How can you maintain high performance levels when custom-fabricating carbon fiber parts?

2025-09-09 09:50:30

The goal of processing carbon fiber composites into various industrial parts is to leverage the material's inherent high mechanical properties for diverse industries and fields. However, processing carbon fiber products is not a simple task. Selecting the appropriate processing technology and paying attention to detail throughout each production step can maximize the preservation of the inherent high performance.

Processing and producing high-performance carbon fiber parts requires meticulous management of the entire process, from material selection, process design, process control, to post-processing. The saying "details determine success or failure" is particularly true when processing carbon fiber parts. A small mistake can significantly reduce the overall performance of a carbon fiber part. To achieve high-performance carbon fiber parts, consider the following key steps and technical points.

1. Primary and Secondary Material Selection

Carbon fiber type: Select high modulus (such as M40J), high strength (such as T800), or high elongation fiber (such as T1000) based on performance requirements. High modulus and high strength fibers are commonly used in aerospace, while sports equipment may prioritize cost-effectiveness.

Resin Matrix Types: General-purpose epoxy resin, high-temperature bismaleimide (BMI), thermoplastic polyetheretherketone (PEEK), etc. Furthermore, the fiber's wettability and curing characteristics must be matched.

Prepreg Control: Ensure resin content (±2% tolerance) and volatile content (<1%) to prevent moisture absorption during storage or expiration.

Release Agent: Choose a high-temperature resistant (such as a polytetrafluoroethylene coating) or semi-permanent release agent to avoid residual contamination.

Core Material and Interlayer: Honeycomb core (Nomex) and foam core (PET) require pre-drying to prevent bubbles during curing.

2. Lay-Up and Mold Design

Lay-up Design: For lay-up angles, use isotropic lay-up to balance anisotropy with 0° (main load-bearing direction), ±45° (shear resistance), and 90° (transverse reinforcement). For lay-up thickness, use stepped or gradient lay-up to avoid stress concentration caused by uneven thickness. Finite element analysis (FEA) can also be used to simulate strain distribution under load and optimize the layup sequence (e.g., using ±45° for impact resistance on the outer layer).

Mold Design: Fully consider the thermal expansion coefficient of the mold material (steel, aluminum, composite material), ensuring it is close to that of the carbon fiber component to avoid deformation during demolding. Parting line design should also be considered to ensure smooth demolding. Modular molds or silicone soft molds should be used for complex curved surfaces.

3. Molding Process Selection and Control

a. Mainstream Molding Processes

Autoclave Molding (Aerospace Grade): Curing under high pressure (0.5-0.7 MPa) and high temperature (120-180°C), resulting in a porosity of<1% and a fiber volume content of 60%-65%.

Resin Transfer Molding (RTM) (Automotive Parts): Closed mold injection with controlled injection speed (to prevent dry spots) and pressure (0.3-0.6 MPa), suitable for complex structures.

Film Filament Winding (Pressure Vessels, Pipes): Precisely control fiber tension (20-50 N) and winding angle (±55° spiral winding).

3D Printing (Rapid Prototyping): For carbon fiber reinforced thermoplastic (e.g., PA-CF) printing, interlayer bonding strength is critical.

b. Process Parameter Control

Curing Curve: Use a step-by-step temperature ramp (e.g., 80°C pre-cure → 120°C main cure → 180°C post-cure) to avoid resin polymerization and internal stress concentration.

Vacuum: Maintain a minimum of -0.095 MPa to ensure adequate resin infiltration and expel air bubbles.

Pressure Uniformity: Maintain a pressure gradient of<5% in the autoclave to avoid localized under-compaction.

4. Post-Processing and Surface Treatment

a. Machining

Cutting: Use water jet cutting (pressure 400 MPa) or diamond-coated tools to prevent fiber delamination.

Drilling: Use a polycrystalline diamond (PCD) drill bit, with a speed of 2000-5000 rpm and a feed rate of 0.01-0.05 mm/rev. Polishing: Use silicon carbide sandpaper (180-400 grit) for gradual polishing to avoid excessive fiber wear.

b. Surface Treatment

Coating: High-temperature resistant polyurethane coating (automotive parts), UV-resistant coating (outdoor equipment).

Metallization: Vacuum coating (aluminum, nickel) to enhance conductivity or electromagnetic shielding performance.

5. High-Performance Optimization Technologies

a. Interface Enhancement

Fiber Surface Treatment: Plasma treatment or sizing (epoxy silane) to improve fiber-resin bonding.

Nano-Modification: Add carbon nanotubes (0.5-2 wt%) or graphene to enhance interlayer toughness and conductivity.

b. Structural Innovation

Hybrid Lamination: Blend carbon fiber with Kevlar or glass fiber to balance cost and impact resistance.

Integrated Molding: Co-curing and embedding metal joints (titanium alloy embedded components) to avoid mechanical joint weakening.