Glass fiber + epoxy (GRP)

Physical properties

Laser processing

⚠️ SERIOUS HAZARD: Thermal cutting and engraving of fiberglass generate glass fiber dust (amorphous silica) and pyrolyzed epoxy resin particulate. Inhaled glass fibers deposit permanently in the lungs. FFP3/P3 mask, dedicated HEPA extraction and sealed goggles are mandatory, non-negotiable.

CO₂: CO2 laser cutting of fiberglass is technically possible at high power but strongly discouraged in maker settings. Glass fiber does not vaporize: it burns the epoxy matrix and leaves protruding fibers on the edges. The silica particulate generated is abrasive to laser optics and hazardous to health. In industrial settings, dedicated HEPA extraction systems are used.

Diode: Not applicable.

Fiber: Used industrially for cutting thin fiberglass laminates. The risk from glass fiber dust remains.

CNC / milling processing

CNC milling of fiberglass is feasible but demanding. Requires dedicated solid tungsten carbide cutters (never HSS): glass fibers are highly abrasive and wear out HSS tooling in just a few passes. High spindle speed (18,000–25,000 RPM), moderate feed rate. HEPA extraction directly on the workpiece mandatory: glass fiber particulate is invisible and hazardous. Consider using air-mist coolant to reduce temperatures.

Post-processing

Sanding: Sanding possible with silicon carbide abrasive paper, always wet to suppress glass fiber particulate. FFP3 mask mandatory even for manual sanding. Wear nitrile gloves: protruding fibers embed in the skin.

Primer: mandatory. For aesthetic painting, first apply a two-component epoxy primer or finishing gelcoat to fill surface porosity and ensure adhesion.

Gluing: Bondable with two-component epoxy adhesives, ideally from the same resin system used in the laminate. The surface must be abraded (80 grit) and degreased. The structural joint can be reinforced with glass fiber fabric plies wet out with resin (wet lay-up).

Over time: Excellent resistance to weathering, UV (if protected by gelcoat or paint) and humidity. The epoxy matrix slowly degrades under UV without protection (yellows and becomes chalky on the surface). Immune to corrosion. Cyclic mechanical fatigue resistance lower than carbon fiber.

Common defects

• Ply delamination due to porosity in the laminate or incorrect resin/hardener ratio
• Visible surface print-through if the fabric is too close to the gelcoat layer
• Extremely rapid HSS tool wear during milling — use tungsten carbide exclusively

Safety

Recommended PPE: mask_p3, eye_protection_goggles, gloves_nitrile

⚠️ WARNING: Glass fibers are irritating to the skin (intense itching), eyes and respiratory tract. During mechanical or thermal processing, wear nitrile gloves, FFP3/P3 mask, sealed goggles. Do not blow away residues with compressed air. Dedicated HEPA extraction mandatory. Uncured epoxy resin is a skin sensitizer: avoid direct skin contact.

Availability and formats

Commercial formats: plain weave fabric 100–600g/m², glass fibre mat 300–600g/m², pre-laminated sheet 1–5mm, pultruded tubes and profiles

Related materials

Sources

• ISO 14125 — Fibre-reinforced plastic composites — Determination of flexural properties
• ASTM D3039 — Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
• Gurit — Guide to Composites (fibreglass processing manual)