Glassy Carbon vs Impervious Graphite
Ceramic · grade comparison
Glassy Carbon and Impervious Graphite are both ceramic grades. Glassy Carbon is the stronger of the two: tensile strength 130 MPa (18.9 ksi) against 25 MPa (3.63 ksi) for Impervious Graphite, about 5.2 times as much. Glassy Carbon is the more ductile: elongation 0.4% versus 0.3% for Impervious Graphite, and Glassy Carbon is harder (340 HV vs 50 HV). Glassy Carbon is lighter (1.42 g/cm³ vs 1.8 g/cm³ for Impervious Graphite) and Glassy Carbon is stiffer (35 GPa vs 12 GPa). On the shop floor, Impervious Graphite machines more easily (very good vs not recommended).
Glassy CarbonChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
Impervious GraphiteChoose it when the part is machined in volume.
Glassy Carbon vs Impervious Graphite: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all ceramic grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all ceramic grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Glassy CarbonImpervious Graphite
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Bulk Modulus
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Flexural Strength
Shear Strength
Fracture Toughness (K_IC)
Hardness, Vickers
Hardness, Knoop
Hardness, Mohs
Same in both: Poisson's Ratio 0.2
Physical
Density and transition temperatures.
Density
Porosity
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Same in both: Specific Heat Capacity 710 J/kg·K0.17 BTU/lb·°F
Electrical
Conductivity and insulation.
Electrical Resistivity
Volume Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Sintering / Firing Temperature
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 0%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every ceramic grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Glassy Carbon | Impervious Graphite |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Glassy Carbon vs Impervious Graphite — frequently asked
Is Glassy Carbon stronger than Impervious Graphite?
Yes. Glassy Carbon has a typical tensile strength of 130 MPa (18.9 ksi) against 25 MPa (3.63 ksi) for Impervious Graphite — about 5.2 times as much.
Which is cheaper, Glassy Carbon or Impervious Graphite?
Both sit in the same relative cost tier ($$$$, high); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, Glassy Carbon or Impervious Graphite?
Impervious Graphite. Its machinability rates very good (80/100) against not recommended (12/100) for Glassy Carbon.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Glassy Carbon and Impervious Graphite side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.