CN108437306B - Composite material microwave indirect heating mold and curing method - Google Patents

Abstract

A microwave indirect heating mould for composite material and its solidifying method features that the microwave is absorbed by the microwave absorbing surface of said indirect heating mould, and the microwave energy is converted into heat energy for heating and solidifying the part made of composite material. The invention can realize the effective heating and curing of the multi-directional layering carbon fiber reinforced resin matrix composite material and the glass fiber reinforced resin matrix composite material, has a series of advantages of short curing time, low energy consumption and the like, greatly improves the microwave curing efficiency of the composite material parts, and provides theoretical basis and technical support for the industrial application of the composite material microwave curing technology.

Description

Composite material microwave indirect heating mold and curing method

technical field

The invention relates to a composite material heating mold and a curing method, in particular to a composite material microwave heating mold and a curing method, in particular to a composite material microwave indirect heating mold and a curing method.

Background technique

Advanced composite materials have many excellent properties, such as high specific strength and specific modulus, good fatigue resistance, good corrosion resistance and good overall formability. It can also greatly reduce the number of parts, simplify the assembly process, and shorten the manufacturing cycle. At present, composite materials have been widely used in the main load-bearing parts of wings and fuselage, and are used more and more in complex curved parts such as air intakes, and are developing towards integral molding and co-curing.

At present, composite materials are mainly formed by heating and pressure curing in the autoclave process. In the autoclave curing process, the air is heated by a resistance wire and circulated under the action of a fan, and the composite material is heated by convection heat exchange and heat conduction. The surface of the composite material is heated first, and then the heat is transferred to the interior. The heating rate of composite parts is slow, the temperature difference in the thickness direction of the parts is large, the molding cycle is long, and both the air and the mold need to be heated to high temperatures, resulting in high energy consumption. The microwave curing method proposed by the applicant in the early stage uses electromagnetic waves to directly penetrate and uniformly heat the composite material inside and outside at the same time. The heating speed is fast, the molding cycle is short, the microwave selectively heats the composite material, neither the air nor the mold is heated, and the energy consumption is low.

However, through extensive research, the applicant found that microwaves are difficult to penetrate and heat the multi-directional layered carbon fiber reinforced resin matrix composites, and the microwave-cured glass fiber reinforced resin matrix composites have problems such as low heating efficiency. In view of the above problems, the present invention proposes a composite material microwave indirect heating mold and a curing method. The microwave absorbing surface of the microwave indirect heating mold is used to absorb microwaves, and the microwave energy is converted into heat energy for heating and curing composite material parts. The invention can realize effective heating and curing of multi-directional layered carbon fiber reinforced resin matrix composite materials and glass fiber reinforced resin matrix composite materials, has a series of advantages such as short curing time and low energy consumption, and greatly improves the microwave power of such composite material parts. The curing efficiency provides theoretical basis and technical support for the industrial application of composite microwave curing technology.

SUMMARY OF THE INVENTION

The purpose of the present invention is to invent a microwave indirect heating mold for composite materials and a curing method in view of the problems that microwaves are difficult to penetrate and heat multi-directional layered carbon fiber reinforced resin-based composite materials, and the heating efficiency of microwave-cured glass fiber reinforced resin-based composite materials is low. .

One of the technical solutions of the present invention is:

A composite material microwave indirect heating mold is characterized in that: the mold is composed of a supporting truss, a wave-transmitting panel, a heat insulating layer and a wave-absorbing profile; the supporting truss and the wave-transmitting panel are mechanically connected to support the wave-transmitting panel; The surface of the wave-transmitting panel is provided with a groove for placing the heat-insulating layer and the wave-absorbing surface, the heat-insulating layer is located at the bottom of the groove, and the composite material to be heated and cured is placed on the wave-absorbing surface. The height of the wave-absorbing profile is consistent with the height around the wave-transmitting panel, that is, the upper surface of the wave-absorbing profile is flush with the upper surface of the wave-transmitting panel.

The supporting truss is composed of a smooth transition metal structure, such as a stainless steel round tube, and there are no sharp corners and burrs on the surface and the connection of the supporting truss.

The wave-transmitting panel is composed of materials with good wave-transmitting performance and certain stiffness and hardness, such as glass fiber reinforced resin-based composite materials, ceramics, polytetrafluoroethylene, etc.; 5mm arc transition, there is no transition sharp corner.

The thermal insulation layer is composed of materials with good thermal insulation properties (such as glass fiber cloth, asbestos cloth, etc.), and is used to reduce the heat loss of the wave absorbing type facing the wave-transmitting panel and the surrounding environment.

The wave-absorbing profile is composed of chopped carbon fiber felt reinforced resin-based composite material, the length of the chopped carbon fiber is 3mm～20mm (preferably 4mm～6mm), and the volume fraction of the chopped carbon fiber is 42%～58% (preferably 48.5mm). %~52.5%), the thickness of the absorbing surface is 5mm~15mm (preferably 8mm~12mm); when the operating temperature is below 150 °C, the resin matrix of the absorbing surface adopts low temperature resin such as epoxy resin or double horse resin. When the operating temperature is above 150 °C, the resin matrix of the absorbing surface adopts a high-temperature resin system such as polyimide resin; the surrounding of the absorbing surface adopts an arc transition with a radius of not less than 5mm, and there is no transition sharp corner; The surrounding edge of the wave absorbing profile should be at least 50mm larger than the surrounding edge of the composite part to be cured.

The second technical solution of the present invention is:

A microwave indirect curing method for composite materials, which is characterized in that: when the thickness of the composite material parts to be cured is not greater than 5 mm, a mold release cloth, the composite material parts to be cured, and the mold release cloth are directly placed on the microwave indirect heating mold in sequence. cloth, absorbent cloth, non-porous isolation film, breathable felt, vacuum bag, etc.; when the thickness of the composite material part to be cured is greater than 5mm, place release cloth, composite material part to be cured, Release cloth, absorbent cloth, non-porous isolation film, wave absorbing layer, breathable felt, vacuum bag, etc.; the vacuum bag is sealed with sealing tape for vacuuming; for the composite material to be cured, there is no need to set the zero-adhesive composite material system Auxiliary materials such as absorbent cloth; when the composite material to be cured is a simple structure such as a flat plate or a single-curvature laminate, the material, shape and thickness of the absorbing layer and the absorbing surface of the mold are consistent. When the part is a complex structure such as a double-curvature or multi-curvature laminate, the wave-absorbing layer is composed of a flexible wave-absorbing diaphragm (such as a carbon black silicone diaphragm, etc.) with the wave-absorbing performance of the wave-absorbing surface of the mold; the microwave The indirect heating mold is placed in the microwave cavity, and the metal structure on the mold is in good contact with the metal wall surface of the microwave cavity (common ground) to avoid the phenomenon of discharge ignition and arc drawing in a strong electromagnetic environment; during curing, real-time measurement of composite parts and For the temperature of the absorbing surface, the difference between the measured temperature of the absorbing surface and the set curing temperature is used to adjust the power in the microwave cavity in real time until the composite parts are completely cured.

Beneficial effects of the present invention:

The invention can realize effective heating and curing of multi-directional layered carbon fiber reinforced resin matrix composite materials and glass fiber reinforced resin matrix composite materials, has a series of advantages such as short curing time and low energy consumption, and greatly improves the microwave power of such composite material parts. The curing efficiency provides theoretical basis and technical support for the industrial application of composite microwave curing technology.

Description of drawings

1 is a composite microwave indirect heating mold and a vacuum packaging system of the present invention;

In the figure: 1 is the supporting truss, 2 is the wave-transmitting panel, 3 is the thermal insulation layer, 4 is the wave-absorbing profile, 5 is the release cloth, 6 is the composite material part, 7 is the absorbent cloth, and 8 is the non-porous isolation film , 9 is the absorbing layer, 10 is the air felt, 11 is the vacuum bag, 12 is the sealing tape.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Example 1.

In this example, 24 layers of carbon fiber reinforced bismuth resin composite material laminates are used as the composite material parts ( ₆ ) to be cured. ×3mm, curing temperature is 200°C. The microwave indirect heating mold is composed of a supporting truss (1), a wave-transmitting panel (2), a heat insulating layer (3) and a wave-absorbing surface (4). Among them, the support truss (1) is welded by stainless steel pipes with an outer diameter of 40mm and an inner diameter of 36mm; the wave-transmitting panel (2) is made of wave-transmitting ceramics, with a size of 500mm×500mm×30mm, and a groove size of 400mm×400mm ×12mm, the corners around the groove are quarter arcs with a radius of 8mm; the support truss (1) and the ceramic wave-transmitting panel (2) are mechanically connected with threads, and the surface of the connection is polished smoothly without sharp corners and Burr; the heat insulation layer (3) is composed of 16 layers of glass fiber cloth, with a thickness of 2mm; the wave absorbing surface (4) is made of chopped carbon fiber felt reinforced polyimide resin composite material, and the length of the chopped carbon fiber is 5mm , the volume fraction of carbon fiber is 50%, the size of the absorbing surface is 399mm × 399mm × 10mm, the surrounding corner is a quarter arc with a radius of 7.8mm, and the maximum operating temperature is 350 ℃.

After the lamination is completed, the aluminum foil tape is pasted around the composite material part (6), the flow glue hole is reserved, and the composite material part (6) and a series of vacuum auxiliary materials are placed on the microwave indirect heating mold. The order of placement is the release cloth (5), the composite material part to be cured (6), the release cloth (5), the non-porous isolation film (8), the air felt (10), the vacuum bag (11), etc.; the vacuum bag (11) Use sealing tape (12) to seal and vacuumize, and the vacuum degree is -0.098MPa. The prepared microwave indirect heating mold is placed in the microwave cavity, and the stainless steel support truss (1) is in good contact with the metal wall of the microwave cavity; during curing, real-time measurement of the composite material part (6) and the wave absorbing profile (4) temperature, using the difference between the measured temperature of the wave absorbing profile (4) and the set curing temperature to adjust the power in the microwave cavity in real time until the composite material part (6) is completely cured.

Example two.

In this example, 200 layers of glass fiber reinforced epoxy resin composite material laminates are used as the composite material parts (6) to be cured, the layering sequence is [0/90] ₁₀₀ , the size of the parts is 300mm×300mm×20mm, and the curing temperature is is 120°C. The microwave indirect heating mold is composed of a supporting truss (1), a wave-transmitting panel (2), a heat insulating layer (3) and a wave-absorbing surface (4). Among them, the supporting truss (1) is made of stainless steel pipes with an outer diameter of 40mm and an inner diameter of 36mm; The size of the groove is 400mm×400mm×12mm, and the corners around the groove are quarter arcs with a radius of 8mm; a screw machine is used between the supporting truss (1) and the glass fiber reinforced epoxy resin composite wave-transmitting panel (2). Connection, the surface of the connection is polished and smooth, and there are no sharp corners and burrs; the heat insulation layer (3) is composed of asbestos cloth with a thickness of 2mm; the wave absorbing surface (4) is made of chopped carbon fiber felt reinforced Shuangma resin composite material , the length of the chopped carbon fiber is 5mm, the volume fraction of the carbon fiber is 50%, the size of the absorbing surface is 399mm×399mm×10mm, the surrounding corner is a quarter arc with a radius of 7.8mm, and the maximum operating temperature is 180℃ .

After the layup is complete, the composite part (6) and a series of vacuum-assisted materials are placed on the microwave indirect heating mold. The order of placement is demoulding cloth (5), composite parts to be cured (6), demoulding cloth (5), absorbent cloth (7), non-porous isolation film (8), wave absorbing layer (9), air felt (10), a vacuum bag (11), etc.; the vacuum bag (11) is sealed with a sealing tape (12) for vacuuming, and the vacuum degree is -0.098MPa. The wave absorbing layer (9) is made of a silica gel diaphragm with a carbon black content of 45%, and the size is 300mm×300mm×8mm. The prepared microwave indirect heating mold is placed in the microwave cavity, and the stainless steel support truss (1) is in good contact with the metal wall of the microwave cavity; during curing, real-time measurement of the composite material part (6) and the wave absorbing profile (4) temperature, using the difference between the measured temperature of the wave absorbing profile (4) and the set curing temperature to adjust the power in the microwave cavity in real time until the composite material part (6) is completely cured.

The above are only specific application examples of the present invention, and do not constitute any limitation to the protection scope of the present invention. All technical solutions formed by equivalent transformation or equivalent replacement fall within the protection scope of the present invention.

The parts not involved in the present invention are the same as or can be implemented by using the prior art.

Claims (6)

1. A composite microwave indirect heating mould is characterized in that: the mould consists of a supporting truss, a wave-transmitting panel, a heat-insulating layer and a wave-absorbing molded surface; the supporting truss is mechanically connected with the wave-transmitting panel and is used for supporting the wave-transmitting panel; the surface of the wave-transmitting panel is provided with a groove for placing a heat insulation layer and a wave-absorbing molded surface, the heat insulation layer is positioned at the bottom of the groove, and the composite material to be heated and cured is placed on the wave-absorbing molded surface; the support truss is a smooth transition metal structural part, and the metal structural part is well contacted with the metal wall surface of the microwave cavity and is grounded so as to avoid the phenomena of discharging, igniting and arcing in a strong electromagnetic environment; the wave-transmitting panel is made of materials with good wave-transmitting performance and certain rigidity and hardness, the periphery of the groove on the surface of the wave-transmitting panel is in arc transition with the diameter not less than 5mm, and transition sharp corners do not exist; the wave-absorbing profile is made of chopped carbon fiber felt reinforced resin matrix composite materials, the length of the chopped carbon fibers is 4 mm-6 mm, the volume fraction of the chopped carbon fibers is 48.5% -52.5%, and the thickness of the wave-absorbing profile is 8 mm-12 mm; when the use temperature is below 150 ℃, the resin matrix of the wave-absorbing profile adopts epoxy resin or bismaleimide resin, and when the use temperature is above 150 ℃, the resin matrix of the wave-absorbing profile adopts polyimide resin; the periphery of the wave-absorbing molded surface is in arc transition with the radius not less than 5mm, and a transition sharp corner does not exist; the peripheral edge of the wave-absorbing molded surface is at least 50mm larger than the peripheral edge of the composite material part to be cured;

when the thickness of the composite material part to be cured is not more than 5mm, directly and sequentially placing demoulding cloth, the composite material part to be cured, the demoulding cloth, the adhesive absorption cloth, the nonporous isolation film, the breathable felt and the vacuum bag on the microwave indirect heating mould; when the thickness of the composite material part to be cured is more than 5mm, sequentially placing demoulding cloth, the composite material part to be cured, the demoulding cloth, the adhesive absorption cloth, the nonporous isolation film, the wave absorbing layer, the breathable felt and the vacuum bag on the microwave indirect heating mould; the vacuum bag is sealed by a sealing adhesive tape and vacuumized; when the composite material part to be cured is a zero-adhesive-absorption composite material system, an adhesive absorption cloth does not need to be arranged; when the composite material part to be cured is of a flat plate or single-curvature laminated plate structure, the wave-absorbing layer is consistent with the wave-absorbing profile of the die in material, shape and thickness, and when the composite material part to be cured is of a double-curvature or multi-curvature laminated plate structure, the wave-absorbing layer is formed by a flexible wave-absorbing diaphragm which has equivalent wave-absorbing performance to the wave-absorbing profile of the die; the microwave indirect heating mould is arranged in the microwave cavity; and during curing, measuring the temperature of the composite part and the wave-absorbing profile in real time, and adjusting the power in the microwave cavity in real time by adopting the difference between the measured temperature of the wave-absorbing profile and the set curing temperature until the composite part is completely cured.

2. The composite microwave indirect heated mold of claim 1, wherein: the metal structural part is a stainless steel round pipe, and the surface and the joint of the metal structural part are free of sharp corners and burrs.

3. The composite microwave indirect heated mold of claim 1, wherein: the wave-transparent panel is made of glass fiber reinforced resin matrix composite, ceramic, polytetrafluoroethylene or glass.

4. The composite microwave indirect heated mold of claim 1, wherein: the heat insulation layer is made of materials with good heat insulation performance and used for reducing heat loss of the wave-absorbing molded surface to the wave-transmitting panel and the surrounding environment.

5. The composite microwave indirect heated mold of claim 4, wherein: the heat insulation layer is made of glass fiber cloth and asbestos cloth.

6. The composite microwave indirect heating mold of claim 1, wherein the flexible wave-absorbing membrane is a carbon black silica gel membrane.

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