DE102017220882A1 - Pressure vessel with thermoplastic and thermoset reinforcement and manufacturing process - Google Patents

Abstract

The technology disclosed herein relates to a pressure vessel 100 for storing fuel having at least one fiber reinforced layer 120 enclosing a fuel storage volume I. The fiber reinforced layer 120 comprises at least two superimposed layers 122, 124. A thermoplastic layer 122 comprises a thermoplastic matrix material and reinforcing fibers. A thermoset layer 124 comprises a thermosetting matrix material and reinforcing fibers. The technology disclosed herein further relates to a method of making, reusing or repairing a pressure vessel.

Description

The technology disclosed herein relates to a pressure vessel and a method of making, recycling or repairing a pressure vessel. Pressure vessels as such are known. As reinforcement, they have a fiber-reinforced layer whose matrix material consists of duroplastic or elastomer. Elastomers have inferior mechanical properties. Therefore, pressure vessels with a thermoplastic reinforcement with the same pressure resistance more fiber layers than pressure vessel with a thermosetting armor. This ultimately leads to a higher space requirement and a higher weight. For this reason, nowadays mainly duroplastics reinforcements are used. A disadvantage of such Duroplast-armor is that they can hardly be repaired and reused. The reason for this is that this resin does not melt at temperatures above 100 ° C, but burns. A separation of the reinforcing fibers from the matrix material is virtually impossible after curing without damaging the reinforcing fiber.

It is a preferred object of the technology disclosed herein to reduce or eliminate at least one disadvantage of a previously known solution or to suggest an alternative solution. In particular, it is a preferred object of the technology disclosed here to provide a pressure vessel with a reinforcement which on the one hand has good mechanical properties and on the other hand can be at least partially repaired or reused. Other preferred objects may result from the beneficial effects of the technology disclosed herein. The object (s) is / are solved by the subject matter of the independent claims. The dependent claims are preferred embodiments.

The pressure vessel is used here for storing gaseous fuel under ambient conditions. The pressure vessel may be used, for example, in a motor vehicle (e.g., passenger cars, motorcycles, utility vehicles) operated with 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 COP) or a high-pressure gas vessel (= CGH2). High-pressure gas containers are designed to store fuel at ambient temperatures permanently at a nominal operating pressure (also called nominal working pressure or NWP) of about 350 bar (= overpressure relative to the atmospheric pressure), furthermore preferably of about 700 bar or more. A cryogenic pressure vessel is suitable to store the fuel at the aforementioned operating pressures even at temperatures well below the operating temperature of the motor vehicle.

The pressure vessel comprises at least one fiber-reinforced layer. The fiber-reinforced layer may preferably completely surround a liner or a fuel storage volume at least in regions. The fiber-reinforced layer is provided in particular in the jacket region and in the region of the cap-shaped ends. The fiber reinforced layer is often referred to as a laminate or armor.

Hereinafter, the term "fiber-reinforced layer" is usually used. As a fiber reinforced layer i.d.R. fiber reinforced plastics (= FVK or FKV or carbon fiber reinforced plastics or CFRP) are used, for example carbon fiber reinforced plastics (= CFRP) and / or glass fiber reinforced plastics (= GRP). The fiber-reinforced layer suitably comprises reinforcing fibers (e.g., glass fibers, carbon fibers, aramid fibers, etc.) embedded in a resin matrix. In particular, matrix material, type and proportion of reinforcing fibers and their orientation can be varied so that the desired mechanical and / or chemical properties are established. Preferably, continuous fibers are used as reinforcing fibers, which can be applied by winding and / or braiding. The fiber reinforced layer has i.d.R. several layers or layers.

The fiber-reinforced layer comprises at least two layers arranged directly or indirectly above one another, wherein a layer of the superimposed layers is a thermoplastic layer which comprises a thermoplastic matrix material and reinforcing fibers; and wherein another layer of the superposed layers is a thermoset layer comprising a thermosetting matrix material and reinforcing fibers.

The thermoplastic layer may comprise a plurality of fiber reinforced layers. Any suitable reinforcing fiber may be used. Thermoplastics, also known as plastomers, are plastics that can be deformed in a specific temperature range (thermo-plastic). This process is reversible, that is, it can be repeated as often as desired by cooling and reheating to the molten state, as long as not using the so-called thermal decomposition of the material by overheating. This is where thermoplastics differ from thermosets and elastomers.

The thermoset layer may also comprise a plurality of fiber-reinforced layers. Thermosets, too Duromere or hardened synthetic resin called, are plastics, which can not be deformed after their hardening by heating or other measures. They contain hard, amorphous, insoluble polymers. The macromolecules are tightly cross-linked via covalent bonds, which causes their lack of softening when heated, so they are only machinable after curing. The precursors are trifunctional or polyfunctional compounds which polymerize with the aid of hardeners and possibly catalysts or by high temperatures and lead to a close-meshed cross-linking. In analogy to the meltable thermoplastics, the thermosets that are no longer fusible after curing are also called thermo polymers. The English name is "thermosetting resin" or short "thermoset", ie "thermosetting resin". As a thermosetting matrix material, for example, an epoxy resin can be used.

The superimposed layers can be arranged directly or indirectly above one another. For example, an intermediate layer may be provided between the thermoplastic layer disclosed herein and the thermoset layer. For example, the thermoplastic layer may be an inner layer separated by a breather layer from a thermoset layer as an outer layer.

The order of the two layers disclosed herein (i.e., thermoplastic layer, thermoset layer) in the laminate of the fiber reinforced layer can be reversed.

According to the technology disclosed herein, the inner layer should comprise the fiber layers lying radially inward more than the outer layer fiber layers covering the inner layer.

In one embodiment, the thermoset layer is the inner layer and the thermoplastic layer is the outer layer, which encloses the inner layer at least partially. An advantage of such a configuration is that the outer layer can thus be better repaired. If damaged, the complete replacement of the pressure vessel can be avoided, depending on the extent of the damage. Also, with such a layer construction, recycling is easier because the outer layers are easier to heat and remove.

In a further embodiment, the thermoplastic layer is the inner layer and the thermoset layer forms the outer layer, which encloses the inner layer at least partially. An advantage of this embodiment is that in the installed state any heat in the event of failure, the thermoplastic matrix weaken or less. Furthermore, the thermoplastic layer can provide protection against fuel permeation.

• - zwischen 20% und 80%; oder
• - zwischen 40% und 60%; oder
• - zwischen 45% und 55%

der gesamten mittleren Wandstärke oder des Matrixmaterials der faserverstärkten Schicht aus.The thermoplastic layer is preferred

• - between 20% and 80%; or
• - between 40% and 60%; or
• - between 45% and 55%

the total mean wall thickness or matrix material of the fiber reinforced layer.

Advantageously, the outer layer, a higher stiffness in the circumferential direction than the inner layer, regardless of whether thermosetting or thermoplastic matrix material is used.

• - mechanische Eigenschaften der Verstärkungsfasern;
• - Fasergehalt der Verstärkungsfasern; und/oder
• - Faserwinkel der Verstärkungsfasern;
• - etc.

The rigidity of the outer layer and the inner layer in the circumferential direction can be adjusted, for example, by varying:

• - mechanical properties of the reinforcing fibers;
• - fiber content of the reinforcing fibers; and or
• - fiber angle of the reinforcing fibers;
• - Etc.

The adjustment of the rigidity can be carried out by known design tools and is familiar to the expert.

In a preferred embodiment, the thermoset layer is configured to compensate for at least 80% or at least 90% or 100% of the pressure loads that may occur at nominal operating pressure or at maximum operating pressure (MOP).

The fiber-reinforced layer, in particular the thermoset layer and / or the thermoplastic layer, has i.d.R. Cross and peripheral layers on. In order to compensate for axial stresses, cross layers (helical layers) are wound or braided over the entire winding core surface. In the i.d.R. cylindrical peripheral area are i.d.R. so-called "hoop layers", which provide for a reinforcement in the circumferential direction. The circumferential positions extend in the circumferential direction U of the pressure vessel and are oriented in a fiber angle of about 90 ° (+/- 5 °) to the pressure vessel longitudinal axis A-A.

The fiber layer can be unidirectional fiber layers. A unidirectional fiber layer is the name for a layer of a fiber-plastic composite, in which preferably all Reinforcing fibers or rovings or substantially all reinforcing fibers or rovings (ie, except for manufacturing tolerances or to a negligible for the function number) are oriented in a single direction. The reinforcing fibers are assumed to be ideally parallel and perpendicular to the grain direction. The unidirectional layer is transversely isotropic. Advantageously, at least two layers of the fiber-reinforced layer can be arranged in a balanced angle composite (AWV, English: Balanced Ply Laminate). A balanced angle composite can be described as a composite of two unidirectional layers, whereby in addition to the scrim also, for example, tissue and wound cross-layers come into question. The reinforcing fibers or rovings of these unidirectional layers have fiber angles to the tissue normal or longitudinal axis AA, which have the same amount but different signs. The fiber angle indicates the angle at which the reinforcing fibers are oriented relative to the pressure vessel longitudinal axis. If the reinforcing fibers are deposited in the winding process, this angle is also referred to as the winding angle. In braiding the term braiding is used accordingly. In general, one could also speak of the shelf angle. The fiber angle is thus the complementary angle to the angle that the reinforcing fibers form with the circumferential direction.

In one embodiment, the thermoplastic layer may be configured to prevent fuel permeation. For this purpose, in particular a plurality of fiber layers can be arranged one above the other sealingly, in particular wound, preferably using towpregs.

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

The technology disclosed herein further includes a method of manufacturing a pressure vessel, particularly the pressure vessel disclosed herein. The method comprises the step of forming the fiber-reinforced layer by, for example, braiding and / or winding. The formation of the fiber reinforced layer may include the step of forming two superposed layers; wherein a layer of the two superposed layers is a thermoplastic layer comprising a thermoplastic matrix material and reinforcing fibers; and wherein another layer of the two superimposed layers is a thermoset layer comprising a thermosetting matrix material and reinforcing fibers.

• - Ausbilden der Duroplast-Schicht als Innenschicht; und
• - Ausbilden der Thermoplast-Schicht als Außenschicht ist, die die Innenschicht zumindest bereichsweise umschließt.

The method disclosed herein may include the steps of:

• - Forming the thermoset layer as an inner layer; and
• - Forming the thermoplastic layer as an outer layer, which encloses the inner layer at least partially.

• - Zumindest teilweises Entfernen der Thermoplast-Schicht; und
• - Zumindest teilweises Ausbilden einer neuen Thermoplast-Schicht.

The technology disclosed herein further relates to a method of repairing a pressure vessel, particularly the pressure vessel disclosed herein. The method comprises the steps:

• - At least partial removal of the thermoplastic layer; and
• - At least partially forming a new thermoplastic layer.

• - zumindest teilweises Entfernen der Thermoplast-Schicht (122); und
• - zumindest teilweises Ausbilden eines neuen thermoplastischen Bauteils aus dem entfernten Verstärkungsfasern und/oder Matrixmaterial.

The technology disclosed herein further relates to a method of reusing a pressure vessel, in particular the pressure vessel disclosed herein, comprising the steps of:

• at least partial removal of the thermoplastic layer ( 122 ); and
• - At least partially forming a new thermoplastic component of the removed reinforcing fibers and / or matrix material.

The new thermoplastic component can have any suitable form or function and can be used for any suitable purpose. In particular, the methods of recycling and repair disclosed herein may also be combined.

1. i) die höher ist als die Schmelztemperatur vom Matrixmaterial der Thermoplast-Schicht, und
2. ii) die niedriger ist als die Glasübergangstemperatur und/oder Brenntemperatur vom duroplastischen Matrixmaterial der Duroplast-Schicht.

The at least partial removal of the thermoplastic layer may include the step of: heating the thermoplastic matrix material to a temperature,

1. i) which is higher than the melting temperature of the matrix material of the thermoplastic layer, and
2. ii) which is lower than the glass transition temperature and / or firing temperature of the thermosetting matrix material of the thermoset layer.

When the glass transition temperature is exceeded, a solid thermoset goes into a rubbery to viscous state. The firing temperature is the temperature at which the thermosetting matrix material begins to burn.

1. i) die größer ist als die Schmelztemperatur vom thermoplastischen Harz; und
2. ii) die geringer ist als die Temperatur, bei der der Duroplast brennt.

In other words, the technology disclosed herein relates to the idea of making a hybrid armor of a pressure tank. The internal structure of the reinforcement (fiber reinforced layers near the liner or fuel storage volume) is made with a thermosetting resin (preferably braiding and / or winding). This reinforcement is the core reinforcement of the pressure tank, which has better mechanical properties (strength) than the thermoplastic layer. This reinforcement is advantageously designed so that it can withstand the nominal operating pressure or the maximum operating pressure or an internal pressure of at least 875 bar or 1000 bar without damage. The outer structure of the reinforcement (fiber-reinforced layers that are applied to the (usually cured) internal structure of the reinforcement) is made with thermoplastic (eg by braiding and / or winding). In this configuration, preferably about half of the fiber-reinforced reinforcement made of thermoset and the other half of thermoplastic is formed. Advantageously, half of the reinforcement (thermoplastic) can be reused more easily.
In general, the outer structure of a pressure tank or the FVK reinforcement is more damaged than the internal structure (due to impact, fire, chemicals, cuts, abrasion, crash ...). If a thermoplastic resin outer structure has been damaged (no damage has been detected in the duroplastic inner structure), it could be removed from the pressure vessel. The thermoplastic resin is heated (between 100 ° C and 200 ° C) and becomes liquid. Only the reinforcing fibers remain on the inner reinforcement and these can be easily removed and reused. A new outer structure with thermoplastic resin and reinforcing fibers can be wound and the pressure vessel can continue to be used until the end of its specified life. For this purpose, at least the outer layer only has to be heated to a temperature,

1. i) which is greater than the melting temperature of the thermoplastic resin; and
2. ii) which is lower than the temperature at which the thermoset burns.

With the hybrid structure disclosed here, advantageously at least a part of the pressure tank can be repaired or reused. For example, reinforcing fibers of a thermoplastic outer layer can be repaired. This can reduce the cost of service as a damaged pressure vessel no longer needs to be replaced. By eliminating the pressure vessel replacement and the partial recycling of unusable pressure vessels, a contribution to resource conservation is made.

Preferably, the outer structure (= outer layer) may have better or stiffer reinforcing fibers than the inner structure (= inner layer). As a result, the rigidity of the outer layers can be increased and the stress distribution over the thickness of the pressure vessel wall can be reduced. Since these reinforcing fibers are usually expensive, the reinforcing fibers recovered from the thermoplastic layer could be used for other applications because they can be separated from the thermoplastic resin.

The technology disclosed herein will now be described with reference to the schematic cross-sectional view of FIG 1 explained.

The 1 shows a pressure vessel 100 who is here a liner 110 and a fiber reinforced layer 120 includes. The fiber reinforced layer 120 surround the liner here 110 and the fuel storage volume I. The fiber reinforced layer 120 here comprises an inner layer, which as a thermoset layer 124 is executed. Furthermore, the fiber-reinforced layer comprises 120 here an outer layer, which as a thermoplastic layer 122 is trained. The reinforcing fibers of the outer layer have a higher rigidity than the reinforcing fibers of the inner layer. This results in a more favorable stress distribution in the pressure vessel wall. In the example shown here, the thermoplastic matrix material makes up about 50% of the matrix material of the fiber-reinforced layer 120 out.

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.

Claims (12)

A pressure vessel (100) for storing fuel having at least one fiber reinforced layer (120) enclosing a fuel storage volume (I); wherein the fiber reinforced layer (120) comprises at least two superimposed layers (122, 124); wherein a thermoplastic layer (122) comprises a thermoplastic matrix material and reinforcing fibers; and wherein a thermoset layer (124) comprises a thermosetting matrix material and reinforcing fibers. Pressure vessel (100) after Claim 1 wherein the thermoset layer (124) is an inner layer, and wherein the thermoplastic layer (122) comprises a Outer layer is that encloses the inner layer at least partially. Pressure vessel (100) after Claim 1 wherein the thermoplastic layer (122) is an inner layer, and wherein the thermoset layer (124) is an outer layer at least partially surrounding the inner layer. Pressure vessel (100) after Claim 1 . 2 or 3 wherein the thermoplastic layer (122) - between 20% and 80%; or - between 40% and 60%; or - between 45% and 55% of the total average wall thickness or matrix material of the fiber reinforced layer (120). Pressure vessel (100) according to one of the preceding claims, wherein the outer layer has a higher rigidity in the circumferential direction than the inner layer. A pressure vessel (100) according to any one of the preceding claims, wherein the thermoplastic layer (124) is arranged to prevent fuel permeation. The pressure vessel (100) of any one of the preceding claims, the thermoset layer (124) adapted to compensate for at least 80% or at least 90% or 100% of the pressure loads that may occur at the nominal operating pressure or the maximum operating pressure from the pressure vessel (100) , A method of manufacturing a pressure vessel (100), wherein forming a fiber reinforced layer (120) comprises the step of: Forming two superposed layers (122, 124); wherein a layer of the two superposed layers (122, 124) is a thermoplastic layer (122) comprising a thermoplastic matrix material and reinforcing fibers; and wherein another layer of the two superimposed layers is a thermoset layer (124) comprising a thermosetting matrix material and reinforcing fibers. Method according to Claim 8 , further comprising the steps of: - forming the thermoset layer (124) as an inner layer; and - forming the thermoplastic layer (122) as an outer layer, which encloses the inner layer at least partially. Method for repairing a pressure vessel according to one of the preceding Claims 1 to 7 comprising the steps of: - at least partially removing the thermoplastic layer (122); and - at least partially forming a new thermoplastic layer (122). Method of reusing a pressure vessel according to one of the previous ones Claims 1 to 7 comprising the steps of: - at least partially removing the thermoplastic layer (122); and - at least partially forming a new thermoplastic component from the removed reinforcing fibers and / or from the removed matrix material. Method according to Claim 10 or 11 wherein at least partially removing the thermoplastic layer (122) comprises the step of: heating the thermoplastic matrix material to a temperature, iii) higher than the melting temperature of the matrix material of the thermoplastic layer (122), and iv) which is lower than the glass transition temperature and / or firing temperature of the thermosetting matrix material of the thermoset layer (124).

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