WO2023187120A1

WO2023187120A1 - Cryogenic tank having complex shape and high gravimetric index and corresponding manufacturing method

Info

Publication number: WO2023187120A1
Application number: PCT/EP2023/058406
Authority: WO
Inventors: Franck Doyen; Eric Torres
Original assignee: Design Tech Centre
Priority date: 2022-04-01
Filing date: 2023-03-30
Publication date: 2023-10-05
Also published as: FR3134163A1

Abstract

The invention relates to a cryogenic tank. More particularly, the invention relates to a cryogenic tank (10), the wall of which comprises a plurality of layers (11, 12, 61), an outer layer (11) of which is in contact with the outside environment and an inner layer (12) of which is in contact with the contents of the tank. According to the invention, at least one of the layers of the wall of the tank (10) is made of composite material comprising a lamination of plies (65, 66) stacked on one another in a stacking direction locally perpendicular to the surface of said layer (61) in which at least one ply (66) of the lamination of plies (65, 66) diverges from the surface of the layer (61), thus forming a reinforcing structure of said layer (61), referred to as a reinforced portion (62), and said layer (61) being known as a composite reinforced layer. Due to its structure, the tank can adopt any shape, in particular complex shapes, and leads to a high gravimetric index.

Description

DESCRIPTION

TITLE: Cryogenic tank of complex shape and high gravimetric index and corresponding manufacturing process

Technical field of the invention

The technical field is that of short-term storage and transport of energy sources, in particular via the use of cryogenic tanks. The technique relates more particularly to a cryogenic tank for the transport and/or use of a liquid (this liquid being in the form of gas at room temperature and atmospheric pressure). Furthermore, the technique also relates to the corresponding manufacturing process.

Technology background

As part of the energy transition that must necessarily be carried out to reduce greenhouse gas emissions, it is essential to completely rethink the temporary storage and transport of clean energy sources, such as hydrogen.

Current manufacturing methods provide heavy and bulky gas tanks. The problem with this type of tank is that the energy source (hydrogen) is stored there in gaseous form, which results in either a tank with a low gravimetric index and therefore a heavy tank, or a reduction in the autonomy provided to the vehicle. in question at constant weight. Solutions are therefore being developed to build cryogenic tanks allowing this gas to be transported and used in liquid form. One of these cryogenic tank solutions is to manufacture the said tank from aluminum, whose density is lower than steel and which has very good mechanical properties at low temperatures.

However, current cryogenic tanks still remain heavy due to their necessary insulation, the density of aluminum and they can only be cylindrical or spherical in shape. They cannot therefore be integrated into all situations or all vehicle configurations. For example, current cryogenic tanks cannot be integrated into the wing of an airplane, unlike kerosene tanks, or into the space of a car tank for example. Thus, to date, such cryogenic tanks must therefore be integrated into dedicated spaces, or even the vehicle carrying one or more tanks of this type must be built around these tanks. For example, in the case of an airplane, current cryogenic tanks are mainly integrated into the fuselage, which further limits the payload and requires the development of new architectures to be certified without the possibility of reusing the existing one. Such hydrogen tanks therefore do not allow the retrofit of existing aircraft (re-equipment of an existing aircraft by replacing the current propulsion system with a propulsion system using hydrogen).

The disadvantages of current cryogenic tanks and gas storage tanks are therefore their weight, their bulk and their limited shapes (sphere, cylinder).

Thus, it is necessary to find a solution making it possible to obtain less bulky tanks with complex shapes, and lighter, while having very good mechanical resistance. Summary of the invention

The present invention aims to respond to at least some of the problems of the prior art.

These objectives, as well as others which will appear subsequently, are achieved using a cryogenic tank whose wall comprises a plurality of layers, among which an external layer is in contact with the external environment, an internal layer is in contact with the contents of the tank, at least one of the layers of the wall of the tank being made of composite material comprising a laminate of plies stacked on top of each other along a stacking direction locally perpendicular to the surface of said layer in which at least one ply of the ply laminate diverges from the surface of the layer, thus forming a reinforcing structure of said layer, called reinforced part, and said layer being named reinforced composite layer.

Thus, it is possible to obtain, by following the general principle of the invention, a tank of complex shape due to the use of composite materials and the absence of excessive pressure within the tank, the latter retaining the contents in liquid and non-gaseous form. Such a complex shape therefore makes it possible to integrate this tank into any space deemed useful by those skilled in the art. In addition, the use of composite materials allows the system to be lighter and the mechanical properties to be improved.

According to a particular embodiment of the invention, the external layer of the tank is a reinforced composite layer.

Thus, the external surface of the tank has improved mechanical properties, making it possible to resist external stress (pressure change, buckling, etc.).

According to a particular embodiment of the invention, two successive layers among the plurality of layers of said wall of said reservoir have an inter-layer space, said inter-layer space being configured to be placed under vacuum or under ultra-high vacuum.

Thus, the tank has improved insulation properties, while remaining compact, the vacuum being created between two successive pre-existing layers.

According to a particular embodiment of the invention, said inter-layer space is maintained using supports.

Thus, the supports (or ribs) make it possible to prevent any collapse of the interlayer space placed under vacuum, and can also contribute to improving the mechanical properties of the tank wall.

According to a particular embodiment of the invention, one of said two successive layers of the plurality of layers is the outer layer, said outer layer being at least partially free from attachment with respect to the following layer, so that the layer external from deforming under the effect of pressure variations.

According to a particular embodiment of the invention, said internal layer of the reservoir is made of composite material.

According to a particular embodiment of the invention, said internal layer (12) of the tank is made of aluminum.

According to a particular embodiment of the invention, said tank is integrated into an aircraft.

According to a particular embodiment of the invention, said tank is integrated within a fuselage or a wing or a tail of an aircraft.

The different particular characteristics listed above can of course be combined with each other, in all possible combinations. The invention also relates to a method of manufacturing a tank as described above. The method comprises the following steps: shaping an internal layer; optional addition of ribs; optional addition of at least one intermediate layer; addition of an external layer around the assembly formed by said internal layer and optionally said at least one intermediate layer; evacuation of at least one inter-layer space; at least one of the layers mentioned above being manufactured according to the following steps: positioning of at least one ply on the external side of said layer, called non-diverging ply; creation of a reinforced part within a laminate of plies according to the following steps: addition of at least one element composed of a low density material on said at least one non-diverging external ply, called support element; addition and shaping of at least one fold on the internal side of the layer, covering the assembly formed by said at least one external fold and said at least one support element, said at least one internal fold conforming to the shapes of the assembly formed by said at least one external fold and said support element; addition of resin to form a matrix encompassing the assembly formed by the laminate of plies and said at least one support element; polymerization of said resin.

Brief description of the figures

Other aims, characteristics and advantages of the invention will appear on reading the following description given for illustrative and non-limiting purposes only, and which refers to the appended figures, in which:

[Fig. 1] represents an example of a cryogenic tank seen in section;

[Fig. 2] represents the phase diagram of hydrogen;

[Fig. 3] represents an example of the production of cryogenic tanks integrated into the fuselage of an aircraft;

[Fig. 4] represents an exemplary embodiment of a cryogenic tank seen in section, the section of which has the shape of an airplane wing profile;

[Fig. 5] represents an example of a cryogenic tank seen in section, the section of which is an assembly of a rectangular parallelepiped and a cylinder;

[Fig. 6] represents an example of making a layer of a cryogenic tank, seen in section;

[Fig. 7] represents an example of an embodiment of an inter-layer space placed under vacuum having transverse ribs, seen in section;

[Fig. 8] represents an example of an embodiment of an inter-layer space placed under vacuum having longitudinal ribs, seen in section;

[Fig. 9] represents an example of a cryogenic tank seen in section;

[Fig. 10] represents an example of making a wall of a cryogenic tank; detailed description

1. General principle

As explained previously, the general principle of the technique consists of manufacturing a tank of complex shape from lighter and more malleable materials, while retaining properties suitable for temporary storage and transport of gas in liquid form. Thus, the manufacturing technique developed by the inventors makes it possible to have a cryogenic tank which can, for example, be used for the transport and/or use of liquid hydrogen by a vehicle. This tank is made of lightweight and mechanically efficient materials, making it possible to define complex geometries and obtain structural weight reduction. Thus, the advantages of such a reservoir are the adaptability of its shape and its high gravimetric index.

The gravimetric index I of a reservoir is defined as: I = - with P _t the weight of the liquid

Pi+P _r contained in the tank, and P _r the weight of the empty tank. The gravimetric index of a gaseous hydrogen tank is currently 5 to 6% while the gravimetric index of the tank described in this document is at least 30%.

The tank, according to the present technique, has a wall composed of at least two layers, including an outer layer (11) and an inner layer (12). At least one of the layers of the wall is a reinforced composite layer, a reinforced composite layer being composed of a composite material and comprising a laminate of plies stacked on top of each other along a stacking direction locally perpendicular to the surface of the layer and in which at least one ply of the ply laminate diverges from the surface of the layer, thus forming a reinforcing structure of the layer, called reinforced part.

Thus, such a tank is mechanically resistant, in particular to buckling, due to the use of a reinforced composite layer as described above. In addition, such a tank can adapt to any volume and any environment in which it must be placed thanks to the adaptability of its shape, due to its composite construction. Finally, such a tank has a high gravimetric index allowing, for example, fuel savings during its transport.

In relation to Figure 1 we describe a tank according to the present technique. The tank (10) has a wall composed of at least two layers, including an outer layer (11) and an inner layer (12). Figure 1 represents a sectional view of a tank of any shape according to an exemplary embodiment, this shape being generally similar to a cylinder having any section.

The assembly can integrate a filling and draining port (13), as well as a gas discharge valve (14), which can be calibrated to trigger at a given pressure.

In the case where an inter-layer space is placed under vacuum or ultra-high vacuum (between 10 ^-3 and 10 ^-6 mbar), an orifice (18) allowing the vacuum to be drawn can be added, this passing through the layer(s) s) external(s) of the tank wall, in order to connect the inter-layer space to the outside of the tank. The orifice is self-sealing thanks to a ball, thus allowing the vacuum to be drawn in one direction and the sealing of the orifice in the other. In addition, this inter-layer space can also have a sensor (19) allowing the measurement of vacuum (or ultra-high vacuum), this sensor transmitting information relating to the measurements carried out to the outside of the tank. This information can then be transmitted via radio waves or via cable, for example. Such devices (orifice 18, sensor 19) can be used for any inter-layer space placed under vacuum (or ultra-high vacuum).

The tank (10) may also include a level sensor or probe (15) in order to know the quantity of liquid gas remaining in the tank, a pressure sensor (16), as well as a temperature sensor (17). The filling and draining orifice (13) as well as the valve (14) pass through the structure in order to connect the interior of the cavity formed by the internal layer (12) to the open air from the outside. The valve (14) allows excess cryogenic fuel to be managed. For example, the liquid hydrogen contained in the tank must be maintained at a temperature of 20 K and a pressure of 1 atm (= 1.013 bar = 101.3 kPa). As illustrated in Figure 2, the phase diagram of hydrogen presents a liquid zone (21) under temperature conditions between 10 K and 30 K, and pressure between 0.1 and 100 bars. However, the coordinates corresponding to the values of 20 K and 1 bar on the diagram coincide with a point (22) of the liquid (21) - gas (23) state change curve. Therefore, the liquid hydrogen in the tank is very close to the liquid-gas boundary and any increase in temperature or decrease in pressure can cause the hydrogen to vaporize. However, the thermal insulation of the tanks can present imperfections with the consequence of a slight boiling of the hydrogen due to the potential heat input, in fact, perfectly adiabatic conditions are materially unachievable. Thus, the valve allows unloading of gaseous hydrogen in order to avoid a possible excessive increase in pressure within the tank. This pressure must therefore not exceed a threshold limit which can be around 10-20 bar for a temperature of 20 K. The gas responsible for the overpressure is therefore either consumed before reaching the threshold pressure value, or discharged by the valve.

In an exemplary embodiment, the reservoir described is a passive reservoir, the role of which is solely to provide a source of energy to be consumed. Thus, the tank makes it possible to maintain the hydrogen in liquid form for a period of 48 hours to 72 hours, a period of time during which the hydrogen contained in the tank is consumed. Furthermore, in this exemplary embodiment, the tank can integrate a heating element within the tank, in order to accelerate, if necessary, the evaporation of the hydrogen when the need for an energy source is increased (in the phase of acceleration for example).

In another embodiment, the tank described is an active tank, making it possible to maintain the hydrogen in liquid form for periods greater than 72 hours, using an integrated cooling system. Thus, the temperature sensor described above can be connected to a thermostatic device integrated into said cooling system. This makes it possible to maintain a stable temperature of 20K within the tank over long periods of time. This type of production, however, makes the whole thing heavier.

Furthermore, the tank can integrate solid or perforated internal partitions occupying all or part of the section of the tank in order to limit the movements of the cryogenic liquid and thus create a flood barrier. Indeed, in an application such as aeronautics or more generally for the transport of a tank containing a cryogenic liquid, an imbalance of the vehicle due to the movement of this liquid within the tank is not desirable.

The general principle of the technique is applicable to many types of industries that can use one or more cryogenic tank(s) such as aeronautics/aerospace, railways, automobiles, heavy goods vehicles/buses. , naval/maritime... Thus, the tank can be integrated into any type of vehicle for land mobility (trains, trucks, buses, cars, tractors, etc.) or for maritime mobility (boats of any type and any dimension, hydrofoil, hovercraft, etc.).

2. Reservoir geometry

Taking the example of an application in aeronautics, a tank as described above can be integrated into the wings, or into the fuselage of the aircraft. Indeed, its adaptable geometry allows the tank to be placed in areas of complex shapes. This complex geometry is made possible by the internal pressure of the tank maintained around 1 atm. Thus, it is not no need to use spherical or oblong geometries or even round the corners of the walls. Broken lines are possible.

Figure 3 illustrates a particular embodiment of the technique, in which two tanks are integrated into the fuselage of an aircraft. The first tank (31) takes the shape of a truncated pyramid with a rectangular base, and is placed at the rear of the cockpit (33). While the second tank (32) is placed under the cockpit (33) and has a rectangular parallelepiped shape.

Any shape deemed adequate by those skilled in the art can be envisaged for the production of such a reservoir: cone, block, cylinder, prism, ovoid, ellipsoid, sphere, any complex shape, etc. (all of these solids can be associated, deformed or even truncated according to all planes of space).

Figures 4 and 5 show two particular embodiments of the tank. Figure 4 represents a section of a tank taking the shape of the profile of an airplane wing (shape resembling a slightly flattened drop of water). This tank has a section whose surface changes according to the length of the tank. Thus, the section (41) seen in section is larger than a section (42) taken further on in the diagram. Figure 5 represents a section of a tank whose shape consists of the association of a cylinder (51) and a rectangular parallelepiped (52), the center of the cylinder being centered around an edge of the rectangular parallelepiped.

3. Description of the layers according to different embodiments

3.1. General

The walls of the tank are made up of at least two layers: an outer layer and an inner layer, between which additional elements or layers can be inserted. These layers can be composed of any material deemed suitable by those skilled in the art. Thus, they can be composed of wood, perlite, foam (polyurethane for example), glass or even metal for example aluminum (or aluminum alloy with for example silicon, copper, magnesium, etc.), titanium (or alloy), etc. The layers can also be made of composite material, for example carbon or glass fibers, GLARE, zylon, kevlar, etc. with resin (epoxy, unsaturated polyester, PEEK, polyimide...) with honeycomb, multilayer, sandwich structure, etc. In the case where the layers include fibers, these can be of a single nature or of different natures, they can have a single orientation or be multidirectional. A layer can be composed of a stack of composite plies.

In an exemplary embodiment, the composite layers comprising a stack of plies can integrate cooling and/or heating films between them, making it possible to control the temperature and therefore the thermal gradient. Another example of integration of elements within the folds of a composite layer consists of the addition of photovoltaic cells under one or more transparent folds at the level of the external layer, thus making it possible to accumulate and/or provide energy. energy to the different systems integrated into the tank.

In an exemplary embodiment, the layers composed of composites are saturated with resin, thus ensuring inter-layer sealing.

Thicknesses and number of layers may vary depending on the materials used and the desired application. These values must be adapted so as to control the temperature gradient, which extends from -260°C at the inner layer (11) to +60°C at the surface of the outer layer (12). The total thickness of the walls of a tank as described in this document is between 50 and 250 mm, depending on the vacuum resistance. In a particular embodiment, two successive layers have an inter-layer space placed under vacuum (between 1CT ³ and 1CT ⁶ mbar) making it possible to improve the thermal performance of the tank wall. These adjacent layers can, in an exemplary embodiment, be kept apart by supports.

3.2. Description of a reinforced composite layer according to different embodiment examples

The tank is composed of at least one reinforced composite layer. In particular, this layer can act as an external layer, this being the last layer in contact with the external atmosphere and having the objective of ensuring that the structure does not buckle.

Thus, the design and manufacture of such a composite layer consists of providing it with reinforced parts. More particularly, the diaper is provided with reinforced parts integrated into the diaper itself. In this way, we have an integrated/compact layer, in which the reinforced parts are an integral part of the layer itself.

The term ply is used to refer to a thin layer that may be composed of fibers. The term laminated or stacking designates a superposition of folds.

In relation to Figure 6, we describe an example of production of a reinforced composite layer (61). Figure 6 represents two sectional views of such a layer (61) having several reinforced parts (62) integrated into its thickness. At the top of Figure 6 is shown a layer (61) seen from above, while at the bottom is shown a layer (61) seen from below. The layer (61) shown is of generally rectangular parallelepiped shape and comprises an external surface

(63) and an internal surface (64). This layer (61) is made up of a laminate or stack of plies (65, 66). The folds (65) of the external surface (63) being non-diverged, and the folds (66) of the internal surface

(64) being diverged to create a reinforced part (62). The divergence of the folds is defined as the distance/spacing from the normal trajectory of the fold in the case where no reinforced part is present. Furthermore, Figure 6 represents a particular embodiment in which the reinforced parts (62) have an isosceles trapezoidal section and are of elongated shape. Furthermore, Figure 6 represents an exemplary embodiment in which the divergence of the folds is allowed by the addition of a support element (67) composed of a low density material. Indeed, the diverging folds conform to the shape of the support elements (67), the folds are deviated from the plane of the panel and thus form reinforced parts (62). The support elements (67) have the function of maintaining the spacing between the diverged and non-diverged plies, and can also have thermal properties suitable for insulation. Thus, in an exemplary embodiment, the diverging folds match the shape of the support elements (67). In addition, the role of the reinforced parts (62) being to reinforce the structure, in an exemplary embodiment, these reinforced parts (62) are of generally elongated shape in the direction to be reinforced, so as to oppose the forces to which is submitted the structure.

Thus, thanks to the use of such an external layer, the tank can take the shape of an airplane wing, resisting the forces linked to lift.

In an exemplary embodiment, all of the characteristics of the reinforced composite layer (61) developed above are applicable to any layer making up the tank wall, including the internal layer.

4. Description of the supports according to different embodiment examples

Supports can be used between two layers of the wall to create a spacing between them, which is maintained under vacuum or ultra-high vacuum, making it possible to improve the thermal performance of the tank. In an exemplary embodiment, the supports occupy the space between the internal layer of the tank and the following solid layer, the vacuum created between these layers making it possible to control the thermal gradient by isolating the liquid hydrogen in contact with the internal layer from the others. layers of the wall.

In an exemplary embodiment, the supports occupy the space between the outer layer of the tank and the next solid layer (inwards), the vacuum created between these layers making it possible to control the thermal gradient by insulating the exterior of the tank from the other layers of the wall. The outer layer being subjected to atmospheric pressure from the outside and to vacuum from the inside, it is therefore pressed onto the supports by atmospheric pressure, and free to deform (in the case of an application in aeronautics for example) with the change in atmospheric pressure, due to its non-fixation to the supports.

In an exemplary embodiment, the supports are in the form of hollowed-out ribs. Their recesses help to limit the weight of the tank, while creating an insulating layer. These recesses can be in any form deemed suitable by those skilled in the art. They can be open or not, square, elliptical, any shape, etc. In addition, the spacing and distribution of these recesses can be determined in design, depending on the forces exerted on the different zones of the tank and the desired application.

In a particular embodiment, these supports can be made of compressed balsa or any other material for which the weight of the support is less than the equivalent weight of a composite material.

The supports can be longitudinal or transverse, depending on the shape of the tank and the optimization of the forces exerted on it. Figures 7 and 8 illustrate two particular embodiments of hollowed ribs (71). Figure 7 represents a 3D sectional view of an evacuated inter-layer space forming part of the wall of a tank of any/complex shape. This inter-layer void space has a succession of hollowed out longitudinal ribs (71). The recesses (72) shown in Figure 7 are through and have an elliptical shape. Figure 8, for its part, represents a 3D view of part of an interlayer space placed under vacuum forming part of the wall of a tank of any/complex shape. This inter-layer space has hollowed out transverse ribs (71). The recesses shown in Figure 8 are through and have an elliptical shape.

Thus, it is possible to associate void inter-layer spaces comprising transverse and/or longitudinal ribs. In one embodiment, the wall of the tank comprises at least two inter-layer spaces of voids, the ribs of which are alternately transverse then longitudinal in order to better distribute the forces exerted on the wall of the tank.

In another embodiment, the reinforced parts of the reinforced composite layer, described previously, can act as inter-layer supports. Thus, an ultra-high vacuum can be made between a reinforced composite layer and the next layer, without adding additional supports.

5. Description of a first specific embodiment

In a particular embodiment, illustrated in Figure 9, the different layers making up the walls of the tank are successively, from the inside to the outside: a first waterproof internal layer (12) made of aluminum or composite (covered on its upper or interior part of a film or fabric resistant to ultra-low temperatures such as polyimide (TECASINT®, KAPTON®), polytetrafluoroethylene (TECAFLON®, GORE-TEX®), polyolefin (Porelle® membrane), or even a layer of NEGs (Non-Evaporable Getters)... an inter-layer space (92) placed under vacuum (or ultra-high vacuum), the adjacent layers being held apart using supports/ribs. a second layer (94) composed of a stack of plies of composite material based on carbon fibers, or other type of fibers, the angle of the plies between them being able to be any angle value deemed adequate by those skilled in the art job. The thickness of this second layer is between 0.5mm to 20mm depending on the required technical specifications. This layer is saturated with a resin ensuring inter-layer and inter-ply sealing. This layer can also be in the form of a composite-foam-composite sandwich in part or in full, it will then be obtained by successive or simultaneous cooking. This second layer (94) is covered on its interior part with an insulator (93) of the Mylar type or with a layer of NEGs, and on its exterior part with an optional insulation layer (95), of the type “cryogenic insulating glass sheet” for example that of the company UNIFRAX or a polyimide or polyamide film. This second layer (94) is repeated as many times as necessary to control the temperature gradient. an inter-layer space (96) placed under vacuum (or ultra-high vacuum), adjacent layers being held apart using supports/ribs. the outer layer (11), the last layer which faces the external atmosphere, is a composite layer making it possible to prevent buckling of the structure, using reinforced portions or parts, as described previously.

6. Description of a second specific embodiment

In a particular embodiment, the different layers making up the walls of the tank are successively, from the inside to the outside: a sealed internal layer made of aluminum or composite, which may have the characteristics of a reinforced composite layer such as as described previously; an inter-layer space placed under vacuum or ultra-high vacuum (that is to say between pressures between 10 ^-3 and 10 ^-6 mbar); an external layer of reinforced composite whose reinforced parts are elongated in the direction of the forces to which the structure is subjected, so as to prevent buckling;

In an exemplary embodiment, the inter-layer space under vacuum or under ultra-high vacuum present between the internal layer and the external layer can be created without adding support, by simply evacuating the spaces formed between the internal layers and layers. external(s) by the reinforced parts. When the internal layer is a composite layer, it may have reinforced parts perpendicular to the reinforced parts of the external layer in order to limit thermal bridge zones.

In another exemplary embodiment, the vacuum inter-layer spacing present between the internal layer and the external layer can be created using rib-type supports making it possible to maintain a spacing between the internal layer and the external layer, the ribs being perpendicular to the reinforced parts of the reinforced composite layer(s). If the internal layer is a reinforced composite layer, as illustrated in Figure 10, it can have reinforced parts (62) parallel to the reinforced parts of the external layer (11, 61), while the ribs (71) are perpendicular to the reinforced parts (62) of the internal (12, 61) and external (11, 61) layers, consequently limiting the thermal bridge zones. In Figure 10, the reinforced parts have a policeman's hat section due to the shape of the support elements (67) which is married by the diverged folds (66). In addition, the ribs have recesses (72) of elliptical section.

7. Description of a manufacturing process

The method of manufacturing the tank as described above therefore uses at least two layers including at least one layer forming a laminated material. The manufacture of such a tank can be carried out in part using processes adapted to composite materials, these processes can be manual (contact molding, vacuum molding, infusion, prepregs, etc.), and/or mechanized ( RTM, thermoforming, molding, filament winding, etc.) or any other type of process deemed suitable by those skilled in the art.

In an exemplary embodiment, the tank consists of an internal layer (composite or metallic), increased from the inside to the outside by layers of composite materials (carbon fibers, glass fibers, zylon, kevlar, with resin), manufactured by the deposition of composite plies and/or by filament winding. The tank is therefore capable of taking any geometric shape. The waterproofing of the composite layers of the entire wall is obtained by saturating the composite plies with resin so as to eliminate any porosity.

In relation to Figures 1 and 6, the general manufacturing method of a tank (10) comprises the following steps: shaping an internal layer (12); optional addition of ribs (71); optional addition of at least one intermediate layer which may be made of composite (94) and/or insulating (93, 95) and/or mechanically resistant (94); addition of an external layer (11) around the assembly formed by said internal layer (12) and optionally said at least one intermediate layer (93, 94, 95); evacuating at least one inter-layer space (92, 96); at least one of the layers mentioned above being manufactured according to the following steps: positioning of at least one ply (65) on the external side of said layer (61), called non-diverging ply; creation of a reinforced part within a laminate of plies (65, 66) according to the following steps addition of at least one element (67) composed of a low density material on said at least one ply (65) external non-diverged, called support element (67); addition and shaping of at least one fold (66) on the internal side of the layer (61), covering the assembly formed by said at least one external fold (65) and said at least one support element (67), said at least one internal fold (66) matching the shapes of the assembly formed by said at least one external fold (65) and said support element (67); addition of resin to form a matrix encompassing the assembly formed by the laminate of plies (65, 66) and said at least one support element (67); polymerization of said resin.

According to a specific example of embodiment, the manufacturing process implements the following steps: shaping of an inner core (or inner layer 12) made of composite or metallic material, this inner core comprising a filling orifice and a filling orifice degassing; addition of ribs, hollowed out as explained above, on the inner core; addition, in the space between the ribs, of a soluble paste (for example soluble polymer) in water (or any other solvent) to a height equal to the height of the ribs at any point; addition of a layer (61) of reinforced composite, by draping the folds, over the assembly formed by the ribs and the paste, this layer comprising a self-sealing orifice intended for drawing the vacuum; the steps of adding ribs, soluble paste and a reinforced composite layer are repeated as many times as necessary to achieve the number of layers and the desired performance; polymerization of the whole and demolding; removal of the soluble paste by dissolution in a solvent (water or other); installation of valves and seals; placing the inter-layer space under vacuum (or ultra-high vacuum) via the vacuum draw-off port; tank test.

Claims

1. Cryogenic tank (10) whose wall comprises a plurality of layers (11, 12, 61), among which an external layer (11) is in contact with the external environment, an internal layer (12) is in contact with the contents of the tank, characterized in that at least one of the layers of the tank wall (10) is made of composite material comprising a laminate of plies (65, 66) stacked on top of each other along a direction d stack locally perpendicular to the surface of said layer (61) in which at least one ply (66) of the laminate of plies (65, 66) diverges from the surface of the layer (61), thus forming a reinforcing structure of said layer (61), called reinforced part (62), said layer (61) being called reinforced composite layer.

2. Cryogenic tank (10) according to claim 1, characterized in that the outer layer (11) of the tank (10) is a reinforced composite layer (61).

3. Cryogenic tank (10) according to claim 1, characterized in that two successive layers among the plurality of layers of said wall of said tank have an interlayer space, said inter-layer space being configured to be placed under vacuum or under ultra-high vacuum.

4. Cryogenic tank (10) according to claim 3, characterized in that said interlayer space is maintained using supports (71, 62).

5. Cryogenic tank (10) according to claim 3, characterized in that one of said two successive layers of the plurality of layers (11, 12, 61) is the outer layer (11), said outer layer (11) being at least partially free from attachment with respect to the next layer, so that the outer layer (11) can deform under the effect of pressure variations.

6. Cryogenic tank (10) according to claim 1, characterized in that said internal layer (12) of the tank is made of composite material.

7. Cryogenic tank (10) according to claim 1, characterized in that said internal layer (12) of the tank is made of aluminum.

8. Cryogenic tank (10) according to claim 1, characterized in that it is integrated into an aircraft.

9. Cryogenic tank (10) according to claim 1, characterized in that it is integrated within a fuselage or a wing or tail of an aircraft.

10. Method for manufacturing a cryogenic tank (10) characterized in that it comprises the following steps: shaping of an internal layer (12); optional addition of ribs (71); optional addition of at least one intermediate layer (93, 94, 95); addition of an external layer (11) around the assembly formed by said internal layer (12) and optionally said at least one intermediate layer (93, 94, 95); evacuating at least one inter-layer space (92, 96); at least one of the layers mentioned above being manufactured according to the following steps: positioning of at least one ply (65) on the external side of said layer (61), called non-diverging ply; creation of a reinforced part within a laminate of plies (65, 66) according to the following steps addition of at least one element (67) composed of a low density material on said at least one ply (65) external non-diverged, called support element (67); addition and shaping of at least one fold (66) on the internal side of the layer (61), covering the assembly formed by said at least one external fold (65) and said at least one support element (67), said at least one internal fold (66) matching the shapes of the assembly formed by said at least one external fold (65) and said support element (67); addition of resin to form a matrix encompassing the assembly formed by the laminate of plies (65, 66) and said at least one support element (67); polymerization of said resin.