Glass types compared
Where to buy| Item | E-glass | S-glass / S2-glass | Source |
|---|---|---|---|
| Role | Electrical grade, low cost | Structural fiberglass of higher strength | FAA-H-8083-31B, p. 7-5 |
| Composition | Borosilicate | Magnesia-alumina-silicate | FAA-H-8083-31B, p. 7-5 |
| Impregnated-strand tensile strength | Reference | 15% higher than conventional glass fiber | AGY, S-2 Glass page |
| Elastic modulus | Reference | 25% higher than conventional glass fiber | AGY, S-2 Glass page |
| Stability at temperature | — | Strength and stability at elevated temperatures up to 760 °C (1,400 °F), fiber level | AGY, S-2 Glass page |
| Colour and forms | White; dry fabric or prepreg | White; dry fabric or prepreg | FAA-H-8083-31B, p. 7-5 |
The AGY percentages compare S2 Glass with conventional glass fiber and are manufacturer claims on the fiber, not laminate values. AGY does not state the test method on its product page.
E-glass or S-glass
E-glass
- Cost
- Lower than other composites
- Typical use
- Fairings, radomes, wing tips
- Fiber claim
- Reference
S-glass
- Cost
- Not stated in the sources
- Typical use
- Structural fiberglass
- Fiber claim
- 15% strand strength and 25% modulus over conventional glass (AGY)
One style pair: 6781 (S-type yarn) against 7781 (E-type yarn)
| Property | 6781 | 7781 |
|---|---|---|
| Warp / fill yarn | SCG 75 1/0 SC9 68 | ECDE 75 1/0 |
| Weave | 8 harness satin | 8 harness satin |
| Weight, oz/yd² (g/m²) | 8.92 (302) | 8.81 (299) |
| Dry thickness | 9.50 mil (0.24 mm) | 8.6 mil (0.22 mm) |
| Count, warp × fill per in | 57 × 54 | 57 × 54 |
| Breaking strength warp / fill, lbf/in | 550 / 450 | 570 / 450 |
Hexcel HexForce data sheets for 6781 and 7781. The dry fabric breaking strengths printed here do not show an S-glass advantage; the strength benefit AGY describes is in the fiber and the impregnated laminate, so a laminate comparison needs resin-specific data.
Where S-glass is used
The FAA handbook names S-glass and S2-glass as the structural fiberglass types and does not assign them to a part. AGY lists filament-wound structures such as rocket motor casings and aircraft fuel tanks, aircraft interior panels and ballistic protection as applications of S2 Glass on its product page.
In a repair the fabric is whatever the SRM or the material specification names. Replacing S-glass cloth with E-glass is a material change that approved data must allow.
Questions people actually ask
Is S2-glass the same as S-glass?
The FAA handbook treats S-glass and S2-glass together as the higher-strength structural types. S-2 Glass is AGY’s product name; the sources here do not define a further difference.
Does 6781 break at a higher load than 7781?
No, not on the Hexcel sheets: 550 / 450 lbf/in against 570 / 450 lbf/in warp / fill, as dry fabric.
Limits — when NOT to use this
- Fiber claims, not laminate allowables. AGY’s percentages are for the fiber against conventional glass.
- Not a substitution. The cloth and finish come from the SRM.
- No quartz here. Quartz fabric is not covered because no publishable data sheet could be verified.
Where to buy
Distributors coming soon.
Sources
- FAA-H-8083-31B, AMT Handbook — Airframe, Volume 1 (2023), Chapter 7 — fiberglass types, E-glass, S-glass and S2-glass (p. 7-5).
- AGY, S-2 Glass fiber product page — S2 Glass strength, modulus and temperature claims against conventional glass fiber.
- Hexcel HexForce Style 7781 Fiber Glass Fabric Product Data (DSF_7781) — 8.81 oz/yd², 8 harness satin, 57 × 54, 8.6 mil, 570 / 450 lbf/in.
- Hexcel HexForce Style 6781 Fiber Glass Fabric Product Data (DSF_6781) — 8.92 oz/yd², 8 harness satin, 57 × 54, 9.50 mil, 550 / 450 lbf/in, S-type yarn.