Carbon fiber + epoxy (CFRP)

Physical properties

Laser processing

⚠️ SERIOUS HAZARD: Thermal or mechanical processing of CFRP generates carbon fiber particulate and fumes from epoxy resin decomposition. Carbon fibers (diameter 5–7 µm) have a biodurable morphology similar to asbestos. Chronic exposure is a potential oncological risk. FFP3/P3 mask, HEPA extraction and sealed goggles are mandatory.

CO₂: CO2 laser cutting possible on thin sheets (0.5–2 mm) at high power: carbon absorbs IR radiation well. However, it generates carbon fiber particulate (potentially carcinogenic) and burns the epoxy matrix with toxic fumes. In industrial settings, dedicated HEPA extraction and filtration systems are used. Not recommended in unequipped spaces.

Diode: Carbon absorbs well at 450 nm: high-power diode laser marking is possible on glossy surfaces. The risk from carbon fiber particulate remains.

Fiber: Fiber lasers are used industrially for cutting and marking carbon fiber. Same safety warnings apply.

CNC / milling processing

CNC milling of CFRP requires PCD (Polycrystalline Diamond) cutters or tungsten carbide cutters with dedicated diamond coating for composites. Carbon fibers are extremely abrasive: HSS or standard carbide cutters wear out within a few centimeters. High spindle speed (24,000–30,000 RPM), medium-high feed rate. HEPA extraction nozzle directly on the workpiece: the particulate is invisible and hazardous. Consider wet machining in a water bath for small parts.

Post-processing

Sanding: Wet sanding with silicon carbide paper. Protruding fibers scratch the abrasive paper rapidly. FFP3 mask and nitrile gloves mandatory even for manual sanding. Do not sand dry.

Primer: The glossy 2x2 twill carbon fiber surface is already aesthetically finished. For matte painting, apply a light two-component epoxy primer (fills the woven texture). On high-aesthetic-quality parts, an epoxy clearcoat is applied to preserve appearance and protect from UV.

Gluing: Bondable with two-component structural epoxy adhesives after abrasion (80 grit) and degreasing with acetone. The surface must be matte after sanding: raw carbon fibers have low surface energy. In aerospace applications, film epoxy adhesives cured in autoclave are used.

Over time: Excellent corrosion and weathering resistance. UV degrades the surface epoxy matrix (yellows in 2–5 years) without affecting the fibers: UV-resistant clearcoat essential for outdoor applications. Elastic modulus and tensile strength are stable over time. Beware of galvanic corrosion in contact with metals (aluminum in particular): always use a layer of glass fiber or tape as an insulator.

Common defects

• Delamination under high-energy impact (CFRP is brittle in transverse impact compared to its exceptional in-plane resistance)
• Galvanic corrosion at the interface with aluminium or steel parts without electrical isolation
• Immediate tool wear with non-dedicated cutters (standard HSS or carbide) — diamond tools mandatory

Safety

Recommended PPE: mask_p3, eye_protection_goggles, gloves_nitrile

⚠️ WARNING: Carbon fibers are irritating to skin and eyes. Particulate generated during mechanical or thermal processing is potentially carcinogenic by inhalation. Nitrile gloves, FFP3/P3 mask and sealed goggles are mandatory. Dedicated HEPA extraction mandatory. Do not blow away residues. Uncured epoxy resin is a strong skin sensitizer.

Availability and formats

Commercial formats: plain weave / 2×2 twill fabric 200–400g/m², pre-laminated sheet 0.5–5mm, pultruded tubes and profiles, prepreg (requires autoclave)

Related materials

Sources

• ASTM D3039 — Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
• ISO 14125 — Fibre-reinforced plastic composites — Flexural properties
• Toray — Carbon Fiber Composite Materials datasheet