Fiber comparison
E-glass fiber vs S-2 glass fiber
Every value below is a typical room-temperature figure with its source, test method and conditions — the same dataset that drives the calculators.
Which to choose
The same family at a higher specification: S-2 glass is meaningfully stronger and somewhat stiffer than standard E-glass and holds its properties better at temperature, for a considerably higher price. E-glass is the default for general composite work; S-2 appears where strength matters enough to pay for it, such as ballistic panels and pressure vessels.
| Property | E-glass fiber | S-2 glass fiber | Difference |
|---|---|---|---|
| Density | 2.54 g/cm³ | 2.46 g/cm³ | E-glass fiber — 3% higher |
| Young's modulus E | 72.4 GPa | 86.9 GPa | S-2 glass fiber — 20% higher |
| Tensile strength | 3450 MPa | 4890 MPa | S-2 glass fiber — 42% higher |
Where these numbers come from
- Daniel & Ishai, Engineering Mechanics of Composite Materials, 2nd ed.
- AGY S-2 Glass product datasheet
Typical room-temperature values for learning and preliminary design; grades vary widely and a supplier datasheet always overrides a textbook figure. Confirm against the datasheet before design work.