Autoclave Technology: A Critical Link in Carbon Fiber Composite Molding Production
High-Quality Molding and Low Porosity
The autoclave process utilizes high pressure (typically 0.5-1.0 MPa) and high temperature (120-200°C) to ensure thorough resin impregnation of fibers, reducing porosity to below 1-2% (superior to RTM’s 3-5%). This significantly enhances mechanical properties, achieving tensile strengths above 2.5 GPa and moduli up to 200 GPa.
Adaptability to Complex Geometries
Using vacuum bags and molds, the autoclave process enables precise molding of complex curved surfaces and intricate components (e.g., aerospace parts), with dimensional accuracy of ±0.1 mm and surface roughness Ra<1.6 μm, meeting high-precision requirements.
Consistency and Repeatability
Process parameters (pressure, temperature, curing time) can be precisely controlled, ensuring high batch-to-batch consistency with mechanical property variations typically <5%. Compared to hand lay-up (with 10-15% performance fluctuation), autoclaves are better suited for large-scale production.
Superior Interfacial Bonding
The high-pressure environment enhances fiber-resin interfacial bonding, achieving interfacial shear strengths of 60-80 MPa, significantly higher than ambient-pressure methods (e.g., vacuum infusion at 40-50 MPa), improving interlaminar shear performance.
Versatility
Compatible with various prepreg systems (epoxy, bismaleimide, etc.), it enables the production of high-performance structural components, widely used in aerospace (e.g., Boeing 787 fuselage, 50% carbon fiber) and automotive applications (e.g., BMW i3 chassis).
Limitations: High equipment costs (in the millions of dollars), high energy consumption (50-100 kWh per cycle), and long cycle times (2-6 hours). However, its comprehensive advantages are significant in high-performance applications.
Customized toner fiber molding case
1.1 Process Principle
Carbon fiber prepreg is laid up on a mold according to the required layering sequence, sealed in a vacuum bag, and placed in an autoclave. Under vacuum conditions, the autoclave undergoes processes such as heating, pressurization, holding, cooling, and depressurization. By simultaneously providing uniform temperature and evenly distributed pressure within the autoclave, curing is achieved, enabling the formation of high-quality surface and internal structures, complex shapes, and large-area carbon fiber composite components.
1.2 Process Development
The autoclave process was developed for the production of second-generation composite materials in the 1940s and began to gain widespread use in the 1960s. It has since been extensively applied in high-tech fields such as aerospace, composite materials, electronics, military, transportation, sports equipment, and new energy. It plays a significant role, particularly in the production of skin-type components, and has become a mature process. Composite products manufactured using the autoclave process account for over 50% of total composite production and more than 80% in the aerospace sector. Currently, as one of the primary methods for molding carbon fiber composite components, the autoclave process is widely adopted by many manufacturers of carbon fiber composite parts.
1.3 Process Equipment
1.3.1 Autoclave
The autoclave is a specialized process equipment designed for the molding characteristics of polymer-based composite materials. It is the primary method for manufacturing continuous fiber-reinforced thermoset composite components, suitable for advanced composite structures, honeycomb sandwich structures, and bonded metal or composite structures. It offers advantages such as high precision in temperature and pressure control, safe and reliable structure, good system stability, low energy consumption, and ease of operation and maintenance. The autoclave can be modularized and serialized to meet the needs of different fields, processes, and specifications.
1.3.2 Equipment Components
As a system designed for curing carbon fiber composites, the autoclave enables sequential and real-time online control of process parameters such as temperature, pressure, vacuum, cooling, and circulation. The equipment consists of the following components:
1. Overall Structure: Comprises the tank body, tank door mechanism, high-temperature motor, and air duct insulation layer, forming a high-pressure and high-temperature resistant tank.
2. Safety Interlock Device: Includes automatic pressure interlock, manual interlock, and ultra-high-pressure alarm system.
3. Quick-Open Door Device: Features a manual-electric dual-mode quick-open door design, allowing normal opening and closing of the tank door during power outages.
4. Sealing Device: The tank door uses silicone inflatable sealing, capable of withstanding high pressure.
5. Pressure System: Consists of a compressor, air storage tank, pressure control valve, pipelines, pressure transmitter, and pressure gauge, forming a pressure delivery and control system. The internal pressure can reach 1.5-2.5 MPa with an error of no more than 0.05 MPa, equipped with a safety explosion-proof device.
6. Heating System: Comprises stainless steel electric heating tubes, high-temperature fan, air duct plates, insulation layer, and temperature control system, with heating power meeting the maximum temperature and heating rate requirements of the chamber.
7. Temperature Circulation System: Includes a circulation fan, air guide plates, and a flow guide cover to accelerate heat conduction and circulation, forming a uniform temperature field.
8. Vacuum System: Comprises a vacuum pump, pipelines, vacuum gauge, and vacuum valve, providing vacuum conditions for encapsulated composite preforms, with multiple vacuum pipe connectors to meet molding process requirements.
9. Automatic Control System: Utilizes a PLC control system to achieve high-precision control and real-time recording of process parameters such as pressure, temperature, and cooling throughout the process.
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