Carbon Fiber vs Glass Fiber: Which Is Better for 3D Printing?

Summary

The video compares carbon-fiber (CF) and glass-fiber (GF) reinforced 3D-printing filaments using 18 matched pairs, or 36 materials total, from the same brands and material types. The presenter analyzes results from earlier tests. The sample is useful for broad comparisons, but fiber content was not controlled and sometimes differed between paired filaments.

Why use fiber-reinforced filament?

Fibers generally make printed parts stiffer, less prone to bending and creep, and less susceptible to shrinkage. This can improve dimensional accuracy and printability, and may increase temperature resistance.

Trade-offs include greater brittleness, sometimes weaker layer adhesion, and abrasive filament that calls for a hardened nozzle. The presenter also notes that these filaments are often unsuitable for AMS units and can be moisture-sensitive, so drying may be needed.

Differences between CF and GF

• CF versions are usually more expensive and typically black or dark; GF can be available in lighter colors.
• CF filaments produce a more matte surface and are electrically conductive. The presenter cautions against putting CF parts in a microwave.
• In his microscope observations, CF fibers were commonly around 5–10 μm in diameter and GF fibers around 10–20 μm. He did not observe a clear difference in fiber length. These are observations, not universal specifications.
• GF may be usable in a microwave in principle, but the spool’s RF tag can be a limitation.

Mechanical-test findings

The results describe how often one reinforcement performed better across the tested pairs—not a guarantee for every filament or application.

• Tensile strength: CF was stronger in 67% of pairs; GF was stronger in 33%.
• Layer adhesion: GF performed better in 67% of pairs.
• Shear: In horizontally printed samples, CF performed better more often (61% versus 28% for GF). The smaller vertical-test dataset also leaned toward CF.
• Torsion: CF led in both orientations, while many results were ties. In horizontal tests, CF was better in 47% of pairs and GF in 18%; vertically, CF was better in 40% of pairs, while GF was better in two cases.
• Bending deformation (stiffness): This was one of the clearest differences: CF had less deformation in 89% of pairs. Smaller deformation indicates greater stiffness.
• Bending strength: Results generally favored CF, although the dataset was limited and the GF wins were small.
• Elastic modulus: CF performed better in every tested pair, again indicating greater stiffness.
• Izod impact: GF was tougher in most cases, but the difference was not large.
• Temperature resistance: The available results showed GF as equal to or worse than CF.
• Creep: CF generally showed less deformation under load, though GF performed better in four cases.

Overall takeaway

The presenter’s tests suggest that CF’s most consistent advantage is stiffness, including resistance to bending and creep. GF may have an advantage in layer adhesion and impact toughness. For many other properties, differences were mixed or modest, and results can vary by filament. The presenter emphasizes that the analysis did not account for differing fiber percentages in each filament.

Main speaker and source

The My Tech Fun presenter explains the filament differences and reports results from his own comparative tests. He says Polymaker sponsored the video, while stating that sponsorship did not affect its content.