CMC (Ceramic Matrix Composite)
A fiber-reinforced ceramic, heat resistant
Typical values for the temper in the title
In CMC, fibers (silicon carbide or carbon) sit in a ceramic matrix. The fibers "bridge" cracks, so instead of breaking suddenly like an ordinary ceramic, the material fails gradually and is much more damage tolerant. It keeps strength at very high temperatures, and is much lighter than superalloys.
It is used for hot parts in jet engines and gas turbines (instead of nickel alloys), ceramic brakes in high-end cars (C/SiC), and space heat shields.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 300-400 MPa | |
| Elongation A | 0.5% | |
| Modulus of elasticity E | 80-120 GPa | |
| Density ρ | 2.1-2.5 g/cm³ | |
| Machinability | diamond/laser | relative rating in the site database |
Structure: fiber and matrix
| Feature | Value | Meaning |
|---|---|---|
| Fiber | SiC or carbon | |
| Matrix | ceramic (usually SiC) | heat resistance |
| Fracture behavior | gradual, not sudden | damage tolerance |
Typical values per producer data.
Constructions and versions
In a composite the "material" is built together with the part: fiber, matrix, ply directions and fiber content are chosen. The same fibers in a different layup give very different properties.
| Version | Properties | When to choose it |
|---|---|---|
| SiC/SiC | better oxidation resistance | hot turbine parts |
| C/SiC | cheaper, good friction | ceramic brakes |
Applications
- Hot jet engine parts
- Gas turbine components
- Ceramic brakes
- Space heat shields
- Furnace components
Fabrication
Machining
By diamond and laser (database: "diamond / laser").
Production
Complex, expensive processes (vapor infiltration, pyrolysis).
Brittleness
Much more tolerant than an ordinary ceramic, but still not ductile like a metal.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| C/C (Carbon-Carbon) | 300 MPa | Not possible | C/C: for higher heat in protective atmosphere, oxidizes · material page |
| Silicon Nitride (Si₃N₄) | 700 MPa | Not possible | silicon nitride: an ordinary ceramic, brittle · material page |
| Inconel 718 | 1240–1380 / 1035–1170 MPa | Good — ERNiCrMo-6 | a superalloy: ductile, heavy, for lower heat · material page |
Common mistakes
Expecting metal-like ductility
It is damage tolerant, but not ductile.
Choosing C/SiC for long hot service in air
SiC/SiC is more oxidation resistant.
Designing without producer data
Properties depend strongly on the process.
Equivalents, standards and supply
| Standards | Producer specification |
|---|---|
| Forms | panel · airfoil |
| Producers | GE Aviation (CMC Shroud) · Safran · COI Ceramics |
Learn more
Values are typical and for comparison only. In composites, properties depend strongly on fiber direction, fiber content, layup and process. For design, rely on data for the specific laminate and tests. The standards mentioned are mainly test methods (ASTM D3039, D3410, D2344 and others). Sources: producer data and the METAL HUB materials database.
Updated: October 31, 2026