Carbon fiber sheets have become irreplaceable structural materials in industries such as aerospace, new energy vehicles, and high-end sports equipment, thanks to their characteristics of lightweight, high strength, corrosion resistance, and fatigue resistance. The birth of a high-performance carbon fiber sheet relies not only on premium raw materials but also on precision forming processes and advanced equipment. As a professional manufacturer specialized in developing carbon fiber hot press machines, this article offers an in-depth look into the entire forming process of carbon fiber sheets and discusses industry trends and the core value of our equipment.
I. Carbon Fiber Sheet Forming Process: A Precision Journey from Fiber to Finished Product
The essence of carbon fiber sheet forming is curing pre-impregnated carbon fiber (prepreg) or chopped fibers mixed with resin under heat and pressure to form a high-performance sheet with directional mechanical properties. The core process includes the following six key steps:
1. Raw Material Preparation: Prepreg Selection and Cutting
The “DNA” of carbon fiber sheets lies in the raw materials. Commonly used materials include:
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Prepregs: carbon fiber tow pre-impregnated with thermosetting resins like epoxy.
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Chopped fiber + resin mixtures: typically used for compression molding.
Prepregs can be unidirectional (UD) or woven fabrics (e.g., plain weave, twill weave), and their selection directly impacts the directional strength of the final sheet. For instance, aerospace applications often use 0°/90° cross-ply layups to balance mechanical properties in all directions.
Preparation tasks include:
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Prepreg inspection: verify resin content, volatiles, and fiber volume fraction.
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Precision cutting: cut prepregs into specific shapes based on layup design, usually leaving 5%-10% excess (flashing). For UD prepregs, layers are sorted by angles (e.g., 0°, ±45°, 90°).
2. Layup Design: “Programming” the Mechanical Performance
Layup is the core factor determining sheet performance. By adjusting fiber direction and the number of layers, mechanical properties such as tensile strength, bending modulus, and impact resistance can be tailored. Examples include:
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Unidirectional strength: multiple 0° layers aligned with the load direction (ideal for structural components).
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Balanced properties: 0°/90° cross-ply with ±45° interlayers (commonly used in wind turbine blades).
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Complex geometry adaptation: localized angle adjustment for uniform stress distribution in curved parts.
During layup, each layer must be carefully bonded without wrinkles or overlaps (tolerance ≤ 0.1mm), which is critical for quality.
3. Wrapping with Release Film and Compression with Glass/Steel Plates
After layup, the prepreg is wrapped in a release film and sandwiched between glass or steel plates to isolate the resin from the press platen.
Important notes:
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Release films can be glossy or matte depending on surface finish requirements.
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Either glass or steel plates are acceptable.
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Keep plates and release film clean to reduce defects.
Some processes also include pre-compaction to remove trapped air and improve laminate density before molding.
4. Heating and Pressurization: The “Critical Window” of Forming
This is the core stage where resin undergoes crosslinking (for thermosets) or melting (for thermoplastics), giving the sheet its final mechanical properties. Process parameters vary by resin type. For epoxy prepregs, for example:
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Temperature profile: Often 3-stage heating (e.g., 110°C for 3 min → 140°C for 25 min → 150°C for 2 min) to ensure even curing.
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Pressure control: 5-15 MPa depending on thickness. Lower pressure for thin sheets to avoid deformation; higher pressure for thick sheets to enhance density. Constant pressure is applied during the resin’s optimal flow period (before gelation).
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Time management: Cure time depends on the resin (typically 0.5–1 hour for epoxy; phenolic resins may require more). Over-curing leads to brittleness; under-curing results in low strength.
5. Demolding and Post-processing: From Mold to Final Product
Once cured, the press opens automatically, and the sheet is removed for cooling. After cooling, release films are removed. Excess resin (flash) and uneven edges (±0.2mm tolerance) are trimmed using CNC milling or waterjet cutting to meet target dimensions (±0.05mm).
For high-end applications, further processing may include:
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Surface finishing: Priming, polishing, or film coating for durability or aesthetics.
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Performance testing: Non-destructive testing (e.g., ultrasonic) for internal defects, and mechanical tests (e.g., tensile, flexural) using universal testing machines. High-performance sheets require tensile strength ≥1500 MPa and modulus ≥100 GPa.
II. Industry Trends: Lightweight & High-Performance Drive Technological Upgrades
With the global push for lightweight and high-efficiency materials, carbon fiber sheets are expanding into more industries. Forming technologies and equipment are evolving along three major trends:
1. Higher Performance: Strength and Heat Resistance
New-generation carbon fibers (e.g., T1000, M60J) and high-temperature resins (e.g., BMI, polyimide) enable sheets with:
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Tensile strength >2000 MPa
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Long-term heat resistance >200°C
These developments demand tighter temperature uniformity (±2°C) and pressure accuracy (±0.1 MPa) from the forming equipment.
2. Larger Sizes & Complex Structures
Applications such as EV battery covers and wind turbine beams require sheets up to 1.5m × 3m or larger, often with integrated stiffeners or curved geometries. This shifts production from simple flat panels to multi-layer laminate & mold-in-one forming, requiring:
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Presses over 1000 tons
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Platens as large as 2m × 4m
3. Automation & Intelligence
Manual layup is slow and inconsistent. The industry is adopting automated fiber placement (AFP) with vision systems for precision, combined with smart hot press machines featuring closed-loop control of temperature, pressure, and time. These upgrades improve:
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Production consistency
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Yield rate (from 85% to over 95%)
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Labor cost reduction
III. Core Application & Technical Parameters of Carbon Fiber Hot Press Machines
As the “heart” of the forming process, the carbon fiber hot press directly determines sheet density, strength, and surface quality. Our press machines are designed specifically for high-performance prepreg forming, offering:
Key Application Fields:
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Aerospace: Interior panels, satellite components, UAV wings
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New Energy Vehicles: Battery covers, crash beams, lightweight interiors
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High-End Equipment: Train body panels, medical casings, robotic joints
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Sports & Leisure: Bicycle frames, golf club faces, ski board cores
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Item Parameter Range Description Nominal Pressure 50–300 tons Matched to sheet thickness (low tonnage for thin sheets, high for thick) Platen Size 600×600mm to 1500×1500mm From small-batch customization to large-scale production Temperature Range Room temp – 400°C (or higher) ±2°C accuracy; programmable multi-step heating profiles Heating Method Oil circulation / electric / hybrid Oil heating for better uniformity (±1°C); electric heating for faster response Pressure Control Hydraulic (servo/proportional valve) ±0.1 MPa precision; supports dynamic pressure compensation Automation Optional auto feeding, PLC touch screen MES integration for full parameter storage and traceability
Conclusion
The forming of carbon fiber sheets represents a synergy of materials science, process control, and equipment precision. As a specialized manufacturer of carbon fiber hot press machines, we not only deliver high-precision, high-stability forming equipment but also participate deeply in process development—from prepreg selection and mold design to parameter tuning and production optimization—ensuring every carbon fiber sheet achieves its full performance potential.
If you’re planning a carbon fiber lightweighting project or have questions about the forming process and equipment selection, feel free to contact our technical team. We’ll provide you with a complete “material-process-equipment” solution tailored to your needs!