Carbon Fiber Solution
Overview
Carbon fiber is a polymer and is sometimes known as graphite fiber. It is a very strong material that is also very lightweight. Carbon fiber is five times stronger than steel and twice as stiff. Though carbon fiber is stronger and stiffer than steel, it is lighter than steel, making it the ideal manufacturing material for many products.
Carbon fiber can be thinner than a strand of human hair and gets its strength when twisted together like yarn, and then woven together. Carbon fibers are created from a process that is part chemical and part mechanical. The precursor is drawn into long strands and heated to a very high temperature without coming in contact with oxygen.
Classification
Ultra high modulus — tensile modulus >450 GPa
High modulus — tensile modulus 350–450 GPa
Medium modulus — tensile modulus 200–350 GPa
Low modulus high tensile — <100 GPa; tensile strength >3.1 GPa
Ultra high tensile strength — tensile modulus >4.5 GPa
PAN-based carbon fiber
Mesophase pitch based carbon fiber
Isotropic pitch based carbon fiber
Rayon carbon fiber
Vapor grown carbon fiber
Final heat treatment temperature >2000°C — use with high modulus fibers
Final heat treatment temperature >1500°C — use with high strength fibers
Final heat treatment temperature <1000°C — low modulus and low strength fibers
Properties
Raw Material
About 90% of carbon fibers are made from polyacrylonitrile (PAN). The remaining 10% are made from rayon or petroleum pitch. All are organic polymers — long strings of molecules bound together by carbon atoms. The precursor is chemically and mechanically processed into fibers through 5 key stages.
PAN is mixed with other ingredients and spun into fibers, then washed and stretched to align the molecules in the desired direction.
Fibers are heated in air at 200–300°C to chemically alter their bonding structure, converting linear atomic bonding to thermally stable laddered bonding.
Stabilised fibers are heated to 1000–3000°C in inert atmosphere. Non-carbon atoms are expelled and tightly bonded carbon crystals aligned along the fiber axis.
Fiber surface is slightly oxidized to improve bonding properties for composite manufacture — adding microscopic pits and grooves that increase surface area.
Fibers are coated with a sizing agent compatible with the intended resin matrix, protecting them during handling and improving adhesion in the final composite.
Molding
Carbon fiber is typically combined with a polymer resin matrix to form CFRP. The choice of molding process determines mechanical properties, surface finish, production speed and cost.
The simplest method. Carbon fiber fabric is laid into a mould by hand and resin applied by brush or roller. Low tooling cost, suitable for large and complex shapes but labour intensive with variable fiber volume fraction.
Dry fiber preforms are placed in a closed mould and resin injected under pressure. Faster cycle times than prepreg, excellent surface finish on both sides — suited to medium-volume structural components.
Pre-impregnated (prepreg) carbon fiber is cured in an autoclave under elevated temperature and pressure. Produces the highest fiber volume fraction and void-free laminates — industry standard for aerospace structural parts.
Cures prepreg laminates using vacuum bag pressure only in an oven. Lower capital cost with acceptable properties for secondary aerospace and automotive structures.
Compression moulding of sheet moulding compound (SMC) with chopped or continuous carbon fiber. High throughput and good dimensional accuracy for medium-performance parts.
Continuous fibers wet-wound onto a rotating mandrel with controlled tension and angle. Cost-effective for tubes, cylinders, pressure vessels and drive shafts requiring high hoop strength.
Fibers continuously pulled through a resin bath and shaped die to produce constant cross-section profiles. Most cost-effective for structural rods, beams, channels and tubes in high volume.
Dry fibers placed in an open mould, sealed under vacuum and resin drawn in by vacuum pressure. Good for large, complex geometries — lower tooling cost than RTM.
Short carbon fiber reinforced thermoplastic pellets injection moulded at high speed. Excellent for high-volume production of non-structural components with moderate stiffness requirements.
Carbon fiber reinforced filaments deposited layer-by-layer. Enables complex lattice structures, rapid prototyping and low-volume production without tooling investment.
Finishing
A clear coat applied over the raw carbon weave to protect and enhance the natural fiber pattern with a high-gloss, mirror-like finish.
The most common carbon fiber weave — a diagonal 2×2 twill gives the characteristic flowing appearance associated with premium carbon fiber products.
High-gloss polyurethane or epoxy topcoat — excellent UV resistance, scratch protection and premium visual appearance.
A flat, non-reflective topcoat — popular in automotive interiors and consumer electronics for a subtle, sophisticated look.
Chopped carbon fiber strands pressed into a mould creating a random swirl pattern. Stronger in complex shapes and unique in appearance.
Design Options
Engineers select fiber type, weave architecture, layup sequence and resin system to achieve exactly the stiffness, strength and weight target required. The table below compares common laminates against alternative materials.
Precautions
Carbon fiber is abrasive and quickly dulls standard tooling. Use diamond-coated or carbide tools, maintain low feed rates and high spindle speeds. Excessive heat causes delamination — use compressed air or mist coolant.
Autoclave systems must be validated for temperature and pressure uniformity. RTM injection equipment must control resin temperature, pot life and injection rate precisely to avoid dry spots or voids.
At LICHT, we treat every carbon fiber application as a systems engineering challenge. We select the fiber grade, weave architecture, resin system and manufacturing process as an integrated package — optimizing for target mechanical properties, surface finish, production volume and total cost. Our composite engineers work with customers from concept through first article inspection.
Finishing Notes
Depending on the surface characteristics of carbon fiber parts, the use of CFRP primer can supplement the thickness of the substrate. The primer provides the measurement in coating appearance, and the greater the thickness of the substrate primer, the greater the cost of metal coating utilisation and durability.
The thickness of the carbon rib is uniformly correlated with the appearance of the composite, ruling and negatively correlated with adhesion and durability. Some carbon fiber reinforcement processing applications use different colored resins to diversify the effect of carbon fiber texture design.
Carbon fiber composite waste should be disposed of responsibly. Cutting and grinding generates fine carbon fiber dust — a respiratory hazard. Always use appropriate PPE and dust extraction. End-of-life CFRP parts can be pyrolysed or mechanically recycled to recover reclaimed carbon fiber.
To customise the finish, the surface combines different colors of the growing stage using various color technologies. To preserve the surface treatment, the technology has achieved hue gold, silver, and white.
Applications
Carbon fiber footrests, frames and side guards — lightweight components that reduce overall chair weight without sacrificing impact resistance.
Brackets, fairings, interior panels and secondary structure for commercial and defense aircraft — certified to AS9100 Rev D.
Hoods, splitters, diffusers, A-pillars and monocoque tubs for performance vehicles where every gram saved improves lap times.
Prosthetic limb components, orthotic braces and surgical table tops — radiolucent, strong, and biocompatible when correctly finished.
Racing bicycle frames, rowing shells, tennis rackets, golf shafts and ski poles — where stiffness-to-weight ratio is the dominant design driver.
Robotic end-effectors, coordinate measuring machine arms and pick-and-place tooling — stiff, light and thermally stable.
