What is PEEK CA (Carbon Fiber) Sheet?
PEEK CA sheet (carbon fiber reinforced polyetheretherketone sheet) is a high-performance specialty engineering plastic sheet made by compounding carbon fiber (CF) with polyetheretherketone (PEEK) resin. Carbon fiber is a high-strength, high-modulus fiber with a carbon content exceeding 90%. By compounding with PEEK resin, PEEK CA sheet retains PEEK's inherent properties of high temperature resistance, chemical corrosion resistance, and self-lubrication while significantly enhancing its mechanical strength, stiffness, and dimensional stability. It is widely used in high-end manufacturing.
How to make PEEK CA sheet?
1. Raw Material Selection
• PEEK resin: Pure or pre-dried resin is commonly used.
• Carbon fiber: Chopped or continuous carbon fiber is often used, and the surface is treated with a sizing agent to improve interfacial bonding with PEEK (untreated carbon fiber is prone to debonding at the PEEK interface).
2. Mixing and Dispersion
The carbon fibers must be evenly dispersed in the PEEK resin; otherwise, they will result in localized strength deficiency or "fiber clumping." Due to PEEK's high melting point, melt blending is primarily used:
• Twin-screw extrusion: PEEK pellets and chopped carbon fibers are added to a twin-screw extruder (barrel temperature 320-360°C) in appropriate proportions. High shear forces (screw speed 150-300 rpm) are used to disperse the fibers and melt blend them with the resin.
• Continuous carbon fibers are chopped into short fibers before blending with PEEK.
• Pelletizing: The melt-blended material is cut into cylindrical pellets (2-5 mm in diameter) in a pelletizer for subsequent molding.
3. Molding
Different molding processes are available depending on the required sheet thickness and size:
• Compression Molding: Suitable for thick sheets. Prepreg (or pellets) are placed in a preheated mold (360-380°C), where a pressure of 15-30 MPa is applied. The pressure is maintained for several minutes, and the sheet is cooled in the furnace to prevent internal stress.
• Extrusion Molding: Pellets are extruded into continuous sheets using an extruder, and then calendered (temperature 350-370°C). Surface roughness can reach Ra ≤ 0.5 μm.
• Autoclave Molding (High-End Applications): Suitable for continuous carbon fiber reinforced sheets. Prepreg layers are laid up and placed in an autoclave (temperature 350-370°C, pressure 0.5-1 MPa). Vacuum curing is performed to achieve sheets with higher fiber content and superior performance.
4. Post-Processing
• Machining: Use diamond-coated or cubic boron nitride (CBN) tools for moderate turning and milling to minimize wear on conventional tools.
• Surface Treatment: Polish to Ra ≤ 0.2 μm to reduce the coefficient of friction. If welding is required, use plasma cleaning to roughen the surface (to improve bonding strength).
• Heat Treatment: Annealing (250-300°C/2-4 hours) can be performed on high-performance sheets to eliminate internal stresses and improve dimensional stability.
Features of CA PEEK Sheet:
• Ultra-high mechanical strength:
Based on the carbon fiber content, PEEK is divided into 10% CF-reinforced PEEK (PEEK 10CF), 30% CF-reinforced PEEK (PEEK 30CF), and 50% CF-reinforced PEEK (PEEK 50CF). Tensile strength and elastic modulus gradually increase.
• High temperature resistance:
Long-term operating temperature:
30% CF-reinforced PEEK can reach 250°C (short-term 310°C); 50% CF-reinforced PEEK has a long-term operating temperature of 300°C (short-term 350°C).
Glass transition temperature (Tg):
Increases from 143°C for pure PEEK to 160-170°C (as the carbon fiber content increases).
• Dimensional Stability:
Coefficient of Thermal Expansion (CTE): Pure PEEK is 3.6×10⁻⁵/°C, which decreases to 1.2×10⁻⁵/°C after 30% CF reinforcement (close to 1.0×10⁻⁵/°C for steel). Deformation is minimal at high temperatures.
Water Absorption: <0.1% (comparable to pure PEEK), with negligible dimensional effects from humidity changes.
• Chemical Resistance:
With the exception of strong oxidizing acids such as concentrated sulfuric acid and nitric acid, it is virtually unreactive with organic solvents such as alcohols, hydrocarbons, and ketones (comparable to pure PEEK).
• Fatigue and Radiation Resistance:
The addition of carbon fibers significantly improves fatigue strength, making it suitable for long-term dynamic load scenarios.
Highly resistant to gamma rays and X-rays.
Advantages (compared to pure PEEK, metal, and other engineering plastics):
• Balanced lightweight and high strength: Its density is only 1/5 that of steel and 1/3 that of aluminum, yet its strength approaches that of titanium alloy, making it suitable for replacing steel with plastic.
• Outstanding high-temperature resistance: Its long-term operating temperature exceeds 250°C.
• High design flexibility: Performance can be customized by adjusting the carbon fiber content (10%-50%), fiber length (short fiber/long fiber), and orientation (unidirectional/multidirectional).
• Excellent fatigue resistance: The addition of carbon fibers increases the fatigue life of PEEK CA by 3-5 times compared to pure PEEK (suitable for long-term vibration scenarios).
Common Applications
PEEK CA sheet, with its combined properties of high strength, high temperature resistance, and lightweight, is widely used in high-end manufacturing:
1. Aerospace
• Structural components: UAV fuselage frames (heat resistant up to 280°C, high strength, and lightweight);
• Connectors and radomes: Conductive/wave-transmitting components for 5G satellite communication equipment (weather-resistant and UV-resistant).
2. Automotive
• Lightweight structural components: Electric vehicle battery pack brackets and motor housings (battery fluid corrosion-resistant, long-term operating temperature of 100-150°C);
• Chassis and suspension: Control arms and shock absorber brackets (high strength, impact resistance, and weight reduction).
3. Electronics and Semiconductors
• Precision equipment structural components: Frames and guide rails for semiconductor manufacturing equipment (heat resistant up to 260°C, vibration-resistant, and with minimal dimensional stability);
• 5G communications equipment: Base station filter brackets and high-frequency circuit board carriers (low dielectric constant and electromagnetic interference resistance).
4. Industrial Equipment
• Industrial Pumps and Valves: Corrosion-resistant valve housings and seals (resistant to strong acids and alkalis, high strength).
5. Rail Transit
• High-speed Rail/Subway Components: Bogie brackets, brake system connectors (vibration and fatigue resistance).
Usage Precautions
1. Temperature Limits:
• Long-term operating temperature: 30% CF-reinforced PEEK ≤ 250°C, 50% CF-reinforced PEEK ≤ 300°C; PEEK can withstand temperatures up to 350°C, but avoid contact with open flames (PEEK begins to decompose above 400°C).
2. Machining:
• Diamond-coated tools must be used for cutting (conventional tools are prone to wear), with cutting speeds ≤ 800 rpm and feed rates ≤ 0.1 mm/min (to avoid fiber pull and surface roughness).
• Avoid high-speed milling to prevent frictional heat generation that may cause PEEK decomposition and release trace amounts of irritating gases.
3. Chemical Compatibility:
• Avoid contact with strong oxidizing acids (such as concentrated nitric acid and aqua regia), as these may break the PEEK backbone.
• Long-term exposure to highly polar solvents (such as dimethyl sulfoxide) requires corrosion resistance testing (some fillers may swell in the solvent).
4. Interface Bonding and Aging:
• Carbon fiber surface treatment (such as sizing) directly affects interface strength. A sizing agent with good compatibility with PEEK should be selected.
• Long-term exposure to heat and humidity may cause hydrolysis of the interface; therefore, tensile strength should be regularly checked.
5. Conductivity and Electromagnetic Shielding:
• Continuous carbon fiber-reinforced PEEK CA is conductive and can be used for electromagnetic shielding. If insulation is required, chopped carbon fibers or an insulating coating should be used.
PEEK CA sheet is a high-performance composite material made of PEEK and carbon fiber. While retaining the core properties of PEEK, the "gold of plastics," it significantly enhances its strength and stiffness through the use of carbon fiber. It is a key metal replacement material in aerospace, automotive, electronics, and other fields. Its core value lies in its balanced design between lightweight and high performance, making it an indispensable functional material in high-end manufacturing.