The composite material forming process is the

(3) Resin transfer molding technology (RTM technology);

(4) Bag pressing method (pressure bag method) forming;

(5) Vacuum bag compression molding;

(6) Autoclave forming technology;

(7) Hydraulic kettle molding technology;

(8) Thermal expansion molding technology;

(9) Sandwich structure forming technology;

(10) Molded material production process;

(11) ZMC molding material injection technology;

(12) Compression molding process;

(13) Laminate production technology;

(14) Rolled tube forming technology;

(15) Filament winding product molding technology;

(16) Continuous board production process;

(17) Casting technology;

(18) Pultrusion process;

(19) Continuous winding pipe making process;

(20) Braided composite material manufacturing technology;

(21) Thermoplastic sheet molding compound manufacturing technology and cold die stamping forming process;

(22) Injection molding process;

(23) Extrusion molding process;

(24) Centrifugal casting tube forming process;

(25) Other molding techniques.

Depending on the selected resin matrix material, the above methods are suitable for the production of thermosetting and thermoplastic composite materials, and some processes are suitable for both. Composite material product molding process characteristics: Compared with other material processing technology, composite material molding process has the following characteristics: (1) Material manufacturing and product molding are completed at the same time. Generally, the production process of composite materials is the molding process of products. The properties of materials must be designed according to the use requirements of the products. Therefore, when selecting materials, designing ratios, determining fiber layup and forming methods, they must meet the physical and chemical properties, structural shape and appearance quality requirements of the products. (2) The molding of the product is relatively simple. Generally, the resin matrix of thermosetting composite material is a flowing liquid before molding, and the reinforcing material is soft fiber or fabric. Therefore, the production of composite products with these materials requires simpler processes and equipment than other materials. Many, for some products, only a set of molds can be produced. 1. Contact low-pressure molding process The characteristic of the contact low-pressure molding process is to manually lay the reinforcement material and impregnate the resin, or use simple tools to assist the placement of the reinforcement material and resin. Another feature of the contact low pressure molding process is that it does not need to apply molding pressure (contact molding) or only a lower molding pressure (0.01-0.7 MPa pressure is applied after contact molding, and the maximum pressure does not exceed 2.0 MPa). The contact low-pressure molding process is to first make the material into a design shape on a female mold, a male mold or a counter mold, then heat or solidify at room temperature, and then undergo auxiliary processing after demolding to obtain the product. This type of molding process includes hand lay-up molding, injection molding, bag compression molding, resin transfer molding, autoclave molding, and thermal expansion molding (low pressure molding). The first two are contact molding. Among the contact low pressure molding processes, the hand lay-up molding process is the first invented in the production of polymer-based composite materials, and has the widest application range. Other methods are the development and improvement of the hand lay-up molding process. The biggest advantage of the contact molding process is simple equipment, wide adaptability, low investment and quick results. According to statistics in recent years, the contact low pressure molding process still occupies a large proportion of the composite material industrial production in various countries in the world, such as the United States accounting for 35%, Western Europe accounting for 25%, Japan accounting for 42%, and China accounting for 75%. This illustrates the importance and irreplaceability of the contact low pressure molding process in the industrial production of composite materials, and it is a process method that never declines. But its biggest disadvantage is low production efficiency, high labor intensity, and poor product repeatability.

1. The raw materials that are exposed to low-pressure molding include reinforcing materials, resins, and auxiliary materials.

(1) Reinforced materials

Contact molding requirements for reinforcement materials:

① Reinforcement materials are easy to be saturated by resin;

② It has sufficient deformability to meet the molding requirements of complex shapes of products;

③Bubble is easy to deduct;

④ It can meet the physical and chemical performance requirements of the product use conditions;

⑤Reasonable price (as cheap as possible) and abundant sources.

The reinforcing materials used for contact molding include glass fiber and its fabric, carbon fiber and its fabric, aramid fiber and its fabric, etc.

(2) Matrix material

The requirements of the contact low-pressure forming process for the base material:

① Under the condition of hand lay-up, it is easy to penetrate the fiber reinforced material, easy to remove air bubbles, and has a strong adhesion to the fiber;

②It can be gelled and cured at room temperature, and requires small shrinkage and less volatile matter;

③Suitable viscosity: generally 0.2～0.5Pa・s, no glue flow phenomenon occurs;

④Non-toxic or low-toxic;

⑤The price is reasonable and the source is guaranteed. Commonly used resins in production are: unsaturated polyester resin, epoxy resin, phenolic resin, bismaleimide resin, polyimide resin and so on.

(3) Supplementary materials

The auxiliary materials in the contact molding process mainly refer to two types of fillers and pigments, while curing agents, diluents, toughening agents, etc., belong to the resin matrix system.

2. Mould and release agent

(1) Mould

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, and it must be carefully designed and manufactured.

When designing a mold, the following requirements must be considered comprehensively:

①Meet the accuracy requirements of product design, with accurate mold size and smooth surface;

② It must have sufficient strength and rigidity;

③Easy to demold;

④Have sufficient thermal stability;

⑤Light weight, sufficient source of materials and low cost.

Mold structure

Contact molding molds are divided into three types: female mold, male mold and counter-mold. Regardless of the type of mold, it can be designed as an integral or assembled mold according to the size and molding requirements.

Mold material

When rebelling against mold materials, the following requirements should be met:

①Able to meet the product's dimensional accuracy, appearance quality and service life requirements;

②The mold material must have sufficient strength and rigidity to ensure that the mold is not easily deformed and damaged during use;

③It is not corroded by resin and does not affect the curing of resin;

④Good heat resistance, the mold will not deform when the product is cured and heated;

⑤Easy to manufacture, easy to demould;

⑥Reduce the weight of the mold during the day to facilitate production;

⑦The price is cheap and the materials are easy to obtain. The materials that can be used as hand lay-up molds include: wood, metal, plaster, cement, low-melting metal, rigid foam and fiberglass, etc.

Basic requirements for release agent:

1. Does not corrode the mold, does not affect the curing of the resin, and the adhesion to the resin is less than 0.01MPa;

② Short film forming time, uniform thickness and smooth surface;

③It is safe to use and non-toxic;

④Heat resistance and can be cured by heating;

⑤Easy to operate and low price.

The mold release agents used in the contact molding process mainly include film mold release agents, liquid mold release agents, ointments, and wax mold release agents.

Hand lay-up process

The process flow of hand lay-up is as follows:

(1) Production preparation

The size of the work site for hand lay-up molding should be determined according to the product size and daily output. The site must be clean, dry, and well ventilated. The air temperature should be kept between 15 and 35℃. The post-processing and renovation section should be equipped with exhaust and dust removal. Water spray device.

Mold preparation includes cleaning, assembling, and applying release agent.

When preparing resin glue, two issues should be paid attention to:

① Prevent air bubbles from being mixed into the glue;

②The amount of glue should not be too much, and each amount should be used up before the resin gel.

Reinforcement material preparation The types and specifications of reinforcement materials are selected according to the design requirements.

(2) Pasting and curing

Lay-up paste system Manually-laid paste system is divided into wet method and dry method:

① Dry layup uses pre-impregnated cloth as raw material, first cut the pre-learned good material (cloth) into bad material according to the template, heat and soften it when laying, and then stick it layer by layer to the mold, and pay attention to removing the layer Between air bubbles to make dense. This method is mostly used for autoclave and bag press forming.

②Wet layup: Dip the reinforcing material directly on the mold and stick it layer by layer to remove air bubbles and make it compact. Generally, this method is used in hand lay-up. Wet layup is divided into gel coat layer paste system and structural layer paste system.

Hand lay-up tools

Hand lay-up tools have a great influence on ensuring product quality. There are wool rollers, bristles rollers, spiral rollers, electric saws, electric drills, and polishing machines.

The curing of the cured product is divided into two stages: hardening and curing: it usually takes 24 hours from gel to triangulation. At this time, the curing degree reaches 50% to 70% (Bakcol hardness is 15), and it can be demoulded and left in the natural environment. Under the condition of curing for 1 to 2 weeks, the product can have mechanical strength, which is called curing, and its curing degree can reach more than 85%. Heating can promote the curing process. For polyester FRP, heating at 80°C for 3 hours, and for epoxy FRP, the post-curing temperature can be controlled within 150°C. There are many heating and curing methods. Small and medium-sized products can be heated and cured in a curing oven, and large products can be heated by in-mold or infrared heating.

(3) Demoulding and trimming

Demoulding The demoulding must ensure that the product is not damaged. There are several demoulding methods:

① Ejection and demolding. The ejection device is embedded in the mold, and the screw is rotated during demolding to eject the product.

②Pressure demoulding There is a compressed air or water inlet on the mold. When demolding, press compressed air or water (0.2MPa) into the mold and the product, and at the same time use a wooden hammer and a rubber hammer to beat the product and the mold.

③The demoulding of large products (such as boats) can be done with tools such as jacks, cranes and hardwood wedges.

④Complex products can use manual demoulding method to first paste two or three layers of FRP on the mold, and then peel off from the mold after it is cured, and then put it on the mold to continue pasting to the design thickness. After curing, it is easy to remove from the mold. Come down.

Trimming There are two types of trimming: one is size trimming and the other is defect repairing.

①Size trimming After forming the product, cut off the excess part according to the design size;

② Defect repair, including perforation repair, bubble, crack repair, and hole reinforcement.

Injection molding technology (1) Principles and advantages and disadvantages of the injection molding process The injection molding process is to spray two polyesters mixed with initiator and accelerator from both sides of the spray gun, and at the same time, the cut glass fiber roving is sprayed from the center of the spray gun. When it is deposited to a certain thickness, it is compacted with a roller to make the fiber soak in the resin, remove air bubbles, and solidify into a product.