Vacuum resin introduction process is a low-cost manufacturing process developed in recent 20 years, which is especially suitable for the manufacture of large-scale products. Its advantages are as follows:
(1) the product has excellent performance and high yield. In the case of the same raw materials, compared with the hand paste components, the strength, stiffness and other physical properties of the vacuum resin molding components can be increased by more than 30% to 50%. After the process is stable, the yield can be close to 100%.
(2) the product quality is stable and the repeatability is good. Product quality is less affected by operators, whether the same component or each component has a high degree of consistency. The fiber dosage of the product has been put into the mould according to the prescribed amount before the resin is injected, and the component has a relatively constant resin ratio, generally 30% to 45%, so the uniformity and repeatability of the product performance is much better than that of the hand paste process product. There are also far fewer defects.
(3) the fatigue resistance can be improved and the weight of the structure can be reduced. Due to the high fiber content, low porosity and high product properties, especially the improvement of interlaminar strength, the fatigue resistance of the product is greatly improved. In the case of the same strength or stiffness requirements, the product made by vacuum introduction process can reduce the weight of the structure.
(4) friendly environment. Vacuum resin introduction process is a closed mold process, volatile organic compounds and toxic air pollutants are limited to vacuum bags. There is only a small amount of volatile matter when the vacuum pump is vented (filterable) and when the resin bucket is opened. VOC emissions do not exceed 5PPm standards. This has also greatly improved the working environment of operators, stabilized the workforce and expanded the range of materials available.
(5) the product integrity is good. The vacuum resin introduction process can form reinforcement, sandwich structure and other inserts at the same time, which improves the integrity of the product, so it can manufacture large products such as fan cover, hull and superstructure.
(6) reduce the use of raw materials and labor. In the same coating, the amount of resin is reduced by 30%. Less waste, resin loss rate less than 5%. The labor productivity is high, which can save more than 50% of the labor force compared with the hand paste process. Especially in the forming of large and complex geometric sandwich and stiffened structural members, the material and manual savings are more considerable. For example, in the manufacture of vertical rudder in the aviation industry, the price of fasteners is reduced by 365% compared with the traditional method, the weight of the product is unchanged, and the performance is better.
(7) the precision of the product is good. The dimensional accuracy (thickness) of vacuum resin imported process products is better than that of hand paste products. Under the same coating, the thickness of the general vacuum resin diffusion product is 2 to 3 of that of the hand paste product. The thickness deviation of the product is about 10%, while the manual paste process is generally 20%. The smoothness of the surface of the product is better than that of the hand paste product. The inner wall of the vacuum resin imported machine cover product is smooth, the surface naturally forms the rich resin layer, does not need to add the additional topcoat. The manual work and materials in the grinding and painting process are reduced.
Of course, the current vacuum resin introduction process also has some shortcomings:
(1) the preparation process is long and complex. It needs correct coating, laying diversion medium, diversion pipe, effective vacuum seal and so on. Therefore, for small size products, the process time is longer than the hand paste process.
(2) the production cost is higher and more waste is produced. Such as vacuum bag film, diversion medium, demoulding cloth and diversion pipe and other auxiliary materials are one-time use, and at present quite a lot of rely on imports, so the production cost is higher than the hand paste process. But the bigger the product, the smaller the difference. With the localization of auxiliary materials, this cost difference is becoming smaller and smaller. At present, the research of auxiliary materials which can be used many times is a development direction of this process.
(3) there are certain risks in process manufacturing. Especially for large and complex structural products, once they fail in resin perfusion, the products are easy to be scrapped. Therefore, it is necessary to have better preliminary research, strict process control and effective remedial measures to ensure the success of the process.