A through-fixed PMI foam sandwich composite material buoyancy tank and its preparation method

Abstract

The present invention discloses a through-fixed PMI foam sandwich composite pontoon and a preparation method thereof. The pontoon comprises a PMI foam sandwich (2) and a composite material skin (1) covering the surface of the PMI foam sandwich and a through-fixing hole (4); the fixing hole and the PMI foam sandwich form an inverted I-shaped structure, and an embedded part (3) is installed on the inner wall of the port at one end of the fixing hole; the PMI foam sandwich is a nylon 6 nanofiber solution-reinforced PMI foam. The pontoon adopts a through-fixing structure, and the fixing position is located inside the pontoon. While improving the strength of the pontoon, it effectively ensures the overall sealing. There are no fixed part protrusions on the outer surface of the pontoon, which does not affect the overall shape and is easy to disassemble. The pontoon adopts fiber solution-reinforced modified PMI foam as the core material. Under the premise of not increasing the density of the pontoon, the compressive strength and toughness of the pontoon are greatly improved, thereby achieving lightweight preparation of the equipment.

Description

Technical Field

[0001] The present invention relates to a composite material pontoon, in particular to a through-fixed PMI foam sandwich composite material pontoon and a preparation method thereof, belonging to the technical field of amphibious vehicle pontoon manufacturing. Background Art

[0002] An amphibious vehicle is a vehicle that can walk on land and sail on water at the same time. It mainly uses pontoons to provide buoyancy for the vehicle. In order to meet the buoyancy requirements, the pontoons are usually required to be large in size, light in weight, and have a certain strength to ensure that they will not be damaged by the impact of water flow. Even if the pontoons are destroyed in an emergency, they will not cause the vehicle to sink due to insufficient buoyancy.

[0003] Traditional pontoons typically utilize a metal skin with a PVC, PET, or PP foam core. To ensure sufficient strength, the foam density must be ≥100kg / m³, making them relatively heavy. Furthermore, reinforcing ribs are added to the foam core for attachment to the vehicle body or structural reinforcement, further increasing the weight. For pontoons with unusual shapes, traditional metal skins are virtually impossible to achieve a fully integrated, encapsulated structure. Instead, auxiliary molds can be fabricated and welded together using multiple pieces, resulting in complex processing and lengthy production cycles. Furthermore, these unusual structures cannot be fully encapsulated, making them difficult to seal.

[0004] Due to the above problems of metal skin pontoons, many research institutions and enterprises have proposed the use of composite materials to replace metal in the manufacture of pontoons, using PP, PET, PVC or EPS foam as the sandwich material. The density of such foam is basically ≥100kg / m 3 , and the strength is low. In order to ensure strength, weight must be sacrificed, so a larger volume is required to meet the buoyancy requirements. For buoyancy tanks with complex and special-shaped structures, it is often necessary to make molds and use them to manufacture products, which takes a long production cycle.

[0005] Patent CN201510735473.0 discloses a method for manufacturing a low-cost composite buoyancy tank. The method involves cutting foamed PP or PVC sheets according to the design drawings, bonding the sheets together with waterproof adhesive to form a foamed buoyancy tank. The interior of the foamed buoyancy tank is filled with EPS buoyancy foam, and a layer of waterproof double-sided adhesive tape is applied to the exterior of the foamed buoyancy tank to bond the PIN structural core layer. The PIN structural core layer, the wood-plastic foam board layer, and the fiberglass wrapping layer are then bonded together in sequence with waterproof adhesive from the inside out to form a composite buoyancy tank. This patent uses a multi-layer structure to manufacture composite buoyancy tanks, solving the low-cost problem. However, the process is complex and the weight is high, making this method unsuitable for manufacturing buoyancy tanks with irregular shapes and complex structures. Summary of the Invention

[0006] In response to the problems existing in the prior art, the first objective of the present invention is to provide a through-fixed PMI foam sandwich composite pontoon. This pontoon utilizes a through-fixed structure, with the fixing points located within the pontoon and reinforcements embedded around the fixing holes. This improves the pontoon's strength while effectively ensuring overall sealing. The pontoon's exterior lacks protruding fixings, which does not affect the overall shape and allows for easy disassembly. This pontoon utilizes fiber solution-reinforced modified PMI foam as its core material, significantly improving its compressive strength and toughness without increasing its density, thereby achieving lightweight equipment.

[0007] A second objective of the present invention is to provide a method for manufacturing a through-and-through fixed PMI foam sandwich composite pontoon. This method utilizes an integrated molding process, using the PMI foam core as a mold, wrapping the outer surface with a skin material, and then curing the resulting structure under pressure. This method eliminates the need for molds for custom-shaped pontoons, significantly shortening the production cycle. Furthermore, the use of lightweight, high-strength PMI foam as the core material reduces weight by over 30% and overall water absorption by 0.8% compared to metal structures, while maintaining the same mechanical properties.

[0008] In order to achieve the above technical objectives, the present invention provides a through-fixed PMI foam sandwich composite buoyancy box, characterized in that it comprises a PMI foam sandwich (2) and a composite material skin (1) covering the surface of the PMI foam sandwich and a through-fixing hole (4); the fixing hole and the PMI foam sandwich form an inverted I-shaped structure, and an embedded part (3) is installed on the inner wall of the port at one end of the fixing hole; the PMI foam sandwich is a fiber solution reinforced PMI foam, which is obtained by polymerization and foaming of raw materials including the following components in parts by mass: 20 to 80 parts of acrylic acid monomer; 20 to 80 parts of acrylonitrile monomer; 0.1 to 40 parts of initiator; 0.1 to 40 parts of foaming agent; 0.1 to 40 parts of nucleating agent; 0.1 to 40 parts of fiber reinforcement solution; the fiber reinforcement solution is a nylon 6 nanofiber solution.

[0009] The foam sandwich composite material pontoon provided by the present invention is an integrated structure, the through-fixing structure is located inside the pontoon, and reinforcement parts are embedded around the through-fixing holes, which improves the strength while ensuring the sealing. There are no fixing part protrusions on the outer surface of the pontoon, which will not affect the overall shape and is easy to disassemble. The through-fixing structure can also enhance the stability of the pontoon, avoid problems such as extrusion and deformation during the use of the pontoon, and increase the service life of the pontoon.

[0010] As a preferred solution, the acrylic monomer is acrylic acid and / or methacrylic acid.

[0011] As a preferred solution, the acrylonitrile monomer is acrylonitrile and / or methacrylonitrile.

[0012] As a preferred solution, the nylon 6 nanofiber solution is obtained by pre-treating the following components in parts by mass: 1 to 10 parts of nylon 6 nanofiber and 10 to 40 parts of acrylic monomer.

[0013] As a preferred solution, the initiator is one of lauroyl peroxide, azobisisobutyronitrile, dibenzoyl peroxide and tert-butyl peroxyvalerate.

[0014] As a preferred solution, the foaming agent is one of ethanol, propanol, isopropanol, water, butanol, tert-butanol, amyl alcohol and isoamyl alcohol.

[0015] As a preferred solution, the nucleating agent is one of carbonamide, formamide, methacrylamide, N-methylformamide, N,N-dimethylformamide, methyl acrylate, tert-butyl acrylate, methyl methacrylate and tert-butyl methacrylate.

[0016] As a preferred solution, the density of the PMI foam is ≤52kg / m 3 , compression strength ≥ 0.9MPa, and heat deformation temperature ≥ 180°C. Lightweight, high-strength PMI foam is one of the key factors in ensuring the overall performance of the pontoon. If the foam density is too high, the pontoon will be heavy, the buoyancy provided will be too low, and the required volume will be too large. If the foam compression strength is too low, the mechanical properties of the pontoon will be too low, and it will not be able to withstand the extrusion and collision generated during use, shortening the pontoon's service life.

[0017] As a preferred solution, the composite material skin is glass fiber reinforced resin and / or carbon fiber reinforced resin; the thickness of the skin is ≤1 mm.

[0018] The present invention also provides a method for preparing a through-fixed PMI foam sandwich composite buoyancy tank, comprising: 1) uniformly mixing raw materials including acrylic monomers, acrylonitrile monomers, an initiator, a foaming agent, a nucleating agent, and a nylon 6 nanofiber solution, and then sequentially performing a polymerization reaction and a thermal foaming treatment to obtain PMI foam;

[0019] 2) A through-fixing hole is formed on the surface of the PMI foam, and the embedded part is glued to one end of the fixing hole to obtain the PMI foam core material;

[0020] 3) Wrap the outer surface of the PMI foam core material with fiber prepreg, release cloth, release film and breathable felt in sequence, and after curing and molding, open an I-shaped hole at the embedded part position to obtain the product.

[0021] The pontoon provided by the present invention adopts an integrated preparation method. The fiber solution-reinforced PMI foam used in the present invention can not only be used as the core material of the pontoon, but also as the pontoon mold, and can be directly used for subsequent skin covering. There is no need to open the mold for the special-shaped pontoon, which greatly shortens the production cycle.

[0022] As a preferred solution, the above preparation method further includes a pretreatment process of the nylon 6 nanofiber solution; the pretreatment process is: immersing the nylon 6 nanofiber in acrylic acid monomer at 10-40°C for 30-90 minutes and stirring; the stirring conditions are: a stirring rate of 100-240 r / min and a time of 1-4 hours.

[0023] As a preferred solution, the polymerization reaction is a two-stage temperature-raising polymerization, wherein the conditions for the first stage temperature-raising polymerization are: temperature of 30-40°C, time of 90-150h; the conditions for the second stage temperature-raising polymerization are: temperature of 40-50°C, time of 30-60h.

[0024] As a preferred solution, the thermal foaming treatment is a two-stage temperature rising foaming, and the conditions for the first stage temperature rising foaming are: temperature 140-180°C, time 2-6h; the conditions for the second stage temperature rising foaming are: temperature 180-220°C, time 2-8h.

[0025] As a preferred solution, the curing method is hot pressing curing, and the conditions are: pressure of 0.1-1.5 MPa, temperature of 60-100°C, and time of 1-6 hours. More preferably, the hot pressing curing time is 1-2 hours.

[0026] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0027] 1) The through-fixed PMI foam sandwich composite pontoon provided by the present invention adopts a through-fixed structure, the fixing position is located inside the pontoon, and reinforcement parts are embedded around the fixing holes, which effectively ensures the overall sealing while improving the strength of the pontoon. There are no fixing part protrusions on the outer surface of the pontoon, which does not affect the overall shape and is easy to disassemble; the pontoon adopts fiber solution reinforced modified PMI foam as the core material, which greatly improves the compressive strength and toughness of the pontoon without increasing the density of the pontoon, thereby realizing the quality preparation of the equipment.

[0028] 2) The technical solution provided by this invention utilizes an integrated molding process, using a PMI foam core material as a mold, wrapping the outer surface with a skin material, and then curing the resulting product through vacuum bagging. This production method eliminates the need for molds for custom-shaped pontoons, significantly shortening the production cycle. Furthermore, the use of lightweight, high-strength PMI foam as a core material reduces weight by over 30% compared to metal structures, while maintaining mechanical properties. The overall water absorption rate is reduced to 0.8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the buoyancy structure provided in Example 1;

[0030] Figure 2 This is a schematic diagram of the fixed structure penetrating the buoyancy tank provided in Example 1;

[0031] Among them, 1-composite material skin, 2-PMI foam core, 3-embedded parts, 4-through fixing holes. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to specific embodiments so that those skilled in the art can better understand the present invention, but the present invention is not limited thereto.

[0033] Example 1

[0034] A PMI foam sandwich composite buoyancy tank, comprising a PMI foam sandwich, wherein the density of the PMI foam sandwich is 52kg / m 3 , compression strength is 0.9MPa, heat deformation temperature is ≥180℃, and the surface of the PMI foam core material is covered with a 0.6mm thick carbon fiber reinforced resin-based composite material skin.

[0035] The specific preparation process of the through-fixed PMI foam sandwich composite material buoyancy tank provided in this embodiment is as follows:

[0036] 1) soaking 2 parts of nylon 6 nanofibers in 16 parts of methacrylic acid at 25° C. for 45 minutes and stirring at 200 rpm for 2 hours to obtain a pretreated nylon 6 nanofiber solution;

[0037] The prepared nylon 6 nanofiber solution (10 parts) was stirred with 30 parts methacrylonitrile, 30 parts methacrylic acid, 0.5 parts lauroyl peroxide, 7 parts isopropyl alcohol, and 7 parts formamide in a 5L glass kettle for 4 hours at a speed of 260 r / min. The mixture was then poured into a mold and polymerized at 35°C for 120 hours and then at 45°C for 36 hours. The mold was then removed to obtain a polymethacrylimide prepolymer. The prepolymer was then foamed at 160°C for 2.5 hours and then at 210°C for 2.5 hours to obtain PMI foam.

[0038] 2) Process the PMI foam blocks into rectangular foam blocks of 1200mm×600mm×80mm, splice multiple foam blocks into the product shape, connect and fix the foam blocks with adhesive, and process φ65mm through holes at specific locations of the foam blocks. Place the embedded parts into the through holes and fix them to the PMI foam with adhesive;

[0039] 3) Using PMI foam as the mold, cover the outer surface with 3 layers of 200g / m 3The carbon fiber prepreg is then wrapped with a release cloth, a release film, and a breathable felt in sequence, and then sealed with a vacuum bag with a vacuum degree of -0.098 MPa. After maintaining the pressure, it is placed in an autoclave and cured at 80°C and 0.1 MPa. After cooling to room temperature, a crude floatation tank is obtained.

[0040] 4) After the rough product of the buoyancy box is cut and polished, an I-shaped opening is machined at the embedded part to obtain the buoyancy box. The bulk density of the buoyancy box obtained in this embodiment is 53 kg / m 3 , the compression strength is 0.9MPa and the water absorption rate is 0.8%.

[0041] Comparative Example 1

[0042] The traditional metal + foam structure buoyancy tank adopts aluminum alloy welding skin with a thickness of more than 0.5mm, and then fills the interior with high-density foam with a foam density of 80kg / m 3 The foam compression strength is 0.8MPa, and all joints are sealed by welding. Only a simple rectangular structure can be made, and it is connected to the car body using aluminum alloy pre-embedded or surface protruding structure.

[0043] The bulk density of the buoyancy tank obtained in this comparative example is 94 kg / m 3 , the compression strength is 0.8MPa and the water absorption rate is 2.4%.

Claims

1. A through-fixed PMI foam sandwich composite material buoyancy tank, characterized in that: The invention comprises a PMI foam core (2) and a composite material skin (1) covering the surface of the PMI foam core and a through-fixing hole (4); the fixing hole and the PMI foam core form an inverted I-shaped structure, and an embedded part (3) is installed on the inner wall of the port at one end of the fixing hole; the PMI foam core is a fiber solution reinforced PMI foam, which is obtained by polymerization and foaming of raw materials including the following components in parts by weight: 20 to 80 parts of acrylic acid monomer; 20 to 80 parts of acrylonitrile monomer; 0.1 to 40 parts of initiator; 0.1 to 40 parts of foaming agent; 0.1 to 40 parts of nucleating agent; 0.1~40 parts of fiber reinforcement solution; The fiber reinforcement solution is a nylon 6 nanofiber solution; The preparation method of the buoyancy tank comprises: 1) uniformly mixing raw materials including acrylic monomer, acrylonitrile monomer, initiator, foaming agent, nucleating agent and nylon 6 nanofiber solution, and then sequentially performing polymerization reaction and thermal foaming treatment to obtain PMI foam; 2) A through-fixing hole is opened on the surface of the PMI foam, and the embedded part is glued to one end of the fixing hole to obtain the PMI foam core material; 3) Wrap the outer surface of the PMI foam core material with fiber prepreg, release cloth, release film and breathable felt in sequence, and after curing and molding, open an I-shaped hole at the embedded part position to obtain the product; The nylon 6 nanofiber solution is obtained by pretreatment of the following components by mass: 1 to 10 parts of nylon 6 nanofiber and 10 to 40 parts of acrylic monomer. The pretreatment process is: immersing the nylon 6 nanofiber in the acrylic monomer at 10 to 40°C for 30 to 90 minutes and stirring to obtain the obtained product; the stirring conditions are: stirring rate of 100 to 240 r / min and time of 1 to 4 hours.

2. The through-fixed PMI foam sandwich composite material buoyancy tank according to claim 1, characterized in that: The acrylic monomer is acrylic acid and / or methacrylic acid; the acrylonitrile monomer is acrylonitrile and / or methacrylonitrile.

3. The through-fixed PMI foam sandwich composite material buoyancy tank according to claim 1, characterized in that: The initiator is one of lauroyl peroxide, azobisisobutyronitrile, dibenzoyl peroxide and tert-butyl peroxyvalerate; the foaming agent is one of ethanol, propanol, water, butanol and amyl alcohol.

4. The through-fixed PMI foam sandwich composite material buoyancy tank according to claim 1, characterized in that: The nucleating agent is one of carbonamide, formamide, methacrylamide, N-methylformamide, N,N-dimethylformamide, methyl acrylate, tert-butyl acrylate, methyl methacrylate and tert-butyl methacrylate.

5. The through-fixed PMI foam sandwich composite material buoyancy tank according to claim 1, characterized in that: The composite material skin is glass fiber reinforced resin and / or carbon fiber reinforced resin; the thickness of the skin is ≤1mm.

6. The through-fixed PMI foam sandwich composite material buoyancy tank according to claim 1, characterized in that: The polymerization reaction is a two-stage temperature-raising polymerization. The conditions for the first stage temperature-raising polymerization are: temperature of 30-40°C, time of 90-150h; the conditions for the second stage temperature-raising polymerization are: temperature of 40-50°C, time of 30-60h.

7. The through-fixed PMI foam sandwich composite material buoyancy tank according to claim 1, characterized in that: The thermal foaming treatment is a two-stage temperature rising foaming process. The conditions for the first stage temperature rising foaming are: temperature of 140-180°C, time of 2-6 hours; the conditions for the second stage temperature rising foaming are: temperature of 180-220°C, time of 2-8 hours.

8. The through-fixed PMI foam sandwich composite material buoyancy tank according to claim 1, characterized in that: The curing molding method is vacuum bag pressure curing, and the conditions are: pressure of -0.5~-0.1MPa, temperature of 60~100℃, and time of 1~6h.

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