Modulus of Elasticity of Carbon Fiber: Technical Data & Engineering Reference

What Is the Elastic Modulus of Carbon Fiber?

The elastic modulus (also called Young's modulus or modulus of elasticity) measures a material's stiffness — how much it deforms under a given load. For carbon fiber reinforcement in structural engineering, this property determines how effectively the CFRP system controls deflection and crack widths in strengthened members.

Our standard carbon fiber products have an elastic modulus of ≥ 230 GPa, and our high-modulus plates reach ≥ 210 GPa. These values place carbon fiber in the same stiffness range as structural steel (200 GPa), but at roughly one-fifth the weight.

Carbon Fiber Modulus by Product Type

Here are the actual elastic modulus values from our product range, measured according to ASTM D3039 and ISO 527:

Product	Elastic Modulus	Tensile Strength	Elongation
Unidirectional Fabric 200g/m²	≥ 230 GPa	≥ 3,400 MPa	≥ 1.7%
Unidirectional Fabric 300g/m²	≥ 230 GPa	≥ 3,400 MPa	≥ 1.7%
Bidirectional Fabric 200g/m²	≥ 230 GPa (each dir.)	≥ 3,400 MPa	≥ 1.7%
Pultruded Plate 1.2mm	≥ 160 GPa	≥ 2,400 MPa	≥ 1.5%
High-Modulus Plate	≥ 210 GPa	≥ 2,800 MPa	≥ 1.3%

Why plates have lower modulus than fabric: The modulus values above are for the fiber itself (fabric) versus the composite laminate (plates). Pultruded plates include approximately 35% resin by volume, which has a much lower modulus (typically 3-4 GPa). The "rule of mixtures" means the composite modulus is lower than the pure fiber modulus: E_composite = E_fiber × V_fiber + E_resin × V_resin.

Comparison with Other Structural Materials

Material	Elastic Modulus (GPa)	Density (g/cm³)	Specific Modulus (GPa·cm³/g)
Standard Carbon Fiber	230	1.8	128
High-Modulus Carbon Fiber	294-390	1.8	163-217
Structural Steel (Q345)	200	7.85	25
Aluminum (6061-T6)	69	2.7	26
Glass Fiber (E-glass)	72	2.54	28
Aramid Fiber (Kevlar 49)	125	1.44	87
Concrete (C30)	30	2.4	13

The specific modulus (modulus divided by density) highlights carbon fiber's advantage: it is 5 times stiffer per unit weight than steel. This is why carbon fiber can replace much heavier steel elements in structural strengthening applications.

How Elastic Modulus Affects Structural Design

In CFRP structural strengthening design, the elastic modulus affects three key aspects:

1. Strain compatibility: The modulus determines how much load the CFRP carries at any given strain level. Higher modulus means the CFRP picks up more load at lower strains, which is beneficial for controlling deflection and crack widths under service loads. 2. Deflection control: Adding CFRP with high modulus to a beam increases its effective stiffness. The degree of stiffness increase depends on the CFRP area, modulus, and location relative to the neutral axis. For beams where deflection is the governing criterion, high-modulus CFRP plates may provide a more efficient solution than standard-modulus fabric. 3. Debonding risk: Higher modulus CFRP develops higher stresses at the bond line for the same applied strain. This can increase the risk of debonding at crack locations in the concrete. Design codes address this by limiting the maximum allowable strain in the CFRP — typically to 0.6-0.8% regardless of the ultimate strain capacity.

Standard vs High Modulus: Which to Specify?

Standard modulus (230 GPa) carbon fiber fabric is appropriate for the majority of structural strengthening applications. It provides a good balance of stiffness, strength, elongation (ductility), and cost. Use it for column confinement, beam flexural and shear strengthening, slab strengthening, and general structural upgrades. High modulus (210+ GPa composite) CFRP plates are preferred when deflection control is critical, when the design requires maximum stiffness per unit of added material, or when the existing structure has very high concrete strength (where the stiffer CFRP is needed to attract load away from the already-stiff concrete section).

Frequently Asked Questions

What is the modulus of a wet lay-up CFRP system after curing? The in-situ modulus of a wet lay-up system is typically 60-70% of the dry fiber modulus, because the resin occupies 40-50% of the laminate volume. For our 230 GPa fiber with typical wet lay-up, expect an effective laminate modulus of approximately 138-161 GPa. Does temperature affect the modulus of carbon fiber? The carbon fiber itself maintains its modulus up to extremely high temperatures (above 1,000°C in inert atmosphere). However, the epoxy resin matrix softens above its glass transition temperature (typically 60-80°C), causing the composite to lose effective stiffness. For structural strengthening applications, the service temperature should remain below 50°C without fire protection. How does the modulus of carbon fiber compare to glass fiber (GFRP)? Glass fiber has an elastic modulus of approximately 72 GPa — about one-third that of standard carbon fiber. This means carbon fiber is three times stiffer per unit area and roughly five times stiffer per unit weight compared to glass fiber. View our product datasheets or request engineering support for your project specifications.