Kevlar 29 vs PBI Fiber (Celazole)
Composite · grade comparison
Kevlar 29 and PBI Fiber (Celazole) are both composite grades. Kevlar 29 is the stronger of the two: tensile strength 2,920 MPa (424 ksi) against 340 MPa (49.3 ksi) for PBI Fiber (Celazole), about 8.6 times as much. In exchange, PBI Fiber (Celazole) is the more ductile: elongation 28% versus 3.6% for Kevlar 29. Kevlar 29 is stiffer (70.5 GPa vs 5.6 GPa) and PBI Fiber (Celazole) runs hotter in service (300°C vs 180°C continuous).
Kevlar 29Choose it when strength drives the design.
PBI Fiber (Celazole)Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
Kevlar 29 vs PBI Fiber (Celazole): propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all composite 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 composite 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.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Limiting Oxygen Index
Max Service Temperature (short-term)
Same in both: Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
UV / Weathering Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
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 composite grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Kevlar 29 | PBI Fiber (Celazole) |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Kevlar 29 vs PBI Fiber (Celazole) — frequently asked
Is Kevlar 29 stronger than PBI Fiber (Celazole)?
Yes. Kevlar 29 has a typical tensile strength of 2,920 MPa (424 ksi) against 340 MPa (49.3 ksi) for PBI Fiber (Celazole) — about 8.6 times as much.
Which is cheaper, Kevlar 29 or PBI Fiber (Celazole)?
Both sit in the same relative cost tier ($$$$, high); the part price will be decided by machining time, tolerance and quantity rather than by the material.
When should I choose Kevlar 29 over PBI Fiber (Celazole)?
Pick Kevlar 29 when strength drives the design. Pick PBI Fiber (Celazole) when the part is bent, formed or impact-loaded, or when the part sees heat.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Kevlar 29 and PBI Fiber (Celazole) 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.