Patent Description:
As interest in the aerospace field increases, research on a launch vehicle that can promote the development of the aerospace field has been actively conducted.

For example, in order to reduce the overall cost and the weight of the propellant tank of the space launch vehicle while maintaining design reliability of an existing metal tank, the National Aeronautics and Space Administration (NASA) in the United States has been conducting various research related to the application of composite materials in collaboration with private companies in the aerospace field.

In particular, for the development of a composite liquefied hydrogen tank, the second generation RLV development and Composite Cryo-tank Technology Demonstration Project (CCTD) under the Space Launch Initiative (SLI) through the National Aerospace Plane (NASP) program and the Single-Stage-to-Orbit (SSTD) launch vehicle X-<NUM> program from <NUM> to <NUM> have been in progress.

Among them, as illustrated in <FIG>, a cryogenic tank of the CCTD is configured with a barrel (Continuous Tank Wall), a skirt (shell) (Fluted Core Skirts & Cylinder Wall), a front cover (Access Opening Joint), and a softening strip (Softening Strip Y-joint).

In addition, referring to <FIG>, a manufacturing process of the cryogenic tank of the CCTD includes a barrel forming step of forming a barrel-shaped mold in which a cylinder portion and a dome portion are integrated with <NUM> segments, laying-up a material on the cylinder portion of the barrel-shaped mold, and then curing and inspecting the cylinder portion; a skirt-barrel assembly step of assembling a skirt mold on a dome portion of the barrel formed in the barrel forming step, coating and curing the skirt mold with a flutted core-type panel, and inspecting the skirt mold; a step of manufacturing a cover and a manhole; a step of removing the barrel mold and the skirt mold by entering an inside of the skirt-barrel assembly; and a step of coupling the cover and the manhole to the skirt-barrel assembly.

Such conventional cryogenic projectile propellant tank has the following problems:.

For this reason, conventionally, as illustrated in <FIG>, the weakness of the Y-joint portion is solved in such a manner that a triangular softening strip is inserted into the skirt-barrel assembly, and a short insert is inserted into the remaining gap.

However, this measure has a disadvantage in that it takes a lot of processing time, the cost is increased, and there is a high possibility of defects due to a large number of bonded parts.

In a case of a tank that stores a liquid such as a fuel or a propellant, a structure is required to prevent the contents from fluctuating. However, the conventional cryogenic tank (projectile propellant tank) does not have such a configuration.

Document <CIT> shows another prior art cryogenic fluid storage tank.

Therefore, there is a need to develop a projectile propellant tank that can solve the problems described above.

The present invention is made in order to solve the problems described above, and an object of the present invention is to provide a composite inner frame multi-bonded barrel, a shell-integrated projectile propellant tank including same, and a method for manufacturing those in which in order to decrease a process time and manufacturing costs, simplify a process, increase the safety of an operator, and minimize defects, a plurality of inner frames are manufactured in a ring shape and a dome shape, and then bonded together after a mold is removed in advance, a shell-integrated projectile propellant tank is manufactured by using a barrel that forms a baffle structure that prevents fluctuation at the time of bonding, and a softening strip, which is formed in a conventional insert form, is formed in a Y-joint portion that is a weak portion between the barrel and the shell (skirt), so as to be integrated with the barrel during the manufacture of the barrel.

A composite inner frame multi-bonded barrel according to an example of the present invention for solving the problems described above, the barrel includes: a cylinder portion that is configured by bonding a plurality of inner frames; and a dome portion configured of dome frames bonded to upper and lower ends of the cylinder portion.

Here, the inner frame and the dome frame forms a baffle structure by secondary bonding through a flange protruding inside in each end thereof.

In addition, a curvature of the dome frame may be formed such that a ratio of short axis/long axis may be <NUM> to <NUM> based on an elliptical composite inner frame multi-bonded barrel.

Next, a shell-integrated projectile propellant tank including a composite inner frame multi-bonded barrel according to an example of the present invention includes: the composite inner frame multi-bonded barrel; a cylindrical shell coated on an outside of the composite inner frame multi-bonded barrel; and a manhole cover that seals a manhole cover coupling hole formed in a center of the dome frame and has a fluid injection port formed on one side thereof.

Further, on a side of the dome frame, a softening strip laterally protruding and integral with the dome frame may be formed along a circumference.

Further, the shell may be formed in a solid laminate type formed by multiply overlapping a composite material.

Next, a method for manufacturing a composite inner frame multi-bonded barrel, the method includes the features of claim <NUM>.

Next, a method for manufacturing a shell-integrated projectile propellant tank including a composite inner frame multi-bonded barrel, the method includes: a step of mounting a shell mold on the composite inner frame multi-bonded barrel; a step of forming a barrel-shell assembly by laying-up and co-bonding a composite material to the shell mold; a step of inspecting the barrel-shell assembly after curing; and a step of completing the propellant tank by coupling a manhole cover to the barrel of the barrel-shell assembly for which the inspection is completed.

The shell-integrated projectile propellant tank according to an example of the present invention is manufactured by making a plurality of frames in a ring shape and a dome shape, and then bonded together after the mold is removed and using the barrel that forms a baffle structure that prevents fluctuation at the time of bonding. The softening strip formed in a conventional insert form is formed in the Y-joint portion that is a weak portion between the barrel and the shell, so as to be integrated with the barrel during the manufacture of the barrel. Therefore, there are advantages in that a process time and manufacturing costs can be decreased, a process can be simplified, the safety of an operator can be increased, defects can be minimized, the fastening of the Y-joint portion can be improved, and the propulsion operation of the projectile is safe.

A composite inner frame multi-bonding barrel according to an example of the present invention includes a cylinder portion that is configured by bonding a plurality of inner frames, and a dome portion configured of dome frames bonded to upper and lower ends of the cylinder portion.

A shell-integrated projectile propellant tank including a composite inner frame multi-bonded barrel according to an example of the present invention includes: the composite inner frame multi-bonded barrel; a cylindrical shell coated on an outside of the composite inner frame multi-bonded barrel; and a manhole cover that seals a manhole cover coupling hole formed in a center of the dome frame and has a fluid injection port formed on one side thereof.

A method for manufacturing a composite inner frame multi-bonded barrel according to an example of the present invention includes a step of manufacturing a plurality of inner frames and two dome frames; a step of performing a non-destructive inspection on the manufactured inner frames and dome frames; and a step of forming a barrel by secondary bonding of the plurality of inner frames and the two dome frames.

A method of manufacturing a shell-integrated projectile propellant tank including a composite inner frame multi-bonded barrel according to an example of the present invention includes a step of mounting a shell mold on the composite inner frame multi-bonded barrel; a step of forming a barrel-shell assembly by laying-up and co-bonding a composite material to the shell mold; a step of inspecting the barrel-shell assembly after curing; and a step of completing the propellant tank by coupling a manhole cover to the barrel of the barrel-shell assembly for which the inspection is completed.

Hereinafter, the description of the present invention with reference to the drawings is not limited to a specific embodiment, and various transformations may be applied and various examples may be provided.

In the following description, terms such as first and second are terms used to describe various configuration elements, are not limited to meanings thereof, and are used only for the purpose of distinguishing one configuration element from another configuration element.

The same reference numbers are used throughout the present specification denote the same configuration elements.

Singular expressions used in the present invention include plural expressions unless the context clearly indicates otherwise. In addition, terms such as "include", "provide" or "have" described below are intended to designate the presence of features, numbers, steps, operations, configuration elements, parts, or combinations thereof described in the specification. It should be understood that a possibility of the presence or addition of one or more other features, numbers, steps, operations, configuration elements, parts, or combinations thereof is not preliminarily excluded.

Hereinafter, a composite inner frame multi-bonded barrel, a shell-integrated projectile propellant tank including same, and a method for manufacturing those according to an example of the present invention will be described in detail with reference to <FIG>.

<FIG> is a perspective view of the composite inner frame multi-bonded barrel according to an example of the present invention, <FIG> is an exploded perspective view of the composite inner frame multi-bonded barrel according to the example of the present invention, and <FIG> is a sectional perspective view of the composite inner frame multi-bonded barrel according to the example of the present invention.

With reference to <FIG>, a composite inner frame multi-bonded barrel <NUM> according to an example of the present invention may be configured to include a cylinder portion <NUM> and a dome portion <NUM>.

Specifically, the cylinder portion <NUM> has a cylindrical structure, and may be configured by bonding a plurality of ring-shaped inner frames <NUM>. Here, four ring-shaped inner frames <NUM> may be bonded to each other but this is exemplary and is not limited to the example, and only a plurality of rings may be formed as described above.

In addition, the bonding may be provided by an adhesive (adhesive bonding joint). However, the bonding method is a preferred form and is not necessarily limited thereto, and may be formed by a fastening type such as welding or rivet coupling, if necessary.

In addition, in the above description, although the cylinder portion <NUM> is exemplified as a ring shape having a predetermined length, but may have a cylindrical shape having a length substantially longer than that of the ring shape. That is, there is a volume required for the propellant tank in assembling the projectile, because when it is intended to be formed only with two ring-shaped inner frames <NUM>, it should be formed in a cylindrical shape.

That is, the inner frames <NUM> constituting the cylinder portion <NUM> may be a ring shape or a cylinder in which a hollow portion is formed therein.

The dome portion <NUM> is a cover of the cylinder portion <NUM> and may be configured of dome frames <NUM> that are bonded to an upper end and a lower end of the cylinder portion <NUM>. That is, the dome portion <NUM> may be configured of a dome-shaped upper dome frame <NUM>-<NUM> and a dome-shaped lower dome frame <NUM>-<NUM>.

The dome frame <NUM> may have a flat end portion constituting the dome, and a manhole cover coupling hole <NUM> may be formed in a center thereof. This is provided for coupling to a manhole cover <NUM> to be described later. A detailed description of the coupling to the manhole cover <NUM> will be described later.

The inner frame <NUM> of the cylinder portion <NUM> and the dome frame <NUM> of the dome portion <NUM> described above are bonded to each other to form the barrel of the present invention, where the bonding between the inner frame <NUM> and the dome frame <NUM> forms a bonding end, that is, a flange <NUM> protruding inside in each end of the inner frame <NUM> and the dome frame <NUM> to be capable of secondary bonding.

That is, referring to the drawings, the ring-shaped inner frame <NUM>, on which the flange <NUM> is formed, has a 'concave' cross-section in a circular shape.

The secondary bonding structure between the inner frame <NUM> and the dome frame <NUM> using the flange <NUM> may increase a bonding strength by increasing a bonding area, and also has an effect of forming a baffle structure. The baffle structure is a structure for preventing the contents such as a liquid contained inside the tank from fluctuating, and the flange <NUM> interferes with the fluctuation of the liquid, thereby capable of preventing a propulsion resistance, orbit deviation, or the like, and exhibiting a sloshing reduction effect.

On the other hand, the composite inner frame multi-bonded barrel <NUM> of the present invention formed by assembling the cylinder portion <NUM> and the dome portion <NUM> may form an elliptical shape when the cylinder portion <NUM> and the dome portion <NUM> are assembled. Here, the dome frame <NUM> of the dome portion <NUM> may have a curvature where a ratio (elliptical ratio) of short axis/long axis is <NUM> to <NUM> based on the elliptical barrel. Here, if the ratio of the short/long axis of the curvature of the dome frame <NUM> based on the elliptical barrel is less than <NUM>, buckling may occur, and if it exceeds <NUM>, an internal volume requirement may not be met.

The composite inner frame multi-bonded barrel <NUM> according to the example of the present invention configured as described above has an advantage in that a baffle structure capable of preventing liquid from fluctuating can be formed while providing a high bonding strength. In addition, by assembling a plurality of inner frames, there are advantages in that the process can be simplified, a design for reducing or expanding a volume thereof can be easily modified, and manufacturing costs and a weight of the mold can be reduced.

On the other hand, the shell-integrated projectile propellant tank according to the example of the present invention is manufactured by including the composite inner frame multi-bonded barrel <NUM> described above. This will be described with reference to <FIG>.

<FIG> is a perspective view of the shell-integrated projectile propellant tank according to the example of the present invention, <FIG> is an exploded perspective view of the shell-integrated projectile propellant tank according to the example of the present invention, <FIG> is an enlarged view of the Y-Joint portion of the shell-integrated projectile propellant tank according to the example of the invention, <FIG> is a detailed view of a dome frame which is a configuration of the shell-integrated projectile propellant tank of <FIG>, and <FIG> are detailed views of a manhole cover fastening portion of the shell-integrated projectile propellant tank according to the example of the invention.

Referring to <FIG>, the shell-integrated projectile propellant tank according to the example of the present invention may include the composite inner frame multi-bonded barrel <NUM>, the shell <NUM>, and the manhole cover <NUM>.

Here, since the composite inner frame multi-bonded barrel <NUM> is the same as the composite inner frame multi-bonded barrel <NUM> described with reference to <FIG>, a detailed description thereof will be omitted.

The shell <NUM> may be formed in a cylindrical shape in a configuration of being coated on the outside of the composite inner frame multi-bonded barrel <NUM>. Here, the shell <NUM> laterally protrudes from the side of the cylinder portion <NUM> and the dome frame <NUM> of the composite inner frame multi-bonded barrel <NUM>, and may be bonded to a softening strip <NUM> formed along a circumference thereof to be abutted.

That is, the softening strip <NUM> laterally protruding on the side of the dome frame <NUM> of the composite inner frame multi-bonded barrel <NUM> may be formed to be integrated with the dome frame <NUM> along the circumference.

This, in the structure of the dome portion <NUM> forming a curved surface, forms a Y-joint portion, which is a weak portion where stress is concentrated with the shell <NUM>. Therefore, it can have an effect of reinforcing the Y-joint portion without other additional insertion members. In addition, due to this, it is possible to reduce the process time and improve the safety of the structure by forming a wide bonding area.

Here, the protruding shape of the softening strip <NUM> may be formed of a concave portion <NUM> and an inclined portion <NUM> extending to be downwardly inclined from the concave portion <NUM>, but is not necessarily limited thereto and may be a shape protruding at a right angle.

In addition, the shell <NUM> may be formed in a solid laminate type formed by multiply overlapping the composite material.

This may increase a weight per volume compared to a case where the shell constituting the conventional projectile propellant tank is formed of multiple hollow and flutted core type panels for weight reduction, but it may be further suitable depending on the capacity of the tank when considering an appropriate shell thickness that satisfies the internal volume and structural stability of the propellant tank.

In addition, there are advantages in that the bonding strength between the barrel and the shell is superior through the co-bonding process in which a mold is mounted on the composite inner frame multi-bonded barrel <NUM> to laminate the shell compared to that of the conventional process, necessary tooling can be simplified, and the manufacturing process can also be simplified.

Further, the manhole cover <NUM> may be coupled to the center of the dome frame <NUM> to seal the manhole cover coupling hole <NUM>. In addition, the manhole cover <NUM> may have a fluid injection port <NUM> formed on one side. Here, the manhole cover <NUM> may be bolted to the dome frame <NUM>, the structure thereof may be fastened by forming a plurality of insertion holes <NUM> along a circumference of the manhole cover coupling hole <NUM> in the dome frame <NUM>, inserting an insert <NUM> into the insertion hole <NUM>, and then injecting an adhesive to be cured, seating the manhole cover <NUM> on an upper end thereof, and inserting a bolt <NUM> into the insert <NUM>.

In addition, one or more seals <NUM> may be mounted between the dome frame <NUM> and the manhole cover <NUM> to seal a gap therebetween.

Hereinafter, a method for manufacturing the composite inner frame multi-bonded barrel and a method for manufacturing the shell-integrated projectile propellant tank including the composite inner frame multi-bonded barrel according to the example of the present invention will be described with reference to <FIG>.

<FIG> is a flow chart of manufacturing for the shell-integrated projectile propellant tank according to the example of the present invention.

Referring to <FIG>, the method for manufacturing the composite inner frame multi-bonded barrel according to the example of the present invention includes a step of manufacturing a plurality of inner frames <NUM> and two dome frames <NUM>, a step of performing a non-destructive inspection on the manufactured inner frames <NUM> and dome frame <NUM>, and a step of forming the barrel by secondary bonding of the plurality of inner frames <NUM> and the two dome frames <NUM>.

Here, the inner frame may have a ring or a cylinder shape.

In addition, the step of manufacturing the plurality of inner frames may include a first step of laying-up a composite material on a mold, a second step of curing the laminated composite material to form the inner frame <NUM>, a third step of removing the mold of the inner frame <NUM> formed as described above, a fourth step of manufacturing the plurality of inner frames <NUM> by repeating the first to third steps, and a fifth step of inspecting the manufactured inner frames <NUM>.

Here, the mold forming the inner frame may be configured by being formed in a ring shape, and assembling a plurality of divided bodies. In this case, the plurality of divided bodies may be formed of divided bodies having the same shape, but preferably, they may be cut in a cross shape (+) in all directions based on the center of the mold as illustrated in the drawing. Thus, there is an advantage in that if one of the plurality of divided bodies is removed in the third step, the remaining divided bodies can be easily removed.

In addition, in the step of manufacturing the two dome frames, the dome frame <NUM> may be manufactured by a dome frame mold which is recessed in a hemispherical shape when the dome frame <NUM> is manufactured, and in which a space is also provided where the softening strip positioned in the Y-joint portion when forming the barrel-shell assembly is formed on the side.

Thus, the softening strip may be manufactured integrally with the dome frame <NUM>.

The manufacturing of the dome frame <NUM> may be carried out in a manner in which the composite material is laminated on the inner surface of the dome frame mold recessed in the hemispherical shape by using an AFP device, and then cured to remove the mold in that state.

In the step of forming the barrel by bonding the plurality of inner frames <NUM> and the two dome frames <NUM>, the bonding may be performed by using a vertical tool including a polygonal lower support portion and a plurality of vertical poles vertically extending from the lower support portion.

Specifically, the lower dome frame <NUM>-<NUM> is fixed to a center of the vertical tool, and then the plurality of inner frames <NUM> may be repeatedly stacked and bonded one by one to finally bond up to the upper dome frame <NUM>-<NUM>. Thereafter, a pressurizing device may be installed on the vertical pole so that the adhesive bonding each surface of the dome frame and the inner frame is more evenly spread, and then the upper dome frame <NUM>-<NUM> may be pressed downward to complete the barrel.

In addition, the completed barrel may be finally inspected and finished, and an ultrasonic inspection may be performed at the time of inspection. However, since the inner frame <NUM> and the dome frame <NUM> are respectively subjected to the non-destructive inspection as described above, the final inspection of the barrel may not necessarily be performed.

In such a method for manufacturing for the composite inner frame multi-bonded barrel, there are effects that since the inner frames having the same shape are made and manufactured, a jig and a fixture can be simplified, the assembly can be simplified, so that the inner frame can be manufactured by using a small tool, and in particular, there is no need to remove the mold after completion of the barrel.

In addition, the method for manufacturing the shell-integrated projectile propellant tank including the composite inner frame multi-bonded barrel according to the example of the present invention is performed by integrally manufacturing a barrel, a softening strip, and a shell by covering the shell, and may include a step of mounting a shell mold on the composite inner frame multi-bonded barrel; a step of forming a barrel-shell assembly by laying-up and co-bonding a composite material to the shell mold; a step of inspecting the barrel-shell assembly after curing; and a step of completing the propellant tank by coupling a manhole cover to the barrel of the barrel-shell assembly for which the inspection is completed.

Here, as described above, in the barrel-shell assembly, in a state where the softening strip laterally protruding is formed along the circumference on the side of the dome frame of the composite inner frame multi-bonded barrel, the barrel is bonded to the shell, and thereby the process time can be reduced and the safety of the structure can be improved by widely forming the bonding area.

In addition, when the composite material is laid-up on the shell mold, the shell mold (skirt alignment fixture (SAF)) can be mounted on an automated fiber placement (AFP) equipment adapter to be laid-up, and an ultrasonic test may be performed to the barrel-shell assembly after curing.

In addition, as described above, the coupling of the manhole cover <NUM> is performed by using the insert <NUM> and airtight by using the seal <NUM>, so that there is an advantage of high airtightness.

Claim 1:
A composite inner frame multi-bonded barrel (<NUM>) comprising:
a cylinder portion (<NUM>) comprising a plurality of inner frames (<NUM>) bonded together; and
a dome portion (<NUM>) comprising an upper dome frame (<NUM>-<NUM>) and a lower dome frame (<NUM>-<NUM>) bonded to an upper end and a lower end of the cylinder portion (<NUM>), respectively,
wherein the plurality of inner frames (<NUM>), the upper dome frame (<NUM>-<NUM>), and the lower dome frame (<NUM>-<NUM>) each comprise at least one flange (<NUM>) protruding inside at each end thereof, and
characterized in that the plurality of inner frames (<NUM>), the upper dome frame (<NUM>-<NUM>), and the lower dome frame (<NUM>-<NUM>) form a baffle structure by secondary bonding of the flanges (<NUM>).