Carbon fiber or fiberglass: which should I use for my part?
Use carbon fiber when stiffness and weight decide the design. Carbon fiber is about three times as stiff as E-glass fiber, at 230–240 GPa against about 72 GPa, and about 30% lighter[1][2]. Use fiberglass when cost, electrical insulation or toughness matter more.
3.2×stiffer: carbon fiber vs E-glass fiber
1.80 vs 2.58density, g/cm³
Conductscarbon fiber; fiberglass insulates
How do the fibers compare?
| Property | Carbon fiber (T300 / T700 grade) | E-glass fiber |
|---|---|---|
| Tensile modulus | 230–240 GPa[1] | about 72 GPa[2] |
| Tensile strength | 4,000–4,900 MPa[1] | about 3,400 MPa[2] |
| Density | about 1.80 g/cm³[3] | about 2.58 g/cm³[2] |
| Electrical | conductive[4] | insulating[5] |
| Behaviour before breaking | stays stiff, then breaks | stretches more, more forgiving |
| Price | higher | lower |
Fiber stiffness
Fiber values. A finished laminate is lower for both, but the ratio between them stays similar.
When is carbon fiber worth it?
- Stiffness limits the design: long arms, booms, poles, frames and plates that must not flex.
- Weight is paid for: drones, robots, moving machine parts and sports gear, where every gram costs energy or speed.
- Fatigue: parts loaded millions of times, such as fins, paddles and moving arms.
- Appearance: the woven look of 3K twill is part of the product.
When is fiberglass the better buy?
- Electrical insulation: PCB laminates, insulating sleeves and electrical housings. Carbon would short them.
- Large areas at low cost: boat hulls, tanks, panels and wall mesh.
- Radio transparency: antenna covers and housings around radios. Carbon blocks signals.
- Impact and abuse: fiberglass stretches more before it breaks, so it is more forgiving.
TipYou do not have to choose one. A hybrid laminate puts carbon where stiffness is needed and fiberglass elsewhere. Keep a fiberglass layer between carbon and any aluminum to stop galvanic corrosion.
A quick decision guide
| If your part… | Choose |
|---|---|
| must be as light and stiff as possible | carbon fiber |
| must insulate or pass radio signals | fiberglass |
| is large and price-driven | fiberglass |
| needs both stiffness and low cost | hybrid: carbon in the load path, fiberglass elsewhere |
Compare our carbon fiber woven fabric and E-glass fiberglass cloth, then send your part and quantity through the quote form. Free A4 swatches are available for carbon fiber fabric[6].
Sources
- Technical data sheets, T300 and T700 carbon fiber fabrics: fiber modulus 230–240 GPa, tensile strength 4,000–4,900 MPa (available on request)
- Wikipedia, “Glass fiber”: E-glass tensile strength about 3,445 MPa, modulus about 72 GPa, density about 2.58 g/cm³
- Carbon fiber chopped strand: PAN-based carbon fiber, density 1.80 g/cm³
- Carbon fiber woven fabric is thermally and electrically conductive
- Electric insulating glass fiber cloth
- Free A4 samples of carbon fiber fabric, fiberglass mesh and chopped strand mat