In one line
Based on the matrix material, composites are classified as polymer matrix composites (PMC), metal matrix composites (MMC) and ceramic matrix composites (CMC), and the matrix largely decides the working temperature and processing route.
Explained simply
The matrix is the "home" of the reinforcement. A plastic home is light and cheap but cannot take high heat. A metal home is tougher and handles more heat. A ceramic home survives extreme heat but is brittle on its own. Engineers choose the matrix first by asking "how hot will it get and how tough must it be?"
How it works
- Polymer matrix composites (PMC)
- Matrix: thermosets (epoxy, unsaturated polyester, vinyl ester, phenolic) or thermoplastics (nylon, PP, PEEK).
- Reinforcement: glass, carbon, aramid fibres.
- Features: low density, high specific strength, corrosion resistant, easy to mould; limited to relatively low service temperatures.
- Uses: aircraft and car parts, boat hulls, sports goods, wind turbine blades, PCB laminates (glass–epoxy).
- Metal matrix composites (MMC)
- Matrix: Al, Mg, Ti, Cu alloys.
- Reinforcement: SiC, Al2O3, B4C particles or fibres, boron or carbon fibres.
- Features: higher temperature capability than PMCs, high stiffness, wear resistance, good thermal and electrical conductivity, non-flammable.
- Uses: engine pistons and cylinder liners, brake rotors, aerospace structural parts, heat sinks for electronics.
- Ceramic matrix composites (CMC)
- Matrix: SiC, Al2O3, Si3N4, carbon.
- Reinforcement: SiC or carbon fibres, whiskers.
- Main purpose: improve the fracture toughness of brittle ceramics (fibres bridge and deflect cracks) while keeping high temperature strength and oxidation resistance.
- Uses: gas turbine parts, heat shields, high-performance brake discs (carbon–carbon and C/SiC), cutting tools.
Key formula
No formula. Rule of thumb on maximum service temperature: PMC < MMC < CMC.
Quick example
| Property | PMC | MMC | CMC |
|---|---|---|---|
| Density | Lowest | Medium | Low to medium |
| Temperature capability | Lowest | Medium | Highest |
| Toughness of matrix | Medium | High | Low (improved by fibres) |
| Typical use | Sports goods, auto panels | Pistons, brake rotors | Turbine parts, heat shields |
Common mistakes
- Saying fibres in CMCs are added mainly for strength; the main purpose is toughness.
- Giving glass fibre as the only reinforcement for every type.
- Forgetting that the matrix limits service temperature in PMCs.
How MU asks it
Often within "Classify composites" (5 marks) or as "Write a short note on MMC/PMC/CMC" (3 marks). For full marks: name the matrix and reinforcement, 2–3 properties and 2 applications for each, and the temperature comparison.