Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) are the two main FRP systems used in structural strengthening. Both are non-corrosive, lightweight, and high-strength — but their mechanical properties, cost, and ideal applications differ significantly. This guide helps engineers choose the right system.
Property Comparison
| Property | CFRP | GFRP (E-glass) | Steel (reference) |
|---|---|---|---|
| Tensile strength | 3,500-7,000 MPa | 1,500-3,000 MPa | 400-550 MPa |
| Elastic modulus | 230-640 GPa | 70-90 GPa | 200 GPa |
| Density | 1.5-1.6 g/cm³ | 2.1-2.5 g/cm³ | 7.85 g/cm³ |
| Elongation at break | 1.0-2.0% | 2.5-4.5% | 15-25% |
| Corrosion resistance | Excellent | Excellent (except in alkali) | Poor |
| Electrical conductivity | Conductive | Non-conductive | Conductive |
| Cost per kN of tensile capacity | Higher | Lower | Lowest |
| Thickness per layer | 0.11-0.17mm | 0.25-0.45mm | N/A |
When to Choose CFRP
CFRP is the right choice when:
Stiffness is critical. CFRP's modulus (230-640 GPa) exceeds steel's (200 GPa), meaning CFRP actually stiffens a structure more than equivalent steel reinforcement. This matters for deflection-controlled applications — bridges with excessive sag, beams that need to meet tighter deflection limits, and slabs with vibration issues. Space is limited. CFRP's higher strength-per-layer means fewer layers are needed. A single layer of 200 g/m² unidirectional carbon fiber fabric provides more tensile capacity than three layers of equivalent GFRP. For repairs where adding thickness is unacceptable (historical buildings, clearance-constrained beams), CFRP is often the only viable option. Long-term durability is paramount. CFRP has superior fatigue resistance and long-term creep performance compared to GFRP. For infrastructure with 50-100 year design life (bridges, dams, tunnels), CFRP's long-term performance justifies the higher initial cost.For flexural strengthening, our CFRP pultruded plates provide the highest stiffness per millimeter of thickness. For confinement, unidirectional fabric wraps are standard.
When to Choose GFRP
GFRP is the right choice when:
Cost is the primary driver. GFRP costs 40-60% less than CFRP per square meter. For large-area applications where multiple layers are acceptable (column confinement, slab strengthening over large areas), GFRP provides adequate performance at significantly lower cost. Electrical insulation is required. GFRP is non-conductive, making it suitable for applications near electrical equipment, in MRI rooms, or where electromagnetic interference must be avoided. CFRP is electrically conductive and can cause galvanic corrosion when in contact with metals in some environments. Higher elongation is needed. GFRP's higher elongation (2.5-4.5% vs 1.0-2.0% for CFRP) provides more ductile behavior. In seismic applications where energy absorption through deformation is desired, GFRP can provide better ductility.Cost-Effectiveness Analysis
The comparison is not simply "CFRP costs more." Because CFRP is stronger and stiffer per layer, fewer layers are needed — reducing labor, adhesive, and installation time. The true comparison is total installed cost per unit of added capacity:
| Application | CFRP Installed Cost | GFRP Installed Cost | Winner |
|---|---|---|---|
| Beam flexural strengthening | $150-250/m | $120-200/m (2-3 layers) | Similar |
| Column confinement | $180-300/m² | $100-180/m² | GFRP (lower cost, adequate stiffness) |
| Slab strengthening | $200-350/m² | $130-220/m² | GFRP for large areas, CFRP for clearance-limited |
| Shear strengthening | $170-280/m² | $120-200/m² | Application-dependent |
For a deeper understanding of FRP systems, see our FRP guide and carbon fiber properties data.
XINCHOR FRP Solutions
We manufacture both CFRP reinforcement systems (carbon fiber fabrics and plates) and the structural adhesives that bond them to concrete and steel substrates. Our engineering team can perform a cost-benefit analysis for your specific project and recommend the optimal FRP system.
Request an FRP system recommendation — send us your structural drawings and strengthening requirements for a detailed material specification and quotation.