Prepreg is a semi cured sheet made by impregnating reinforced fibers or fabrics into a matrix, and is an intermediate material in composite materials.
The main reinforcing materials include carbon fiber, glass fiber, aramid, and their fabrics.
The main matrix materials include epoxy resin, vinyl ester, phenolic resin, bismaleimide, cyanate ester, polyimide, and thermoplastic resin.
Compared to other materials, composite materials produced using prepreg can improve various characteristics such as strength, hardness, corrosion resistance, fatigue life, wear resistance, impact resistance, and lightweight.
Due to its many advantages such as ease of use, consistent performance, and high-quality surface finish, it is becoming increasingly common in the application of composite materials industry.
According to the type of fiber, the arrangement of fibers, and the type of matrix material used, it can be used in the production and manufacturing of civil aircraft, automotive industry, energy industry, sports and leisure products industry, etc.
Scope of prepreg products
1. Pre impregnated material width: 15mm~1600mm
2. Fiber mass per unit area (FAW) of prepreg: 50-400 g/㎡
3. Pre impregnated resin content:
Unidirectional fiber prepreg: 30-45% ± 2%
Pre impregnated fabric: 35-60% ± 3%
4. Unidirectional prepreg fiber types: carbon fiber, glass fiber, aramid, PBO fiber, basalt fiber, etc.
5. Pre impregnated fabric types: plain weave fabric, forged weave fabric, twill weave fabric.
6. Resin matrix for prepreg:
120 ° C curing modified epoxy resin matrix
180 ° C curing modified epoxy resin matrix
Why are pre impregnated materials becoming increasingly popular among users?
1. Maximum intensity characteristic. A typical manual layer will have a large amount of excess resin, which will increase brittleness and reduce overall performance. Most pre impregnated materials contain about 35% resin, which is an ideal choice for achieving maximum curing performance and is usually not achievable in conventional manual lamination.
2. Uniformity and repeatability. The thickness of the prepreg is uniform, and theoretically, each part coming out of the mold may be the same. Vacuum bagging technology still has certain errors in processing and other aspects, but pre impregnated materials can greatly reduce these problems.
3. Reduce curing time. After the heat curing cycle, there is no need to wait for the standard 48 hours to fully cure.
4. Good appearance. Although pre impregnated material processing still requires mold preparation and demolding, pre impregnated material processing can eliminate bubbles and make it easier to obtain a smooth and glossy surface.
Reinforcing materials for prepreg:
1. Fiberglass class:
2. Carbon fiber:
3. Aramid class
Requirements of prepreg for fiber cloth:
As a reinforcing material for prepreg, fiber cloth usually needs to have high strength and modulus, high elongation at break, and minimal dispersion of performance. The linear density of fibers or the surface density of fiberglass fabrics should be stable, and the fibers should have good interfacial properties when combined with resin after surface treatment. The packaging requirements are uniform tension and no wrinkles or folds during rewinding.
How is prepreg processed?
The commonly used molding processes for prepreg mainly include vacuum bag process, hot press tank process, molding process, tube rolling process, extrusion molding process, winding molding process, etc.
There are two main production methods for fiber prepreg: one is to directly heat the resin to reduce its viscosity and facilitate uniform dispersion between fibers, which is called hot melt method. Another method is to dissolve the resin in a solvent to reduce viscosity, and then heat it to evaporate the solvent after the resin is impregnated with fibers, which is called solution impregnation method.
At present, the commonly used hot melt methods for carbon fiber prepreg can be divided into one-step and two-step methods. In the two-step process, the first step requires the preparation of a resin film, followed by pre impregnation treatment. Currently, about 90% of the carbon fiber pre impregnated materials in China are processed using the hot melt two-step method.
Application areas of prepreg
The application of prepreg has not only developed rapidly in the aerospace field, but also in industries such as wind power generation, boats, automobiles, rail transit, drones, sports equipment, national defense and military industry, industrial machinery, etc. The application of prepreg has been increasing day by day. As a result, some components are pursuing higher specific strength, specific stiffness, fatigue resistance, and design freedom of products, which has led to the use of prepreg surpassing metal materials and showing a continuous growth trend.
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