C/C-SiC CVI (CVI C/SiC)
Matrix
also Sigrasic
Highest-performance route: pure SiC matrix, no free silicon, best strength and temperature capability — used for turbine and nozzle hardware, but slow and expensive with ~10–15 % residual porosity.
Values for the CVI condition
Other C/C-SiC grades and fills
C/C-SiC is listed in 5 conditions; see the grade overview at C/C-SiC.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Short/chopped carbon fibre, liquid silicon infiltrated | Near-net-shape pressed short-fibre grade for carbon-ceramic brake discs and clutches — cheapest route, isotropic in-plane, lower strength but excellent wear and thermal shock. | — | 45 | 0.2 | — |
Needled felt / 3D preform, liquid silicon infiltrated | Needled or 3D-woven preform giving through-thickness reinforcement — pick for thick sections, bolted joints and delamination-critical parts. | — | 90 | 0.2 | — |
LSI-2DDefault 2D carbon-fabric preform, liquid silicon infiltrated | Standard structural C/C-SiC: highest in-plane strength and damage tolerance, use for panels, hot structures, TPS and nozzle liners. | — | 110 | 0.3 | — |
PIP C/SiC | Autoclave-friendly route for large thin-walled shells; moderate strength, higher porosity, cheaper tooling than CVI but many densification cycles. | — | 240 | 0.5 | — |
CVIThis page CVI C/SiC | Highest-performance route: pure SiC matrix, no free silicon, best strength and temperature capability — used for turbine and nozzle hardware, but slow and expensive with ~10–15 % residual porosity. | — | 300 | 0.6 | — |
What is C/C-SiC CVI?
C/C-SiC CVI is C/C-SiC in the CVI condition — highest-performance route: pure SiC matrix, no free silicon, best strength and temperature capability — used for turbine and nozzle hardware, but slow and expensive with ~10–15 % residual porosity. C/C-SiC CVI has a tensile strength of 300 MPa (43.5 ksi), stronger than 53% of composite grades. Elongation at break is 0.6% and the elastic modulus is 95 GPa (13.8 Msi). C/C-SiC CVI has a density of 2.2 g/cm³ (0.0795 lb/in³), heavier than 80% of composite grades. LSI-2D is the default condition FabDigit quotes; CVI is available on request or by drawing note.
Advantages
- High service temperature — 1,500°C (2,732 °F), better than 100% of composite grades
- Good UV / weathering resistance — 98/100, better than 85% of composite grades
- Tough — resists crack growth — 25 MPa·√m (22.8 ksi·√in), better than 80% of composite grades
- Conducts heat well — 14 W/m·K (8.09 BTU/hr·ft·°F), better than 77% of composite grades
Limitations
- High embodied carbon — 60 kg CO₂/kg, worse than 96% of composite grades
- Difficult to machine — 8/100, worse than 94% of composite grades
- Limited ductility — 0.6%, worse than 88% of composite grades
- Heavy — 2.2 g/cm³ (0.0795 lb/in³), worse than 80% of composite grades
C/C-SiC CVI properties
Typical room-temperature values for C/C-SiC CVI; 11 are specific to this condition. Other listed values are C/C-SiC reference data and may not represent this condition. Bars are the position among composite grades.
Physical1
C/C-SiC CVI has a density of 2.2 g/cm³ (0.0795 lb/in³), heavier than 80% of composite grades.
Mechanical11
C/C-SiC CVI has a tensile strength of 300 MPa (43.5 ksi), stronger than 53% of composite grades. Elongation at break is 0.6% and the elastic modulus is 95 GPa (13.8 Msi).
Thermal6
C/C-SiC CVI is rated for continuous service to 1,500°C (2,732 °F). It conducts heat at 14 W/m·K (8.09 BTU/hr·ft·°F), better than 77% of composite grades. Thermal expansion is 1.5 µm/m·K (0.833 µin/in·°F).
Electrical1
C/C-SiC CVI has an electrical resistivity of 5×10⁻⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (75/100), worse than 55% of composite grades. UV resistance is excellent.
Sustainability3
Producing a kilogram of C/C-SiC CVI takes about 900 MJ of energy and emits 60 kg of CO₂ — more than 95% of composite grades. Typical recycled content is 0%.
Manufacturability2
C/C-SiC CVI's machinability is not recommended (8/100, worse than 94% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C/C-SiC CVI
Is C/C-SiC easy to machine?
Machine the porous C/C preform green with carbide/PCD tooling before siliconization; after conversion only diamond grinding, lapping, waterjet or laser is practical.
Can C/C-SiC be welded?
Not weldable — join by reaction brazing with Si/Ti-based fillers, ceramic adhesives, or mechanical fastening through CMC/metal bushings.
Can C/C-SiC be formed, bent or molded?
Made near-net-shape: prepreg lay-up or warm-pressed chopped-fibre moulding, cure, pyrolysis to C/C, then liquid-Si infiltration at 1450–1650 °C in vacuum; allow ~1–2 % pyrolysis shrinkage.
What surface finishes work on C/C-SiC?
CVD-SiC or SiC/glass seal coats for oxidation protection; friction faces are ground flat; no plating or anodizing, paints are pointless above 400 °C.
C/C-SiC chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C (carbon fibre reinforcement)PAN-based fibre, 2D fabric, needled felt or chopped bundles | 35 – 60 | 50 |
| SiC (reaction-formed matrix)formed by Si + pyrolytic C reaction during siliconization | 20 – 45 | 32 |
| Si (residual free silicon)LSI grades only; near zero in CVI/PIP grades | 1 – 15 | 8 |
| C (pyrolytic/resin-derived matrix carbonbalance, plus 1–5 % open porosity | balance | — |
C/C-SiC CVI — frequently asked
What is C/C-SiC CVI used for?
C/C-SiC CVI is typically used for high-performance automotive brake discs ("ceramic brakes"), clutch friction components, aircraft brake systems, high-temperature seals and friction bearings. In short: standard ceramic brake material; oxidation-resistant C/C upgrade; 1350 °C service temperature.
What is the tensile strength of C/C-SiC CVI?
C/C-SiC CVI has a typical tensile strength of 300 MPa (43.5 ksi) — stronger than 53% of composite grades. Strength varies by condition: see the 5 listed tempers.
Is C/C-SiC CVI easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 94% of composite grades). Machine the porous C/C preform green with carbide/PCD tooling before siliconization; after conversion only diamond grinding, lapping, waterjet or laser is practical.
Can C/C-SiC CVI be welded?
Not weldable — join by reaction brazing with Si/Ti-based fillers, ceramic adhesives, or mechanical fastening through CMC/metal bushings.
What surface finishes work on C/C-SiC CVI?
CVD-SiC or SiC/glass seal coats for oxidation protection; friction faces are ground flat; no plating or anodizing, paints are pointless above 400 °C.
Can C/C-SiC CVI be formed, bent or molded?
Made near-net-shape: prepreg lay-up or warm-pressed chopped-fibre moulding, cure, pyrolysis to C/C, then liquid-Si infiltration at 1450–1650 °C in vacuum; allow ~1–2 % pyrolysis shrinkage.
What is the maximum service temperature of C/C-SiC CVI?
C/C-SiC CVI is rated for continuous use to about 1,500°C (2,732 °F), and briefly to 1,800°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Ceramic Matrix Composites: Fiber Reinforced Ceramics and their Applications (Krenkel, ed.) — Wiley-VCH (2008)
- SIGRASIC C/SiC materials datasheet — SGL Carbon (2022)
- ASM Handbook Vol. 21: Composites — ASM International (2001)
- DLR Institute of Structures and Design — LSI C/C-SiC property reports — DLR (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.