The tensile properties of glass fiber-reinforced polymer (GFRP) reinforcing bars are determined in accordance with ASTM D7205 — the standard test method for tensile properties of fiber-reinforced polymer matrix composite bars. The values tabulated below represent reference values for vinyl ester GFRP rebar with a glass fiber content by weight of 70% to 80%. Tensile strength varies according to bar diameter and manufacturing process. The design tensile strength used in structural calculations per ACI 440.1R is obtained by multiplying the guaranteed strength by an environmental reduction factor CE — commonly 0.7 to 0.8 for GFRP in concrete exposed to earth and weather.
Mechanical Properties — GFRP Rebar per ASTM D7205
| Bar Size (US / Metric) |
Nominal Diameter (mm) |
Nominal Cross‑sectional Area (mm²) |
Reference Tensile Strength (MPa) |
Tensile Modulus (GPa) |
Ultimate Strain at Break (%) |
|---|---|---|---|---|---|
| #3 (10M) | 9.5 | 71 | 830 | 46 | 1.8 |
| #4 (13M) | 12.7 | 129 | 780 | 46 | 1.7 |
| #5 (16M) | 15.9 | 199 | 730 | 45 | 1.6 |
| #6 (19M) | 19.1 | 284 | 690 | 45 | 1.5 |
| #7 (22M) | 22.2 | 387 | 650 | 44 | 1.5 |
| #8 (25M) | 25.4 | 510 | 620 | 44 | 1.4 |
Notes: The tensile strength and modulus values in the table are for the longitudinal direction of the bar. GFRP rebar is anisotropic; transverse properties are lower and are not used in conventional flexural or shear design. The ultimate strain is the strain at rupture under pure tension. Unlike steel rebar, GFRP does not yield — the stress-strain relationship is linear to failure. Tensile strength varies according to bar diameter and manufacturing process; consult the bar manufacturer for lot-specific test reports when designing critical members.
Source: Advanced FRP Systems Engineering Data. Free to cite with link. Last verified: 2026-05-15.
For rebar specifications and application guidance, see GFRP Rebar.