Introduction to the application of vacuum introduction process

Introduction to the application of vacuum introduction process

Abstract: Vacuum introduction is a recently emerging composite material processing method. This article introduces the principle of the vacuum introduction process, and compares the mechanical properties with other processes, expounds the advantages of the products made by the vacuum introduction process, and at the same time has an impact on the production process The process is briefly introduced. Vacuum introduction of resin glass fiber reinforced plastic glass fiber Among the current materials, composite materials are widely used because of their light weight and high strength. The manufacturing process for composite materials is constantly improving and innovating. From the initial hand lay-up to mechanized spraying, pultrusion, molding and other processes, to the emerging vacuum introduction process, the processes related to vacuum introduction include resin transfer molding (RTM) and vacuum assisted RTM (VARTM), Vacuum bag pressing, SCRIMP, SRIM (Structural Reaction Molding), RTI (resin filminfusion). But there are some differences, which have been introduced in many articles, so I won't repeat them here. Vacuum infusion process (Vacuum infusion process, VIP) The vacuum introduction process, referred to as VIP, is to lay reinforcement materials (glass fiber, carbon fiber, sandwich materials, etc., different from the vacuum bag process) on the mold, then lay the vacuum bag, and extract the air in the system to form a mold in the mold cavity Negative pressure, using the pressure generated by the vacuum to press the unsaturated resin into the fiber layer through the pre-laid pipeline, let the resin infiltrate the reinforcing material and finally fill the entire mold. After the product is cured, remove the vacuum bag material to obtain the required material from the mold. Products. VIP uses single-sided molds (like the usual hand lay-up and spray molds) to build a closed system. The vacuum introduction process has been known to the world for a long time, and this process has a patent record in 1950. However, it has only been developed in recent years. Since this process is introduced from abroad, there are many names in the naming, such as vacuum introduction, vacuum perfusion, vacuum injection, etc.

1.2 Application fields of vacuum introduction process (VIP)

• 1) Boat industry-hull, deck, rudder, radar shield

• 2) Wind power energy-blades, cabin cover

• 3) Sports and leisure-helmets, windsurfing

• 4) Automobile industry-all kinds of roofs, windshields, carriages

• 5) Construction field-building roof components, construction templates

• 6) Agriculture and gardening-round cover for granary, protective cover for agricultural machinery

1.3 VIP process flow

To understand how the materials are used and how to arrange them. For the convenience of understanding, we take the schematic diagram as an example. Step 1: Prepare the mold Like other multi-layer processes, high-quality molds are also necessary for VIPs. The surface should have higher hardness and higher gloss, and the edge of the mold should be kept at least 15 cm to facilitate the laying of sealing strips and pipelines. Clean the mold, then apply mold release wax or wipe mold release water.

 step2: The construction of the gel coat surface can be based on the requirements of the product, and the product gel coat and polished gel coat can be used. The types of choice are o-phthalic, isophthalic and vinyl. Apply the gel coat by brushing and spraying by hand.

Step 3: Reinforce material laying The choice of reinforcing materials-glass fiber, carbon fiber, sandwich material... It depends on the strength requirements of the product. The selection of reinforcement materials is an important step for the build-up process, but there are several points to consider for VIP. Although all fabrics can be used, different materials and weaves will affect the resin flow rate.

Step 4: Laying of vacuum bag materials Spread the release cloth first, then the diversion cloth, and finally the vacuum bag. Before closing the vacuum bag, carefully consider the direction of the resin and the vacuum pipeline, otherwise the resin will not be infiltrated in some places. Be very careful when laying, lest some sharp objects pierce the vacuum bag.

Step 5: Vacuum After laying these materials, clamp each inlet resin tube, vacuum the entire system, try to evacuate the air in the system, and check the air tightness. This step is very important. If there is a leak, when the resin is introduced, the air will Into the body into the system, air bubbles will seep into other places at the leak point, and even the entire product may be scrapped. This control system is used for program control of two Leybold vacuum pumps. The electrical control system has the following characteristics: The system can choose manual and automatic control modes; The motor adopts direct start, with thermal protection; The system is one main and one auxiliary. If the main pump fails during operation, the standby pump will be automatically switched to run; The control panel is equipped with start and stop knobs, automatic/manual switch knobs, running indicator, fault indicator, alarm indicator, power indicator, and alarm reset button; Manual control mode: start and stop any vacuum pump through the start-stop button, and is not affected by the degree of vacuum; Automatic control method:

A. Automatically turn on or turn off the pump according to the air consumption in the workshop, and adjust the number of pumps in operation to make the system output flow close to the demand flow of the workshop equipment.

B. The two pumps are controlled by PLC program to switch in turn as one main pump and one auxiliary pump;

C. When the system control is running in the automatic state, when one of the vacuum pumps stops working due to a failure, the vacuum pump failure indicator will light up, and the auxiliary vacuum pump will immediately start to replace the work. If the system vacuum is lower than the set minimum pressure value for 30 seconds, the system alarm will alarm immediately.

Step6: with resin After the vacuum reaches certain requirements, prepare the resin. Add the corresponding curing agent according to the gel time, and remember not to forget to add the curing agent, otherwise it will be difficult to make up. However, generally the vacuum-introduced resin contains a curing indicator, which can be judged from the color.

Step 7: Import resin Insert the resin pipeline into the prepared resin barrel, open the clamps according to the order of feeding, pay attention to the amount of resin, and replenish it in time if necessary.

Step 8: Demoulding After the resin gel has cured to a certain degree, remove the vacuum bag material. Remove the product from the mold and perform post-processing.