CN109282139B - Composite material gas cylinder and preparation method thereof - Google Patents

Abstract

The invention provides a composite material gas cylinder and a preparation method thereof, which is composed of a metal inner liner and a composite material outer shell, the composite material outer shell is composed of a buffer layer and a winding layer, and the buffer layer is a thermoplastic polyimide film The winding layer is a fiber bundle impregnated with polyimide resin, the buffer layer is pasted on the outer surface of the metal liner, the winding layer is wound on the outer layer of the buffer layer, and the buffer layer and the winding layer are co-cured to obtain a composite shell. In the invention, a thermoplastic polyimide buffer layer is introduced between the metal liner and the polyimide winding layer, so as to enhance the thermal stress matching between the metal liner and the composite material during the high temperature curing and cooling of the resin, and at the same time, the thermoplastic polyimide The imine film and the main thermosetting polyimide resin can achieve co-curing, increase the adhesion between the metal liner and the outer composite material, and improve the pressure bearing capacity of the gas cylinder.

Description

A kind of composite material gas cylinder and preparation method thereof

technical field

The invention relates to a composite material gas cylinder and a preparation method thereof, in particular to a high temperature and high pressure polyimide composite material gas cylinder and a preparation method thereof, belonging to the technical field of composite materials.

Background technique

With the rapid development of aerospace technology, missiles and aircraft are developing in the direction of high-speed, long-range, and structural and functional integration. The flight speed of missiles and aircraft can reach Ma3 to 4, and some even break through Ma6. Long-range high speed has caused serious serious problems The problem of aerodynamic heating makes the projectile structure face more and more harsh working environment, and the high temperature environment also restricts the application of many commonly used projectile structural materials such as aluminum alloy and epoxy composite materials at subsonic speed. Due to the multiple requirements of the bomb volume and the long range of the missile, the projectile structure needs to be further reduced in weight.

The high-pressure gas cylinder is a container for one-time storage of compressed nitrogen. Its main function is to pressurize the fuel tank during the flight of the missile. It is a dangerous key component of the spacecraft. It stores high energy inside. The early high-pressure gas cylinders were mainly Metal structure. With the rapid development of aerospace technology, the range of aircraft is getting longer and farther. In order to effectively reduce the proportion of the structure, composite gas cylinders are gradually replacing metal gas cylinders. Due to its high structural efficiency, composite gas cylinders have developed into one of the key components of aerospace structural power systems. The gunshot failure mode of energy shock fragments gradually replaces metallic materials.

At present, high-pressure gas cylinders are mainly composed of metal-lined fully wound composite gas cylinders. There are two main structural forms. One is metal lining + composite material winding layer + outer protective layer. This type of composite material winding layer mainly adopts Epoxy resin system, the outer layer is covered with a heat-proof layer, the epoxy resin winding layer mainly plays a bearing role, and the outer heat-proof layer functions to block or reduce the transmission of heat sources to the interior. This structure often has a thicker outer heat-proof layer, The weight is large, the structural efficiency is low, and the heat-proof layer mainly plays the role of heat-proof and has no bearing function. At the same time, the position of the cylinder head is a special-shaped surface, and the coating process of the heat-proof layer is difficult. Another structural form is metal lining + interface buffer layer + composite material winding layer, the interface buffer layer is a thermal insulation layer or an adhesive, the composite material winding layer is mainly epoxy resin system, and the interface buffer layer is mainly made of rubber or adhesive. Epoxy adhesives and epoxy resin systems cannot meet the temperature resistance requirements.

At present, the resin system used in high-pressure composite gas cylinders is mainly epoxy. Due to the limitation of the line, high-pressure gas cylinders are increasingly required to improve the structural efficiency, that is, under the same external temperature environment, the composite material winding layer itself is required to have high temperature resistance and high load-bearing characteristics, and at the same time, the gas cylinder winding can be minimized in a limited space. Layer thickness, and epoxy composite materials have been unable to meet the needs of high temperature bearing.

Polyimide is one of the organic polymer materials with the best comprehensive performance. Its heat-resistant temperature can reach above 600℃, and the long-term use temperature range is 200-500℃. At present, polyimide composite materials are commonly used in the world. Main material of high temperature resistant, high load bearing structure. Using it in composite gas cylinders is an idea to solve the weak high-temperature bearing capacity of existing materials. However, during the research process, it was found that due to the high curing temperature of polyimide, the thermal expansion of the metal liner and the composite material is inconsistent. The curing process is difficult to control. In the reaction process, it needs to go through multiple stages such as solvent volatilization, amidation, imidization, and cross-linking curing. The whole process is relatively complicated, and there are many process parameters that need to be controlled. In addition, the high temperature resistant polyimide resin can only be suitable for the solution winding process. The polyimide resin contains solvent, and the solvent needs to be removed after winding. After the solvent is removed, the fiber will shrink, and the fiber will buckle after curing. Reduce the burst pressure of the gas cylinder and affect the bearing strength.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art, and to provide a lightweight, simple process, high temperature and high pressure resistant polyimide composite material gas cylinder and a preparation method thereof.

The technical solution of the present invention: a composite gas cylinder, which is composed of a metal inner tank and a composite material outer shell, the composite material outer shell is composed of a buffer layer and a winding layer, and the buffer layer is a thermoplastic polyimide film , the winding layer is a fiber bundle impregnated with polyimide resin, the buffer layer is pasted on the outer surface of the metal liner, and the winding layer is alternately wound in the order of H-Z-H-Z-…-H-Z-H on the outer layer of the buffer layer, where H is a ring winding, Z is spiral winding, and the buffer layer and the winding layer are co-cured to obtain a composite shell.

Hoop winding is that the mandrel rotates around itself at a constant speed, and the winding nozzle moves in a direction parallel to the axis of the mandrel body. Every time the mandrel rotates, the wire nozzle moves one yarn width; helical winding is that the mandrel rotates at a constant speed around its own axis. , the wire winding nozzle reciprocates along the axis of the mandrel at a specific speed, and the basic line shape is composed of the space curve on the head and the helical line of the cylinder segment; hoop winding and helical winding are well-known technical terms in the art.

In the alternate winding process, the number of hoop winding layers is 2 to 3 times that of the spiral winding layers, and the solvent is removed once every 6 to 12 layers of winding, and then the winding is continued.

The number of layers for each winding of the helical winding is 1-2 layers.

The main function of the present invention for stepwise solvent removal is that the polyimide winding is wet winding, and there is some solvent in the winding layer during the winding process. Solvent volatilization will lead to buckling of the wound fibers, while a large amount of solvent volatilization will increase the porosity of the wound layer and affect the load-bearing. After each winding a certain number of layers, the solvent is removed in stages. Because the solvent content is relatively small, the solvent is easy to remove, and at the same time, the fiber is effectively prevented from buckling and the porosity is reduced.

The process of removing the solvent adopts the method of removing the solvent by vacuum, and is cooled to room temperature after being treated at a temperature of 180-240° C. for 1-2 hours. Specifically, a vacuum bag can be used, or other vacuum forms can be used, as long as it can ensure that the small molecule solvent in the winding layer and the solvent generated by imidization can be discharged during the treatment process.

The winding tension decreases during the winding process, that is, the winding tension decreases by 3% to 8% of the initial tension every time 6 to 12 layers are wound.

Winding tension refers to the tension of the fibers during the winding process, the tension of the fibers during the winding process, the uniformity of the tension of each bundle of fibers, and the uniformity of the tension of the fibers between the winding layers, which affects the performance of the product. Greater impact.

The winding tension has a great influence on the pressure bearing capacity of the gas cylinder. The initial winding tension is based on 5% to 10% of the fiber strength. Weak ability and low tension will lead to high resin content, thick winding thickness, excessive tension, and increased fiber wear, resulting in partial fiber breakage, affecting bearing capacity, and increased winding tension, resulting in reduced glue content. The winding tension decreases during the winding process, that is, 3% to 8% of the initial tension decreases every time 6 to 12 layers are wound. In order to avoid the phenomenon of inner loosening and outer tightening, if the tension does not decrease or the decreasing amount is not enough, the tension of the inner layer fibers will be reduced, resulting in loose and wrinkled fibers, resulting in a decrease in bearing strength and fatigue performance. If the tension decreases too much, the resin content of the outer fiber winding layer will be too high, and at the same time, micropores will be generated in the product, resulting in a decrease in mechanical properties.

The techniques of other winding processes are known in the art, and the preparation of the winding tape is known in the art.

The spiral winding angle is calculated and determined according to the inner diameter of the gas cylinder and the pressure resistance requirements. Generally, the winding angle is 10-25°.

The angle between the wound fiber and the axis of rotation of the mandrel is called the winding angle. When the winding angle is close to 90°, it is the circumferential winding, so the circumferential winding angle of the pressure vessel is 90°, and the theoretical winding angle of the helical winding is obtained by theoretical calculation, α ₀ =arcsin(r/R), where α ₀ is the theoretical Winding angle, R is the radius of the barrel, r is the radius of the pole hole, the actual winding angle is selected within the range of _{α∈α0 ±} 1%α0 to ensure no slippage during winding, and also meet the strength requirements of the head and other strengths.

The metal liner of the invention provides a structure with good air tightness and reliability for the composite gas cylinder, and the load mainly depends on the continuous winding layer of the outer layer. Since the polyimide gas cylinder needs to withstand a high temperature of 350°C or more, the liner material needs to have a certain resistance to The thermal grade can be titanium alloy, stainless steel, heat-resistant steel, etc. The thickness of the metal liner is determined according to the pressure bearing capacity of the gas cylinder, generally 0.2mm to 1.5mm. The inner tank head and the cylinder body can be integrally formed by spinning and stretching, or the cylinder body can be formed by spinning, the head is formed by mechanical processing, and then the head and the cylinder body are formed by welding.

The polyimide resin system used in the present invention is a thermosetting polyimide resin, and its type is not particularly limited, as long as the heat resistance satisfies the use, such as acetylene end capping, allyl norbornene end capping or benzene end capping. One or more of acetylene-terminated polyimide resins, etc.

The buffer layer of the invention adopts thermoplastic polyimide film, and the main function is to enhance the thermal stress matching between the metal liner and the polyimide composite material during the high temperature curing and cooling process of the polyimide resin, while the thermoplastic polyimide The amine film material and the main thermosetting polyimide resin can be co-cured to increase the adhesion between the metal liner and the outer composite material. The thickness of the buffer layer is generally 0.05 to 0.5 mm, and the specific thickness is determined by the diameter of the metal liner and the thermal expansion coefficient of the material. Through theoretical calculation, an appropriate thickness is selected. If the thickness is large, the outer layer of the winding fiber cannot guarantee the fiber tension under the action of tension. Straightness will affect the strength. If the thickness is small, it will not be able to play the role of thermal stress matching during high temperature curing and cooling.

Thermal expansion: Δl=α _r *ΔT*l, where Δl is the thermal expansion, α _r is the thermal expansion coefficient of the metal liner, ΔT is the temperature change from room temperature to the curing temperature of the polyimide resin, and l is the initial temperature of the metal liner length (length at room temperature).

The thickness of the buffer layer d≥Δl.

The present invention has no special restrictions on the type of thermoplastic polyimide resin, as long as it can play the above-mentioned role, and polycondensation type polyimide is generally used in engineering, such as Vespel polyimide, Ultem and Extem polyetherimide, One or more of Torlon polyamide-imide, UPIMOL polyimide and Aurum polyimide.

The type of fiber used in the winding layer of the present invention is selected according to the bearing pressure and temperature resistance grade of the gas cylinder, and high-modulus carbon fibers, such as one or more of T700 grade, T800 grade, T1000 grade, etc., can be used, and other types of fibers can also be used. , such as high-strength glass fiber, aramid fiber, quartz fiber, ultra-high molecular weight polyethylene fiber, polyphenylpropoxazole fiber, etc.

The main function of the solvent-removing treatment process of the invention is to remove the organic solvent in the wet entangled fibers, and the reaction characteristics of the polyimide resin are that it needs to undergo multiple processes such as solvent volatilization, amidation, imidization, cross-linking and curing during the reaction process. The first three steps are the pretreatment stage, which is mainly due to the mutual reaction between the monomers and the generation of a large amount of gas. Therefore, the system must be desolventized and exhausted during the resin imidization process to reduce the amount of entangled fibers. At the same time, the imidization treatment is carried out, and the small molecules in the imidization process can be removed in time through the vacuum removal of the solvent, the porosity of the winding layer is reduced, and the bearing strength of the gas cylinder is improved.

In the present invention, the process of removing the solvent by stages during the winding process is as follows: after winding the inner tank of the gas cylinder with a certain thickness, the internal solvent is removed above the boiling point temperature of the solvent by a vacuum solvent removal method, cooled to room temperature, and then continued. Wrap until the design wrap thickness is reached. Its main function is to fix the fiber position in time, reduce fiber folds and looseness, avoid fiber buckling, and improve the uniformity of gas cylinder quality.

The gas cylinder curing method adopted in the present invention is the overall curing. Since some small molecules are released from the polyimide resin during the curing process, the vacuum heating and pressure curing method is adopted. The released small molecules are discharged, and at the same time, the composite gas cylinder is pressurized to improve the compactness and molding quality. Specifically, an autoclave can be used.

A preparation method of a composite gas cylinder is realized by the following steps:

The first step is to treat the outer surface of the metal liner;

Sand blasting is performed on the outer surface of the metal inner tank to ensure that the outer surface is evenly blown; the treatment of the metal inner tank is a well-known technique in the art.

The second step is to lay the buffer layer,

The polyimide resin solution is painted on the outer surface of the metal inner tank, and the thermoplastic polyimide resin film is pasted on the outer surface of the metal inner tank to obtain a buffer layer;

Before laying the buffer layer, the outer surface of the metal inner tank should be cleaned to remove oil stains and impurities, and the treatment process is known in the art.

The third step, winding,

A3.1. The fibers are soaked in the polyimide resin solution to obtain fiber bundles;

It is a well-known technique in the art.

A3.2. Use the soaked fiber bundle to wrap on the buffer layer in the second step,

The fiber bundles are alternately wound in the order of H-Z-H-Z-…-H-Z-H on the outer layer of the buffer layer, where H is hoop winding, Z is helical winding, and the solvent is removed once every 6 to 12 layers of winding, and the winding tension decreases by 3% of the initial tension. ~8%;

The fourth step is to vacuumize, pressurize and heat to solidify as a whole, and obtain a composite gas cylinder.

The specific process is determined according to the type of polyimide resin solution.

Specifically, the following processes can be used, and can also be adjusted according to actual production:

Put the wound composite gas cylinder into a high temperature autoclave for curing, the vacuum degree is about -0.090MPa, the curing temperature is 240℃～370℃, and the pressure point is about 350℃. After curing, a high temperature resistant polyamide is obtained. Imine composite gas cylinders.

The beneficial effects of the present invention compared with the prior art:

(1) In the present invention, a thermoplastic polyimide buffer layer is introduced between the metal liner and the polyimide winding layer to enhance the thermal stress matching between the metal liner and the composite material during the high temperature curing and cooling of the resin, and at the same time The thermoplastic polyimide film and the main thermosetting polyimide resin can achieve co-curing, increase the adhesion between the metal liner and the outer composite material, and improve the pressure bearing capacity of the gas cylinder;

(2) In the alternate winding process of the present invention, the process method of removing the solvent by stages is adopted, and the solvent in the resin and the small molecules produced in the imidization process of the resin can be effectively removed by vacuuming at a certain temperature, and at the same time, the solvent in the resin and the small molecules generated during the imidization of the resin can be effectively removed. Pretreatment under the temperature conditions can further promote the imidization of the resin, reduce the porosity of the winding layer, and improve the bearing strength of the gas cylinder;

(3) In the present invention, by alternately winding and then removing the solvent in stages, the solidification method of vacuum heating and pressure curing as a whole can, on the one hand, be able to discharge the small molecules released by the reaction in time by vacuuming, and on the other hand, the composite material gas cylinder can be added pressure to improve compactness and molding quality.

Detailed ways

The present invention will be described in detail below with reference to specific examples.

Example 1

After sandblasting the stainless steel metal liner, use alcohol to remove surface impurities and oil stains, install the metal liner on the winding machine, and apply YH-550 polyimide solution on the outer surface of the metal liner, and 0.1mm thermoplastic Vespel polyimide film is spread on the outer surface of the metal liner. Then take the two-axis T1000 carbon fiber, prepare the YH-550 polyimide solution, pour the prepared polyimide resin solution into the dipping tank, use the soaked fiber bundle to wrap around the metal liner, and wrap The linear arrangement is: 2-layer hoop - 1-layer helix - 2-layer hoop - 1-layer helix - 2-layer hoop - 1-layer helix... - 2-layer hoop.

The solvent is removed once every 9-11 layers of winding. The solvent removal process is as follows: wrap the wound gas cylinder with perforated film and air felt in turn from the inside to the outside, then vacuum the bag, and treat it in an oven at a temperature of 200 ° C for 2 hours , the vacuum degree is -0.095MPa, and then cooled to room temperature, and then continue winding. After every 9-11 layers of winding, the tension decreases by 3% of the initial tension (40N in this example).

The whole winding process is desolventized three times, and finally cured in an autoclave. The wound composite gas cylinder is put into a high temperature autoclave for curing. The vacuum degree is -0.090MPa, and the curing system is 240℃/2h+370℃/ 3h, the pressure point is 350°C, and the high temperature resistant polyimide composite material gas cylinder is obtained after curing is completed.

The high temperature resistant polyimide gas cylinder was subjected to the room temperature water pressure blasting test and the high temperature pressure resistance test.

The parts of the present invention that are not described in detail are well known to those skilled in the art.

Claims (8)

1. The utility model provides a combined material gas cylinder comprises metal inner bag and combined material shell, its characterized in that: the composite material shell is composed of a buffer layer and a winding layer, wherein the buffer layer is a thermoplastic polyimide film, the winding layer is a fiber bundle impregnated with polyimide resin, the buffer layer is adhered to the outer surface of the metal liner, the winding layer is wound on the outer layer of the buffer layer alternately in the sequence of H-Z-H-Z- … -H-Z-H, H is circumferential winding, Z is spiral winding, and the buffer layer and the winding layer are co-cured to obtain the composite material shell;

the thickness d of the buffer layer is more than or equal to delta l, wherein delta l is thermal expansion amount, and delta l is alpha_r*ΔT*l，α_rIs the thermal expansion coefficient of the metal liner, delta T is the temperature variation from room temperature to the curing temperature of the polyimide resin, and l is the initial length of the metal liner.

2. A composite gas cylinder according to claim 1, characterized in that: in the alternate winding process, the number of the hoop winding layers at each time is 2-3 times of the number of the spiral winding layers, the solvent is removed once when every 6-12 layers are wound, and then the winding is continued, wherein the solvent removing process adopts a vacuum solvent removing mode, and the solution is cooled to the room temperature after being processed at the temperature of 180-240 ℃ for 1-2 hours.

3. A composite gas cylinder according to claim 1, characterized in that: the number of layers of the spiral winding is 1-2.

4. A composite gas cylinder according to claim 1, characterized in that: and the winding tension is decreased progressively in the alternate winding process, namely the winding tension is decreased progressively by 3-8% of the initial tension every time 6-12 layers are wound.

5. The preparation method of the composite material gas cylinder is characterized by comprising the following steps of:

firstly, treating the outer surface of a metal liner;

secondly, paving a buffer layer,

coating a polyimide resin solution on the outer surface of the metal liner, and attaching a thermoplastic polyimide resin film on the outer surface of the metal liner to obtain a buffer layer, wherein the thickness d of the buffer layer is more than or equal to delta l, the delta l is the thermal expansion amount, and the delta l is alpha_r*ΔT*l，α_rIs the thermal expansion coefficient of the metal liner, delta T is the temperature variation from room temperature to the curing temperature of the polyimide resin, and l is the initial temperature of the metal linerA length;

the third step, winding,

a3.1, soaking fibers in a polyimide resin solution to obtain fiber bundles;

a3.2, winding the wetted fiber bundles on the buffer layer in the second step,

alternately winding the fiber bundles on the outer layer of the buffer layer in the sequence of H-Z-H-Z- … -H-Z-H, wherein H is hoop winding, and Z is spiral winding;

and fourthly, vacuumizing, pressurizing, heating and integrally curing to obtain the composite material gas cylinder.

6. The method for preparing the composite material gas cylinder according to claim 5, characterized in that: the winding angle alpha e alpha of the helical winding in step A3.2₀±1％α₀And α is₀Arcsin (R/R), wherein₀For a theoretical winding angle, R is the radius of the barrel body, and R is the radius of the polar hole.

7. The method for preparing the composite material gas cylinder according to claim 5, characterized in that: and B, removing the solvent once every 6-12 layers of the wound film in the step A3.2, wherein the solvent removing process adopts a vacuum solvent removing mode, processes the film at the temperature of 180-240 ℃ for 1-2 hours, and then cools the film to the room temperature.

8. The method for preparing the composite material gas cylinder according to claim 5, characterized in that: and D, adopting winding tension decreasing in the alternative winding process in the step A3.2, namely, when 6-12 layers are wound, the winding tension decreases by 3% -8% of the initial tension.