Fiberglass GFRP properties
E-glass fiber accounts for approximately 90 % of the global production of reinforcing fibers for plastics. It is an inorganic glass filament with low alkali content (< 1 % Na₂O + K₂O) that, once embedded in a polymer matrix, forms the so-called glass fiber reinforced plastic composites (GFRP). Its excellent strength‑to‑weight ratio, dimensional stability, fire resistance, and moderate cost make it the most widely used reinforcing fiber in the construction, automotive, marine, and aerospace industries.
Chemical composition
Section titled “Chemical composition”The silica (SiO₂) content ranges between 52 % and 56 %, with a typical value of 54 %. The chemical composition of E-glass is designed to maintain low electrical conductivity and high moisture resistance.
| Oxide | Typical content (wt.%) |
|---|---|
| SiO₂ | 52 – 56 |
| Al₂O₃ | 12 – 16 |
| CaO | 12 – 25 |
| Others (MgO, B₂O₃, Na₂O, K₂O, etc.) | Balance to 100 % |
Mechanical properties
Section titled “Mechanical properties”E-glass fiber has a tensile strength of 3500 MPa (510 ksi) and a Young’s modulus of 72.5 GPa (10.5 Mpsi). Exact properties depend on filament diameter, surface treatment (sizing), and test conditions.
| Property | Value (SI) | Value (Imperial) |
|---|---|---|
| Tensile strength | 1950 – 3500 MPa | 283 – 510 ksi |
| Young’s modulus (tension) | 72.0 – 85.0 GPa | 10.4 – 12.3 Mpsi |
| Elongation at break | 2.6 – 4.9 % | — |
| Compressive strength | 4000 – 5000 MPa | 580 – 725 ksi |
| Shear modulus | 30 – 36 GPa | 4.4 – 5.2 Mpsi |
| Poisson’s ratio | 0.21 – 0.23 | — |
| Knoop hardness | 3000 – 6000 MPa | 435 – 870 ksi |
| Fracture toughness (K_IC) | 0.5 – 1.0 MPa·m¹/² | 0.46 – 0.91 ksi·in¹/² |
Physical properties
Section titled “Physical properties”The density of E-glass ranges from 2.55 to 2.63 g/cm³, equivalent to a specific weight of approximately 159–164 lb/ft³. It is an isotropic material at the elementary fiber level, and its surface is coated with a sizing that facilitates adhesion to the matrix.
| Property | Value (SI) | Value (Imperial) |
|---|---|---|
| Density | 2.55 – 2.63 Mg/m³ | 159 – 164 lb/ft³ |
| Water absorption (bare fiber) | < 0.1 % in 24 h | — |
Thermal properties
Section titled “Thermal properties”The glass transition temperature (Tg) of E-glass fiber is around 820–850 K (1016–1070 °F), while the maximum continuous service temperature reaches 620–630 K (656–674 °F). Its low coefficient of thermal expansion contributes to the dimensional stability of laminates.
| Property | Value (SI) | Value (Imperial) |
|---|---|---|
| Glass transition temperature | 820 – 850 K | 1016 – 1070 °F |
| Maximum service temperature | 620 – 630 K | 656 – 674 °F |
| Specific heat | 800 – 805 J/(kg·K) | 0.619 – 0.623 BTU/(lb·°F) |
| Thermal conductivity | 1.20 – 1.35 W/(m·K) | 2.25 – 2.53 BTU·ft/(h·ft²·°F) |
| Coefficient of thermal expansion | 4.9 – 5.1 × 10⁻⁶ K⁻¹ | 8.8 – 9.2 × 10⁻⁶ °F⁻¹ |
Electrical properties
Section titled “Electrical properties”The dielectric strength of E-glass ranges from 15 to 20 MV/m, and its dielectric constant at 1 MHz is between 6.13 and 6.33. Due to its low ionic conductivity (high resistivity), it is the preferred fiber for electrical insulation applications.
| Property | Value (SI) | Value (Imperial) |
|---|---|---|
| Dielectric strength | 15 – 20 MV/m | 381 – 508 V/mil |
| Dielectric constant (1 MHz) | 6.13 – 6.33 | — |
| Volume resistivity | 1 × 10²² – 1 × 10²³ × 10⁻⁸ Ω·m | — |
Chemical and environmental resistance
Section titled “Chemical and environmental resistance”E-glass fiber is highly resistant to fresh water, seawater, organic solvents, and strong acids, with a rating of 5/5 (excellent) in most environments. It shows slight sensitivity to strong alkalis (rating 4/5), which should be considered when designing matrices for alkaline environments.
| Environment | Resistance (1 = poor, 5 = excellent) |
|---|---|
| Flammability | 5 |
| Fresh water | 5 |
| Seawater | 5 |
| Organic solvents | 5 |
| Oxidation at 500 °C | 5 |
| Strong acids | 5 |
| Weak acids | 5 |
| Strong alkalis | 4 |
| Weak alkalis | 5 |
| UV radiation | 5 |
| Wear | 5 |
Applications
Section titled “Applications”Glass fiber reinforced plastic (GFRP) is used in more than 10 key industries, including construction, automotive, aerospace, marine, and wind energy. Its main advantages include high mechanical strength, light weight, corrosion resistance, and relatively low cost.
| Industry | Typical applications |
|---|---|
| Construction | Rebar, structural profiles, panels, roofing |
| Automotive | Body panels, leaf springs, underhood components |
| Aerospace | Radomes, fairings, cabin interiors |
| Marine | Boat hulls, masts, structural reinforcements |
| Wind energy | Wind turbine blades, nacelles, hybrid towers |
| Electronics | Printed circuit boards (PCB), insulators, enclosures |
| Sports | Fishing rods, golf clubs, bicycle frames |
Comparison with similar materials
Section titled “Comparison with similar materials”Compared to high-modulus carbon fiber, E-glass fiber offers 30–40 % lower tensile strength, but at approximately 5 times lower cost and significantly higher elongation at break, giving it greater deformation capacity before failure.
| Fiber | Tensile strength (MPa) | Young’s modulus (GPa) | Elongation (%) | Density (g/cm³) |
|---|---|---|---|---|
| E-glass | 3500 | 72.5 | 4.9 | 2.63 |
| S-glass | 4600 | 88.0 | 5.5 | 2.49 |
| PAN AS-4 carbon | 4000 | 245.0 | 1.6 | 1.80 |
| PAN IM-7 carbon | 4900 | 317.0 | 1.7 | 1.74 |
| Aramid (Kevlar 49) | 3650 | 124.0 | 2.5 | 1.44 |
Regulations and standards
Section titled “Regulations and standards”Glass fibers for reinforcement are covered by numerous ASTM standards, including ASTM D578 for glass fiber strands and ASTM D4029 for fabrics. International nomenclature follows ISO 2078, which classifies glass types (E, S, C, AR, etc.) according to their composition and suitability.
| Standard | Description |
|---|---|
| ASTM D578 | Specification for glass fiber strands for reinforced plastics |
| ASTM D4029 | Specification for finished glass fabrics |
| ISO 2078 | Textile glass — Designation of glass types |
| ASTM D2105 | Determination of tensile strength of glass strands |
| DIN 61850 | Textile glass — Designation and main types |
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the tensile strength of a unidirectional GFRP composite?
Section titled “What is the tensile strength of a unidirectional GFRP composite?”A unidirectional GFRP laminate with 60 % fiber volume fraction typically reaches 1000–1200 MPa in the fiber direction, which is 50–60 % of the dry fiber strength.
What is the density of a typical GFRP laminate?
Section titled “What is the density of a typical GFRP laminate?”The density of a laminate with polyester or epoxy matrix ranges from 1.8 to 2.0 g/cm³, approximately 70 % that of aluminum.
Up to what temperature can GFRP be used?
Section titled “Up to what temperature can GFRP be used?”The maximum continuous service temperature of a composite with a hot-cured polymer matrix is between 120 and 150 °C, although the fiber itself retains its properties up to over 600 °C.
Is GFRP resistant to acids?
Section titled “Is GFRP resistant to acids?”GFRP laminates with vinyl ester or epoxy matrix withstand exposure to most mineral and organic acids, achieving a rating of 5/5 in immersion tests, provided they do not contain hydrofluoric acid.
What is the thermal conductivity of GFRP?
Section titled “What is the thermal conductivity of GFRP?”The transverse thermal conductivity of a GFRP laminate is typically between 0.3 and 0.5 W/(m·K), about 80 times lower than that of carbon steel.
How much lighter is GFRP compared to steel?
Section titled “How much lighter is GFRP compared to steel?”With a density 4 times lower (1.9 vs. 7.85 g/cm³), a GFRP component can reduce weight by 50–60 % for the same specific stiffness, provided the design takes advantage of the reinforcement directions.
References
Section titled “References”- azom.com: https://www.azom.com/properties.aspx?ArticleID=764
- engineeringtoolbox.com: https://www.engineeringtoolbox.com/polymer-composite-fibers-d_1226.html
- steelnumber.com: https://www.steelnumber.com/en/search_form_eu.php