Focus on Vacuum Infusion Process

Analysis of Consumables and Auxiliary Materials for Vacuum Infusion Process and Promotion of Standardized Processes to Upgrade High-End Composite Material Manufacturing

With the wide application of carbon fiber composite materials in high-end fields such as wind power, shipping, automotive, and aerospace, the Vacuum Infusion Process (VIP), as an advanced molding technology, is gradually replacing traditional processes like hand lay-up and spray-up to become the industry mainstream. This article focuses on analyzing the key consumables and auxiliary material systems in the vacuum infusion process, and systematically sorts out its standardized process flow, providing technical references and practical guidance for industry practitioners.

I. Core Advantages and Application Fields of Vacuum Infusion Process

The vacuum infusion process establishes a negative pressure environment inside the mold cavity and uses pressure difference to accurately infuse resin into the "dry" reinforcement materials, realizing uniform wetting of resin and efficient molding. This process has significant advantages, including low bubble rate in products, high fiber content (up to 70%), low resin loss, environmental friendliness, and adaptability to single-sided molds. It is widely applied in the following fields:

• Marine industry: Hull, deck, rudder

• Wind power energy: Blades, nacelle cover

• Automotive industry: Roof, windshield, carriage

• Sports and leisure: Helmets, windsurfers

• Construction and agriculture: Construction formwork, grain silo cover, etc.

II. Key Consumables and Auxiliary Material System for Vacuum Infusion Process

The successful implementation of the vacuum infusion process highly depends on the scientific selection and matching of consumables and auxiliary material systems. The main components are as follows:

1. Resin System

• Type selection: Special vacuum infusion resin must be used, commonly epoxy resin or unsaturated polyester resin; ordinary resin cannot be used as a substitute.

• Performance requirements: Low viscosity (facilitating rapid mold filling), controllable gel time, appropriate exothermic peak, and good wettability. Specific parameters need to be determined in collaboration with suppliers.

1. Curing System

• Epoxy resin requires a special curing agent; methyl ethyl ketone peroxide (MEKP) is commonly used as the curing agent for unsaturated resin.

• The quality of the curing agent directly affects the performance of the product. Strict evaluation of suppliers’ products is necessary to avoid major losses due to inferior materials.

1. Reinforcement Materials

• Common materials: Glass fiber (continuous mat, composite stitched mat, single cloth, etc.), carbon fiber.

• Key selection points: Materials should be selected based on mechanical design, and their permeability should be verified through experiments. Different sizing agents and adhesives will affect the resin wetting effect, thereby influencing the final product performance.

1. Core Materials

• Common types: Balsa wood, PVC foam, PUR foam, rigid core mat, wood board, etc.

• Function: Improve structural rigidity and lightweight level; rational selection should be made according to the functional requirements of the product.

1. Equipment and Disposable Auxiliary Materials

• Core equipment: Vacuum pump, pressure gauge, interface, infusion hose.

• Disposable consumables: Release fabric, distribution medium, vacuum bag, sealing tape, etc.

• Important note: All materials must be verified for applicability through experiments and cannot be replaced arbitrarily; some high-end consumables still rely on imports, so a balance between cost and performance must be coordinated.

III. Detailed Standardized Process of Vacuum Infusion Process

To ensure stable product quality and process repeatability, the vacuum infusion process must strictly follow the following eight steps:

Step 1: Mold Preparation

• Select a mold with high hardness and high gloss, and reserve a space of ≥15cm at the edges to facilitate sealing and pipeline layout.

• Thoroughly clean the mold and evenly apply mold release wax or mold release agent.

Step 2: Gel Coat Application

• Select product gel coat or sandable gel coat (orthophthalic, isophthalic, or vinyl type) according to product requirements.

• Apply evenly by brushing or spraying to ensure surface quality.

Step 3: Laying of Reinforcement Materials

• Lay glass fiber, carbon fiber, or core materials in accordance with design requirements.

• Pay attention to the influence of material weaving method on resin flow rate, and reasonably plan the layering sequence and direction.

Step 4: Laying of Vacuum Bag System

• Lay the release fabric and distribution medium in sequence, and finally cover with the vacuum bag.

• Key points: Pre-plan the layout of resin and vacuum pipelines to avoid dead corners; operate carefully to prevent the vacuum bag from being punctured by sharp objects.

Step 5: Vacuuming and Air Tightness Inspection

• Clamp the resin inlet hose and start the vacuum pump to remove all air from the system.

• Inspect the air tightness of the system to ensure no air leakage points. Air leakage will cause bubbles to infiltrate, which may lead to the scrapping of the entire product.

Step 6: Resin Preparation

• Accurately add the curing agent according to the gel time requirements. Never omit the curing agent.

• Use the curing indicator (e.g., color change) inherent in the resin to assist in judging the mixing state.

Step 7: Resin Infusion

• Insert the inlet hose into the resin bucket, open the clamps in the predetermined sequence, and start resin infusion.

• Monitor the remaining amount of resin in the bucket in real time and replenish it in a timely manner to ensure continuous material supply.

Step 8: Demolding and Post-Processing

• After the resin is gelled and cured to an appropriate degree, remove the vacuum bag and auxiliary materials.

• Take the product out of the mold and perform post-processing procedures such as trimming and sanding.

IV. Challenges and Prospects

Although the vacuum infusion process has significant advantages, it still faces challenges such as high cost of disposable consumables (some relying on imports) and high requirements for operators’ skills. The industry needs to continuously lower the application threshold through domestic substitution, process training, and standardization.

At present, this process has been widely used in the manufacturing of high-value-added FRP (Fiber Reinforced Plastic) components, such as wind turbine blades, yachts, and sports equipment. With the growing demand for high-performance materials and the development of intelligent manufacturing, the vacuum infusion process is being recognized and adopted by more and more enterprises, and will become a key technical path to promote the high-quality development of China’s composite material industry.

(The information in this article is comprehensively compiled from public materials of authoritative industry websites, technical bloggers, and leading industrial enterprises. Welcome to exchange and discuss.)