DE102016220154B3 - Pressure vessel for storing a fuel with auxetic material - Google Patents

Abstract

The invention relates to a pressure vessel system comprising a pressure vessel (1) for storing a fuel, in particular hydrogen, the pressure vessel (1) comprising a matrix and fibers embedded in the matrix, in particular fiber layers (20, 21, 22) Matrix comprises an auxetic material (30) such that the spacings (70, 71) of the fibers, in particular of the fiber layers (20, 21, 22), grow in a radial direction (90) of the pressure vessel (1) relative to each other when the matrix is due to a pressure increase of the fuel in the pressure vessel (1) along the fibers is stretched.

Description

The invention relates to a pressure vessel system comprising a pressure vessel for storing a fuel, in particular hydrogen.

In pressure vessels in motor vehicles, a fuel, e.g. Hydrogen, stored. The fuel is used to drive a motor vehicle. The fuel may e.g. Be hydrogen, which is supplied to a fuel cell, which serves to drive the motor vehicle.

The pressure vessel typically includes a liner and an outer shell. The outer shell essentially carries the pressure load of the pressure vessel. The outer shell of the pressure vessel comprises fibers / fiber layers which are surrounded by a matrix or fibers / fiber layers which are embedded in a matrix. In previously known pressure vessel systems, as the fuel in the pressure vessel increases in pressure, the fiber / fiber layers located farther inward (i.e., closer to the interior volume or storage space of the pressure vessel) are more heavily loaded than fibers / fiber layers further outward. Such a pressure vessel can have a high weight and a lot of material. This can cause a comparatively heavy weight and comparatively high manufacturing costs.

It is a preferred object of the technology disclosed herein to reduce or eliminate at least one disadvantage of previously known solutions. In particular, it is an object to provide a pressure vessel optimized in terms of space, weight and / or cost.

The object (s) is / are solved by the subject matter of claim 1. The dependent claims are preferred embodiments.

The proposed solution is based on the finding that, in previously known solutions, the radial spacing between the individual fibers / fiber layers decreases with increasing pressure of the fuel in the pressure vessel. The reason for this is that the fibers / fiber layers lying further inside are pressed outwards and thus move outwards relative to the outer layers and thus approach them. The more outer fibers / fiber layers are less stretched than the more inner fibers / fiber layers. Consequently, the further outward fibers / fiber layers of the pressure vessel are generally under a lower tension than the more inner fibers / fiber layers of the pressure vessel. Therefore, the fibers / fiber layers or the material of the pressure vessel i.d.R. unevenly loaded. Thus i.d.R. no optimal or even utilization of the material of the pressure vessel before.

The object is achieved here by a pressure vessel system comprising a pressure vessel for storing a fuel, in particular hydrogen, the pressure vessel having a matrix and fibers embedded in the matrix, in particular fiber layers, wherein the matrix comprises an auxetic material at least as an additive. The auxetic material is here provided to cause a reduction in the Poisson's number of the matrix. The reduction in Poisson's number causes the fiber / fiber layers to converge less strongly in the radial direction with an increase in internal pressure than in an otherwise identical matrix without auxetic material. This causes the difference in the fiber direction stresses resulting between radially inner fiber / fiber layer (s) and outer fiber / fiber layer (s) located further outward to be smaller than the difference for them inner / outer fibers / fiber layer (s) having a matrix (in particular having otherwise the same matrix composition) without the auxetic material. Thus, the matrix comprises the auxetic material in such a way that the profile of the respective fiber tension is more uniform in the radial direction in an outer shell at least partially surrounding a liner than in the same outer shell with an otherwise identical matrix without auxetic material.

"Otherwise, the same matrix / outer shell" in this context means that in the comparison matrix / comparison outer shell, only the auxetic material / additive was omitted or substituted, without otherwise the chemical composition or the physical structure of the fiber-plastic composite was changed. Provided at least as an additive means that an auxetic material can be admixed with a fiber-retaining matrix. In a preferred embodiment, an auxetic material itself forms the entire matrix (material). Preferably, the auxetic material is provided at the molecular level, as described in more detail below.

The matrix may comprise the auxetic material such that the distances of the fiber / fiber layers from one another in a radial direction of the pressure vessel are less reduced due to a pressure increase of the fuel than in an otherwise equal matrix without auxetic material.

The matrix may comprise the auxetic material such that the distances of the fibers, particularly the fiber layers, from each other grow in a radial direction of the pressure vessel as the matrix is stretched along the fibers due to a pressure increase of the fuel in the pressure vessel. An advantage of this is that with increasing pressure of the fuel in the pressure vessel and corresponding expansion of the fiber / fiber layers and consequently of the auxetic matrix material, the distance between the fibers / fiber layers increases and does not decrease. As a result, further outward fibers / fiber layers, ie fibers / fiber layers, which have a larger distance to the interior or storage space of the pressure vessel, also stretched or stretched, so that the fibers / fiber layers (regardless of the distance to the interior of the pressure vessel, in the fuel is stored) are loaded evenly or put under tension. Consequently, the material of the pressure vessel is utilized more optimally. Thus, the pressure vessel with the same or similar material use and the same weight greater pressures (without material damage) withstand or at constant maximum pressure (maximum operating pressure) that the pressure vessel can withstand (without material damage), have less material and a lower weight. This lowers the weight and manufacturing cost of the pressure vessel system.

Auxetic material has a negative Poisson number, i. the cross section of the auxetic material increases when it is stretched in a given direction (preferred direction).

The radial direction of the pressure vessel may be perpendicular to a center line and away from the center line in a central area of the pressure vessel (also called a cylindrical area). In two dome-like end portions, each adjacent to the central portion, the radial direction may extend outwardly from the center of the end portions (i.e., in the direction from the inner space to the outer shell), respectively. Thus, the radial direction may extend outwardly from a point of symmetry (e.g., midpoint) or a line of symmetry (e.g., the center line) or the pressure vessel longitudinal axis of the pressure vessel (i.e., in the direction away from the interior).

If the pressure vessel has a different shape, e.g. has an ellipsoidal shape, which does not allow a direct definition of the radial direction by means of simple symmetries, the (local) radial direction can be defined via the tangents to the pressure vessel walls or to the fiber / fiber layers: The radial direction can be the perpendicular to the tangents to the pressure vessel walls or to the fibers / fiber layers. The radial direction is directed from the inside to the outside. For curved surfaces, this is often from the concave surface to the convex surface. The radial direction can thus run perpendicular to each local tangent planes of the pressure vessel walls or the walls of the outer shell of the pressure vessel. For fiber layers in which the fibers generally run locally parallel, for example, a tangent ("longitudinal") in the fiber direction and another, perpendicular to tangent, which runs in the fiber layer, but transverse to the fiber direction define. The radial direction in this case may then be the perpendicular to the two tangents ("longitudinal" and "transverse" to the fiber direction). Along this radial direction and the distance of the fiber layers can be measured.

The fibers may be at least partially disposed in the matrix and the auxetic material may be at least partially formed and arranged such that, as the matrix is stretched along the fibers, the spacing of the respective fiber, in particular the respective fiber layer, from a center or centerline of the pressure vessel increases in proportion to the distance of the respective fiber to the center or the center line of the pressure vessel prior to expansion of the matrix. As a result, an even better or more even distribution of the occurring stresses or forces on the fibers / fiber layers is achieved. The fibers / fiber layers, regardless of the distance of the fiber / fiber layer from the center or the center line, loaded substantially equally strong. Consequently, the pressure vessel with the same or similar material use greater pressures (without material damage), withstand or have a higher maximum operating pressure. This lowers the weight and manufacturing cost of the pressure vessel system. The center line extends from a dome-like end portion to the other dome-like end portion at a cylindrical central portion of the pressure vessel and two dome-like end portions through the center of the center portion. parallel to the height of the cylindrical central part and perpendicular to the radius of the cylindrical central part.

The auxetic material may comprise an auxetic material at the molecular level, in particular an auxetic material at the molecular level. This prevents existing cavities in the auxetic material from collapsing due to the applied pressure of the fuel, and thus the auxetic material loses the auxetic property or is no longer functional. Thus, an advantage of this is that the operability of the pressure vessel system is ensured even at high pressures.

The auxetic material may be evenly distributed in the matrix. The advantage of this is that the stresses occurring in the pressure vessel are evenly distributed to the different fibers / fiber layers.

The matrix may comprise a plastic, in particular a polymer plastic. As a result, the pressure vessel system can have a particularly low weight.

 The pressure vessel may have a cylindrical central part and two dome-shaped end regions. An advantage of this is that the forces are distributed particularly evenly on the pressure vessel. In addition, such a pressure vessel system can be arranged to save space in a motor vehicle.

The matrix may comprise at least two different auxetic materials which differ in their Poisson number. As a result, the fibers or fiber layer can be evenly targeted evenly loaded.

The pressure vessel may comprise at least three fiber layers. An advantage of this is that the pressure is distributed over a plurality of fibers / fiber layers. This increases the permissible maximum pressure of the pressure vessel.

The spacing of the fibers, particularly the fiber layers, from the interior of the pressure vessel may grow as the matrix is stretched along the fibers due to a pressure increase of the fuel in the pressure vessel. An advantage of this is that the matrix is stretched particularly uniformly when the fibers / fiber layers are stretched along or in the direction of their longitudinal direction or main direction of extension. Thus, the pressure of the fuel causes an even more uniform distribution of the mechanical stress over the fibers / fiber layers of the pressure vessel.

The auxetic material may have anisotropic properties such that the auxetic material expands differently in different directions perpendicular to the direction along the fibers as the matrix is stretched along the fibers due to a pressure increase of the fuel in the pressure vessel. One advantage of this is that the forces occurring can be distributed in a targeted manner to fibers or fiber bundles or fiber layers of different regions of the pressure vessel. The auxetic material may have a first coefficient of expansion in a first direction perpendicular to the direction of the fibers or fiber layers or to the longitudinal direction of the fibers or fiber layers. The coefficient of expansion indicates how much the auxetic material expands as the matrix is stretched toward the fiber / fiber layers. In a second direction, which is perpendicular to the direction of the fiber layers or to the longitudinal direction of the fiber layers and perpendicular to the first direction, the auxetic material may have a second expansion coefficient, the first expansion coefficient being greater or smaller than the second expansion coefficient can be.

In particular, the fuel may be a fuel which is gaseous at standard temperature (0 ° C) and standard pressure (1,000 bar). Preferably, the fuel may be hydrogen. The fuel can be supplied from the pressure vessel to a fuel cell. The pressure vessel and the fuel cell may be mounted in a vehicle, e.g. a car, a motorcycle, a truck, a bus, and the fuel cell can be used to drive the vehicle.

The auxetic material may be nanostructured and / or formed by a nanostructuring process. More than one auxetic material may be used in the pressure vessel, i. e.g. two, three, four or more than four different auxetic materials. The different auxetic materials can differ in their Poisson number or the course of their Poisson number on the strain. The distribution of the auxetic material in the middle part may differ from the distribution of the auxetic material in the dome-like end regions. It is also conceivable that there are areas between areas of the matrix which comprise auxetic material which have no auxetic material.

The technology disclosed herein relates to a compressed hydrogen storage (CHS) system for storing gaseous fuel under ambient conditions. Such a pressure vessel is in particular a pressure vessel which is installed or can be installed in a motor vehicle. The pressure vessel can be used in a motor vehicle, which is operated for example with compressed ("compressed natural gas" = CNG) or liquefied (LNG) natural gas or with hydrogen. The pressure vessel may be, for example, a cryogenic pressure vessel (= CcH2) or a high-pressure gas vessel (= CGH2). High pressure gas containers are designed to hold fuel (e.g., hydrogen) at ambient temperatures substantially at a max. Operating pressure (also called maximum operating pressure or MOP) of about 350 barü (= overpressure relative to the atmospheric pressure), further preferably of about 500 barü and more preferably of about 700 barü store. A cryogenic pressure vessel comprises an inner vessel and an outer vessel surrounding it to form a super-isolated (e.g., evacuated) space.

The pressure vessel may include a liner. The liner may be the hollow body in which the fuel is stored. The liner can For example, be made of aluminum or steel or their alloys. Further preferably, the liner may be made of a plastic or it may also be provided a linerless pressure vessel.

The technology disclosed herein will now be explained with reference to figures. Show it:

1 a schematic cross-sectional view of a pressure vessel at a first pressure of the fuel in the pressure vessel;

2 a schematic cross-sectional view of the pressure vessel from 1 at a second pressure of the fuel that is higher than the first pressure;

3 a schematic cross-sectional view of some fiber layers of a pressure vessel at a first pressure of the fuel; and

4 a schematic cross-sectional view of some fiber layers of the pressure vessel from 3 at a second pressure of the fuel, which is higher than the first pressure.

1 shows a schematic cross-sectional view of a pressure vessel 1 at a first pressure of the fuel in the pressure vessel 1 , 2 shows a schematic cross-sectional view of the pressure vessel 1 out 1 at a second pressure of the fuel, wherein the second pressure is higher than the first pressure. The pressure vessel system comprises a pressure vessel 1 for storing a fuel. The fuel is a fuel that is gaseous at standard temperature (0 ° C) and standard pressure (1,000 mbar). The fuel may be, for example, hydrogen. The pressure vessel 1 is in a motor vehicle, such as a car, arranged. The fuel can be supplied to a fuel cell. The fuel cell can be used to drive the motor vehicle.

The pressure vessel 1 may be a cryogenic pressure vessel for storing a cryogenic fuel, such as cryogenic hydrogen, or a non-cryogenic pressure vessel.

The fuel is in an interior 50 or in the internal volume or storage space of the pressure vessel 1 saved. If the pressure vessel is designed as a cryogenic pressure vessel, it may have an outer container (not shown) and an inner container. Between the outer container and the inner container, an evacuated space may be arranged.

The pressure vessel has an inner shell (so-called liner, not shown) and an outer shell. The outer shell carries the major part or main part of the pressure load of the fuel in the pressure vessel 1 , It is also conceivable that no liner is present. In this case, the matrix of the outer shell assumes the function of the liner. The interior 50 is located inside the pressure vessel.

The outer shell has a matrix structure or composite structure with fibers or fiber layers embedded therein 20 . 21 . 22 (multiple bundled fibers) or fiber layers.

The fibers / fiber layers 20 . 21 . 22 are surrounded by the matrix or embedded in the matrix. The matrix may comprise a plastic or be a plastic. The fibers are made of a material which can withstand tensile forces along or in the direction of their longitudinal direction, ie the direction of maximum extension of the fibers. To simplify the graphic representation of the basic idea, it is assumed that the longitudinal direction of the fiber or fiber layers 20 . 21 . 22 in 1 in the area of the middle part 12 or middle region of the pressure vessel 1 from left to right or vice versa.

The matrix comprises an auxetic material 30 , Auxetic materials have a negative Poisson number, ie, their cross-section increases when stretched in a given direction (preferred direction).

The outer shell of the pressure vessel 1 comprises a matrix and embedded in the matrix fibers or fiber layers 20 . 21 . 22 , The fiber layers 20 . 21 . 22 usually comprise a plurality of fiber bundles and these in turn each have a plurality of fibers, for example 12,000 fibers per fiber bundle.

The pressure vessel 1 or the outer shell has a cylindrical central part here 12 or central region and two dome-shaped end regions 15 . 16 at two opposite ends of the cylindrical central part 12 on (in 1 or in 2 far left or far right). The shape of the pressure vessel 1 is thus cigar-shaped. Other forms of pressure vessel 1 are conceivable. The dome-shaped end areas 15 . 16 each resemble hemispheres. Through the cylindrical middle part 12 of the pressure vessel 1 runs centrally a center line 40 (in 1 left to right). The center line 40 runs parallel to the height of the cylindrical middle part 12 , The center line 40 is also a symmetry line of the pressure vessel 1 , The middle part 12 is generally significantly larger or houses a larger volume than the two dome-like end regions 15 . 16 ,

The fibers or fiber layers 20 . 21 . 22 in 1 extend in a first direction, the main (ie in the central region of the pressure vessel 1 ) parallel to the longitudinal extent of the pressure vessel 1 (in 1 from right to left) or parallel to the center line 40 runs. Not all fibers or fiber layers 20 . 21 . 22 go in the same direction. The fibers or fiber layers 20 . 21 . 22 are in 1 and in 2 shown closed. This represents a simplified drawing and does not accurately reflect reality. In fact, or in reality, the fibers or fiber layers 20 . 21 . 22 For example, wound and are thus in a cross-sectional view according to 1 respectively. 2 typically not closed. In particular, in reality, the fiber path will not lie in the plane of the drawing, inter alia because a pressure vessel opening, not shown, lies on the center line or center line 40 would not allow this fiber path. In reality, the fibers will cut the plane of the drawing at an angle (called the wrap angle, braid angle, jaw angle, or generally as the layer angle, depending on the manufacturing method). Peripheral layers are doing the drawing plane in the cylindrical area 12 cut at an angle of close to 90 ° and are particularly well suited to accommodate stresses in the circumferential direction. Helix layers (also called cross layers or polar layers) become the plane of the drawing in the cylindrical area 12 cut at relatively small angles (typically between 5 ° and 30 °) and are particularly well suited to accommodate axial stresses. To bending stresses in the shoulder area of the dome or dome-like end areas 15 . 16 Frequently, so-called "high-angle helicals" with winding angles in the cylindrical area are also included 12 supplemented by approx. 70 °. The exact layer structure - ie the sequence of the individual layers, their respective thicknesses and the respective angles - is essentially dependent on the geometry of the pressure vessel 1 , the required compressive strength, as well as the material used and results from strength considerations, usually in the form of finite element simulations. The schematic representation of the fibers or fiber layers 20 . 21 . 22 in the drawings serves to illustrate the movement of the fibers or fiber layers 20 . 21 . 22 at a stretch of the auxetic material 30 the matrix, which is located between the fibers or fiber layers 20 . 21 . 22 located. The fibers or a part of the fibers / fiber layers 20 . 21 . 22 can also be perpendicular to the drawing plane 1 or the 2 and thus perpendicular to the center line 40 run. This would correspond to a circumferential position. Other forms of the fibers / fiber layers 20 . 21 . 22 , eg helical, are conceivable.

In 1 and in 2 is also a fiber layer 25 seen perpendicular to the other three fiber layers 20 . 21 . 22 wound or arranged.

The radial direction 90 of the pressure vessel 1 runs in the cylindrical area 12 from the center 42 or more generally the center line 40 of the pressure vessel 1 to the outside (from the interior 50 away to the outside). The middle-point 42 of the pressure vessel 1 is located in 1 and in 2 in the middle of the middle section 12 of the pressure vessel 1 , In the two dome-like end areas 15 . 16 runs the radial direction 90 each from the center 45 . 46 the semicircular end portions 15 . 16 outward.

The auxetic material 30 , which are in close proximity to the fibers / fiber layers 20 . 21 . 22 is located, expands when the fibers / fiber layers 20 . 21 . 22 in their longitudinal direction or largest expansion direction (in 1 and in 2 in the middle part 12 from left to right) are stretched or stretched. The auxetic material 30 The matrix thus expands upon stretching / stretching of the fiber / fiber layer 20 . 21 . 22 in the running direction or longitudinal direction of the fibers / fiber layers 20 . 21 . 22 consequently perpendicular to the course direction or longitudinal direction of the fibers / fiber layers 20 . 21 . 22 out. At an elongation of the fibers / fiber layers 20 . 21 . 22 in 1 or in 2 in the area of the middle part 12 in a direction that runs from left to right, or vice versa, the auxetic material expands 30 in a direction perpendicular to the elongation of the fibers / fiber layers 20 . 21 . 22 out, ie the auxetic material 30 stretches up and down and into the drawing plane of the 1 respectively. 2 in and out of the drawing plane.

It is also conceivable that a first part of the fibers / fiber layers 20 . 21 . 22 , as in 1 respectively. 2 shown in the middle section 12 parallel to the center line 40 runs and a second part of the fibers / fiber layers in the middle part 12 perpendicular to the first fibers / fiber layers 20 . 21 . 22 in the middle part 12 runs. All other angles are possible within the layer structure.

The auxetic material 30 the matrix in the vicinity of the fibers or fiber layers 20 . 21 . 22 is arranged and configured such that the auxetic material 30 expands when the auxetic material 30 in the direction of the running direction or longitudinal direction of the fibers / fiber layers 20 . 21 . 22 is stretched or stretched. The preferred direction of the auxetic material 30 (ie the direction to which the auxetic material 30 expands vertically when the auxetic material 30 is stretched in the direction) is respectively aligned parallel to the longitudinal direction or running direction of the adjacent or adjacent fiber / fiber layers 20 . 21 . 22 ,

With different orientation of the preferred direction of the auxetic material 30 (depending on the course of the fibers / fiber layers 20 . 21 . 22 , in the respective area or in the respective neighborhood of the auxetic material 30 embedded) shear forces occur in the material of the pressure vessel 1 on. The occurrence of shear forces between the fiber layers is already known from conventional composite pressure vessels (ie without the use of auxetic materials).

In the drawings, the so-called liner or the inner shell of the pressure vessel 1 Not shown. The liner abuts the inside of the outer shell. Thus, the liner is between the outer shell of the pressure vessel and the interior 50 , The liner may comprise or be metal and / or a plastic, eg polyethylene and / or polyamide. The pressure vessel 1 may in particular be a type III pressure vessel (metal liner) or a type IV pressure vessel (plastic liner). It is also conceivable that no liner is present.

The auxetic material 30 The matrix enlarges its cross-section as it is stretched towards the fiber / fiber layers. The direction of the fibers or fiber layers 20 . 21 . 22 runs in the cylindrical middle part 12 of the pressure vessel 1 parallel to the center line 40 ie from left to right in 1 and in 2 , At an increase in the pressure of the fuel in the pressure vessel 1 become the fibers (or the first fiber layer 20 ) near the interior 50 stretched, as the fuel against the pressure vessel 1 or the inner liner (liner) presses, which in turn against the outer shell of the pressure vessel 1 pushes, ie outward (in the radial direction 90 of the pressure vessel 1 ). The increase in pressure can eg by increasing the temperature of the fuel or by filling of fuel in the pressure vessel 1 occur. The diameter of the pressure vessel is increased by the pressure increase. As a result, the fibers or fiber layers 20 . 21 . 22 stretched, as they now have to travel a long way or further away from the center 42 of the pressure vessel 1 or the center line 40 of the pressure vessel 1 run. By stretching the fibers or fiber layers 20 . 21 . 22 becomes the auxetic material 30 of the pressure vessel 1 or the outer shell also stretched in the direction of the fibers, since the fibers / fiber layers 20 . 21 . 22 in the auxetic material 30 embedded in the matrix.

The fibers or fiber layers 20 . 21 . 22 can stand up to the auxetic material 30 do not move the matrix or vice versa.

The auxetic material 30 increased by the stretching of the auxetic material 30 or the matrix along the direction of the fibers / fiber layers 20 . 21 . 22 its cross section perpendicular to the direction of elongation. This means that the expansion of the auxetic material 30 perpendicular to the direction of the fibers / fiber layers 20 . 21 . 22 and thus perpendicular to the direction of elongation of the auxetic material 30 increases. As between two immediately adjacent fibers / fiber layers 20 . 21 . 22 (eg first 20 and second 21 Fiber layer in 1 or in 2 ) Auxetic material 30 the matrix is arranged, thereby increasing the distance between the two immediately adjacent fibers / fiber layers 20 . 21 . 22 , This means that stretching of a first fiber / fiber layer 20 close to the interior 50 of the pressure vessel 1 is arranged, to an elongation of the auxetic material 30 between the first fiber / fiber layer 20 and one of the interior 50 further than the first fiber / fiber layer 20 removed second fiber / fiber layer 21 leads. This will make the second fiber / fiber layer 21 also stretched and, as the fibers / fiber layers 20 . 21 . 22 are firmly connected to the matrix or embedded in the matrix, also the auxetic material 30 the matrix near the second fiber / fiber layer 21 , Consequently, also becomes auxetic material 30 The matrix stretched farther away from the interior 50 of the pressure vessel 1 located as the second fiber / fiber layer 21 , in the direction of the direction of the second fiber / fiber layer 21 , This in turn increases the cross-section of the auxetic material 30 at this point perpendicular to the direction of the second fiber / fiber layer 21 and the distance 62 between the second fiber / fiber layer 21 and the third fiber layer 22 increases. This then sets itself accordingly for the other fibers / fiber layers and the corresponding auxetic material 30 or the corresponding part of the auxetic material 30 the matrix continues.

Thus, increasing the pressure of the fuel in the pressure vessel increases 1 the distance of the respective fibers / fiber layers 20 . 21 . 22 (in radial direction 90 ) to each other. In addition, the distance of the respective fiber / fiber layer increases 20 . 21 . 22 from the center 42 of the pressure vessel 1 or the center line 40 of the pressure vessel 1 or from the midpoints 45 . 46 the dome-like end areas 15 . 16 ,

The fibers may comprise or be carbon or carbon. The matrix may comprise one or more plastics or consist of one or more plastics. Thus, the outer shell of the pressure vessel comprises 1 a so-called carbon fiber reinforced plastic (CFRP) or fiber reinforced plastic (FRP) or consists of this.

The auxetic material 30 and the fiber layers 20 . 21 . 22 are arranged and designed such that at a pressure increase of the fuel in the pressure vessel 1 and a thereby induced elongation of the fibers and consequently an elongation of the (to the respective fiber / fiber layer 20 . 21 . 22 adjacent) auxetic material 30 along or in the direction of the fibers, (at least in the cylindrical midsection 12 of the pressure vessel 1 ) the distance of the respective fibers / fiber layer 20 . 21 . 22 to the center line 40 proportional to the distance 61 . 62 . 63 the respective fiber to the center line 40 grows before the stretching / stretching of the fiber. This means that the change (dr) of the distance 61 . 62 . 63 the respective fiber layer 20 . 21 . 22 to the center line 40 proportional to the distance 61 . 62 . 63 the respective fiber layer 20 . 21 . 22 to the center line 40 (this distance is called r) (before stretching the fiber / fiber layer 20 . 21 . 22 and the auxetic material 30 or increasing the pressure of the fuel in the pressure vessel 1 ) is:
dr ~ r

The above relationship is derived from the uniform distribution of hoop stresses across the vessel wall thickness and strictly applies only to a circumferential grain such as occurs in the cylindrical region at the circumferential locations. Also for a fiber flow, in a hemispherical dome or in a hemispherical end region 15 . 16 Approximately follows a great circle, applies in good approximation, the above context.

For the axial stresses in the cylindrical region, it is first of all true that they are independent of r in principle. Now the cylindrical area 12 with the domes 15 . 16 is connected and accordingly fibers through the cylindrical portion 12 and the dome 15 . 16 run, suitable transitions have been created here.

The fiber angle in the cylindrical area determines how strong the fiber or the fiber layer 20 . 21 . 22 contributes to the absorption of each axial stresses and each circumferential stresses. The fiber angle can thus be used as a design parameter to come close to optimal fiber utilization.

It is possible that the distance of the respective fiber layer 20 . 21 . 22 not over the entire length or extent of the fiber layer 20 . 21 . 22 is constant. In this case, the information on the proportional extent or the proportional change of the distance in each case relate to areas of the fiber layers 20 . 21 . 22 which are (essentially) the same distance to the center line 40 or the center 42 exhibit.

In 1 are the distances d1 61 , d2 62 , d3 63 the three fibers / fiber layers 20 . 21 . 22 in the middle part 12 of the pressure vessel 1 from the center line 40 at a first pressure of the fuel (in the interior 50 or storage volume of the pressure vessel 1 to see). In 2 are the distances d4 64 , d5 65 , d6 66 the three fibers / fiber layers 20 . 21 . 22 from the center line 40 seen at a second pressure of the fuel, wherein the second pressure is higher than the first pressure. The distance 61 the (inside, ie close to the interior 50 of the pressure vessel 1 , to the outside, ie away from the interior 50 of the pressure vessel 1 , seen) first fiber / fiber layer 20 from the center line 40 is of the distance value d1 61 only slightly to the distance value d4 64 gone up. The distance of the second fiber / fiber layer 21 is of the distance value d2 62 to the distance value d5 65 gone up. The difference between the distance value d5 and the distance value d2 is greater than the difference or the difference between the distance value d4 64 and the distance value d1 61 , Even greater than these two values is the difference or the difference of the distances 63 . 66 the third fiber / fiber layer 22 before the pressure increase of the fuel (ie distance value d6) and after the pressure increase of the fuel (distance value d3).

In the dome-like end areas 15 . 16 can the fibers / fiber layers 20 . 21 . 22 be formed and arranged such that the distance between the respective fiber layer 20 . 21 . 22 from a center 45 . 46 of the (nearly) hemispherical, dome-shaped end region with increasing pressure proportional to the distance of the respective fiber layer 20 . 21 . 22 from the respective center 45 . 46 of the respective dome-like area increases.

The movement of the fibers due to a pressure increase of the fuel in the pressure vessel 1 is seen in cross-section, as in 1 and in 2 shown is a kind of centric extension.

By the described expansion of the auxetic material 30 become the more external fibers / fiber layers 20 . 21 . 22 (ie fibers / fiber layers 20 . 21 . 22 with a greater distance from the interior 50 of the pressure vessel 1 ) stretched or stretched as much as the fibers / fiber layers lying further inside 20 . 21 . 22 of the pressure vessel 1 , This results in an optimal or more uniform utilization of the existing fibers / fiber layers 20 . 21 . 22 instead of. This means that the existing material of the outer shell of the pressure vessel 1 optimally utilized. Thus, the pressure vessel points 1 relative to its compressive strength and its maximum pressure or operating pressure on a particularly low weight and is particularly inexpensive to produce. The distance of the fibers / fiber layers 20 . 21 . 22 does not decrease with increasing pressure of the fuel, but the distance to each other grows due to the expansion of the auxetic material 30 the matrix.

It is possible that the outer shell next to the matrix and the fiber / fiber layers 20 . 21 . 22 has no other materials.

The auxetic material 30 For example, a molecular-level auxetic material, such as a liquid crystalline polymer (see He, C., Liu, P. & Griffin, AC, "Toward Negative Poisson Ratio polymers through molecular design" in Macromolecules, 31, 3145, Year 1998), crystalline cellulose, cubic pure metals, zeolite, α-cristobalite and / or α-quartz. This ensures that the auxetic material 30 due to the pressure does not collapse and does not lose its auxetic property.

The auxetic material 30 may be nanostructured and / or formed by a nanostructuring process.

The auxetic material 30 may have anisotropic properties. In particular, it can react to elongation or stretching in the preferred direction with different elongation or extension in the two spatial directions perpendicular to the preferred direction.

It can be in a pressure vessel 1 more than auxetic material 30 . 30 ' be used. The materials 30 . 30 ' can differ in their Poisson number or, more precisely, the course of their Poisson number on the strain.

Due to the expansion of the auxetic material 30 due to the stretching of the fibers / fiber layers 20 . 21 . 22 Ideally, the thickness of the outer shell of the pressure vessel grows 1 , This increase in thickness theoretically leads to a completely uniform utilization of all fibers and thus represents the optimal container design.

In unfavorable or unfavorable circumstances it can happen that despite the use of auxetic materials 30 the stretching of the fibers / fiber layers 20 . 21 . 22 does not lead to an ideal increase in the thickness of the outer shell. But at least that without the use of auxetic material 30 Decreasing the thickness of the outer shell with increasing internal pressure can be achieved through the use of auxetic materials 30 be compensated in whole or in part. As a result, at least the fiber load can be made more uniform by the without the use of auxetic materials 30 considerably less loaded outer fibers / fiber layers are brought more strongly to carry the load or the forces occurring and thus a relation to the starting position or the prior art more uniform utilization of the material and thus an improved container design can be achieved.

In a cryopressure container adjacent to the outermost fiber layer 22 outside the evacuated space between the inner container and the outer container.

It is also conceivable that outside the outermost fiber layer again auxetic material or non-auxetic material of the matrix is present.

It is also conceivable that between areas of the matrix, the auxetic material 30 include areas that have no auxetic material. It is also conceivable that the distribution of the auxetic material 30 in the middle section 12 and in the dome-like end areas 15 . 16 different.

In 1 and in 2 only a small number of fiber layers are shown. The pressure vessel or outer shell of the pressure vessel may comprise a wide variety of fiber layers, each comprising a large number of fibers.

3 shows a schematic cross-sectional view of some fiber layers 20 . 21 . 22 a pressure vessel 1 at a first pressure of the fuel in the pressure vessel 1 , 4 shows a schematic cross-sectional view of some fiber layers 20 . 21 . 22 of the pressure vessel 1 out 3 at a second pressure of the fuel in the pressure vessel 1 , wherein the second pressure is higher than the first pressure. Only the outer shell is shown in each case, ie, the inner liner is not shown. The distance 70 the second fiber layer 21 from the first fiber layer 20 has grown less than the distance 71 the third fiber layer 22 from the second fiber layer 21 , It is clear in 3 and 4 to recognize that the more inward fibers / fiber layers 20 . 21 . 22 Move less far from their position before the pressure increase than the more external fibers / fiber layers 20 . 21 . 22 , The ends of the fibers 20 . 21 . 22 are held stationary in the embodiment shown. This is an abstracted representation and serves only to simplify the illustration of the basic structure of the matrix material comprising fibers / fiber layer 20 . 21 . 22 and auxetic material 30 ,

The drawings are not to scale. In particular, the extent of the auxetic material 30 typically larger in the drawings than in reality. In the drawings, the extent of the matrix or the auxetic material 30 exaggerated, so that the change in the distances of the fibers is clearly visible in the drawings.

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

LIST OF REFERENCE NUMBERS

1

pressure vessel

12

midsection

15, 16

 dome-shaped end areas

20

first fiber layer

21

second fiber layer

22

third fiber layer

25

fiber layer

30

auxetic material

40

Center line of the pressure vessel

42

Center of the pressure vessel

45, 46

 Center of the dome-like end region

50

inner space

61

Distance d1

62

Distance d2

63

Distance d3

64

Distance d4

65

Distance d5

66

Distance d6

70

Distance d7

71

Distance d8

90

radial direction

Claims (10)

Pressure vessel system comprising a pressure vessel ( 1 ) for storing a fuel, in particular hydrogen, wherein the pressure vessel ( 1 ) a matrix and embedded in the matrix fibers, in particular fiber layers ( 20 . 21 . 22 ), wherein the matrix is an auxetic material ( 30 ) at least as an additive which causes a reduction in the Poisson number of the matrix. A pressure vessel system according to claim 1, wherein the matrix comprises the auxetic material ( 30 ) such that the stress curve in a liner at least partially surrounding outer shell is more uniform than in an outer shell with a matrix without auxetic material. A pressure vessel system according to claim 1 or 2, wherein the matrix comprises the auxetic material ( 30 ) such that the distances ( 70 . 71 ) of the fibers, in particular the fiber layers ( 20 . 21 . 22 ), to each other in the radial direction ( 90 ) of the pressure vessel ( 1 ) decrease less due to a pressure increase of the fuel than in an otherwise same matrix without auxetic material. A pressure vessel system according to claim 1 or 2, wherein the matrix comprises the auxetic material ( 30 ) such that the distances ( 70 . 71 ) of the fibers, in particular the fiber layers ( 20 . 21 . 22 ), to each other in the radial direction ( 90 ) of the pressure vessel ( 1 ) grow when the matrix due to a pressure increase of the fuel in the pressure vessel ( 1 ) is stretched along the fibers. Pressure vessel system according to one of the preceding claims, wherein the fibers in the matrix are arranged at least partially and the auxetic material ( 30 ) is at least partially designed and arranged such that when the matrix is stretched along the fibers, the distance ( 61 . 62 . 63 ) of the respective fiber, in particular the respective fiber layer ( 20 . 21 . 22 ), from a midpoint ( 42 ) or a center line ( 40 ) of the pressure vessel ( 1 ) proportional to the distance ( 61 . 62 . 63 ) of the respective fiber to the center ( 42 ) or the center line ( 40 ) of the pressure vessel ( 1 ) grows before stretching the matrix. Pressure vessel system according to one of the preceding claims, wherein the auxetic material ( 30 ) comprises or is an auxetic material at the molecular level. Pressure vessel system according to one of the preceding claims, wherein the auxetic material ( 30 ) is evenly distributed in the matrix; and / or wherein the auxetic material ( 30 ) has an inverted hexagonal structure; and / or wherein the matrix and the fibers embedded in the matrix at least partially in a central part ( 12 ) and / or in an end region ( 15 . 16 ) is arranged.  Pressure vessel system according to one of the preceding claims, wherein the matrix comprises at least two different materials which differ in their Poisson number. Pressure vessel system according to one of the preceding claims, wherein the distances ( 61 . 62 . 63 ) of the fibers, in particular the fiber layers ( 20 . 21 . 22 ), from the interior ( 50 ) of the pressure vessel ( 1 ) grow when the matrix due to a pressure increase of the fuel in the pressure vessel ( 1 ) is stretched along the fibers. Pressure vessel system according to one of the preceding claims, wherein the auxetic material ( 30 ) has anisotropic properties such that the auxetic material ( 30 ) varies in different directions perpendicular to the direction along the fibers to different extents when the matrix due to a pressure increase of the fuel in the pressure vessel ( 1 ) is stretched along the fibers.

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