The composite material forming process is the basis and conditions for the development of the composite material industry. With the widening of the application fields of composite materials, the composite material industry has developed rapidly, some molding processes are improving day by day, new molding methods are emerging, and current polymer-based composite materials More than 20 molding methods have been used and successfully used in industrial production, such as:
(1) hand lay-up process - wet lay-up;
(2) injection molding process;
(3) Resin transfer molding technology (RTM technology);
(4) bag pressure method (pressure bag method) molding;
(5) Vacuum bag molding;
(6) autoclave molding technology;
(7) Hydraulic caulking molding technology;
(8) Thermal expansion molding molding technology;
(9) sandwich structure molding technology;
(10) molding material production process;
(11) ZMC molding material injection technology;
(12) Molding process;
(13) Laminate production technology;
(14) Rolling tube forming technology;
(15) Filament winding products molding technology;
(16) continuous board production process;
(17) Casting technology;
(18) Pultrusion process;
(19) Continuously wound pipe manufacturing process;
(20) Braided composite material manufacturing technology;
(21) Thermoplastic sheet molding compound manufacturing technology and cold stamping molding process;
(22) injection molding process;
(23) Extrusion molding process;
(24) Centrifugal cast pipe molding process;
(25) Other molding technologies.
Depending on the chosen resin matrix material, the above methods are applicable to the production of thermosetting and thermoplastic composite materials respectively, and some processes are suitable for both.
Composite material product molding process characteristics: Compared with other materials processing technology, composite material molding process has the following characteristics:
(1) Material manufacturing and product molding are completed at the same time under normal circumstances, the production process of composite materials, that is, the molding process of the product. The performance of the material must be designed according to the requirements of the use of the product. Therefore, in the selection of materials, the design ratio, the fiber is determined. When laying layers and molding methods, they must satisfy the physical and chemical properties of the products, structural shapes and appearance quality requirements.
(2) Product molding is relatively simple. Generally, the resin matrix of the thermosetting composite material is a flowing liquid before molding, and the reinforcing material is a soft fiber or a fabric. Therefore, the production of a composite material product using these materials requires simpler procedures and equipment than other materials. More, for some products only need a set of molds to produce.
First, contact with low pressure molding process
The contact low-pressure molding process is characterized by manually placing reinforcing materials, dipping the resin, or assisting in the placement of reinforcing materials and resins with simple tools. Another feature of the low-pressure molding process is that the molding pressure does not need to be applied ( Contact molding), or only apply lower molding pressure (0.01 to 0.7MPa pressure after contact molding, maximum pressure does not exceed 2.0MPa).
In contact with the low-pressure molding process, the material is first made into a design shape on a female die, a male die, or on a die, and then heated or cured at room temperature. After the die is demolded and then subjected to auxiliary processing, the article is obtained. Hand lay-up, injection molding, bag press molding, resin transfer molding, autoclave molding and thermal expansion molding (low pressure molding), etc. The first two are contact molding.
In contact with the low-pressure molding process, the hand lay-up process is the first invented in the production of polymer-based composite materials, and has the widest range of applications. Other methods are the development and improvement of the hand lay-up process. The biggest advantage of the contact-molding process is that the equipment is simple. , Wide adaptability, low investment, quick results. According to recent statistics, exposure to low-pressure molding technology still occupies a large proportion in the composite material industry in various countries, such as the United States accounted for 35%, Western Europe accounted for 25%, Japan accounted for 42 %, China accounted for 75%. This shows the importance and irreplaceability of exposure to low pressure molding processes in the composite industry. It is a never-fading process. However, its biggest drawback is its low productivity and labor intensity. Large, poor product repeatability.
1, raw materials
Contact with low-pressure molding raw materials are reinforced materials, resins and auxiliary materials.
(1) Reinforcement
Contact molding requirements for reinforcing materials: 1 Reinforcing material is easy to be impregnated with resin; 2 It has sufficient deformation and can meet the molding requirements for complex shape of the product; 3 Bubbles can be easily deducted; 4 Physical and chemical performance requirements that can meet the use conditions of the product; 5 Reasonable prices (as cheap as possible), rich sources.
Reinforcing materials for contact molding include glass fibers and fabrics, carbon fibers and fabrics, aramid fibers and fabrics.
(2) Base material
Contacting low-pressure molding process on the substrate material requirements: 1 easy to soak through the fiber reinforced material in hand paste conditions, easy to remove air bubbles, strong adhesion with the fiber; 2 at room temperature can gel, curing, and requires a small shrinkage, volatilization Few objects; 3 viscosity is suitable: generally 0.2 ~ 0.5Pa · s, can not produce flow phenomenon; 4 non-toxic or low toxicity; 5 reasonable prices, sources are guaranteed.
The commonly used resins in production are: unsaturated polyester resins, epoxy resins, phenolic resins, bismaleimide resins, polyimide resins, etc.
Several contact molding process performance requirements of the resin:
Molding method
Resin performance requirements
Gelcoat production
1, no flow during molding, easy to defoam
2, uniform color, no floating color
3, Fast curing, no wrinkles, good adhesion to laminate resin
Hand lay-up
1, good impregnation, easy to soak the fiber, easy to eliminate air bubbles
2, Fast curing after laying, low heat release, small shrinkage
3, less volatile matter, no sticky surface
4, good interlayer adhesion
Injection molding
1, ensure the hand-paste forming requirements
2, Thixotropy recovers earlier
3, the effect of temperature on the viscosity of the resin is small
4, The resin has a long pot life. After adding the accelerator, the viscosity should not increase.
Bag forming
1, good infiltration, easy to penetrate the fiber, easy to discharge bubbles
2, fast curing, curing heat release should be small
3, not easy to flow, strong adhesion between layers
(3) Auxiliary materials
The auxiliary materials in the contact molding process mainly refer to the two types of fillers and colorants, and curing agents, thinners, tougheners, etc., belong to the resin matrix system.
2, mold and release agent
(1) mold
The mold is the main equipment in various contact molding processes. The quality of the mold directly affects the quality and cost of the product. It must be carefully designed and manufactured.
When designing a mold, the following requirements must be comprehensively considered: 1) Satisfy the precision requirements of the product design, the mold size is accurate, and the surface is smooth; 2) have sufficient strength and rigidity; 3) easy demolding; 4) sufficient thermal stability; 5) light weight , Full source of materials and low cost.
Mold construction Contact forming mold is divided into: female mold, positive mold and the right mold three, no matter what kind of mold, can according to size, shape requirements, design as a whole or assembled mold.
Mold materials When reversing mold materials, the following requirements should be met:
1 can meet the product's dimensional accuracy, appearance quality and service life requirements;
2 The mold material must have enough strength and rigidity to ensure that the mold is not easily deformed and damaged during use;
3 is not affected by resin, does not affect the resin curing;
4 The heat resistance is good. When the product is cured and heat cured, the mold is not deformed;
5 easy to manufacture, easy to release;
6昼Reducing the weight of the mold, convenient for production;
7 The price is cheap, the material is easy to obtain. The materials that can be used as hand lay-up moulds are: wood, metal, plaster, cement, low-melting-point metal, rigid foam plastic and FRP.
Mold release agent basic requirements:
1. Does not corrode the mold, does not affect the curing of the resin, and the adhesive force to the resin is less than 0.01MPa;
2 The film formation time is short, the thickness is uniform, and the surface is smooth;
3 use safety, no toxic effects;
4 heat resistance, can be affected by the temperature of heat curing;
5 easy to operate, cheap.
Mold release agents for contact molding processes include film release agents, liquid release agents and ointments, and wax release agents.
Hand lay-up process
Hand lay-up process is as follows:
(1) Production preparation
The size of the hand lay-up working site on the site shall be determined according to the product size and daily output. The site shall be clean, dry and well ventilated. The air temperature shall be maintained between 15 and 35°C. The finishing section shall be afterwards processed, and the ventilation and dust removal shall be provided. Water spray device.
Mould preparation Preparation includes cleaning, assembly and coating release agents.
When preparing the resin glue, two problems should be paid attention to: 1 Prevent the air bubbles from being mixed in the glue; 2 The amount of glue should not be too much, and each dosage should be used up before the resin gel.
Reinforcement Material Preparation Types and specifications of reinforcement materials are selected according to design requirements.
(2) Paste and cure
Paste layer paste Paste layer paste method Wet and dry methods: 1 Dry prepreg fabric used as raw material, the first pre-study good material (cloth) cut according to the template into a bad material, when layer heating softening , and then close up on the mold layer by layer, and pay attention to the exclusion of air bubbles between the layers, so that compaction. This method is used for autoclave and bag compression molding. 2 Wet layup directly on the mold to enhance the material dipping , Layer by layer close to the mold, the deduction of bubbles, to make it dense. The general hand lay-up process used this method to lay. Wet lay is divided into gel coat layer paste and structure layer paste.
Hand lay-up tools Hand lay-up tools have a great impact on product quality. There are wool rollers, bristle rollers, spiral rollers and chainsaws, electric drills, sanding and polishing machines.
Curing products curing curing and curing two stages: From gel to triangulation generally 24h, at this time the degree of curing up to 50% to 70% (Bauck hardness of 15), can be demoulded, after off in the natural environment Curing for 1 to 2 weeks under conditions can make the products have mechanical strength, called curing, the curing degree of more than 85%. Heating can promote the aging process, the polyester fiberglass, 80 °C heating 3h, epoxy glass, post curing temperature Control within 150 ° C. Many methods of heat curing, small and medium-sized products can be cured in the curing oven, large-scale products can be used in-mold heating or infrared heating.
(3) Demoulding and trimming
The demoulding and demoulding ensure that the product is not damaged. The demoulding methods are as follows: 1 The ejector is ejected on the mold and the ejector is embedded. When the mold is released, the screw is turned to eject the product. 2 The pressure is released on the mold Compressed air or water inlet is left. When demoulding, compressed air or water (0.2 MPa) is pressed between the mold and the product, and a wooden hammer and a rubber hammer are used to separate the product and the mold. 3 Large-scale products (such as ships) Demoulding can be done with tools such as jacks, cranes, and hardwood wedges. 4Complex products can be made by hand-molding first and then two or three layers of glass-fiber reinforced plastics. After they are cured, they can be peeled from the mold, and then placed on the mold to continue the paste. Made to the design thickness, it can be easily removed from the mold after curing.
Trimming is divided into two types: one is size trimming and the other is repaired by a defect. 1 The product after trimming and shaping is cut to exceed the excess part according to the design size; 2 The defect repair includes perforation repair, air bubble, crack repair, hole-breaking reinforcement, etc. .
Injection molding technology
Injection molding is an improvement in hand lay-up, semi-mechanized. Injection molding technology accounts for a large proportion of composite molding processes, such as 9.1% in the United States, 11.3% in Western Europe, and 21% in Japan. The molding machine is mainly imported from the United States.
(1) principle and advantages and disadvantages of injection molding process
In the injection molding process, two polyesters mixed with an initiator and an accelerator are sprayed from both sides of the spray gun, and the cut glass fiber roving is sprayed from the center of the spray gun to be uniformly mixed with the resin and deposited on the mold. , When deposited to a certain thickness, compaction with a roller, so that the fiber soaked resin, eliminate air bubbles, after curing into a product.
Advantages of injection molding: 1 Replacing fabrics with glass rovings can reduce material costs; 2 The production efficiency is 2 to 4 times higher than that of hand lay-up; 3 The product has good integrity, no seams, high interlaminar shear strength, resin content High, anti-corrosion, good resistance to leakage; 4 can reduce the flash, cut cloth and the remaining glue consumption; 5 product size, shape is not limited. The disadvantages are: 1 high resin content, low product strength; 2 Products can only be unilaterally smooth; 3 polluting the environment, harmful to the health of workers.
Injection molding efficiency of 15kg/min, it is suitable for large-scale hull manufacturing. Has been widely used in processing tubs, machine covers, toilets, auto body parts and large relief products.
(2) Production preparation
Site In addition to meeting the hand layup process requirements, the injection molding site should pay special attention to the environment. According to the size of the product, the operation room can be built in closed type to save energy.
Material Preparation Raw materials are mainly resins (mainly unsaturated polyester resins) and glass fiber rovings.
Mould preparation Preparation includes cleaning, assembly and coating release agents.
Injection molding equipment Injection molding machines are divided into two types, pressure tank type and pump type: 1 Pump type plastic injection molding machine, which sends the resin initiator and accelerator to the static mixer separately from the pump. Ejection, referred to as gun-in-handle type. Its components are pneumatic control systems, resin pumps, auxiliary pumps, mixers, spray guns, fiber cutting jets, etc. The resin pump and auxiliary pump are rigidly connected by a rocker arm. The position of the pump on the rocker arm ensures the proportion of the ingredients. Under the action of the air compressor, the resin and additives are evenly mixed in the mixer, and the spray gun forms droplets, which are continuously sprayed onto the mold surface with the cut fibers. The sprayer has only one glue gun, which is simple in structure, light in weight and less in waste of initiator. However, due to the mixing in the system, it should be cleaned immediately after completion to prevent jet clogging. 2 Pressure tank type glue spraying machine is resin glue The liquids are placed in pressure tanks, respectively. The pressure of the gas entering the tank causes the glue to enter the spray gun continuously. The safety system consists of two resin tanks, pipes, valves, spray guns, fiber cutting jets, trolleys and supports. , turn on compression The gas source allows the compressed air to pass through the air-water separator into the resin tank, the glass fiber cutter and the spray gun, so that the resin and glass fibers are continuously sprayed by the spray gun, the resin is atomized, the glass fiber is dispersed, and the glass fiber is uniformly mixed and then sinks to On the mold. This sprayer is resin mixed outside the spray gun, so it is not easy to plug the spray gun mouth.
(3) Injection molding process control
Injection process parameters selection: 1 resin content injection molding products, resin content controlled at about 60%. 2 spray pressure when the resin viscosity is 0.2Pa · s, the resin tank pressure is 0.05 ~ 0.15MPa, the atomization pressure is 0.3 ~ 0.55MPa, in order to ensure that the components mixed evenly. 3 spray gun angle of different angles of the resin sprayed out of different mixing distance, generally choose the angle of 20 °, the distance between the gun and the mold is 350 ~ 400mm. Change the distance, to high-speed spray gun The included angle ensures that the components are mixed and mixed near the surface of the mold to prevent the glue from being lost.
Spray molding should pay attention to matters: 1 the ambient temperature should be controlled at (25 ± 5) °C, is too high, can easily cause the gun to block; too low, uneven mixing, curing slow; 2 jet system does not allow the presence of water, otherwise it will Affect product quality; 3 Before molding, first spray a layer of resin on the mold, and then spray the resin fiber mixed layer; 4 before injection molding, first adjust the air pressure, control the content of resin and glass fiber; 5 spray gun to move evenly to prevent leakage of spray, Can not walk the arc, the overlap between the two lines is less than 1/3, to ensure uniform coverage and uniform thickness; 6 After spraying a layer, immediately compacted with a roller, pay attention to angular and concave and convex surfaces, ensure that each layer pressure Flat, discharge air bubbles to prevent burrs from being caused by fibers; 7 After each layer is sprayed, it should be inspected and then sprayed after it is qualified; 8 The last layer should be thinned to make the surface smooth; 9 After the jet machine is used up Clean immediately to prevent the resin from curing and damage the equipment.
Resin transfer molding
Resin transfer molding is abbreviated as RTM (Resin Transfer Molding). RTM began in the 50's and is a closed-mold molding technology improved by hand lay-up process. It can produce two-sided light products. It belongs to this process category in foreign countries. There are Resin Injection and Pressure Infection.
The basic principle of RTM is to lay the glass fiber reinforced material into a closed mold cavity, and then use pressure to inject the resin glue into the mold cavity, soak the glass fiber reinforced material, and then solidify and release the molded product.
From the previous research level, RTM technology research and development will include microcomputer-controlled injection unit, reinforced material pre-molding technology, low-cost mold, fast resin curing system, process stability and adaptability.
RTM molding technology features: 1 can produce two-sided light products; 2 high forming efficiency, suitable for medium-sized production of glass and steel products (20000 / year or less); 3RTM is a closed mold operation, does not pollute the environment, does not harm the health of workers; 4 Reinforcement materials can be placed in any direction, easy to realize reinforcement of materials according to product stress conditions; 5 less consumption of raw materials and energy; 6 less investment in construction, faster development.
RTM technology has a wide range of applications. It has been widely used in the fields of construction, transportation, telecommunications, health, aerospace and other industries. The products that have been developed include: automotive shells and components, recreational vehicle components, propeller, 8.5m wind power Generator blades, radomes, machine covers, tubs, bathing rooms, swimming pool boards, seats, water tanks, telephone booths, utility poles, small yachts, etc.
(1) RTM Process and Equipment
Forming process RTM All production processes are divided into 11 processes (as shown in the figure). The operators and tools of each process are fixed in position. The molds are transported by the trolley and go through each process step by step to realize the flow operation. The cycle time of the mold on the assembly line is Basically reflects the production cycle of products, small products generally only need ten minutes, the production cycle of large products can be controlled within 1h.
Molding equipment RTM molding equipment is mainly resin injection molding machine and mold.
1 resin injection molding machine The resin injection molding machine consists of a resin pump and an injection gun. The resin pump is a set of piston-type reciprocating pumps with an aerodynamic pump at the top. When the compressed air drives the air pump piston up and down, the resin pump will The resin flows through the flow controller, and the filter is quantitatively drawn into the resin reservoir. The lateral lever moves the catalyst pump and the catalyst is quantified to the reservoir. The compressed air is charged into the two reservoirs, resulting in buffering against the pressure of the pump. The force ensures that the resin and the catalyst can flow stably to the injection gun head. After the injection of the muzzle there is a static turbulent flow mixer, which allows the resin and catalyst to mix evenly in an airless state, and then injected into the mold through the muzzle. There is a detergent inlet, which is connected to a solvent tank with a pressure of 0.28 MPa. When the machine is used up, the switch is turned on and the solvent is automatically sprayed to clean the injection gun.
2 mold RTM mold split glass mold, FRP surface metal mold and metal mold 3. FRP mold is easy to manufacture, the price is lower, polyester fiberglass mold can be used 2000 times, epoxy glass fiber reinforced plastic mold can be used 4000 times. FRP molds can be used more than 10,000 times. Metal molds are rarely used in RTM processes. In general, RTM molds cost only 2% to 16% of SMC.
(2) RTM raw materials
Raw materials for RTM are resin systems, reinforcing materials and fillers.
Resin system RTM process resin is mainly unsaturated polyester resin.
Reinforcing Material The reinforcing material of the general RTM is mainly glass fiber, its content is 25% ~ 45% (by weight); commonly used reinforcing materials are glass fiber continuous felt, composite felt and woven cloth.
Filler fillers are important for the RTM process, which not only reduces costs, improves performance, but also absorbs heat during the resin curing exothermic phase. Common fillers are aluminum hydroxide, glass beads, calcium carbonate, mica, etc. The dosage is 20 %~ 40%.
Bag pressing method, autoclave method, hydraulic kettle method and thermal expansion molding
Bag pressing method, autoclave method, hydraulic caulking method and thermal expansion molding method are collectively referred to as low-pressure molding process. The molding process is a manual lay-up method in which the reinforcing material and the resin (including the prepreg material) are arranged in the design direction and order. The layers are laid on a mold, and after reaching a specified thickness, they are pressed, heated, cured, demolded, and trimmed to obtain the product. The four methods are different from the hand lay-up process in that they only pressurize the process. Therefore, they Only the improvement of the hand lay-up process is to increase the compactness of the product and the bond strength between the layers.
High-performance composite products made of high-strength glass fiber, carbon fiber, boron fiber, aramid fiber and epoxy resin, manufactured by low-pressure molding method, have been widely used in aircraft, missiles, satellites and space shuttles. Such as aircraft cabin doors , fairings, airborne radome, brackets, wings, tailplanes, bulkheads, siding and stealth aircraft.
(1) bag pressure method
Bag-forming is an uncured product in which a hand-paste is formed, and a gas or liquid pressure is applied to it by a rubber bag or other elastic material so that the product is compacted under pressure and cured.
The advantages of the bag compression molding method are: 1 smooth on both sides of the product; 2 can adapt to polyester, epoxy and phenolic resin; 3 product weight is higher than the hand paste.
There are two types of bag press molding methods, namely pressure bag method and vacuum bag method: 1 Pressure bag method The pressure bag method is to put uncured products of hand lay-up into a rubber bag, fix the cover plate, and then pass in compressed air or steam (0.25 ~ 0.5 MPa) to cure the product under hot pressing conditions. 2 Vacuum bag method This method is to hand lay-up the uncured product, cover with a layer of rubber film, the product is between the rubber film and the mold, seal the surrounding, pumping Vacuum (0.05 ~ 0.07 MPa) eliminates bubbles and volatiles in the product. The vacuum bag forming method is used for the wet forming of polyester and epoxy composite products due to the small vacuum pressure.
(2) autoclave and hydraulic kettle method
The autoclave and the autoclave are processes in which a non-cured hand-paste product is heated, pressurized, and cured by a compressed gas or liquid in a metal container.
The autoclave autoclave is a horizontal metal pressure vessel, uncured hand-paste product, plus a sealant bag, vacuum, and then pushed into the autoclave with a small cart to pass steam (pressure 1.5~ 2.5MPa), and vacuum, pressurize the product, heat, discharge air bubbles, make it cured under hot press conditions. It combines the advantages of pressure bag method and vacuum bag method, short production cycle, high product quality. The kettle method can produce large-size, complex-shaped high-quality, high-performance composite products. The product size is limited by an autoclave. Currently, the largest autoclave in China is 2.5m in diameter and 18m long. The organic wing has been developed and applied. , tail, satellite antenna reflector, missile reentry body, airborne sandwich structure radome, etc. The biggest drawback of this method is large equipment investment, heavy weight, complex structure, high cost.
Hydraulic cauldron hydraulic cauldron is a closed pressure vessel, which is smaller than autoclave and is placed upright. It is fed with hot water under pressure. It heats and pressurizes uncured hand-paste product to make it solidify. Can reach 2MPa or higher, temperature is 80~100°C. With oil carrier, the heat can reach 200°C. The product produced by this method is compact, the cycle is short, the disadvantage of the hydraulic kettle method is that the equipment investment is large.
(3) Thermal expansion molding
Thermal expansion molding is a process for the production of fast-opening, thin-walled high-performance composite products. Its working principle is the use of different expansion coefficient of the mold material, the use of its heated volume expansion of different extrusion pressure, pressure on the product construction The male mold of the thermal expansion molding method is a silicone rubber having a large expansion coefficient. The female mold is a metal material having a small expansion coefficient. The uncured product of the hand paste is placed between the male mold and the female mold. Different expansion coefficients produce a large difference in deformation, allowing the product to cure under hot pressure.
Second, sandwich structure manufacturing technology
The sandwich structure is generally a composite material made of three layers of material. The upper and lower layers of the sandwich composite are high strength, high modulus materials, the middle layer is a thick lightweight material, and the FRP sandwich structure is actually a composite material and others. Recombination of lightweight materials. The sandwich structure method is used to increase the effective utilization of materials and reduce the structural weight. For example, the beam and plate components are used as examples. In the process of use, one must meet the strength requirements, and the other must satisfy the need for rigidity. The material is characterized by high strength and low modulus. Therefore, when a single glass fiber reinforced plastic material is used to meet the strength requirements, the deflection is often very large. If the design is allowed to be flexible, the strength is greatly exceeded, causing waste. Only the sandwich layer is used. The structural form is designed to properly resolve this contradiction. This is also the main reason for the development of the mezzanine structure.
Due to its high strength, light weight, high stiffness, corrosion resistance, electrical insulation, and microwave penetration, FRP sandwich structures have been widely used in aircraft industry, aerospace industry and aerospace industry, missiles, spacecraft and prototypes, roofing panels, etc. Reducing the weight and improving the function of the building. Transparent glass-fiber sandwich panels have been widely used in industrial plants in cold regions, and in roofs of large public buildings and greenhouses. In the shipbuilding and transportation fields, FRP sandwich structures are widely used in fiberglass submarines, Minesweeper boat, many components in the yacht. China's design and manufacture of fiberglass pedestrian crossing bridges, highway bridges, automobile and train insulation collection vehicles, etc., have adopted a glass steel sandwich structure, to meet the light weight, high strength, stiffness, heat insulation , Thermal insulation and other performance requirements. In the microwave radiation through the shield, FRP sandwich structure has become other materials can not be compared with the special material.
1, the type and characteristics of glass fiber reinforced plastic sandwich structure
According to different types and forms of core materials used in sandwich structure, FRP sandwich structure is divided into: foam sandwich structure, honeycomb sandwich structure, trapezoidal sandwich structure, rectangular sandwich structure and circular sandwich structure.
(1) Foam sandwich structure Foam sandwich structure uses FRP sheet as skin (panel) and foam as sandwich layer. The most important feature of foam sandwich structure is that the skin and foam plastic core layer are firmly bonded. Strength and heat insulation performance requirements of the components, such as aircraft tail, insulation ventilation ducts and templates.
(2) Honeycomb sandwich structure Honeycomb sandwich structure uses glass fiber reinforced plastic sheet as cover, honeycomb material (glass cloth honeycomb, paper honeycomb or other cotton cloth and aluminum honeycomb, etc.) as the sandwich layer. Honeycomb sandwich structure is light in weight, high in strength and rigidity. Large, mostly used as structural parts with large size and high strength requirements, such as load-bearing plates for fiberglass bridges, spherical roof structures, radomes, reflective surfaces, refrigerated truck floors, and box structures.
(3) Trapezoid and Rectangular Leading Layers The structure of the leading layer structure of the panel (skin) is made of FRP sheet and the sandwich layer is made of FRP trapezoidal or rectangular plates. This sandwich structure has strong directionality and is only suitable for high strength applications. Flat plate, should not be used to bend the shape of the product.
(4) Circular ring sandwich structure It is made of glass fiber reinforced plastic sheet as the skin, and the glass fiber reinforced plastic ring is used as the sandwich layer. This sandwich structure is characterized by low consumption of core material, high strength, and no stress on the plate. It is the most suitable transparent glass fiber reinforced plastic sandwich plate for daylighting, with less shielding and high light transmittance.
Honeycomb sandwich structure manufacturing technology
(1) Honeycomb type The strength of honeycomb is related to the choice of raw materials and honeycomb geometry. According to the planar projection geometry, the honeycomb sandwich material can be divided into hexagonal, rhombic, rectangular, sinusoidal and reinforced hexagons. Among these honeycomb sandwich materials, the strength of the reinforcing strip hexagon is the highest, and that of the square honeycomb is the next highest. Since the hexagonal honeycomb is simple in manufacturing, the material is saved and the strength is high, so it is the most widely used.
(2) There are many types of skin and sandwich materials for the sandwich structure of raw materials. If aluminum and titanium alloys are used as skins and core materials, they are called metal sandwich structures; they are made of FRP sheets, wood plywood and inorganic composite sheets. The use of fiberglass honeycomb, paper honeycomb and foam as sandwich materials, is called non-metallic sandwich structure. At present, the use of glass fiber reinforced plastic sheet to do skin, glass fiber reinforced plastic honeycomb and foam as the sandwich material is the most widely used. Fiber cloth (reinforced material) Glass cloth with FRP sandwich structure is divided into surface cloth and honeycomb cloth. The surface cloth is reinforced alkali-resin and alkali-free plain cloth. Its thickness is generally 0.1~0.2mm. Strengthen the viscosity strength between the skin and the honeycomb, often add a layer of chopped glass fiber mat between them. Use waxy glass cloth as honeycomb material to prevent the resin from penetrating to the back of the glass cloth and reduce the layer between honeycomb blocks. Adhesion, favorable for honeycomb hole stretching. 2 paper production honeycomb sandwich structure of the paper, requiring good resin infiltration and sufficient tensile strength. 3 adhesive (resin) resin for manufacturing honeycomb sandwich structure Resins for skins, resins for honeycombs and resins for bonding honeycombs and skins. Epoxy resins, unsaturated polyester resins, phenolic resins, silicone resins and phthalates can be used depending on the conditions of use of the sandwich structure. Acrylates, etc. When manufacturing honeycomb strips, epoxy resins, modified phenolic resins, polyvinyl acetate adhesives, and polyvinyl butyral adhesives are commonly used. Among these adhesives, epoxy resins have high bonding strength and are modified. Phenolic resin is low in price, so it is used more. Polyvinyl acetate adhesive is non-toxic, cheap, and can be cured at room temperature, but the bee strip made of this glue cannot be immersed in polyester adhesive glue because of the benzene in the polyester resin. Ethylene can dissolve polyacetal, making the bee glue open and destroyed.
(3) Fabrication of glass sandwich cores When producing glass cloth core materials, the main color-bonded plastics are used for stretching. The process involves first coating the glass cloth on the honeycomb core material and then overlaying and bonding into a honeycomb stack. After curing, the honeycomb height is cut into honeycomb strips as required. After being stretched and preformed, the resin is finally dipped and solidified into a honeycomb core material. The adhesive strip gluing method for manufacturing the honeycomb sandwich core stack can be hand-rubbed with rubber. Use mechanical coating.
(4) Honeycomb sandwich structure manufacturing Glass cloth honeycomb sandwich structure manufacturing technology is divided into two kinds of wet method and dry method. 1 Dry method This method is to first make the honeycomb sandwich and panel, and then they are bonded into a sandwich structure. In order to ensure the firm adhesion between the core material and the panel, a thin layer of felt (impregnated with glue) is often placed on the panel, covered with a honeycomb, and heated and pressed to solidify into one. The sandwich structure made by this method, the core and the The adhesive strength of the panel can be increased to 3MPa or more. The advantages of dry forming are mainly that the surface of the product is smooth and smooth. Each process in the production process can be inspected in a timely manner, and the product quality is easy to guarantee. The disadvantage is that the production cycle is long. 2 Wet forming In this method, both the panel and the honeycomb sandwich are in the uncured state, and they are glued together in a mold. During production, the upper and lower panels are made on the mold, and then the honeycomb strips are pulled apart and put on and off. Between panels, pressure (0.01 ~ 0.08MPa), curing, trimming into product after demoulding. The advantages of wet forming are high bonding strength between honeycomb and panel, short production cycle, best suited for spherical, shell and other shaped Structural product production. The disadvantage is the product surface Amount difference, the production process is difficult to control.
Foam plastic sandwich structure manufacturing technology
(1) Raw materials The raw materials for the foam sandwich structure are divided into panel (skin) materials, sandwich materials and adhesives.
1 Panel material: It is mainly made of glass cloth and resin. It is the same material used for honeycomb sandwich panel.
2 Adhesives Adhesives for panels and sandwich materials depend primarily on the type of foam, such as polystyrene foam, which cannot be bonded with unsaturated polyester resins.
3 foam sandwich materials There are many types of foam plastics. There are two types of foams: One is based on resin matrix and can be divided into: PVC foam, polystyrene foam, polyethylene foam, polyurethane foam , Phenolic, Epoxy and unsaturated polyester and other thermosetting foams, etc. The other is the near hardness, can be divided into hard, semi-rigid and soft three. The biggest advantage of the production of sandwich structure with foam core material It is cold-proof, heat-insulating, sound-insulating performance, light weight, large bonding surface with masking surface, uniform load transmission, good impact resistance, etc.
(2) Foam manufacturing technology There are many foaming methods for producing foam plastics, including mechanical foaming, inert gas-miscible pressure-reduction foaming, low-boiling point liquid evaporation foaming, and foaming agent-free deflation air foaming. And the raw material components react with each other deflation foaming method. 1 mechanical foaming method using strong mechanical stirring, the gas is mixed into the polymer solution, emulsion or suspension to form a foam, and then cured to obtain a foam. 2 Inert gas-miscible pressure-reduction foaming method uses inert gas (such as nitrogen, carbon dioxide, etc.) as a colorless, odorless, compounding principle with other chemical elements, and it is pressed into polymer under high pressure, heated, depressurized, Gas expansion foaming. '14; low-boiling point liquid evaporative foaming method presses the low-boiling liquid into the polymer, and then heats the polymer. When the polymer softens and the liquid reaches the boiling point, the vapor pressure generated by the liquid gasification makes it Foaming polymer into a foam. 4 chemical foaming agent foaming method With the aid of foaming agent under the action of heat decomposition of the gas, so that the volume of polymer expansion, the formation of foam plastics. 5 raw chemical reaction foaming This method is to use Can foam Feedstock components, each reaction emit carbon dioxide or nitrogen and the like swell the polymer foam to a foam.
(3) Manufacturing method of foam sandwich structure Foam plastic sandwich structure manufacturing method includes: prefabricated bonding method, in-situ casting molding method and continuous mechanical molding method. 1Prefabricated bonding method to manufacture skin and foam core material separately. And then they are bonded into a whole. The advantage of prefabricated molding method is that it can apply a variety of foam plastics, the process is simple, does not require complex mechanical equipment, etc. The disadvantage is that the production efficiency is low, and the quality is not easy to guarantee. 2 The whole casting method is prefabricated The shell with good sandwich structure, then the mixed foam slurry is poured into the shell, through foaming and curing treatment, so that the bubble fills the cavity, and bonded to the shell into a whole structure. 3 continuous molding method applies to Production of foam sandwich panels.
Third, the molding process
Molding process is the oldest and infinitely dynamic molding method in composite material production. It is a method of adding a certain amount of premix or prepreg into a metal mold, heating, pressurizing and solidifying.
The main advantages of the molding process:
1 high production efficiency, easy to achieve professional and automated production; 2 product size, high precision, good repeatability; 3 smooth surface, no need for secondary modification; 4 can form a complex structure of a product; 5 because of mass production, the price is relatively low.
The inadequacies of the press molding are the complex manufacturing of the mold, the large investment, and the limitation of the press machine, which are most suitable for the mass production of small and medium-sized composite products. With the metal processing technology, the level of press manufacturing and the performance of the synthetic resin technology continue Improvements and developments have resulted in ever-increasing press tonnage and countertop dimensions. The molding temperature and pressure of the molding materials have also been relatively reduced. This has led to the progressive development of size of molded products, and it has been able to produce large-scale automotive parts, bathtubs and integral toilet assemblies. Wait.
Molding process can be divided into the following types according to the state of reinforcing material and mold material: 1 The fiber molding method is to put the pre-mixed or pre-impregnated fibrous molding material into the metal mold at a certain temperature and pressure. The method of forming a composite material product. The method is simple and easy to use, and has a wide range of uses. According to the specific operation, there are premix molding and prepreg molding. 2 The fiberglass cloth will be impregnated with resin glue. The scraps of cloth or other fabrics such as linen, organic fiber cloth, asbestos cloth or cotton cloth are cut into pieces and then heated and pressed in a metal mold to form a composite product. 3 The fabric molding method will be pre-woven into the desired shape. The two-dimensional or three-dimensional fabrics are impregnated with the resin glue and then put into a metal mold to form a composite product by heating and pressurizing. The four-layer molding and pressing method cuts the glass fiber cloth or other fabric preimpregnated with the resin glue into a desired one. Shape, and then in the metal mold by heating or pressure molding composite products. 5 winding molding method of pre-impregnated with resin glue continuous fiber or cloth (band), through a dedicated winding machine to provide a certain Tension and temperature, wrapped around the mandrel, and then placed in a mold for heating and pressing to form a composite product. 6 Pellets (SMC) Molding Method SMC Sheets are cut to size according to product size, shape, thickness, etc. , Then the multi-layer sheet is laminated into a metal mold in the heat and pressure molding products. 7 preform molding method First, the short-cutting fiber products to be similar to the shape and size of the preform, put it into the metal mold In the mold, the prepared adhesive (resin mixture) is then injected into the mold and molded at a certain temperature and pressure.
There are many varieties of molding materials, which can be prepreg materials, premix materials, or blanks. Currently, the types of molding materials used are: prepreg, fiber premix, BMC, DMC, HMC, SMC, XMC, TMC and ZMC and other varieties.
1, raw materials
(1) Molded materials used for molded articles of synthetic resin composites Synthetic resins are required to have: 1 pair of reinforcing materials having good wetting properties so as to form a good bond at the interface between the synthetic resin and the reinforcing material; 2 having proper viscosity and good The fluidity, under the pressing condition, can evenly fill the entire mold cavity together with the reinforcing material; 3 has an appropriate curing speed under the pressing condition, and does not produce any by-product or less by-product during the curing process, and the volume shrinkage is small; 4 Can meet the specific performance requirements of molded products. According to the above material requirements, commonly used synthetic resins are: unsaturated polyester resin, epoxy resin, phenolic resin, vinyl resin, furan resin, silicone resin, polybutadiene resin , Allyl esters, melamine resins, polyimide resins, etc. In order to achieve specific performance specifications of molded products, the corresponding auxiliary materials, fillers and pigments should be selected after selecting the resin varieties and grades.
(2) Reinforcing materials The commonly used reinforcing materials in molding materials include glass fiber cutting wire, roving, roving, continuous glass fiber, glass fiber, glass fiber, etc. Textile (cloth) and asbestos paper and high silica fiber, carbon fiber, organic fiber (such as aramid fiber, nylon fiber, etc.) and natural fiber (such as linen, cotton cloth, scouring cloth, not cooking cloth, etc.) and other varieties. Sometimes two or more fiber blends are used as reinforcing materials.
(3) Auxiliary materials generally include curing agents (initiators), accelerators, thinners, surface treatment agents, low-shrinkage additives, mold release agents, colorants (pigments), and fillers.
2, the preparation of molding materials
Taking glass fiber (or glass cloth) impregnated resin molding material as an example, its production process can be divided into pre-mixing method and pre-immersion method.
(1) Premixed glass fibers are first cut into chopped fibers of 30 to 50 mm, and then kneaded in a kneader with a resin glue to fully infiltrate the glass fibers, and then dried (dry) until appropriate. Viscosity can be. It is characterized by loose and non-directional fibers, large production volume, the molding material produced by this method has a larger specific volume and better fluidity, but the fiber strength loss during the preparation process is large.
(2) Prepreg method The fiber prepreg method consists of dipping, drying, and shortening the entire bundle of continuous glass fibers (or fabrics). It is characterized by a bundle of fibers, which is relatively compact, and during the preparation of the molding material. The loss of fiber strength is small, but the fluidity of the molding material and the compatibility between the material bundles are slightly inferior.
SMC, BMC, HMC, XMC, TMC and ZMC Production Technology
Sheet molding compound (SMC) is a type of sheet molding material impregnated with resin paste or chopped fiber mat, covered with polyethylene film on both sides. It belongs to the range of pre-impregnated felts. One of the most widely used molding materials.
SMC is an unsaturated polyester resin, thickener, initiator, cross-linking agent, low-shrinkage additive, filler, internal mold release agent and colorant, etc. Both sides are coated with polyethylene or polypropylene film to form a sheet of molding material. SMC as a rapidly developing new molding material, has many characteristics: 1 good reproducibility, not affected by the operator and the external conditions; 2 Convenient operation and processing; 3 Clean operating environment, hygiene, improved working conditions; 4 Good flowability, can be shaped shaped products; 5 Molding process is not required for temperature and pressure, variable range, can greatly reduce the cost of equipment and molds 6Fiber length 40~50mm, good quality uniformity, suitable for pressing large thin-walled products with little change in cross-section; 7 high smoothness of finished products, low surface shrinkage additives, better surface quality; 8 high production efficiency; The molding cycle is short, it is easy to realize fully automatic mechanized operation, and the production cost is relatively low.
SMC, as a new type of material, has developed a series of new varieties based on specific uses and requirements, such as BMC, TMC, HNC, XMC, etc. 1 Bulk Molding Compound (BMC) The composition is very similar to that of SMC. , It is an improved premixed agglomerate moulding material, which can be used for moulding and extrusion molding. The difference between the two is only in the material form and production process. The BMC has a lower fiber content and a shorter fiber length, about 6~ 18mm, the filler material is large, so the strength of BMC products is lower than that of SMC products. BMC is more suitable for compressing small products, while SMC is suitable for large-scale thin-wall products. 2 Thick Molding Compound (TMC) Its composition and production are similar to those of SMC, and its thickness is up to 50mm. Due to the large thickness of TMC, glass fibers can be randomly distributed to improve the resin's wettability to glass fibers. In addition, the material can also be injection molded and transferred. 3 High-strength molding materials (Hight Molding Compound, HMC) and high-strength sheet molding compound XMC are mainly used for manufacturing automotive parts. HMC has no or little filler, chopped glass fiber, fiber content is about 65%, glass fiber orientation distribution, with Excellent fluidity and molding surface, its product strength is about 3 times that of SMC products. XMC oriented continuous fiber, fiber content of 70% to 80%, without filler. 4ZMC ZMC is a molding technology, The three letters of ZMC have no practical meaning, but instead contain three meanings: moulding plastic, injection moulding machine and mould. ZMC products not only maintain a high strength index, but also have excellent appearance and high production efficiency. The advantages of SMC and BMC have achieved rapid development.
1, SMC raw materials
SMC's raw materials consist of synthetic resins, reinforcing materials and auxiliary materials.
(1) Synthetic resins Synthetic resins are unsaturated polyester resins. Different unsaturated resins have a direct effect on the thickening effect, process properties, product properties, shrinkage, and surface state of the resin paste. SMC to unsaturated polyester The resin has the following requirements: 1 Low viscosity, good infiltration of glass fiber; 2 With thickener sufficient reactivity to meet thickening requirements; 3 Fast curing, Short production cycle, high efficiency; 4 Cured material has enough heat State strength, easy to heat release of the product; 5 cured material has sufficient toughness, the product does not crack when some deformation occurs; 6 lower shrinkage.
(2) Reinforcing material The reinforcing material is a chopped glass fiber roving or strand. In the unsaturated polyester resin molding compound, the reinforcing material for SMC is currently only a chopped glass fiber mat, and the reinforcing material used for the premix There are more chopped glass fibers, asbestos fibers, hemp, and various other organic fibers. In SMC, the glass fiber content can be adjusted between 5% and 50%.
(3) Auxiliary materials Auxiliary materials include curing agents (initiators), surface treatment agents, thickeners, low-shrinkage additives, mold release agents, colorants, fillers and cross-linking agents.
2, SMC preparation process
The process flow produced by SMC mainly includes the following steps: resin paste preparation, pasting operation, fiber cutting settlement and impregnation, and resin thickening. The process flow chart is as follows:
(1) Preparation of resin paste and paste-on operation There are two methods for preparation of resin paste--batch method and continuous method. The batch method is as follows: 1Pour the unsaturated polyester resin and styrene into the compounding kettle and mix well. 2 The initiator is poured into the mixing kettle and mixed with the resin and styrene; 3 The thickening agent and mold release agent are added under stirring; 4 The filler and low shrinkage additive are added under low speed stirring; 5 is listed in the formula Before the components are dispersed, the stirring is stopped, and the mixture is left standing. The continuous method is to divide the resin paste in the SMC formulation into two parts, ie, a thickener, a release agent, a part of the filler and styrene as a part, and the remaining components are The other part is separately measured, and after mixing, it is fed into the corresponding storage container set on the SMC unit. When required, it is measured by the pipeline metering pump and entered into the static mixer. After mixing, it is transferred to the upper paste area of the SMC unit. Recoated on polyethylene film.
(2) Impregnation and compaction The lower load-bearing film of the coated resin paste enters the chopped glass fiber settling chamber under the traction of the unit, and the cut chopped glass fiber is uniformly deposited on the resin paste to reach the required settlement amount. With the transmission device leaving the settling chamber and superimposed with the upper load-bearing film coated with the resin paste, and then into a matrix of a series of misaligned arrays, under the action of the tension and the roller, carrying the film to the resin paste The chopped glass fibers are tightly pressed together. After repeated iterations, the chopped glass fibers are impregnated with resin and the air bubbles therein are driven off to form a dense and uniform continuous SMC sheet.
Product pressing process
The basic flow of composite product pressing process is shown in the figure:
Composite molding materials according to the length of the molding cycle, generally divided into rapid molding process and slow-speed molding process. Rapid molding process for suppressing small thin-wall composite products, slow-speed molding process is suitable for the suppression of large-scale thick-walled composite Material products.
Fourth, laminating and roll forming process
1, Laminate molding process
Laminate molding is to cut pre-impregnated tapes according to the shape and size of the products, stack them, and place them between two polished metal molds to heat and pressurize the production process of the composites. It is the development of the composite material molding process. An earlier and more mature molding method. The process is mainly used to produce electrical insulation boards and printed circuit boards. Nowadays, printed circuit boards have been widely used in all types of radios, televisions, telephones and mobile phones, computers. Products, all kinds of control circuits and other products that require planar integrated circuits.
The laminating process is mainly used to produce various specifications of composite materials. It has the characteristics of mechanization, high degree of automation, and stable product quality. However, it has a one-time investment, is suitable for mass production, and can only produce plates, and the specifications are subject to equipment. limits.
The lamination process generally includes: prepreg preparation, tape cutting, hot pressing, cooling, demoulding, processing, post-processing, etc., as shown in the figure:
2, roll forming process
Roll forming machine is a kind of composite material forming method using prepreg tape on the coiling machine. The principle is to use the hot roller on the coiling machine to soften the tape to melt the resin on the tape. Under the action of tension, during the operation of the roller, the adhesive tape is continuously rolled onto the core pipe by the friction between the roller and the mandrel until the required thickness, and then the roller is cooled and cooled to form and removed from the pipe rolling machine. , Into the curing oven curing. After the pipe is cured, remove the mandrel, that is to get the composite roll tube.
Roll forming can be divided into two methods: manual cloth method and continuous mechanical method. The basic process is: First, clean the rollers, then heat the roller to the set temperature, adjust the tension of the tape. With the pressure roller applied without pressure, wrap the leader cloth around the die head coated with release agent by about 1 turn, then lower the press roller and attach the leader cloth to the heat roller. On the plastic brace, the cover is attached to the heating part of the leader cloth and overlaps with the leader cloth. The length of the leader cloth is about 800-1200mm, depending on the diameter of the tube, the length of the overlap between the leader cloth and the tape, generally For 150~250mm. When making thick-walled pipes, after the normal operation of the rolling system, the rotation speed of the mandrel is appropriately accelerated. When the thickness is close to the designed wall thickness, the rotation speed is further reduced. When the design thickness is reached, the adhesive tape is cut off. Then, while keeping the pressure of the pressure roller, continue to rotate the mandrel for one or two turns. Finally, lift the pressure roller and measure the outer diameter of the pipe blank. After passing the inspection, remove the roller from the coiling machine and send it to the curing oven for solidification.
3, prepreg tape preparation process
Prepreg is a semi-finished product for the production of composite laminates, coils and tape-wound articles.
(1) The main raw materials required for the production of raw material prepreg tapes are reinforcing materials (such as glass cloth, asbestos cloth, synthetic fiber cloth, glass fiber mat, asbestos mat, carbon fiber, aramid fiber, asbestos paper, cowhide, etc.) and synthetic resins. (such as phenolic resin, amino resin, epoxy resin, unsaturated polyester resin, silicone resin, etc.).
(2) Preparation process of prepreg tape The prepreg tape is prepared by using heat-treated or chemically-treated glass cloth impregnated with a resin glue solution through a dipping tank and controlling the resin content of the tape through a squeegee device and a traction device. At a temperature, after a certain period of time, the resin is turned from A to B to obtain the desired prepreg. Usually this process is called glass dipping. The process is shown in the figure below:
Fifth, winding forming process
Winding molding process is the continuous fiber (or tape, pre-impregnated) impregnated with resin glue is wound on the mandrel according to a certain law, and then cured, demolded to obtain products. According to the physical properties of the resin matrix when the fiber is wound and formed Different chemical states, divided into dry winding, wet winding and semi-dry winding three.
(1) Dry-wound dry winding is the use of pre-impregnated pre-impregnated yarn or tape, which is heated and softened on a winding machine to a viscous flow state and then wound onto a mandrel. As the pre-impregnated yarn (or tape) is specialized Production, can strictly control the resin content (accurate to 2% or less) and the quality of pre-impregnated yarn. Therefore, dry winding can accurately control the quality of the product. The biggest feature of the dry winding process is high production efficiency, winding speed up to 100 ~ 200m/min, winding machine cleaning, good work and sanitary conditions, high product quality. The disadvantage is expensive winding equipment, need to increase prepreg yarn manufacturing equipment, so the investment is large. In addition, the interlaminar shear strength of dry wound products is low. .
(2) Wet-wound wet-winding is the process of tensioning the fiber bundle (yarn-type belt) after being dipped into the core die. The advantages of wet-winding are as follows: 1 The cost is 40% lower than that of dry-winding; 2 The product has good airtightness because the winding tension makes the excess resin glue squeeze out the air bubbles and fill up the gaps; 3 The fiber alignment is good; 4 The resin glue on the fiber during the wet winding can reduce the fiber abrasion. ;5High production efficiency (up to 200m/min). The disadvantages of wet winding are: 1 The resin is wasted, the operating environment is poor; 2 the amount of glue and the quality of the finished product are not easy to control; 3 The types of resins available for wet wrapping are less.
(3) Semi-dry winding Semi-dry winding is after the fiber is dipped into the core, and a set of drying equipment is added to remove the solvent from the dipped yarn. Compared with the dry method, it saves the pre Dip process and equipment; compared with the wet method, can reduce the content of air bubbles in the product.
Of the three winding methods, wet winding applications are the most common; dry winding is only used in high-performance, high-precision cutting-edge technical fields.
Advantages of Filament Winding Molding1 The winding law can be designed according to the stress conditions of the product, so as to give full play to the strength of the fiber; 2 The specific strength is higher: Generally speaking, the fiber winding pressure vessel is compared with a steel container of the same volume and pressure. , The weight can be reduced by 40~60%; 3 High reliability: The filament winding products can be easily mechanized and automated. After the process conditions are determined, the quality of the wrapped product is stable and accurate; 4 The production efficiency is high: Mechanized or automated production is required. With a small number of workers, the winding speed is fast (240m/min), so the labor productivity is high; 5 the cost is low: On the same product, several materials (including resin, fiber and inner lining) can be reasonably selected and recombined to achieve The best technical and economic effect.
Disadvantages of Winding Molding 1 The adaptability of the winding molding is small, and it is not possible to wrap the product in any structural form, especially the concave product on the surface, since the fiber cannot be tightly adhered to the surface of the mandrel when wound; the winding machine is needed for winding; Molds, curing ovens, demoulding machines, and skilled workers require high investment and high technical requirements. Therefore, only high-volume production can reduce the cost, and can obtain more technical and economic benefits.
1, raw materials
The winding raw materials are mainly fiber reinforced materials, resins and fillers.
(1) Reinforcing materials Reinforcing materials for winding molding are mainly various kinds of fiber yarns: eg alkali-free glass fiber yarns, alkali alkali glass fiber yarns, carbon fiber yarns, high-strength glass fiber yarns, aramid fiber yarns and surface felts, etc.
(2) Resin Matrix Resin matrix refers to a glue system composed of a resin and a curing agent. The heat resistance, chemical resistance and natural aging resistance of the wound products mainly depend on the properties of the resin. At the same time, the processability and mechanical properties are also very high. Large influence. Winding molding commonly used resin is mainly unsaturated polyester resin, and sometimes epoxy resin and bismaleimide resin, etc. For general civilian products such as pipes, cans, etc., the use of unsaturated polyester resin. Elastomer can be used for winding products with high compressive strength and interlaminar shear strength for mechanical properties. Aerospace products use bismaleimide resin with high fracture toughness and good moisture resistance.
(3) There are many types of fillers, which can improve some of the functions of the resin matrix, such as improving wear resistance, increasing flame retardancy and reducing the shrinkage rate, etc. Hollow glass beads can be added to the glue to increase the rigidity of the product. , Reduce the density and reduce the cost. When producing large-diameter buried pipelines, often add 30% quartz sand, in order to improve the product's rigidity and reduce costs. In order to improve the bonding strength between the filler and the resin, the filler should ensure clean and Surface active treatment.
2, mandrel
The inner mold of the molded hollow product is called the core mold. Under normal circumstances, after the winding product is cured, the core mold is removed from the product.
The basic requirements of the mandrel design are to have sufficient strength and rigidity to withstand various loads applied to the mandrel during the forming process of the product, such as self-weight, product weight, winding tension, curing stress, and cutting force during secondary machining. (2) can meet product shape and dimensional accuracy requirements, such as shape size, concentricity, ellipticity, taper (stripping), surface finish and flatness, etc.; 3 ensure that the product can be smoothly removed from the product after curing; Simple, cheap, easy to draw.
Mandrel material winding mandrel mold material is divided into two categories: molten, soluble materials and assembled materials. Melt, soluble materials refer to paraffin, water-soluble polyvinyl alcohol sand, low melting point metal, etc., these materials can be made hollow by casting method or Solid mandrel, After the product is wound, the hot water or high pressure steam is blown through the opening to dissolve it, melt it, flow out of the product, and the solution flows out. After cooling, it is repeatedly used. The assembled core material is commonly used in aluminum, Steel, sandwich structure, wood and gypsum, etc. There are also lining materials. The inner lining material is an integral part of the product and is not removed from the product after curing. The function of the lining material is mainly antisepsis and sealing. Of course, it can also play a role. Mandrel role, belonging to this type of material are rubber, plastic, stainless steel and aluminum alloy.
3, winding machine
Winding machine is the main equipment to realize the winding forming process. The requirements for the winding machine are as follows: 1 It can realize the winding law and accurate arrangement of the product design; 2 The operation is simple; 3 The production efficiency is high; 4 The equipment cost is low.
The winding machine is mainly composed of a mandrel drive and a wire-winding drive. In order to eliminate the loosening of the fiber during the reversal movement of the wire-winding nozzle, the tension is kept stable and the yarn arrangement in the head or conical winding product is precise, achieving small winding Angle (0°~15°) winding, in the winding machine is designed with vertical spindle direction of the cross-feed (throw) mechanism. In order to prevent reverse rotation of the yarn reel yarn twist, arm is equipped with Turning the mouth of the mouth turned the agency.
In the 1960s, China successfully developed a chain winding machine. In the 1970s, it introduced the German WE-250 CNC winding machine. After the improvement, it achieved domestic production. After the 1980s, China introduced more than 40 types of various types of winding machines. After improvement, it was designed and manufactured by itself. Successful microcomputer controlled winding machine and entered the international market.
Mechanical winding machine type
(1) The wrap around plane type wrapper is characterized in that the arm (with spinning nozzle) is made to rotate uniformly around the core mold, the core mold is uniformly and slowly rotated around its own axis, and the arm is rotated (that is, around the wire nozzle) every rotation. In one week, the mandrel rotates through a small angle. This small angle corresponds to the width of a piece of yarn wound on the wrapper, ensuring that the piece of yarn covers the surface of the container one on top of the mandrel. When the mandrel rotates rapidly, the wrapper mouth is vertical The direction of the ground is slowly moving up and down. At this time, the hoop winding can be achieved. The advantage of using this winding machine is that the core mold is evenly distributed, the mechanism runs smoothly, and the cables are evenly distributed. It is suitable for dry winding small and medium-sized cylindrical containers. .
(2) Tumble-wrapping machine The winding mandrel of this winding machine is supported by two shakes. When winding, the mandrel's own axis rotates. The two arms rotate synchronously to make the mandrel roll one week. The rotation of the mandrel is an angle suitable for the width of the yarn. The fiber yarn is supplied by a fixed arm to achieve planar winding, and the circumferential winding is achieved by an additional device. Since the rollover mechanism should not be too large, such a wrapping machine is only applicable to small products and is not widely used.
(3) Horizontal winding machine This type of winding machine is driven by the chain to move the carriage (winding nozzle) to make a reciprocating movement, and there is a momentary stop at the end of the head. The core mold rotates at constant speed around its own axis. Adjusting the speed between the two can be realized. Plane winding, hoop winding and spiral winding, this winding machine is simple in construction, widely used, suitable for winding elongated tubes and containers.
(4) Track-type winding machine Track-type winding machine is divided into two types: discrete and horizontal. The yarn group, rubber groove and wire winding nozzle are all mounted on the car. When the car moves along the circular track around the mandrel for one week, the mandrel rotates by itself. The width of a piece of yarn, the angle between the axis of the mandrel and the horizontal plane is the plane winding angle α. Thus forming a plane winding type, the speed of the mandrel and the car can be adjusted to realize the hoop winding and spiral winding. The orbital winding machine is suitable for producing large-scale products. .
(5) The planetary winding core axis and the horizontal plane are slanted into angle α (namely, winding angle). When the winding is formed, the core mold is used for both rotation and revolution, and the wire winding nozzle is fixed. The rotation speed and revolution speed of the core mold can be adjusted. Plane winding, hoop winding and spiral winding. The core mold revolution is the main movement, rotation to feed movement. This winding machine is suitable for the production of small products.
(6) Spherical winding machine The ball winding machine has 4 movement axes. The spinning nozzle of the ball winding machine rotates. The rotation of the mandrel and the deflection of the mandrel are basically the same as those of the swing arm type winding machine. The fourth axis motion is used. The yarn winding stepping realizes winding of the yarn, reduces the accumulation of fibers outside the pole hole, and improves the uniformity of the thickness of the container arm. The rotation of the mandrel and the spinning nozzle make the fiber cover the surface of the ball. The movement of the mandrel axis can be changed by winding the pole. Hole size and adjust the winding angle to meet the product requirements.
(7) Cable-type vertical loop-winding machine Longitudinal-loop cable-winding machine is suitable for the production of non-headed cylindrical containers and various pipes. The rotating ring equipped with longitudinal yarn groups rotates synchronously with the mandrel and can move along the core. The mold axially reciprocates and completes the longitudinal yarn laying. The circular yarn is mounted on the trolleys on both sides of the swivel. When the core mold rotates, the trolley reciprocates along the axial direction of the core mold, completing the looped yarn winding. In this case, the number of longitudinal loop yarns can be arbitrarily adjusted.
(8) The new winding machine The new winding machine is different from the current winding machine in that it relies on the rotation of the die and can also reciprocate along the length of the pipe to complete the winding process. The advantages of this new type of winding machine are: Fixing around the silk nozzle, it is very convenient for workers to deal with broken ends, hair filaments and tubes; multi-feed yarns can realize large-capacity filament winding, high winding speed, uniform yarn distribution, and it is beneficial to increase product weight and output.
Six, continuous molding process
The continuous molding process of composite products refers to the process of dipping, forming, curing, demoulding, cutting, etc., from the input of raw materials, until the final process of obtaining the finished products is carried out continuously.
According to the different products produced, the continuous molding process is divided into continuous pultrusion process, continuous winding process and continuous board manufacturing process three.
The continuous winding molding process is mainly used for producing glass tubes and can bodies with different diameters. The characteristics of continuous winding machines are: high production efficiency, stable product quality, low labor intensity, saving raw materials, and reducing the number of mandrels, but this process technology High in content, large investment in equipment, difficulty in reducing the diameter. Another process is the combination of plastic pipe extrusion technology and filament winding technology. The plastic lined with glass steel pipe, extruded plastic pipe at the same time play the core mold and anticorrosion lining Two functions.
The pultrusion process is mainly used for the production of various FRP profiles, such as fiberglass rods, I-shaped, angled, grooved, square, fasting and profiled sections, etc. The largest pultrusion machine currently available can produce cross-sections 800mm×800mm fast-acting FRP profiles. New pultrusion molding technologies are emerging, such as RIM pultrusion machines, bending profile extrusion processes, etc.
The continuous board making process mainly uses glass fiber felt and cloth as reinforcing material to continuously produce various specifications of flat plates, corrugated plates and sandwich structure boards.
The common features of the continuous molding process are: 1 The production process fully realizes the mechanical avatar automation, and the production efficiency is high; 2 The production process is uninterrupted, and the product length is not limited; 3 The product does not require post-processing, and there are fewer scraps in the production process, saving raw materials and energy; 4 The product quality is stable, the repeatability is good, the finished product rate is high; 5 the operation is convenient, the manpower is saved, the working condition is good; 6 the cost is low.
Pultrusion process
The pultrusion process is the continuous glass fiber bundles, belts or cloths impregnated with the resin glue, which are formed by extrusion molding under the action of the traction force, and are cured to continuously produce FRP profiles of unlimited length. Suitable for the production of various sections of glass fiber reinforced plastic profiles, such as rods, tubes, solid profiles (I-shaped, trough, square profiles) and open-web profiles (window profiles, blades, etc.).
Pultrusion is a special process in the composite material forming process. Its advantages are: 1 The production process is fully automated and the production efficiency is high; 2 The fiber content in the pultrusion products can be as high as 80%. The dipping is performed under tension. , Can give full play to the role of reinforcing materials, high product strength; 3 Product vertical and horizontal strength can be arbitrarily adjusted to meet the requirements of different mechanical properties of the product; 4 no waste in the production process, the product does not require post-processing, so it is more than other Process labor, provincial raw materials, energy consumption; 5 product quality is stable, good repeatability, length can be cut off.
The disadvantage of the pultrusion process is that the product has a monotonous shape and can only produce linear profiles, and the transverse strength is not high.
(1) Raw materials for pultrusion process
1 resin matrix In the pultrusion process, the most commonly used is the unsaturated polyester resin, accounting for about 90 or more of the amount of the process resin, and also epoxy resin, vinyl resin, thermosetting methacrylic resin, modified phenolic resin , Flame retardant resins, etc.
2 Reinforcing materials for the pultruded process of reinforcing materials are mainly glass fiber and its products, such as rovings, continuous fiber mats, etc. In order to meet the special performance requirements of products, aramid fiber, carbon fiber and metal fiber can be selected. What kind of fiber is used in the pultrusion process, the surface must be processed so that it can be well bonded to the resin matrix.
3. Auxiliary materials The auxiliary materials for the pultrusion process include release agents and fillers.
(2) Pultrusion Mould
The mold is an important tool for pultrusion molding technology. It is generally composed of two parts: the preform mold and the mold. 1 During the pultrusion process of the preform mold, the reinforcement material is impregnated with the resin (or it is impregnated) and enters the mold Before, it must go through a preforming mold composed of a group of yarn guide elements. The function of the preform molding mold is to gradually form the pre-formed body of the reinforcing material after dipping, in accordance with the section profile configuration of the profile, to form the approximate shape and size of the molding model. Then enter the forming mold, which can ensure uniform yarn content in the section of the product. 2 The cross-sectional area of the forming mold and the cross-sectional area of the product should generally be greater than or equal to 10, in order to ensure that the mold has sufficient strength and rigidity, and the heat after heating The distribution is uniform and stable. The length of the pultrusion die is determined according to the pulling speed in the forming process and the curing speed of the resin gel, so as to ensure the degree of release and curing when the product is pulled out. Generally, the steel is chrome plated, and the cavity surface is required to be smooth and wear-resistant. In order to reduce the pultrusion is the frictional resistance and improve the life of the mold.
(3) Pultrusion process
The pultrusion process consists of yarn feeding, dipping, preforming, curing, traction, cutting and other processes. After the roving has been taken out of the creel, it passes through the yarn feeder into the dipping tank to penetrate the resin glue solution, and then enters. Preform mold, excess resin and air bubbles are discharged, and then enter the molding mold gel to solidify. The cured product is continuously pulled out from the mold by the tractor, and finally cut by the cutting machine fixed length. In the molding process, each There may be different methods for the processes: For the yarn feeding process, continuous fiber mats, hoop winding yarns or three-direction fabrics may be used to increase the transverse strength of the products; the traction process may be a track-type tractor or a robot; the curing method may be In-mold curing, it can also be heated in a heating furnace; heating method can be high-frequency electric heating, but also can use molten metal (low melting point metal).
(4) Other pultrusion processes
In addition to vertical and horizontal units, the pultrusion process includes pultrusion process of bending products, reaction injection pultrusion process and pultruded process with fillers.
Continuous winding process
Compared with fixed-length glass-fiber reinforced plastic pipe, continuous winding pipe has the following characteristics: 1 Continuous production, easy to achieve automated management and rapid solidification, high production efficiency; 2 less auxiliary equipment required, especially the mold needs less, product replacement investment less ;3The length of the product can be cut off arbitrarily. Using this long (12m or 15m) can reduce the number of pipe joints and reduce the project cost; 4The production process is automated, the process parameters are controlled centrally, and the product quality is easy to guarantee.
Another continuous pipe-making process uses plastic pipe and FRP composite technology, namely EPF method. The composite pipe produced by this method is better than ordinary glass pipe and has good impermeability.
(1) Continuously wrapped raw materials
The raw materials used for continuous winding must meet the requirements for the use of the product and the process requirements.
1 Reinforced materials According to the requirements of the production of glass-fiber reinforced plastic pipes and PVC/glass reinforced plastic composite pipes, the reinforcing materials include surface felts, chopped glass fiber felts or needled composite felts and surface felts, and non-woven rovings.
2 The resins used for continuous winding of the resin matrix are mainly unsaturated polyester resins. The requirements for resin in the continuous winding process are: suitable viscosity, easy impregnation of fibers, long gelation time, short curing time, low heat of curing, low curing shrinkage .
(3) Auxiliary materials In order to improve the rigidity of the pipe, quartz sand is often added, and its amount can be up to 30% (highest). Polyester film for release agent, film cut into tape, width is twice as wide as steel band, winding overlap 1 /2.
(2) Continuous winding process
Continuously wrapped tubes are wrapped with pre-impregnated glass fiber yarn or tape (or impregnated), wrapped in a mandrel according to the design's winding rules, heated and cured by internal heating, and driven continuously by the steel strip on the mandrel. Before proceeding, demoulding, and then fixed after the second curing cut. Change the pipe diameter, only need to replace the mandrel of the pipe machine can be, the process flow is as follows:
Continuous board manufacturing process
The continuous board making process began in the post-World War II FRP industry from the military to the civilian era. China began its research in early 1965. The first successful research was the wire mesh reinforced polychloroethylene corrugated board producing red. The product was a horizontal wave tile developed in Shanghai in the 1970s. Into the longitudinal wave polyester fiberglass production line, in the 80's has introduced three continuous production lines, its production technology reached the international advanced level.
FRP corrugated board is one of the most used products in the construction industry. It is mainly used in temporary construction projects, roof lighting in industrial buildings and agricultural greenhouses. Compared with traditional asbestos, it has light weight, high strength, impact resistance and permeability. Light and beautiful durable features.
Fiberglass corrugated plate is divided into longitudinal wave plate and transverse wave plate. The wave direction of longitudinal wave plate is parallel to the long side of plate. The corrugation direction of transverse wave plate is perpendicular to the long side of the plate. As for the corrugated shape, there are standard continuous arc waves. , continuous profiled ripples and discontinuous shaped ripples.
The continuous board making process is roughly the same at home and abroad. It is only slightly different in terms of the local construction of the equipment and the technological measures.
Seventh, thermoplastic composite molding process
Thermoplastic composite materials are glass fiber, carbon fiber, aramid fiber, etc. It is a generic name for reinforcing various thermoplastic resins. It is called FRTP (Fiber Rinforced Thermo Plastics) abroad. Due to different kinds of thermoplastic resins and reinforcing materials, its production process and composites The performance varies greatly.
From the point of view of production process, plastic composite materials are divided into short fiber reinforced composite materials and continuous fiber reinforced composite materials: (1) Injection molding process of short fiber reinforced composite materials; 2 Extrusion molding process; 3 Centrifugal molding process. (2) Continuous fiber-reinforced and long-fibre-reinforced composites 1 Prepreg molding; 2 sheet-shaped molding plastics stamping; 3 sheet molding vacuum forming; 4 prepreg winding forming; 5 pultrusion molding.
The special properties of thermoplastic composites are as follows:
(1) Low density, high strength thermoplastic composites have a density of 1.1 to 1.6 g/cm3, which is only 1/5 to 1/7 of steel, and 1/3 to 1/4 lighter than thermoset glass. It can be smaller The unit's mass gains higher mechanical strength. Generally speaking, whether it is general plastics or engineering plastics, with glass fiber reinforced, it will get higher enhancement effect and improve the strength of the application.
(2) Freedom of performance designability The physical properties, chemical properties, and mechanical properties of large thermoplastic composites are designed by rational selection of raw material types, proportions, processing methods, fiber content, and layup methods. The material of the matrix material is much more than the thermoset composite material, so the degree of freedom in designing the material is much greater.
(3) Thermal properties The general plastics use temperature is 50~100°C. After being reinforced with glass fiber, it can be increased to above 100°C. The heat distortion temperature of nylon 6 is 65°C. After being reinforced with 30% glass fiber, the heat temperature is It can be increased to 190°C. The polyetheretherketone resin has a heat resistance up to 220°C. After being reinforced with 30% glass fiber, the use temperature can be increased to 310°C. This high heat resistance, thermoset composite material can not be achieved. The linear expansion coefficient of thermoplastic composites is 1/4 to 1/2 lower than that of non-reinforced plastics, which can reduce the shrinkage during the molding process of the products and improve the dimensional accuracy of the products. Its thermal conductivity is 0.3~0.36W(m2·K). , Similar to thermoset composites.
(4) Chemical resistance of chemically resistant composite materials is mainly determined by the properties of the base material. There are many types of thermoplastic resins. Each type of resin has its own anti-corrosion characteristics. Therefore, it can be used according to the environment and media of the composite materials. Conditions, the preferred base resin, can generally meet the requirements of use. Thermoplastic composites are superior to thermoset composites in water resistance.
(5) Electrical properties General thermoplastic composites have good dielectric properties, do not reflect radio waves, and have good microwave performance. Because the thermoplastic composite has a lower water absorption rate than thermoset glass, its electrical properties are superior to the latter. The addition of conductive materials in thermoplastic composites improves their electrical conductivity and prevents static electricity.
(6) Recycling of waste materials Thermoplastic composite materials can be repetitively processed and molded. Scraps and corners can be reused without causing environmental pollution.
Because thermoplastic composite materials have many special properties superior to thermosetting glass steel, the application fields are very extensive. From the analysis of the application situation abroad, thermoplastic composite materials are mainly used in vehicle manufacturing industry, mechanical and electrical industry, chemical anti-corrosion and construction engineering.
1, injection molding process
Injection molding is the main production method for thermoplastic composites. It has a long history and widest application. Its advantages are: short cycle time, minimal energy consumption, high product accuracy, and the ability to form complex and switchable products at one time. Production of several products, high production efficiency. Disadvantage is not to produce fiber-reinforced composite products and mold quality requirements are higher. According to the current level of technological development, the largest injection molding product is 5kg, the smallest to 1g, this method is mainly used To produce a variety of mechanical parts, building products, appliance housings, electrical materials, vehicle accessories and so on.
2, extrusion molding process
Extrusion molding is one of the widely used processes in the production of thermoplastic composite products. Its main features are continuous production process, high production efficiency, simple equipment, and easy to grasp technology. Extrusion molding process is mainly used to produce tubes and rods. Plates and special-shaped cross-section products, etc. Reinforced plastic tubes and glass fiber reinforced doors and windows profiled cross-section profiles have a large market in China. The extrusion process for composite products is as follows:
3, winding molding process
The principle of winding and molding of thermoplastic composites is similar to that of thermosetting glass. The difference is that the reinforcing material of the thermoplastic composite winding products is not a glass roving, but a prepreg made of a dipping (thermoplastic resin). Therefore, It is necessary to add a prepreg yarn preheating device and a heating and pressure roller on the winding machine. During the winding process, the prepreg is heated to a softening point, then the contact point of the mandrel is heated, and the pressure roller is pressed to weld it. Become a whole.
4, Pultruded thermoplastic composites
The pultrusion process of thermoplastic composites is basically similar to that of thermosetting glass steel. As long as the dipping method before entering the mold is modified, the equipment for producing thermosetting glass steel can be used. There are two types of reinforcing materials for the production of thermoplastic composite pultruded products: One is a pre-impregnated or pre-impregnated tape, the other is an unimpregnated fiber or fiber tape.
5, legal welding layer
This method utilizes the weldability of thermoplastic composite materials to produce composite sheet materials. The method is as follows: First, a layer of prepreg (typically 500mm wide) is placed on the workbench. When the second layer of dipping material is applied, the pressure roller is actuated. The welder allows the prepreg to go under the press roll. The welder heats the upper and lower prepregs at the same time in several seconds. When the machine moves forward, the prepreg pressure on the press roll (0.3MPa) Under the action of bonding into one. So repeated, can produce any thickness of the plate.
6, Thermoplastic Sheet Molding Products Press Forming Process
Thermoplastic sheet molding products are different from the thermosetting SMC press molding in stamping and forming. It requires preheating of the billet first, and then placing a mold for press molding.
7, thermoplastic composite connection technology
There are many methods of joining thermoplastic composites. Here are some examples: 1 Rivets Rivets used for riveting thermoplastic composites are generally made of continuous fiber-reinforced thermoplastics, preferably made from pultruded rods. During construction, rivets are used Heat to a temperature that can be pressurized and plasticized. Rivets and apertures should be able to fit tightly, not large or small. Metal bolts can also be used. The advantages of riveting are good impact resistance, no electrochemical corrosion, and low price. 2 Welding The welding treatment of thermoplastic composite materials is to heat the welding surface of the materials to be welded to a molten state, and then lapped and pressed to make them integrated. The welding principle of composite materials is similar to that of plastic welding, but attention must be paid to the fiber reinforcement of the welding place. Can not be reduced a lot. 3 pipe butt welding thermoplastic composite pipe butt welding method direct butt welding and reinforcement butt welding two. This connection method has the advantage of simple process, can be on-site construction, without the need for mechanical processing of the pipe, High strength of connection, not easy to break. Disadvantages are high cost, strict process requirements, to ensure close fit. 4 Prepreg for winding welding Welding along the weld seam manually or mechanically, with the flame spray gun heating and melting the contact point, making it firmly bonded to the connected parts. When selecting the prepreg tape, pay attention to the direction and content of the fiber. This method is more practical, the material to be joined Can retain better performance, but prone to uneven heating phenomenon. 5 ultrasonic welding of thin plates This method is the use of ultrasonic welding of the joints are heated, generally can obtain higher connection strength.
Eight, other molding processes
Other molding techniques of polymer matrix composites, mainly referred to centrifugal molding process, casting molding process, elastomer storage resin molding process (ERM), enhanced reaction injection molding process (RRIM) and so on.
1, centrifugal molding process
Centrifugal molding process is mainly used to produce pipe (ground pipe) in the production of composite products. It adds resin, glass fiber and filler to the rotating cavity in a certain proportion and method, relying on high-speed rotation to produce centrifugal force. , Make the material compacted and solidified.
Centrifugal FRP pipe is divided into two types: non-pressure pipe of pressure pipe, and its use pressure is 0~18MPa. The pipe diameter of this pipe is generally φ400~φ2500mm, the maximum pipe diameter is up to 5m, and the pipe diameter above φ1200mm is the best economic effect. The length of the centrifuge tube is 2~12m, generally 6m.
Centrifugal FRP pipe has many advantages. Compared with ordinary FRP pipe and concrete pipe, it has high strength, light weight, corrosion resistance, and wear resistance (5 to 10 times that of asbestos cement pipe), energy saving, durability (more than 50 years) and comprehensive The project cost is low, especially for large-diameter pipes, etc. Compared with the sand-encrusted glass pipe, its greatest feature is its high rigidity and low cost. The pipe wall can be designed into a multi-layer structure according to its function. Centrifugal pipe quality is stable and the raw material is depleted. Less, its overall cost is lower than steel pipe. Centrifugal glass steel pipe can be buried 15m deep, with vacuum and external pressure. The disadvantage is that the internal surface is not smooth enough, hydraulic properties are relatively poor.
Centrifugal FRP pipe has a broad application prospect. Its main applications include: water supply and drainage engineering dry pipe, oil field water injection pipe, sewage pipe, chemical anti-corrosion pipe and so on.
(1) Raw materials
The raw materials for the production of centrifuge tube are resin, glass fiber and filler (powder and granular filler).
Resin is the most widely used unsaturated polyester resin, according to the use of conditions and process requirements to choose the resin grade and curing agent.
Reinforcing materials The main workers are glass fibers and their products. Glass fiber products include continuous fiber mats, grid cloths, and unidirectional fabrics. When manufacturing profiled cross-section products, glass fiber can be made into preforms and then put into molds.
Filler Filler is used to increase the product's stiffness, thickness, and reduce costs. The type of filler is selected according to the use requirements, generally quartz sand, quartz powder, diabase powder, etc.
(2) Process flow
Centrifugal pipe manufacturing process is as follows:
The method of feeding the centrifugal pipe is different from the winding forming method. The feeding system is a device for feeding the resin, fiber and filler, and is installed on the reciprocating car.
(3) mold
Centrifugal production of glass steel molds, mainly steel molds, molds divided into two types and assembled: less than φ800mm tube mold, with integral type, greater than φ800mm tube mold, can be assembled.
The mould design must ensure sufficient strength and rigidity to prevent rotation and deformation during vibration. The mould is composed of the body, head, and the support wheel. The body is made of steel plate and the small diameter body can be used for seamless steel pipe. The role of the head is to increase the strength of the end of the die and to prevent the material from flowing out. The role of the carrier is to support the mold, transfer the rotational force, so that the mold rotates at a high speed on the centrifuge, the inner surface of the body of the mold must be smooth and smooth. All must be finished and polished to ensure smooth release.
2, pouring molding process
Casting is mainly used to produce non-fiber reinforced composite products, such as artificial marble, buttons, embedding, plant specimens, handicrafts, anchor fixing agents, decorative panels, etc.
Casting is relatively simple, but to produce quality products, skilled operation techniques are required.
(1) Button Production Process
The buttons cast with polyester resin have the advantages of high hardness, good gloss, wear resistance, heat resistance, dry cleaning resistance, variety of colors, and low price. At present, they have basically replaced organic glass buttons at home and abroad. More than 80% of the market.
The raw materials for the production of buttons are mainly unsaturated polyester resins, curing agents (methyl ethyl ketone peroxide is used as an initiator) and auxiliary materials (including color paste, pearl powder, thixotropic agents, etc.).
Polyester buttons are produced by centrifugal cast bar casting method. Plates or rods are made first, then cut into plates, cut into rods to make buttons, then heat-treated, scraped, scraped, grooved, drilled, polished Processes such as buttons.
(2) Man-made stone production process
Artificial stone is made of unsaturated polyester resin and filler. Due to the different fillers used, artificial stone is made of artificial marble, artificial agate, artificial granite and polyester concrete.
The raw materials for the production of artificial stone are unsaturated polyester resins, fillers and pigments: 1 The resins are used for the production of man-made stone resin and the structural layers. The resin of the surface decoration layer requires low shrinkage, toughness, good hardness, heat resistance, Wear resistance, water resistance, etc., while requiring easy color correction. Xin Xin glycol phthalic resin for artificial stone, octanediol benzene resin for the production of sanitary ware. Curing system, commonly used methyl ethyl ketone peroxide, cobalt naphthalate Solution. 2 Filler There are many kinds of artificial stone fillers. Marble, quartz powder, dolomite powder, and calcium carbonate powder are the fillers used to produce artificial marble. Granules are used to produce artificial granite. Grading is used for different types of granite. Stone with different colors of granules, production of human agate filler to have a certain degree of transparency, the general choice of aluminum hydroxide or aluminum oxide, etc. 3 pigment production artificial stone needs colored pigments, such as artificial marble or artificial agate tub, should Choose a heat-resistant, water-resistant color paste. When making decorative plates and crafts, use pigments that are resistant to light, water, and durability.
For the production of artificial marble, the mold materials used for granite slabs are glass steel, stainless steel, plastics, glass, etc. The template for the production of artificial stone slabs requires a smooth surface, luster, sufficient strength and stiffness, and can withstand thermal stress during the production process. , Handling loads, collisions, etc.
3, elastomer storage resin molding technology
Elastic Reservir Molding (Elmer Reservir Molding, ERM) is a new process that emerged in Europe and America in the 1980s. It uses a flexible material (open-celled polyurethane foam) as a core material and penetrates into the resin paste. The foam is left in the middle of the formed ERM material. The foam reduces the density of the product made of ERM, and improves the impact strength and stiffness. Therefore, it can be referred to as a pressed sandwich structure product.
ERM is the same as SMC, which belongs to the stamped molded sheet molding compound. Because ERM has a structure with a sandwich structure, it has advantages over SMC: (1) Light weight: ERM is made of felt and SMC Lighter than 30%; (2) ERM products have higher specific stiffness than SMC, aluminum and steel products; (3) High impact strength: ERM has higher impact strength than SMC at the same reinforced material content Many; (4) High physical and mechanical properties: ERM products have better physical and mechanical properties than SMC products under the same reinforcing material content; (5) Low investment costs: ERM molding units are simpler than SMC units, and the molding pressure ratio of ERM products is lower than that of SMC products. SMC products are about 10 times lower. Therefore, low tonnage presses and low-strength material molds can be used to produce ERM products, thereby reducing construction investment.
The ERM product production process is divided into two processes: ERM manufacturing and ERM product forming:
(1) ERM production process The raw materials for ERM production are open-cell polyurethane foam, various fiber products (such as glass fiber, carbon fiber, chopped strand mat made of aramid fiber, continuous fiber mat, knitted mat, etc.) and various thermosetting resins. The production process is as follows: First, in the ERM unit, the adjusted resin paste is impregnated into open-cell polyurethane foam, the resin is pasted onto the foam by means of a squeegee, and the resin paste is pressed into the pores of the foam by a pressure roller. The two layers of foam are then compounded together. Finally, glass fiber mats or other fiber products are placed on the upper and lower sides to form an ERM sandwich material that is cut to a suitable size for press forming or storage.
(2) Production process of ERM products Compared with other thermosetting molding materials (glass fabric or felt prepreg, SMC, etc.), the production process of ERM products needs to be cured under hot pressing conditions, but the molding pressure is much lower than that of SMC. It is 1/10 of the SMC molding pressure, 0.5~0.7MPa.
ERM technology is currently mainly used in the automotive industry materials and lightweight building composites industry. Because ERM has the characteristics of sandwich structure materials, it is suitable for the production of large-scale structural components, a variety of lightweight panels, mobile homes, radome, door Etc. Products in the automotive industry include luggage trailers, covers, instrument panels, bumpers, doors, and floor panels.
4, enhanced reaction injection molding technology
Reinforced Reaction Injection Molding (RRIM) is the use of high pressure impact to mix two monomer materials and short fiber reinforcement materials, and inject them into the mold cavity to form a product through rapid curing reaction. Method. If no reinforcement is used, it is called Reaction Injection Moling (RIM). When continuous fiber reinforcement is used, it is called Structural Reaction Injection Molding (SRIM).
RRIM's raw materials are divided into resin and reinforcement materials
(1) The resin used to produce RRIM resin system should be delayed as follows: 1 It must be composed of two or more monomers; 2 The monomer can be kept stable at room temperature; 3 The viscosity is appropriate and it can be easily transported by the pump; 4 After the monomer is mixed , Can quickly cure; 5 curing reaction does not produce by-products. The most widely used is polyurethane resin, unsaturated polyester resin and epoxy resin.
(2) Reinforcing materials The commonly used reinforcing materials are glass fiber powder, glass fiber and glass microspheres. In order to increase the bonding strength between the reinforcing material and the resin, the above-mentioned reinforcing materials are surface-treated with an enhanced coupling agent.
RRIM process features: 1 product design freedom, can produce large-size components; 2 molding pressure is low (0.35 ~ 0.7MPa), reaction molding, no molding stress, the product heat in the mold is small; 3 product shrinkage is low , Good dimensional stability, due to a large number of fillers and reinforcing materials, reducing the resin curing shrinkage; 4 product inserts process is simple; 5 product surface quality is good, glass powder and glass beads can improve the wear resistance and heat resistance of the products 6 The production equipment is simple, the mould cost is low, the molding cycle is short, and the product production cost is low.
The largest user of RRIM products is automotive, can be used as car bumpers, dashboards, high-strength RRIM products can be used as automotive structural materials, bearing materials. Because of its short molding cycle, performance can be designed, in electrical insulation engineering, anti-corrosion engineering , Mechanical and instrumentation industry in place of engineering plastics and polymer alloy applications.