S-Glass
S-Glass is a magnesium-aluminosilicate reinforcement fibre, offered as S-2, S-994, R and HS variants, that carries more load than E-glass at a density of 2.49 g/cm³.
Reference datasheet — S-Glass is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the S-2 condition
S-Glass tempers and conditions
S-Glass is supplied in 3 conditions, soft to hard. S-2 is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Chinese domestic high-strength glass fibre | Cost-driven domestic substitute for S-glass in pressure vessels, sporting goods and armour backing; property scatter is wider than AGY S-2. | 4,300 | 5.2 | 630 HV | 1 W/m·K | |
R-Glass | European/3B HiPer-tex style high-strength fibre; slightly lower strength than S-2 but cheaper and widely available for wind and pressure-vessel parts. | 4,400 | 4.8 | 650 HV | 1 W/m·K | |
S-2Default S-2 Glass | Default commercial high-strength grade for filament winding, ballistic laminates and aerospace prepreg. | 4,890 | 5.7 | 640 HV | 1 W/m·K |
Supply forms, finishes and certifications
Ways S-Glass is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
S-994 | Original military-specification S-Glass | Certification |
What is S-Glass?
S-Glass is a magnesium-aluminosilicate reinforcement fibre, offered as S-2, S-994, R and HS variants, that carries more load than E-glass at a density of 2.49 g/cm³. Filament tensile strength is 4890 MPa with 86.9 GPa modulus, 5.7 % elongation and a fibre service ceiling near 650 °C, which is why it is used in aerospace, ballistic and pressure-vessel laminates; it is supplied as roving, woven fabric and prepreg. Cost is several times that of E-glass and stock availability is narrower, so it is normally reserved for parts where strength-to-weight or impact energy absorption governs. S-Glass has a density of 2.49 g/cm³ (0.09 lb/in³), lighter than 76% of glass grades. It melts at 1,500°C (2,732 °F). S-Glass has a tensile strength of 4,890 MPa (709 ksi), stronger than 100% of glass grades. Elongation at break is 5.7% and the elastic modulus is 86.9 GPa (12.6 Msi).
What is S-Glass used for?
- Aerospace composites
- Ballistic armor
- Pressure vessels
- Sporting goods
Advantages
- Ductile — tolerates forming and impact — 5.7%, better than 95% of glass grades
Limitations
- Hard to polish — 45/100, worse than 92% of glass grades
S-Glass properties
Typical room-temperature values for S-Glass-S-2; bars are the position among glass grades.
Physical4
S-Glass has a density of 2.49 g/cm³ (0.09 lb/in³), lighter than 76% of glass grades. It melts at 1,500°C (2,732 °F).
Mechanical11
S-Glass has a tensile strength of 4,890 MPa (709 ksi), stronger than 100% of glass grades. Elongation at break is 5.7% and the elastic modulus is 86.9 GPa (12.6 Msi).
Thermal5
S-Glass is rated for continuous service to 650°C (1,202 °F). It conducts heat at 1.5 W/m·K (0.838 BTU/hr·ft·°F), better than 58% of glass grades. Thermal expansion is 1.6 µm/m·K (0.889 µin/in·°F).
Electrical4
S-Glass has an electrical resistivity of 1×10¹³ Ω·m.
Chemical & Environmental2
Corrosion resistance is very good (72/100), worse than 53% of glass grades.
Sustainability4
Producing a kilogram of S-Glass takes about 75 MJ of energy and emits 4.2 kg of CO₂ — more than 63% of glass grades. Typical recycled content is 0%.
Manufacturability2
S-Glass's machinability is not recommended (12/100, worse than 68% of glass grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the glass family
Yield strength against density for every glass grade FabDigit runs. S-Glass is highlighted; hover a dot for its name, or open the interactive family chart.
Working with S-Glass
Is S-Glass easy to machine?
Cured S-glass laminates are highly abrasive — use PCD or diamond-coated routers/drills, high speed with low feed, and dust extraction; dry cutting glazes the tool quickly.
Can S-Glass be welded?
Not weldable; join composites by adhesive bonding or co-curing, mechanical fastening with oversize bearing plies.
Can S-Glass be formed, bent or molded?
Supplied as roving, fabric or prepreg; processed by filament winding, pultrusion, RTM or autoclave cure at 120–180 °C — silane sizing must match the resin (epoxy, phenolic, PA).
S-Glass chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| SiO2glass former | 64 – 66 | 65 |
| Al2O3raises modulus and strength | 24 – 25.5 | 25 |
| MgOnetwork modifier | 9.5 – 10.5 | 10 |
| Na2O+K2Oalkali kept low for durability | 0 – 0.3 | 0.1 |
| Fe2O3impurity | 0 – 0.2 | 0.05 |
| B2O3essentially boron-free | 0 – 0.1 | 0 |
What surface finishes work on S-Glass?
Edge-seal with resin or gelcoat to stop moisture wicking along fibres; peel-ply or light abrasion before bonding, no plating or anodizing applicable.
How much does S-Glass cost?
S-Glass is a high-cost glass ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
S-Glass — frequently asked
What is S-Glass used for?
S-Glass is typically used for aerospace composites, ballistic armor, pressure vessels and sporting goods. In short: strongest common glass fibre; higher modulus than E-glass; aerospace and ballistic grade.
What is the tensile strength of S-Glass?
S-Glass has a typical tensile strength of 4,890 MPa (709 ksi) — stronger than 100% of glass grades. Strength varies by condition: see the 3 listed tempers.
Is S-Glass easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 68% of glass grades). Cured S-glass laminates are highly abrasive — use PCD or diamond-coated routers/drills, high speed with low feed, and dust extraction; dry cutting glazes the tool quickly.
Can S-Glass be welded?
Not weldable; join composites by adhesive bonding or co-curing, mechanical fastening with oversize bearing plies.
What surface finishes work on S-Glass?
Edge-seal with resin or gelcoat to stop moisture wicking along fibres; peel-ply or light abrasion before bonding, no plating or anodizing applicable.
Can S-Glass be formed, bent or molded?
Supplied as roving, fabric or prepreg; processed by filament winding, pultrusion, RTM or autoclave cure at 120–180 °C — silane sizing must match the resin (epoxy, phenolic, PA).
What is the maximum service temperature of S-Glass?
S-Glass is rated for continuous use to about 650°C (1,202 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does S-Glass cost?
S-Glass is a high-cost glass ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- S-2 Glass Fiber Product Information — AGY (2020)
- ASM Handbook Vol. 21: Composites — Glass Fibers — ASM International (2001)
- Engineered Materials Handbook Vol. 1: Composites — ASM International (1987)
- HiPer-tex W2020 High Performance Glass Rovings — 3B Fibreglass (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.