Patent Application
20250155079
The invention relates to a liner for a pressure vessel, especially a hydrogen tank, and to a pressure vessel.
Hydrogen tanks that are used in vehicles, especially motor vehicles, must firstly be light in order not to unnecessarily increase the vehicle weight and must secondly be very stable in order to withstand the necessary high pressures for storage of the hydrogen. Moreover, the tanks must not fail critically in the event of a vehicle crash.
Different tank systems are being developed for storage of hydrogen. In addition to steel tanks, fiber-reinforced pressure vessels may be used, as known, for example, from document DE 10 2017 206 521 A1. Such pressure vessels typically comprise a liner and a fiber composite body surrounding the liner. The liner may have been produced from a metal or from plastic. The hydrogen is stored in the liner, and the liner is generally responsible for the integrity of the pressure vessel and acts as a barrier layer for the hydrogen. If the liner has been produced from plastic, it is usually a cylindrical hollow body bounded at each of its two ends by a cap, so-called bosses. The assembly of liner and caps is then surrounded by the fiber composite body.
The mechanical strength of fiber-reinforced pressure vessels is typically provided by the fiber composite body that surrounds the liner. Hydrogen is stored at very high pressure. In order that fiber-reinforced tank systems meet the pressure demands, the fibers have to be laid in the direction of load. Since there is a hydrostatic pressure in the tank system, it is necessary to provide fiber reinforcements in virtually every orientation (spatial direction).
One means of producing a tank is winding technology. This involves wrapping the liner in a wide variety of different orientations and with a multitude of fiber plies. For manufacturing-related and geometric reasons, the fiber material cannot be laid completely as desired. The result is thus fiber accumulations that would not be absolutely necessary in terms of the requirements. These increase the component costs and the component weight, and have an adverse effect on the requisite build space.
An alternative mode of production is the combination of various fiber application technologies. This combines, for example, braiding and winding methods. Although it is possible thereby to increase the efficiency of the fiber application, the use of multiple different fiber application methods is associated with elevated logistics expenditure and an extended process chain. This also leads to elevated testing expenditure for assurance of the quality. Unless impregnated fibers are used, there is the risk that the fibers will be moved or damaged because of the logistics processes required.
Against this background, it is an object of the disclosure to specify a way by which the manufacture of a fiber-reinforced pressure vessel can be improved. In particular, some or all of the aforementioned disadvantages are to be avoided.
The object may be achieved by a liner for a pressure vessel according to the independent claim and a pressure vessel according to a dependent claim. Further advantageous configurations will be apparent from the dependent claims and the description that follows.
A liner for a pressure vessel is specified, especially for a hydrogen tank, with a body made of a gas-tight polymer material having an outer surface in which depressions are formed. A fiber reinforcement is disposed in the depressions.
The liner serves firstly to seal the pressure vessel. The expression “gas-tight body” in this context shall be understood to mean that the permeability of the body wall for gases or fluids to be stored in the pressure vessel, preferably hydrogen, is sufficiently low, or that the body wall is impermeable to these substances. The gas-tight body acts as a barrier layer for these substances.
According to the disclosure, the liner additionally has a fiber reinforcement disposed in depressions of the outer body surface. The depressions may also be transmitted to the inside, where they appear as projections. The fiber reinforcement is preferably incorporated completely in the depressions, meaning that it does not protrude with respect to the surface of the liner that bounds the liner outside the depressions.
The liner of the disclosure may meet structural demands that are placed on the pressure vessel as well as sealing functions. Thus, it is possible to reduce the number of fiber plies in the fiber composite body that surrounds the circumference of the liner in the later pressure vessel. In this way, it is possible to dispense with process steps. The arrangement of the fiber reinforcement in depressions additionally has the advantage that the fiber reinforcement is held in place and cannot slip in the course of further processing of the liner during the process of production of the pressure vessel. This can simplify handling. In addition, the laying quality can be verified directly and with little difficulty. The risk of rejects is reduced.
The liner may be equipped with the fiber reinforcement directly in the production process. For example, the liner may be produced in an injection molding process in which the fiber reinforcement has been introduced into the injection mold beforehand. The injection molding material is then injected onto the fiber reinforcement. It is likewise possible to apply the fiber reinforcement in a process step downstream of the liner production process. For example, the liner may be produced in a blow molding process, wherein the depressions are formed by appropriate shaping of the blow mold. In a subsequent step, the fiber reinforcement is then introduced into the depressions.
It is particularly advantageous when the reinforcing fibers are deliberately laid along the directions of loading to which the liner is subjected on later use in the pressure vessel. Such an arrangement of the reinforcing fibers in conformance with the load path may be ensured in one configuration in that the depressions are already formed in the liner so as to conform with the load path. The arrangements of the depressions in the body and hence the arrangement of the fiber reinforcement may especially be in skeletal form. In other words, the fiber reinforcement may have multiple fiber strands that come into contact or cross, but in particular do not form a structure that covers a large area of the body of the liner, as would be the case for use of a weave or braid.
For example, load paths may run along the longitudinal extent of the liner. In that case, it may be advantageous in one configuration when the body is a hollow body having a body circumference and a longitudinal extent running transverse to the circumferential direction, and the depressions and the fiber reinforcement run in the direction of the longitudinal extent of the body. Of course, further orientations of the depressions and hence of the reinforcing fibers are conceivable. For example, these may run at an angle to the longitudinal extent of the liner, for example at an angle in the range from 5 to 45 degrees.
In one configuration, it is preferable that the fiber reinforcement is cohesively bonded to the body. This is the case, for example, when the liner is injected onto the fiber reinforcement. It is likewise possible, for example, to impregnate the fiber reinforcement with a matrix material before, during or after the application to the liner. The consolidated or cured matrix material then binds the fiber reinforcement to the liner.
The body of the liner is preferably formed from a thermoplastic material. The use of a thermoplastic material offers the option of resorting to manufacturing methods that enable a simple and inexpensive integration of the fiber reinforcement even during the production of the liner. Mention is made here by way of example of an injection molding method or else various spinning methods. Suitable thermoplastics are, for example, polyamide (PA) or ethylene-vinyl alcohol copolymer (EVOH).
The fiber reinforcement may include customary reinforcing fibers, for example carbon fibers, glass fibers, aramid fibers etc. The reinforcing fibers are preferably used as continuous fibers and extend, for example, across the whole length of the depression or the liner.
The reinforcing fibers can be laid with a simple laying head and programmed paths. Such load path-conforming laying methods for fiber reinforcements are known in principle to the person skilled in the art. The reinforcing fibers have preferably already been impregnated with matrix material on application, which may be consolidated or cured immediately after the application of the reinforcing fibers in the depressions.
In one configuration, it is provided that the fiber reinforcement used are unidirectional (UD) fiber tapes. UD fiber tapes are material in tape form with a thermoplastic polymer matrix into which there are embedded a multitude of reinforcing fibers arranged unidirectionally in longitudinal direction of the material in tape form. The tapes may have a thickness, for example, of a few tenths of a millimeter and frequently a width of between 5 and 25 mm. For laying of the fiber tapes, the polymer matrix thereof is heated, such that it sticks to the body of the liner on laying. This achieves immediate fixing of the fibers in the depressions.
It may be preferable that the base material of the body and of the matrix material with which the reinforcing fibers are impregnated are identical in order to achieve the best possible binding even on application of the reinforcing fibers. In this way, it is possible to transmit the force under load uniformly and without additional stress peaks.
Additionally specified is a pressure vessel, especially a hydrogen tank, with a liner as described above and a fiber reinforcement that surrounds the liner and is incorporated into a matrix material.
The liner may especially be sealed at each end by a cap (boss). The caps may be formed from plastic or metal and may, for example, provide an opening for a connection. The fiber reinforcement disposed in the depressions of the liner may extend only over the liner. This is the case particularly when the liner is already provided with the fiber reinforcement in the production of the body. It is alternatively conceivable that the fiber reinforcement disposed in the depressions of the liner body likewise extends over the caps, which for this purpose, for example, may likewise have depressions for guiding of the reinforcing fibers.
The fiber composite body surrounds the circumference of the liner (and optionally of the caps). The fiber composite body may include, for example, one or more layers of wound fibers, fiber braids and/or fiber weaves that are incorporated into a matrix material. In a preferred embodiment, the matrix material of the fiber composite body is a thermoset matrix material.
Features and details described in association with the liner are also applicable in association with the pressure vessel, and respectively vice versa, such that, with regard to the disclosure relating to the individual aspects of the invention, there is always the possibility of mutual reference.
Further advantages, features and details of the invention will be apparent from the description that follows, in which working examples of the invention are described individually with reference to the drawings. The features mentioned in the claims and in the description may each be essential to the invention here individually or in any combination. Where the word “can” or “may” is used in this application, this either means the technical possibility or the actual technical implementation.
Working examples are elucidated hereinafter with reference to the appended drawings, which are schematic representations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 110 152.5 | Apr 2022 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/058827 | 4/4/2023 | WO |
