Choosing the wrong carbon fiber can increase costs by 40% and cause project failure. This carbon fiber selection guide reveals how aerospace, automotive & robotics engineers select optimal materials .

carbon fiber selection guide

1. Understanding Carbon Fiber Fundamentals

Composition: >90% carbon atoms (from PAN or pitch precursors).

Key Properties:

  • High Strength-to-Weight Ratio (5x stronger than steel at 1/4 the weight)
  • High Stiffness-to-Weight Ratio
  • Low Thermal Expansion
  • Excellent Fatigue Resistance
  • Corrosion Resistance
  • Electrical Conductivity
  • Anisotropic: Properties vary with fiber direction.

2. Critical Selection Parameters

• Unidirectional (UD): Fibers all in 0°. Max strength/stiffness in primary direction. Laminates.

• Plain Weave: Simple over/under. Good stability, balanced properties. Easiest handling.

• Twill Weave (2×2, 4×4): Smoother drape, better conformability than plain. Complex contours.

• Satin Weave (e.g., 5HS, 8HS): Excellent drape, reduced crimp. Complex molds, high-quality surfaces.

• Non-Crimp Fabric (NCF): Stitched layers of UD or woven plies. Higher mechanical performance.

  • Small Tow (1K-12K):
  • Better drape, surface finish. Complex shapes, sports goods.
  • Large Tow (24K-50K+):
  • Lower cost per kg, higher deposition rates. Automotive, industrial.

• Unidirectional (UD): Fibers all in 0°. Max strength/stiffness in primary direction. Laminates.

• Plain Weave: Simple over/under. Good stability, balanced properties. Easiest handling.

• Twill Weave (2×2, 4×4): Smoother drape, better conformability than plain. Complex contours.

• Satin Weave (e.g., 5HS, 8HS): Excellent drape, reduced crimp. Complex molds, high-quality surfaces.

• Non-Crimp Fabric (NCF): Stitched layers of UD or woven plies. Higher mechanical performance.

some common weaves

carbon fiber weave

Weight per unit area (g/m² or oz/yd²). Affects laminate thickness, resin content, process time.

Ensure compatibility with chosen resin system (Epoxy, Polyester, Vinyl Ester, Bismaleimide, Thermoplastic).

Critical for fiber-matrix adhesion (bond strength). Specify based on resin type.

• Dry Fabric: Requires resin infusion.

• Prepreg: Pre-impregnated with resin (frozen storage). Consistent quality, easier layup.

• Chopped Strand/Mat: For molding compounds, short fiber reinforcement.

• Pultruded Profiles: Constant cross-sections (rods, tubes).

3. Application-Based Recommendations

  • Aerospace (Primary Structures): IM or HM fibers, Thin-ply UD or woven prepregs, High resin content control.
  • Automotive (Performance): SM or IM fibers, Large tow fabrics or NCF, Fast-cure prepregs/resin systems.
  • Sporting Goods (Bikes, Rackets): SM or IM fibers, 3K twill weaves for aesthetics, UD for performance zones, Prepreg or wet layup.
  • Consumer Electronics: HM fibers for stiffness, Thin weaves or UD for sleek profiles, EMI shielding grades.
  • Industrial/Robotics: SM or IM fibers, Cost-effective large tow fabrics, Epoxy or vinyl ester resins.
  • Marine: SM fibers, Woven fabrics (twill/satin), Vinylester or epoxy for corrosion resistance.

4. Supplier & Quality Considerations

  • Supplier Reputation: Certifications (AS9100, ISO 9001), Aerospace heritage.
  • Consistency: Batch-to-batch variability in properties, sizing, weight.
  • Data Availability: Access to certified mechanical property data (tensile, compressive, shear).
  • Lead Times & Availability: Critical for project planning.

5. Processing Considerations

  • Manual Layup (Wet): Choose fabrics with good drape (twill, satin), manageable areal weight.
  • Resin Infusion (VARTM, RTM): Select permeable fabrics/NCFs, compatible flow media.
  • Prepreg Layup: Requires autoclave/oven cure. Consider tack, out-life, cure cycle.
  • Compression Molding: Chopped fiber, SMC, or preformed fabrics.
  • Automated Processes (ATL/AFP): UD tapes or slit fabrics. Precision width control.

6. Cost Optimization

  • Evaluate: Large tow vs. small tow, Dry fabric vs. prepreg, Standard modulus vs. high modulus.

  • Minimize Waste: Efficient nesting, optimal cutting methods.

  • Process Efficiency: Faster cure resins, reduced labor techniques (automation, infusion).

7. Key Decision Flowchart

  1. Define Application Requirements: Loads (tension, compression, shear), stiffness, weight targets, environment, safety factors.
  2. Identify Critical Properties: Is strength, stiffness, impact resistance, or fatigue life paramount?
  3. Consider Manufacturing Method: Wet layup, prepreg, infusion, molding?
  4. Select Fiber Type & Tow Size: SM, IM, HM? 3K, 12K, 50K?
  5. Choose Weave & Areal Weight: UD, plain, twill, satin? What g/m²?
  6. Specify Resin Compatibility & Form: Prepreg or dry fabric? Compatible resin system.
  7. Evaluate Suppliers & Cost: Balance performance, quality, and budget.
  8. Prototype & Test: Validate selection before full-scale production.

8. Important Notes

  • Consult Experts: Engage material scientists or composite engineers early.
  • Test: Material data sheets are guides; perform application-specific testing.
  • Consider the Entire System: Fiber is only one component. Resin, core (if sandwich), and manufacturing process are equally critical.
  • Sustainability: Explore recycled carbon fiber options where performance allows.

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