Carbon fibre vs Invar
Carbon fibre and Invar are genuine alternatives to one another — a choice somebody actually makes — and differ on 2 measured properties, density most clearly.
Carbon fibre vs Invar
These are different kinds of thing (material, alloy). Fewer properties mean the same thing across both, so a like-for-like reading may not be available.
Carbon fibre
Filaments of near-pure carbon with extraordinary stiffness-to-weight, used in composites rather than alone.
Invar
An alloy that barely changes size with temperature — a coincidence of magnetism that turned out to be worth a Nobel Prize.
| Property | Carbon fibre | Invar |
|---|---|---|
| Density | 1.75–1.95 g/cm³ | 8.1 g/cm³ higher |
| Melting point Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 1427 °C |
| Tensile strength One of these is a directional measurement (along the fibre axis) and the other is not. The comparison holds only in that direction. | 3500–7000 MPa higher | 450–590 MPa |
Choosing between them
Invar is recorded as a substitute for Carbon fibre — cheaper, easier to work.
What it gives up: Eight times the density, which for a mould that has to be moved in and out of an autoclave is the deciding objection.
In this application, on the evidence cited above.