Composite high-pressure vessel, method of its fabrication and a connection stub for the composite high-pressure vessel

Abstract

A composite high-pressure vessel comprises a casing (1) made by blow molding a preform made of a thermoplastic material, a connection stub (3), a bottom dome (4) and a composite reinforcing coating made of a supporting braid (2) that consists of a bundle of filaments (5) embedded in resin, preferably containing nano-additives. The connection stub (3) has a section (6) intended for fastening the supporting braid (2) between a retaining collar (7) and an annular protrusion (8). The section (6) has a shape of a right prism with an axisymmetric polygon base (9), e.g. a square, having rounded corners (10) with blind cylindrical recesses (11) of a depth not exceeding 0.1 mm. The bundle of filaments (5) in the supporting braid (2) is guided on the vessel casing (1) in a closed loop between the section (6) of the connection stub (3) and the bottom dome (4) within the range of a first angle a of inclination relative to the tangent to the generatrice of the surface of the casing (1) ranging from 5° to 30°, while in the area close to the bottom dome (4) the bundle of filaments (5) is guided within the range of a second angle of inclination p relative to the tangent to the generatrice of the casing (1) surface ranging from 2° to 45°. The bundle of filaments (5) is guided on the casing (1) of the vessel in loops between the connection stub (3) and the bottom dome (4), starting from the flat wall of the section (6) of the connection stub (3), then on the cylindrical part of the casing (1) and then turns at the bottom dome (4), braiding the lower insert, wherein in the next loop the bundle of filaments (5) is guided with an offset in relation to the previous loop of at least one width of the guided bundle, and wherein the supporting braid (2) contains not less than 40 loops or not less than two layers.

Description

[0001] COMPOSITE HIGH-PRESSURE VESSEL, METHOD OF ITS FABRICATION AND A CONNECTION STUB FOR THE COMPOSITE HIGH-PRESSURE VESSEL

[0002] The subject of the invention is a composite high-pressure vessel for storing liquids and / or gas under increased pressure, a method for its production and a connection stub for such a vessel.

[0003] Polish patent PL228200B1 (also: W02010059068A2, EP2531769A2) discloses a cylindrical high-pressure vessel containing a casing made by blow-molding a preform of thermoplastic PET, a connection stub, a bottom washer (bottom dome) and external reinforcement. The connection stub is provided with at least one groove for connection to the preform, with at least one sealing ring placed therein, as well as a groove for an O-ring seal. The connection stub also has a top cap (retaining collar) and an annular protrusion around the opening of the connection stub. The casing made of the blown preform and the connection stub between the top cap and the annular projection are wrapped with at least one reinforcing layer, which consists of a resin-coated and thermally hardened layer of filaments applied on the entire surface of the tank in the cross-polar pattern, and additionally in a part of the tank having constant diameter (i.e. a cylindrical part) using the helical pattern. The angle of inclination of the filament applied in the cross-polar pattern, measured in relation to the axis of the tank, ranges from 49° to 59°. The filaments of the reinforcing layer are carbon, glass, aramid, basalt or ceramide fibers.

[0004] Another Polish patent PL226196B1 (also, among others: WO2015108429A1 , EP3Q94914B1 , US10487981 B2) presents a method of manufacturing a composite high- pressure vessel, including production of a casing by blowing a preform made of thermoplastic material to the desired size using any suitable technique, then connecting the casing with a connection stub and strengthening the external surface of the tank by creating a composite layer. The preform equipped with a collar is previously subjected to a controlled crystallization process and then an annular groove is made in the preform's collar. Then the preform is blown to the desired size and connected to the connection stub equipped with a stop collar. An O-ring seal is placed in the sealing groove of the connection stub, and a snap ring is placed in the groove of the retaining ring, and then the connection stub is clamped onto the casing ring. Then, the interior of the created tank is filled with gas to obtain a constant value of pressure inside the tank and a composite layer is made by making a supporting braid from bundles of reinforcing filaments, using three winding methods: cross, polar and hoop, after which the whole device is thermally hardened. Curable resins, preferably epoxy, and filaments, preferably a bundle of carbon and aramid fibers, are used to make the composite layer. When making the supporting braid using the cross-polar pattern, the filamentr bundles are wound each time during the passages of the winding head between the poles of the tank and the passages around the connection stub while maintaining a constant angle of inclination of the rotation axis, preferably 53o-55°.

[0005] European patent application EP3795340A1 discloses a method of producing a high- pressure tank having a casing reinforced with an external composite reinforcing layer, consisting of the following steps: A) the outer surface of the tank casing is covered with a thin anti-adhesive layer to prevent the reinforcing layer from sticking to the casing; B) an impregnating mixture of the resin composition and the nanoadditive is prepared in a mixing device at a pressure lower than normal pressure; C) the impregnating mixture is poured into the resin tray of the winding machine; D) at least one spool of carbon fiber bundles is mounted on the winding machine, each carbon fiber bundle containing at least 4 thousand, preferably 24 to 36 thousand carbon fibers; E) a curing agent is added to the impregnating mixture in a proportion of 29-30 wt. % of the impregnating mixture; F) the carbon fiber bundles are impregnated in a resin bath using a resin tray so that the impregnated carbon fiber bundle contains at least 65 wt. % of carbon fibers and at most 35 wt. % of the composition of the impregnating mixture and curing agent; G) the carbon fiber bundles are wound onto the casing by wrapping the impregnated carbon fiber bundles in at least 6 different winding patterns; H) the resulting composite reinforcing layer is thermally cured.

[0006] The same patent application also discloses a high-pressure vessel consisting of a casing and an outer composite reinforcing layer made of carbon fiber bundles wound around the outer surface of the casing and fastened with a hardened impregnating mixture composed of a resin composition and a nano-additive. The resin composition contains at least 75 wt. %, preferably 75-95 wt. % of bis-[4-(2,3-epoxypropoxy)phenyl]propane and up to 25 wt. %, preferably 5-25 wt. % of 1 ,4-bis(2,3-epoxypropoxy)butane. The nanoadditive consists of at least 80 wt. % of graphene nanotubes (GNT), at most 15 wt. % of iron (Fe) nanoparticles and at most 5 wt. % of other allotropic forms of carbon, such as graphene flakes or fullerenes. GNTs are single-walled graphene nanotubes (SWGNT) with a diameter of 1 -2 nm and a length of at most 20 micrometers, and a length-to-diameter ratio of at least 100. The impregnating mixture contains 99.9-99.99 wt. % of resin composition and 0.01-0.1 wt. % of nanoadditive.

[0007] Known inventions do not propose a solution to the problem of securing the connection stub against angular and axial displacement relative to the polymer composite of the pressure vessel, especially when connecting the vessel to the installation or disconnecting it from it. This is an important issue for safety reasons, because the connection stub is the most important connection node of the composite tank with the elements of the pressure installation receiving the medium stored in the tank. The occurrence of a leak, especially when screwing in or unscrewing elements of the pressure installation, is dangerous and eliminates the pressure vessel from further use.

[0008] According to the state of the art discussed above, the connection stub is mounted in an opening in the casing of the vessel, on which a supporting braid is wound, e.g. in the form of a composite made of filaments and hardened resin. The supporting braid takes the stress from the tank casing caused by the internal pressure of the stored medium. During assembly or disassembly of the vessel, partial or complete loss of cohesion between the connection stub and the supporting braid, or deformation of the supporting braid, may occur. The resulting damage may be invisible and therefore all the more dangerous during operation due to the risk of insufficiently tight assembly and reduced strength of the pressure vessel.

[0009] The technical problem solved by the invention consists in increasing the strength of the mechanical-adhesive connection of the high-strength polymer composite reinforcing coating with the connection stub, especially the one made of metal.

[0010] During research and development work, it turned out that the critical place where the supporting braid can become detached from the connection stub is its cylindrical section between the retaining collar and the annular protrusion. The invention solves the identified technical problem by changing the shape of this section of the connection stub and changing the method of winding the supporting braid, adapted to the modified shape of the stub.

[0011] The composite high-pressure vessel according to the invention comprises a casing manufactured by blow molding from a preform made of thermoplastic material, a connection stub, a bottom dome and a composite reinforcing coating made of a supporting braid composed of a bundle of filaments embedded in resin. The essence of the invention consists in the fact that the connection stub, in the section intended for fastening the supporting braid between the retaining collar and the annular protrusion, instead of a cylindrical shape, has the shape of a right prism with the base of an axisymmetric polygon.

[0012] It is advisable for the corners of the parallelepiped section for attaching the supporting braid to be rounded, as this ensures better contact between the filaments bundle and the connection stub. It is also recommended that the rounded corners contain non-through (blind), preferably cylindrical recesses, with a depth not exceeding 0.1 mm. The resin filling these recesses, after hardening, additionally anchors the filaments bundle to the connection stub. Such anchoring significantly protects the supporting braid from detaching from the connection stub, especially when shear forces occur during connection or disconnection of the vessel to / from the installation.

[0013] In a preferred but non-limiting variant, also illustrated in the drawings, the aforementioned axisymmetric polygon is a square. Then, in one embodiment of the invention, the axis of the recess, e.g. cylindrical, forms in cross-section an angle of 45° with the adjacent side of the square.

[0014] In the composite vessel according to the invention, the bundle of filaments in the supporting braid is guided on the vessel casing in a closed loop between the polyhedral section of the connection stub and the bottom dome, preferably in the range of the first angle a of the bundle direction inclination relative to the tangent to the generatrice of the surface of the casing ranging from 5° to 30°.

[0015] In turn, in the area close to the bottom dome, the filaments bundle in the supporting braid can be guided on the vessel casing within the range of the second angle p of inclination relative to the tangent to the generatrice of the casing surface ranging from 2° to 45°.

[0016] Advantageously, in the composite vessel according to the invention, the bundle of filaments is guided on the vessel casing in loops between the connection stub and the bottom dome, starting from the flat wall of the connection stub section, then on the cylindrical part of the casing and then returns at the bottom dome, braiding the lower insert (e.g. made of metal, polyamide, etc.), wherein in the next loop the bundle of filaments is guided with an offset relative to the previous loop of at least one width of the guided bundle, and wherein the supporting braid guided in this way contains not less than 40 loops or not less than two layers.

[0017] In an exemplary embodiment of the invention, the amount of offset between successive loops is 6 times the width of the filaments bundle.

[0018] It is recommended that in the supporting braid of the composite vessel the filaments bundle is a carbon or aramid or carbon-aramid filament bundle, preferably consisting of two outer carbon fibers and a middle aramid fiber.

[0019] The best results are achieved when the carbon filament bundle in the carrier braid contains 4-36 thousand, preferably 24-36 thousand carbon fibers with a diameter of 5-7 pm.

[0020] In the recommended variant of the composite reinforcement coating, the supporting braid contains 65 wt. % of the filament bundle and 35 wt. % of resin.

[0021] In a particularly recommended variant, the resin in the composite reinforcing coating contains a nanoadditive containing carbon nanotubes, preferably at least 80 wt. % of graphene nanotubes (GNT), at most 15 wt. % of iron nanoparticles and at most 5 wt. % of other allotropic forms of carbon such as graphene flakes or fullerenes. The best effect is obtained if the graphene nanotubes are single-walled (SWGNT) and have a diameter of 1-2 nm, a length not exceeding 20 pm and a length-to-diameter ratio of at least 100.

[0022] The proposed invention also includes the connection stub itself for the composite high- pressure vessel specified above. The invented stub has a section in the shape of a simple prism with an axisymmetric polygon base, intended for fastening the supporting braid, between the retaining collar and the annular protrusion. In the recommended variant of the connection stub, the parallelepiped part for fastening the supporting braid has rounded corners, in which it is recommended to make non-through and preferably cylindrical recesses with a depth not exceeding 0.1 mm.

[0023] In a particularly recommended variant of the connection stub, the axially symmetrical polygon constituting the base of the parallelepiped part is a square.

[0024] The method of manufacturing a composite high-pressure vessel specified above comprises manufacturing a casing by blowing a preform manufactured by any technique from a thermoplastic material to the desired dimensions, connecting the casing with a connection stub also specified above and a bottom dome, and reinforcing the outer surface of the vessel by manufacturing a composite reinforcing coating made of a supporting braid composed of a bundle of filaments embedded in resin. According to the invented method, the bundle of filaments is led in loops between a section of the connection stub having the shape of a simple prism with an axisymmetric polygon as its base, and the bottom dome, starting from the flat wall of this section of the connection stub, then the bundle of filaments is led along the cylindrical part of the vessel casing towards the bottom dome, after which the bundle of filaments is turned back at the bottom dome, braiding the lower insert (e.g. metal, polyamide) and is led along the cylindrical part of the vessel casing towards the parallelepiped section of the connection stub. The bundle of filaments is then guided in a second loop, with an offset relative to the first loop of at least one width of the guided bundle of filaments, and the operation is repeated until no less than 40 loops or no less than two layers in the supporting braid are obtained.

[0025] In particular, according to the proposed variant of the method, the filament bundle is guided over a cylindrical part of the vessel casing at a first angle a comprised between 5° and 30° relative to the tangent to the generatrice of the surface of the vessel casing.

[0026] In a special variant of the method, in the area close to the bottom dome, the bundle of filaments in the supporting braid is guided on the vessel casing in the range of the second angle p of inclination relative to the tangent to the generatrice of the surface of the casing ranging from 2° to 45°.

[0027] Preferably, in the developed method, a bundle of carbon or aramid or carbon-aramid fibers consisting of two outer carbon fibers and a middle aramid fiber is used as the filament bundle in the supporting braid, and it is best if the bundle of carbon fibers in the supporting braid contains 4-36 thousand, preferably 24-36 thousand, carbon fibers with a diameter of 5-7 pm.

[0028] The best results are obtained if the supporting braid contains 65 wt. % of the filament bundle and 35 wt. % of resin.

[0029] Furthermore, the invented method comprises the particular embodiment that the resin in the composite reinforcement layer comprises a nano-additive comprising carbon nanotubes, preferably at least 80 wt. % of graphene nanotubes (GNTs), at most 15 wt. % of iron nanoparticles and at most 5 wt. % of other allotropic forms of carbon such as graphene flakes or fullerenes.

[0030] Ideally, graphene nanotubes are single-walled (SWGNT) and have a diameter of 1-2 nm, a length not exceeding 20 pm and a length-to-diameter ratio of at least 100.

[0031] In particular, according to the claimed method, the production of a composite reinforcing coating made of a supporting braid composed of a bundle of filaments embedded in a resin comprises the following steps: a) at least one spool of the bundle of filaments, preferably carbon fibers, and optionally at least one spool of the optical fiber are mounted on the winding machine; b) the outer surface of the casing is covered with a thin anti-adhesive layer to prevent the composite reinforcing coating from bonding to the casing; c) the resin, preferably with the nano-additive, is prepared in a mixing device at a pressure lower than normal; d) the resin, preferably with the nano-additive, is poured into a resin tray in the winding machine; e) a curing agent is added in a ratio of 29-30 wt. % of the resulting impregnating mixture to the resin, preferably with the nano-additive, poured into the resin tray in the winding machine; f) at least one bundle of filaments, preferably carbon fibers, is impregnated in a resin bath using the resin tray, maintaining in the impregnated bundle a proportion of at least 65 wt. % of bundle of filaments, preferably carbon fibers, and at most 35 wt. % of the impregnating mixture consisting of a resin, preferably with the nano-additive, and the curing agent; g) at least one impregnated bundle of filaments, preferably carbon fibers, is wound, preferably in a hoop, polar or cross-weave braid, onto the casing by wrapping in at least six different winding patterns, wherein optionally the at least one impregnated bundle of filaments, preferably carbon fibers, is wound in the selected at least one layer together with at least one optical fiber; h) the composite reinforcing layer is thermally cured.

[0032] Besides the method of fabrication of the composite vessel includes a variant wherein by making the supporting braid in a cross-polar pattern, the bundles of filaments, preferably carbon fibers, are wound each time during the passages of the winding head between the poles of the vessel casing and during the passages of the winding head around the connection stub while maintaining the angle of inclination of the rotation axis, preferably 53°-55°, and preferably causing the vessel to vibrate slightly.

[0033] In a special, additional variant the winding of the filament bundles, preferably carbon fibers, is carried out at a constant internal pressure in the vessel casing, ranging from 2.0 to 2.8 bar, with the value of the internal pressure in the vessel casing being inversely proportional to its size, and the tension of the filament bundles, preferably carbon, in the winding machine is at least 10 N.

[0034] In addition, when making subsequent layers of the supporting braid, 10 to 12 turns of filament bundles, preferably the carbon ones, are wound successively, including preferably four braids using the polar pattern, preferably three braids using the cross pattern, preferably three braids using the hoop pattern, and preferably one braid using again the polar pattern

[0035] As a result of the method according to the invention, an adhesive bond is formed between the surface of the connection stub, which in particular can be made of metal, and the epoxy construction resin, which is strongest afterthe resin has completely hardened. The surface of the connection stub part in contact with the supporting braid should be prepared by developing the surface, i.e. increasing its roughness. The recommended surface roughness profile should be within the range of 25-55 pm.

[0036] Additionally, a pro-adhesive coating is applied to this part of the connection stub surface, i.e. the polyhedral section with the annular projection and the retaining collar - in contrast to the surface of the vessel casing, which is covered with an anti-adhesive coating. For example, the connection stub can be made of an aluminum alloy and can be coated with a coating created by anodizing. Anodizing leaves the substrate clean, and the micropores provide the basis for increasing the adhesive strength between the curable resin and the metal surface.

[0037] The attachment of the supporting braid by mechanically connecting the connection stub with the resin-filament composite consists in winding a continuous filament around the connection stub in a place where the cross-section has the shape of an axisymmetric polygon, preferably with additional recesses on the circumference increasing the contact surface of the resin with the connection stub. The recesses may be round or elliptical, and up to several dozen micrometres deep. Flat, at least three, contact surfaces of the filament bundle with the parallelepiped part of the connection stub prevent angulardisplacement of the connection stub relative to the composite reinforcing coating of the vessel after the entire system has hardened.

[0038] The filament bundle may contact an even or odd number of faces in the parallelepiped portion of the connection stub and may be wrapped around that portion of the connection stub in a full circumference or at an angle of at least 90° so as to completely fill the polygonal cross-section.

[0039] The exemplary embodiments of the composite high-pressure vessel, the connection stub for this tank and the method of winding the supporting braid during the manufacture of the vessel are shown in the drawings, in which:

[0040] - Fig. 1 shows a schematic axial cross-section of a high-pressure vessel, with a composite reinforcement coating applied to the casing with a connection stub and bottom dome mounted;

[0041] - Fig. 2 shows a side view and axial cross-section through the connection stub;

[0042] - Fig. 3 shows the connection stub in a top view, in a variant with a square prism base, with exemplary dimensions relating to specific embodiments of the invention;

[0043] - Fig. 4 shows a side view of a diagram of winding a bundle of filaments onto the vessel casing;

[0044] - Fig. 5 illustrates a diagram of guiding a bundle of filaments along opposite walls of a regular prism with a square base;

[0045] - Fig. 6 shows an alternative diagram of guiding a bundle of filaments along adjacent walls of a regular prism with a square base;

[0046] - Fig. 7 shows the course of the bundle of filaments in the area close to the bottom dome. The composite high-pressure vessel in the recommended embodiment comprises a casing

[0047] (1) manufactured by blow molding from a preform made of thermoplastic material, a connection stub (3), a bottom dome (4) and a composite reinforcing coating made of a supporting braid (2) composed of a bundle of filaments (5) embedded in resin. The connection stub (3) in the section (6) intended for fastening the supporting braid (2) between the retaining collar (7) and the annular protrusion (8) has the shape of a right prism with a base of an axisymmetric polygon (9), with rounded corners (10), wherein the prism is regular and has a square base.

[0048] The rounded corners (10) contain blind cylindrical recesses (11) with a depth not exceeding 0.1 mm, and the axis of the recess (11) forms an angle of 45° with the adjacent side of the square (9) in cross-section.

[0049] The bundle of filaments (5) in the supporting braid (2) is guided on the vessel casing (1) in a closed loop between the section (6) of the connection stub (3) and the bottom dome (4) in the range of a first angle a of inclination relative to the tangent to the generatrice of the surface of the casing (1) ranging from 5° to 30°, wherein in the area close to the bottom dome (4) the bundle of filaments (5) in the supporting braid (2) is guided on the vessel casing (1) in the range of a second angle p of inclination relative to the tangent to the generatrice of the casing (1) surface ranging from 2° to 45°. The bundle of filaments (5) is guided on the vessel casing (1) starting from the flat wall of the section (6) of the connection stub (3), then on the cylindrical part of the casing (1) and then turns back at the bottom dome (4) braiding the metal lower insert, wherein in the next loop the bundle of filaments (5) is guided with an offset relative to the previous loop of at least one, and preferably two widths of the bundle being guided. In one embodiment, the supporting braid (2) comprises 40 loops guided in this way, and in the second embodiment, in which the offset between successive loops is 6 widths of the bundle of filaments (5), the supporting braid (2) comprises any number of loops, but arranged in two layers.

[0050] To make the composite reinforcing layer, the filaments bundle (5) in the supporting braid

[0051] (2) is made of carbon fibers, and the carbon fiber bundle contains 24-36 thousand carbon fibers with a diameter of 5-7 pm.

[0052] The supporting braid (2) comprises 65 wt. % of the filaments bundle (5) and 35 wt. % of resin. Furthermore, in this embodiment of the high-pressure composite vessel, the resin in the composite reinforcement layer comprises a nano-additive comprising carbon nanotubes, preferably at least 80 wt. % of graphene nanotubes (GNTs), at most 15 wt. % of iron nanoparticles, and at most 5 wt. % of other allotropic forms of carbon such as graphene flakes or fullerenes. The GNTs used are single-walled (SWGNTs) and have a diameter of 1 -2 nm, a length not exceeding 20 pm, and a length to diameter ratio of at least 100.

[0053] In an exemplary embodiment of the invention, the connection stub for the composite high- pressure vessel specified above, between the retaining collar (7) and the annular protrusion (8) has a section (6) in the shape of a simple prism with a base of an axisymmetric polygon (9), preferably a square, intended for fastening the supporting braid (2). This section of the pipe has rounded corners (10), in which there are non-through (blind) cylindrical recesses (11) with a depth not exceeding 0.1 mm.

[0054] An exemplary method of manufacturing a composite high-pressure vessel as defined above comprises manufacturing a casing (1) by blowing a preform manufactured using any technique from a thermoplastic material to the desired size, connecting the casing (1) with a connection stub (3) as defined in the previous paragraph and a bottom dome (4), and reinforcing the outer surface of the vessel by manufacturing a composite reinforcing coating made of a supporting braid (2) composed of a bundle of filaments (5) embedded in resin. The bundle of filaments (5) is led in loops between the section (6) of the connection stub (3) in the shape of a simple prism with the base of an axisymmetric polygon (9) and the bottom dome (4), starting from the flat wall of the section (6) of the connection stub (3), then the bundle of filaments (5) is led along the cylindrical part of the casing (1) of the vessel towards the bottom dome (4), after which the bundle of filaments (5) is turned at the bottom dome (4), braiding the lower metal insert and is led along the cylindrical part of the casing (1) of the vessel towards the section (6) of the connection stub (3). After completing the first loop, the bundle of filaments (5) is led in the second loop, with an offset in relation to the first loop of at least one, or better two widths of the led bundle of filaments (5), after which the operation is repeated until no less than 40 loops or no less than two layers in the supporting braid (2) are obtained.

[0055] In producing the supporting braid (2) on the composite vessel, the bundle of filaments (5) was guided along the cylindrical part of the vessel casing (1) at a first angle a between 5° and 30° relative to the tangent to the generatrice of the vessel casing (1) surface, and in the area close to the bottom dome (4), the bundle of filaments (5) was guided within the second angle p of inclination relative to the tangent to the generatrice of the surface of the casing (1) ranging from 2° to 45°.

[0056] To produce the supporting braid (2) on the composite high-pressure vessel, a carbon fibers bundle containing 24-36 thousand carbon fibers with a diameter of 5-7 pm was used as the filament bundle (5) in the supporting braid (2). In carrying out the claimed method, the components were selected so that the supporting braid (2) contained 65 wt. % of the filament bundle (5) and 35 wt. % of the resin with a nano-additive containing carbon nanotubes (GNTs), specifically: at least 80 wt. % of GNTs, at most 15 wt. % of iron nanoparticles and at most 5 wt. % of other allotropic forms of carbon such as graphene flakes or fullerenes, wherein the graphene nanotubes are singlewalled (SWGNTs) and have a diameter of 1-2 nm, a length not exceeding 20 pm and a length-to-diameter ratio of at least 100.

[0057] In an exemplary embodiment, the claimed method of manufacturing a composite vessel included manufacturing a composite reinforcing coating made of a supporting braid (2) composed of a bundle of filaments (5) embedded in a resin and included the following steps: a) at least one spool with a bundle of carbon fibers (5) and one spool of the optical fiber were mounted on the winding machine; b) the outer surface of the vessel casing (1) was covered with a thin anti-adhesive layer preventing the composite reinforcing layer from bonding with the casing (1); c) the resin with the nano-additive was prepared in a mixing device at a pressure lower than normal; d) the resin with the nano-additive was poured into the resin tray in the winding machine; e) the hardener was added to the resin with the nano-additive in the resin tray in the winding machine in a ratio of 29-30 wt. % of the impregnating mixture thus obtained; f) one or more bundles of carbon fibers (5) - depending on the number of spools mounted in step a) - were impregnated in a resin bath using a resin tray, maintaining in the impregnated bundle a proportion of at least 65 wt. % of the bundle of carbon fibers (5) and at most 35 wt. % of the impregnating mixture consisting of resin with a nanoadditive and a hardener; g) at least one impregnated bundle of carbon fibers (5) was wound in hoop, polar or crosswise pattern, onto the casing (1) by wrapping in at least six different winding patterns, wherein at least one impregnated bundle of carbon fibers (5) was wound in at least one selected layer, preferably in a hoop braid, together with the bundle of optical fibers; h) the composite reinforcing layer was thermally cured.

[0058] While making successive layers of the supporting braid (2) using the cross-polar method, bundles of carbon fibers (5) were wound each time during the winding head passes between the poles of the vessel casing (1) and during the winding head passes around the connecting pipe (3), while maintaining the angle of the axis of rotation within the range of 53°-55° and causing the vessel to vibrate slightly.

[0059] The winding of the carbon fiber bundles (5) was carried out at a constant internal pressure in the vessel casing (1) in the range of 2.0 to 2.8 bar, wherein the value of the internal pressure in the vessel casing (1) was inversely proportional to its size, and the tension of the carbon fiber bundles (5) in the winding machine was at least 10 N.

[0060] While making subsequent layers of the supporting braid (2), 10 to 11 turns of carbon fiber bundles (5) were wound successively, including three or four braids in the polar method, three braids in the cross method, three braids in the hoop method, and finally one braid in the polar method.

[0061] The connection stub was made of aluminium alloy marked with the symbol EN AW-6061 , in which the Al content was 97.25 wt. %, and the additional and trace components were: Mg - 1 .03 wt. %; Si - 0.75 wt. %; Cu - 0.37 wt. %; Cr - 0.31 wt. %, Fe - 0.17 wt. %; Mn - 0.06 wt. %; Zn - 0.04 wt. % and Ti - 0.02 wt. %.

[0062] For the tested sample of this alloy (rod with a diameter of 65.0 mm and a length of 2 m), the corresponding material coefficients were:

[0063] Ro2 = 364 MPa (conventional yield strength - stress at 0.2% elongation);

[0064] Rm= 386 MPa (tensile stress limit during stretching);

[0065] A = 14.5% (elongation at break);

[0066] S = 23.2 MS / m (electrical conductivity);

[0067] H = 114HB (hardness).

Claims

Claims1. A composite high-pressure vessel comprising a casing (1) made by blow molding a preform made of a thermoplastic material, a connection stub (3), a bottom dome (4) and a composite reinforcing coating made of a supporting braid (2) that consists of a bundle of filaments (5) embedded in resin, wherein the connection stub (3) in a section (6) intended for fastening the supporting braid (2) between a retaining collar (7) and an annular protrusion (8) has a shape of a right prism with an axisymmetric polygon base (9).

2. The composite vessel according to claim 1 , characterized in that the section (6) for fastening the supporting braid (2) has rounded corners (10).

3. The composite vessel according to claim 2, characterized in that in the rounded corners (10) there are blind recesses (11) with a depth not exceeding 0.1 mm.

4. The composite vessel according to claim 3, characterized in that the blind recesses (11) are cylindrical.

5. The composite vessel according to any of claims 1 to 4, characterized in that the axisymmetric polygon base (9) is square.

6. The composite vessel according to claim 5, characterized in that the axis of the blind recess (11) makes in cross-section an angle of 45° with the adjacent side of the square base (9).

7. The composite vessel according to any of claims 1 to 6, characterized in that the bundle of filaments (5) in the supporting braid (2) is guided on the casing (1) of the vessel in a closed loop between the section (6) of the connection stub (3) and the bottom dome (4) within the range of a first angle a of inclination relative to the tangent to the generatrice of the surface of the casing (1) ranging from 5° to 30°.

8. The composite vessel according to any of claims 1 to 7, characterized in that in the area close to the bottom dome (4) the bundle of filaments (5) in the supporting braid (2) is guided on the casing (1) of the vessel within the range of a second angle of inclination p relative to the tangent to the generatrice of the surface of the casing (1) ranging from 2° to 45°.

9. The composite vessel according to any of claims 1 to 8, characterized in that the bundle of filaments (5) is guided on the casing (1) of the vessel in loops between the connection stub (3) and the bottom dome (4), starting from the flat wall of the section (6) of the connection stub (3), then on the cylindrical part of the casing (1) and thenturns at the bottom dome (4), braiding the lower insert, wherein in the next loop the bundle of filaments (5) is guided with an offset in relation to the previous loop of at least one width of the guided bundle, and wherein the supporting braid (2) contains not less than 40 loops or not less than two layers.

10. The composite vessel according to claim 9, characterized in that the amount of shift between successive loops is 6 times the width of the bundle of filaments (5).

11. The composite vessel according to any of claims 1 to 10, characterized in that the bundle of filaments (5) in the supporting braid (2) is a bundle of carbon or aramid or carbon-aramid fibers, the latter preferably consisting of two outer carbon fibers and a middle aramid fiber.

12. The composite vessel according to claim 11 , characterized in that the bundle of carbon fibers in the supporting braid (2) contains 4-36 thousand, preferably 24-36 thousand carbon fibers with a diameter of 5-7 pm.

13. The composite vessel according to any of claims 1 to 12, characterized in that the supporting braid (2) contains 65 wt. % of bundle of filaments (5) and 35 wt. % of resin.

14. The composite vessel according to any of claims 1 to 13, characterized in that the resin in the composite reinforcement coating comprises a nano-additive comprising carbon nanotubes, preferably at least 80 wt. % of graphene nanotubes, at most 15 wt. % of iron nanoparticles, and at most 5 wt. % of other allotropic forms of carbon such as graphene flakes or fullerenes.

15. The composite vessel according to claim 14, characterized in that the graphene nanotubes are single-walled and have a diameter of 1-2 nm, a length not exceeding 20 pm and a length-to-diameter ratio of at least 100.

16. A connection stub for a composite high-pressure tank as defined in claims 1-15, characterized in that between the retaining collar (7) and the annular protrusion (8) it has a section (6) in a shape of a right prism with an axisymmetric polygon base (9), intended for fastening the supporting braid (2).

17. The connection stub according to claim 16, characterized in that the section (6) for fastening the supporting braid (2) has rounded corners (10).

18. The connection stub according to claim 17, characterized in that the rounded corners (10) have blind recesses (11) with a depth not exceeding 0.1 mm.

19. The connection stub according to claim 18, characterized in that the blind recesses (11) are cylindrical.

20. The connection stub according to any of claims 16 to 19, characterized in that the axisymmetric polygon base (9) is square.21 . A method of manufacturing a composite high-pressure vessel as described in claims 1- 15, including manufacturing of a casing (1) by blow-molding a preform made of a thermoplastic material by any technique to the desired size, connecting the casing (1) with a connection stub (3) as defined in claims 16-20 and the bottom dome (4), and strengthening the outer surface of the vessel by forming a composite reinforcing coating made of a supporting braid (2) composed of a bundle of filaments (5) embedded in resin, wherein the bundle of filaments (5) is led in loops between a section (6) of the connection stub (3) having a shape of a simple prism with the base of an axisymmetric polygon (9), and the bottom dome (4), starting from the flat wall of the section (6) of the connection stub (3), then the bundle of filaments (5) is led along the cylindrical part of the casing (1) of the vessel towards the bottom dome (4), after which the bundle of filaments (5) is turned at the bottom dome (4), wrapping around the lower insert and is led along the cylindrical part of the casing (1) of the vessel towards the section (6) of the connection stub (3), then the bundle of filaments (5) is led in the second loop, with an offset in relation to the first loop of at least one width of the guided bundle of filaments (5), and then the operation is repeated until no less than 40 loops or no less than two layers in the supporting braid (2) are obtained.

22. The method according to claim 21 , characterized in that the bundle of filaments (5) is guided along a cylindrical part of the tank casing (1) at a first angle a between 5° and 30° relative to the tangent to the generatrice of the surface of the vessel casing (1).

23. The method according to claim 21 or 22, characterized in that in the area close to the bottom dome (4) the bundle of filaments (5) in the supporting braid (2) is guided on the casing (1) of the vessel in the range of the second angle of inclination p in relation to the tangent to the generatrice of the surface of the casing (1) ranging from 2° to 45° .

24. The method according to any one of claims 21 to 23, characterized in that a bundle of carbon or aramid or carbon-aramid fibers, the latter preferably consisting of two outer carbon fibers and a middle aramid fiber is used as the bundle of filaments (5) in the supporting braid (2).

25. The method according to claim 24, characterized in that the bundle of carbon fibers in the supporting braid (2) contains 4-36 thousand, preferably 24-36 thousand carbon fibers with a diameter of 5-7 pm.

26. The method according to any of claims 21 to 25, characterized in that the supporting braid (2) contains 65 wt. % of bundle of filaments (5) and 35 wt. % of resin.

27. The method according to any of claims 21 to 26, characterized in that the resin in the composite reinforcing coating contains a nano-additive containing carbon nanotubes, preferably at least 80 wt. % of graphene nanotubes, at most 15 wt. % of iron nanoparticles, and at most 5 wt. % of other allotropic forms of carbon such as graphene flakes or fullerenes.

28. The method according to claim 27, characterized in that the graphene nanotubes are single-walled and have a diameter of 1-2 nm, a length not exceeding 20 pm and a length-to-diameter ratio of at least 100.

29. The method according to any of claims 21 to 28, characterized in that manufacturing of the composite reinforcing coating made of the supporting braid (2) composed of a bundle of filaments (5) embedded in resin includes the following steps: a) at least one spool with a bundle of filaments (5), preferably carbon fibers, and optionally at least one spool of the optical fiber are mounted on the winding machine; b) the outer surface of the casing (1) is covered with a thin anti-adhesive layer to prevent the composite reinforcing coating from bonding to the casing (1); c) the resin, preferably with the nano-additive, is prepared in a mixing device at a pressure lower than normal; d) the resin, preferably with the nano-additive, is poured into a resin tray in the winding machine; e) a curing agent is added in a ratio of 29-30 wt. % of the resulting impregnating mixture to the resin, preferably with the nano-additive, poured into the resin tray in the winding machine; f) at least one bundle of filaments (5), preferably carbon fibers, is impregnated in a resin bath using the resin tray, maintaining in the impregnated bundle a proportion of at least 65 wt. % of bundle of filaments (5), preferably carbon fibers, and at most 35 wt. % of the impregnating mixture consisting of a resin, preferably with the nanoadditive, and the curing agent; g) at least one impregnated bundle of filaments (5), preferably carbon fibers, is wound, preferably in a hoop, polar or cross-weave braid, onto the casing (1) by wrapping inat least six different winding patterns, wherein the at least one impregnated bundle of filaments (5), preferably carbon fibers, is wound in at least one selected layer together with a bundle of optical fibers; h) the composite reinforcing layer is thermally cured.

30. The method according to claim 29, characterized in that when making the supporting braid (2) with a polar-cross weaving pattern, the bundles of filaments (5), preferably carbon fibers, are wound each time during the passages of the winding head between the poles of the casing (1) and during the passages of the winding head around the connection stub (3) while maintaining the angle of inclination to the rotation axis of the casing (1), preferably 53°-55°, and preferably causing the casing (1) to vibrate slightly.

31. The method according to claim 29 or 30, characterized in that the winding of the bundles of filaments (5), preferably carbon fibers, is carried out at a constant internal pressure in the casing (1), ranging from 2.0 to 2.8 bar, wherein the value of the internal pressure in the casing (1) is inversely proportional to its size, and tension of the bundle of filaments (5), preferably carbon fibers, in the winding machine is of at least 10 N.

32. The method according to claim 29 or 30 or 31 , characterized in that, when making the supporting braid (2), 10 to 12 windings of the bundle of filaments (5), preferably carbon fibers, are wound successively, including preferably four braids in polar pattern, preferably three braids in cross-weave pattern, preferably three braids in hoop pattern and, preferably, another one braid in polar pattern, and preferably at least one optical fiber (6) is wound together with the bundle of filaments (5), preferably carbon fibers, in the last polar braid.