Fiberglass vs carbon fiber: choose fiberglass (E-glass) when you need low cost, electrical insulation, and proven corrosion resistance at a solid strength level; choose carbon fiber when maximum stiffness, minimum weight, or near-zero thermal drift justifies a material cost roughly 10–20× higher.
Fiberglass vs Carbon Fiber: The Short Answer
Both fibers reinforce pultruded FRP profiles, rods, and tubes — but they solve different problems. E-glass is the industry workhorse: inexpensive, strong enough for most structural and corrosion applications, and electrically non-conductive. Carbon fiber is the premium option: three to eight times stiffer, about 30% lighter, with nearly zero thermal expansion — at a much higher price. The table below puts the key numbers side by side.
Head-to-Head Comparison
| Property | Fiberglass (E-glass) | Carbon Fiber (PAN-based) |
|---|---|---|
| Tensile strength | ≈3,450 MPa | 3,500–7,000 MPa (grade-dependent) |
| Elastic modulus | ≈72–73 GPa | 230–600 GPa |
| Density | 2.54–2.60 g/cm³ | 1.75–1.95 g/cm³ |
| Elongation at break | ≈4.8% | 1.3–2.2% |
| Thermal expansion (fiber direction) | ≈5.0–5.3 × 10−6/°C | ≈−0.5 to +1 × 10−6/°C |
| Electrical behavior | Insulator (non-conductive) | Conductive |
| Impact tolerance | Higher — more elastic strain before failure | Lower — brittle, fails suddenly |
| Relative material cost | 1× (baseline) | ≈10–20× |
Note: these are fiber-level values drawn from standard material datasheets. A finished pultruded part’s properties depend on fiber volume fraction, fiber orientation, and the resin system (polyester, vinyl ester, or epoxy), so treat the numbers as a design guide, not a material certificate. Send us your load case and we’ll size the profile correctly.
Strength and Stiffness
On raw tensile strength, E-glass (about 3,450 MPa) and standard-modulus carbon fiber are surprisingly close. Carbon only pulls clearly ahead in the higher grades, which reach 7,000 MPa. The real difference is stiffness: carbon fiber’s modulus of 230–600 GPa is three to eight times E-glass’s 72–73 GPa.
That gap decides most real designs. If your part is limited by deflection rather than breakage — long unsupported spans, precision beams, thin-walled tubes that must not flex — carbon fiber is the answer, because stiffening an E-glass section usually means making it bigger and heavier. If the part only needs to carry load without bending much, E-glass does the job at a fraction of the cost.
One more note: E-glass’s higher elongation at break (≈4.8% vs 1.3–2.2%) means it absorbs more energy before failing. Under impact or shock loads, that ductility is a genuine advantage — carbon parts fail suddenly rather than bend.
Weight and Density
Carbon fiber (1.75–1.95 g/cm³) is roughly 30% lighter than E-glass (2.54–2.60 g/cm³). Combined with the stiffness gap, carbon gives the best stiffness-to-weight ratio of any common reinforcement fiber — which is why it dominates drones, robotics, and high-end sporting goods. E-glass is still far lighter than steel or aluminum, so for stationary industrial profiles — cable trays, handrails, grating — the weight saving rarely pays for the price premium.
Cost: Why Carbon Fiber Costs 10–20× More
Carbon fiber starts as a polyacrylonitrile (PAN) precursor that goes through controlled oxidation, carbonization at high temperature, and surface treatment — an energy-intensive, multi-step process. E-glass is simply melted and drawn from abundant silica sand. That raw-material and process difference is why carbon tows cost roughly 10–20× more per kilogram.
Pultruded carbon fiber parts are still economical when:
- Weight savings cascade through the whole assembly — aerospace, UAV, automation, moving machine parts.
- Stiffness requirements would otherwise force a much larger or heavier E-glass section.
- Dimensional stability under temperature swings is critical — metrology frames, optical mounts, antenna structures.
- A smaller, stiffer carbon section cuts freight, installation labor, or support-structure cost enough to offset the premium.
It’s worth running the numbers on the full assembly rather than material price alone. In most corrosion-service applications, though, E-glass wins on cost per meter with performance to spare.
Corrosion, UV, and Electrical Properties
- Corrosion: both fibers are chemically stable, so the resin system governs chemical resistance. E-glass needs the right resin in strong-alkali or wet service; carbon fiber’s main caveat is galvanic corrosion when it contacts metals — isolate it with a glass veil, coating, or insulating layer.
- UV: neither fiber is degraded by sunlight; outdoor durability is controlled by the resin and a UV-stable surface veil or gel coat, regardless of fiber type.
- Electrical: E-glass is an insulator, which is essential for utility crossarms, ladder rails near power lines, and antenna structures. Carbon fiber conducts electricity — an asset for EMI shielding, a hazard where electrical isolation is required.
When to Choose Fiberglass
- Utility crossarms, cable trays, and any part that must stay electrically non-conductive
- FRP/GFRP rebar and rock bolts where cost per meter drives the decision
- Ladder rails, window and door profiles, handrails, and grating
- General structural rods, tubes, and profiles in corrosive environments
- Parts exposed to impact or rough handling, where ductility prevents sudden failure
When to Choose Carbon Fiber
- Drone and UAV spars, robotic arms, and automation end-effectors
- Precision beams and metrology structures needing near-zero thermal drift
- High-end sporting goods, antenna supports, and lightweight stiff members
- Any design where deflection control is the limiting factor and section size is constrained
The Pultrusion Angle: You Don’t Always Have to Pick One
Both fibers come through the same pultrusion process — continuous rovings pulled through a resin bath and a heated die — so switching from E-glass to carbon fiber is a materials decision, not a process change. More interesting: they can be combined. Hybrid pultrusion places carbon fiber only where stiffness is needed (typically the outer surfaces of a beam, furthest from the neutral axis) and E-glass through the rest of the section. The result is near-carbon stiffness at a fraction of full-carbon cost — a practical middle path for spars, beams, and long straight members.
As a Nanjing-based FRP pultrusion manufacturer, we run E-glass, carbon fiber, and hybrid layups across our pultruded FRP profiles, and we support custom dies and OEM work for buyers with their own drawings. For carbon-specific parts, see our pultruded carbon fiber tubes; for cost-sensitive concrete reinforcement, our FRP rebar line uses E-glass. Send a drawing and we’ll recommend the fiber mix that fits both the load case and the budget.
FAQ
Is carbon fiber stronger than fiberglass?
In tensile strength they overlap: E-glass is around 3,450 MPa, carbon fiber 3,500–7,000 MPa depending on grade. Carbon fiber is clearly stiffer (three to eight times the modulus) and lighter, but at standard grades it is not dramatically “stronger.”
Is carbon fiber worth the extra cost?
Only when stiffness-to-weight or dimensional stability is the binding constraint. For most corrosion-resistant structural profiles, E-glass delivers the required performance at roughly one-tenth to one-twentieth of the material cost.
Can you combine fiberglass and carbon fiber in one profile?
Yes. Hybrid pultrusion puts carbon fiber where stiffness matters and E-glass everywhere else, giving near-carbon performance at much lower cost. It’s a standard option for beams and spars — ask about a hybrid layup for your section.
Is carbon fiber electrically conductive?
Yes. Carbon fiber conducts electricity and can trigger galvanic corrosion against metals like aluminum or steel. E-glass is an insulator. For utility, ladder, or antenna applications, choose accordingly.
Which is better for outdoor or marine use?
Both resist corrosion; the resin and surface veil control UV and chemical durability. E-glass is the common, cost-effective choice; carbon fiber is used where weight and stiffness justify the premium.
Does fiberglass or carbon fiber handle impact better?
Fiberglass. Its higher elongation at break lets it absorb impact energy and deform before failing, while carbon fiber is brittle and tends to fail suddenly. For parts that will see knocks, drops, or rough handling, glass is the safer fiber.
Not sure which fiber fits your profile? Send us your drawing, load requirement, and target budget — our engineers will recommend E-glass, carbon, or a hybrid layup and quote factory-direct. Contact us for a quote.
