 comprises two valves 20 allowing the supply of hydrogen and the extraction thereof, respectively.

[0093] As illustrated in [Fig.2], the tank 10 comprises an inner body formed by a hydrogen-tight liner 1, forming a closed cavity 11 intended to receive the hydrogen under pressure.

[0094] The liner 1 is made of a thermoplastic polymer material.

[0095] The liner 1 has two opposite main walls 2 and a peripheral wall 3 connecting the main walls 2 at their periphery.

[0096] The main walls 2 extend, in this example, substantially parallel to each other.

[0097] The peripheral wall 3 has a curved shape, convex towards the outside, for example substantially hemicircular in section.

[0098] The liner 1 also comprises a plurality of through wells 4 connecting the opposite main walls 2.

[0099] The tank 10 also comprises a first casing 5 which externally covers the main walls 2 and the peripheral wall 3.

[0100] The first envelope 5 is made of a composite material with a thermoplastic matrix, for example carbon fibers with a PMMA matrix.

[0101] The first envelope has, for example, a maximum thickness El of 10 mm.

[0102] In this example, the tank 10 also comprises a second envelope 6 which covers the peripheral wall 3 and part of the main walls 2 from their edge, this second envelope 6 superimposing externally on the first envelope 5 in a covering zone Zr.

[0103] The second envelope 6 is also made of a composite material and has a maximum thickness E2 of, for example, 30 mm.

[0104] The second envelope 6 comprises, for example, carbon fibers and a thermoplastic polymer matrix, for example the same thermoplastic polymer material as that of the matrix of the first envelope 5.

[0105] The second envelope 6 substantially matches the external shape of the first envelope 5 and the liner 1.

[0106] The cavity formed by the liner 1 may have a smaller thickness at the periphery, in particular at the level of the second envelope 6. This reduced thickness makes it possible to maintain the thickness of the reservoir 10 substantially constant despite the overlap between the first and second envelopes 6.

[0107] According to the invention, the tank 10 comprises a plurality of rivets 15, each engaged in a corresponding well 4 of the liner 1.

[0108] The rivets 15 each comprise two widened ends 16 produced by thermoforming during the manufacture of the tank, as detailed below.

[0109] The widened end 16 is, in this example, either in abutment against the external surface of the first casing 5 for the rivets 15 outside the periphery, or in abutment against the second casing 6, for the rivets 15 located at the level of the superposition between the two casings 5 ​​and 6.

[0110] As illustrated in [Fig.3], the wells 4 and therefore the rivets 15 can be positioned in longitudinal 17 and transverse 18 rows on the tank 10. [YES] Advantageously, as illustrated in [Fig. 3], all the rivets 15 located on the periphery bear on the second casing 6. This configuration makes it possible to reinforce the mechanical resistance at the periphery of the tank, because these rivets also take up part of the mechanical stresses of the second casing 6.

[0112] Because the widened ends 16 are thermoformed, there are little or no residual stresses that tend to cause the rivets to return to their initial shape.

[0113] As illustrated in [Fig.2], the rivets 15 may comprise cups 17 centered on their longitudinal axis L. These cups 17 correspond to the mark left by the tool which was used for thermoforming.

[0114] Each rivet 15 comprises long fibers, for example carbon fibers, which extend at the level of the body of the rivets engaged in the well, parallel to each other and to the axis of the well 4.

[0115] At the level of the enlarged head of the rivet, these fibers diverge away from the axis of the well, substantially forming a cone open towards the outside.

[0116] In this example, the rivets 15 have, apart from the widened ends 16, for example a circular section, for example of the order of 15 mm in diameter.

[0117] It is possible to have identical wells 4 throughout the tank and use identical rivets. It is also possible to have wells 4 whose section varies depending on the location on the tank 10 and use corresponding rivets 15 of varied sections, depending on those of the corresponding wells 4.

[0118] In particular, the section of the wells 4 may be larger in the center of the reservoir 10 than on the periphery.

[0119] It is also possible to have a variable spacing between the wells 4. In particular, the density of wells 4 can be greater in the center of the reservoir 10 than at the periphery.

[0120] To manufacture the tank 10, one can proceed as follows.

[0121] The liner is produced with the desired shape, by injection molding for example, in one or more pieces assembled after molding.

[0122] The rivets 15 are also made. As illustrated in [Fig.5], before their engagement, the rivets 15 are of elongated shape on a longitudinal axis L. They are manufactured by pultrusion of fibers, for example carbon.

[0123] The rivets 15 may have a single end 21 with a beveled shape, as in example (a). The rivets 15 may also have an end 21 with a pointed shape, as in example (b).

[0124] The rivets 15 thus manufactured comprise a set of fibers parallel to each other which extend from one end 21 to another. The fibers are, due to the pultrusion, correctly tensioned.

[0125] Then, as illustrated in [Fig.4], the first envelope 5 of fibers is draped over the liner 1 so as to cover the main walls 2 and the peripheral wall 3. The draping can be done with dry or pre-impregnated fibers.

[0126] The second envelope 6 is also draped over the periphery of the liner so as to cover the peripheral wall 3 and the first envelope over a certain distance. This draping can also be done with dry or pre-impregnated fibers.

[0127] As illustrated, the draping of the first envelope 5 and the second envelope 6 can be done by partially or totally covering the openings of the wells 4 of the liner 1.

[0128] The rivets 15 are then engaged in the wells 4 of the liner 1, as illustrated in [Fig.6].

[0129] During this engagement, the rivets 15 pass through the first casing 5 and, where appropriate, the second casing 6. This passage is facilitated by the beveled shape of the rivets 15 which makes it possible to gradually separate the fibers of the casings 5 ​​and 6.

[0130] The length Lr of the rivets 15 is at this stage greater than the thickness Ep of the tank 10 being manufactured given by the external surface 18 of the first casing 5.

[0131] In a next step, illustrated in [Fig.7], the ends 21 of the rivets 15 are thermoformed, in this example using a sonotrode 30, according to an automated process, for example on a production line with one or more sonotrodes 30. The sonotrode 30 has a head 31, allowing ultrasound to be transmitted. The head 31 is preferably of pointed shape, which facilitates the separation and the formation of the enlarged end 16 of the rivets.

[0132] The tip 32 of the head 31a for example has a conical shape.

[0133] The head 31 is preferably, as illustrated, of revolution around an axis R. During the thermoforming operation, the axis R of the head 31 and the longitudinal axis L of the rivet 15 to be thermoformed are aligned.

[0134] The shape of the head 31, in particular of its point 32, is at the origin of the formation of the cup 17 of the widened end 16.

[0135] Thermoforming makes it possible to separate the fibers F in order to push them towards the first envelope 5 or, where appropriate, towards the second envelope 6 and to form a widened end 16. Once the widened end 16 has cooled, it retains its shape to fully play its role of absorbing mechanical pressure stresses.

[0136] The fibers F of the rivet located in the non-thermoformed zone present in the well 4 remain parallel to each other.

[0137] As visible in Figure 8a, the widened ends 16 formed by the thermoforming of rivets 15 with a beveled end 21 may have a substantially circular shape, eccentric from the axis of the well 4.

[0138] In the case of rivets 15 having a pointed or flat end 21, the widened end 16 may have a circular shape centered on the well 4, as illustrated in FIG. 8b.

[0139] Finally, in a last step, the assembly formed for the rivets 15, the liner 1 and the envelopes 5 and 6 is placed in a mold to carry out an injection of a thermoplastic polymer material and thus obtain the tank 10.

[0140] The injection of the material can be done in a mold in which the semi-finished tank is placed. A pressurized fluid is placed inside the liner, and the material is injected under pressure from the outside. The fluid in the liner makes it possible to maintain the shape of the tank during this step and to avoid the collapse of the tank under external pressure constraints. In the case of using a PMMA resin (for example ELIUM®), the polymerization begins in the mold which is heated to 70-90°C and will continue during cooling outside the mold, down to room temperature.

[0141] The invention is not limited to the examples which have just been described.

[0142] Thermoforming devices other than sonotrodes, for example induction or infrared devices, can be used for thermoforming rivets.

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

[0144] The tank can be compartmentalized, if necessary.

Claims

Claims

1. Method for manufacturing a high-pressure gas, in particular hydrogen, tank (10), comprising the following steps: a) depositing, in particular by draping, at least a first envelope (5) made of a thermoplastic matrix composite material on a liner (1) impervious to said gas, in particular to hydrogen, having at least two opposite main walls (2) connected by through-wells (4), so as to externally cover at least the opposite main walls (2), b) engaging rivets (15) made of a thermoplastic matrix composite material in through-wells (14) of the liner (1) through the first envelope (5), before consolidating the latter, c) widening by thermoforming at least one end (21) of the rivets (15) emerging from the through-wells (4), preferably their two ends (21),so as to form widened ends (16) capable of taking up at least part of the pressure forces exerted on the opposite main walls (2) of the liner (1).,

2. Method according to the preceding claim, in which at least one second envelope (6) made of composite material is deposited, in particular by draping, externally covering at least one peripheral wall (3) connecting the main walls (2) opposite each other at their periphery and overlapping at least partially the first envelope (5) and a plurality of wells (14) passing through the liner (1).

3. Method according to one of claims 1 and 2, in which the rivets (15) are manufactured by pultrusion of long fibers impregnated with a thermoplastic polymer material.

4. Method according to any one of the preceding claims, in which the rivets (15) manufactured have, over at least 50% of their length, a circular section.

5. Method according to any one of the preceding claims, in which the end (21) of the rivets by which they are inserted into the through wells (4) has a tapered shape, in particular a beveled or pointed shape.

6. Method according to any one of the preceding claims, in which the thermoforming step is carried out using a tool (30), in particular a sonotrode, allowing the application of pressure on one end (21) of a rivet (15) simultaneously with the heating of this end (21).

7. Method according to any one of the preceding claims, comprising a step of impregnating with a polymer material, preferably thermoplastic, in particular in a mold, the assembly formed by the liner (1), the rivets (15), the first envelope (5) and, where appropriate, the second envelope (6).

8. Tank (10) for gas, in particular hydrogen, at high pressure, in particular obtained according to the method according to any one of the preceding claims, comprising: - a liner (1) impervious to said gas, in particular hydrogen, having at least two main walls (2) opposite and through wells (14) connecting these main walls (2), - at least a first envelope (5) made of thermoplastic matrix composite material externally covering at least the main walls (2) opposite of the liner (1), - rivets (15) made of thermoplastic matrix composite material each engaged in a corresponding well (14) of the liner (1) and having at least one widened end (16) thermoformed after passing through at least the first envelope (5), so as to take up at least part of the pressure forces exerted on the main walls (2) opposite of the liner (1).

9. Tank (10) according to the preceding claim, in which the liner (1) comprises a peripheral wall (3) connecting the main walls (2) opposite each other at their periphery, at least one second envelope (6) made of composite material externally covering at least the peripheral wall (3) of the liner (1) and overlapping at least partially the first envelope (5) and a plurality of wells (14) passing through the liner (1).

10. Tank (10) according to the preceding claim, in which the second envelope (6) partially covers the opposite main walls (2).

11. Tank (10) according to one of claims 9 and 10, in which the second envelope (6) externally covers the first envelope (5).

12. Tank (10) according to any one of claims 8 to 11, in which the rivets (15) each comprise a bundle of long fibers oriented over part of their length substantially parallel to the well (14), preferably glass, carbon or aramid fibers.

13. Tank (10) according to any one of claims 8 to 12, in which the opposing main walls (2) are substantially parallel to each other.

14. Tank (10) according to any one of claims 8 to 13, in which the liner (1) comprises a peripheral wall (3) connecting the main walls (2) opposite each other at their periphery, the first envelope (5) entirely covering the peripheral wall (3).

15. A reservoir (10) according to any one of claims 8 to 14, wherein the surface density of wells (14) on the opposite main walls (2) is between 1 well / dm2 and 43 wells / dm2.

16. Tank (10) according to any one of claims 8 to 15, in which the liner (1) comprises a peripheral wall (3) connecting the main walls (2) opposite each other at their periphery, the section of the rivets (15) increasing with the distance from the peripheral wall (3).

17. A tank (10) according to any one of claims 8 to 16, wherein at least one rivet (15), preferably each rivet (15), has two ends (21) with an enlarged end (16) formed by thermoforming.

18. Tank (10) according to any one of claims 8 to 17, wherein the liner (1) is made of a thermoplastic polymer material.

19. Tank (10) according to any one of claims 8 to 18, containing hydrogen at a pressure of between 350 and 1000 bar, in particular at 700 bar.

20. Tank (10) according to any one of claims 8 to 19, in which the cavity (11) formed by the liner (1) has a smaller thickness at the periphery of the main walls (2).

Images