IM8
IM8 is a Hexcel high-strength intermediate-modulus PAN carbon fiber at 5930 MPa tensile strength, 304 GPa tensile modulus, 1.95 % elongation and 1.79 g/cm3, giving both higher strength and higher stiffness than IM7.
Reference datasheet — IM8 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the TOW-12K-G condition
IM8 grades and fills
IM8 is supplied in 8 conditions, soft to hard. TOW-12K-G is the default FabDigit quotes; the values on this page are for it.
Compare all 8 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Quasi-isotropic epoxy laminate | Pick the 25/50/25 quasi-isotropic layup for multi-axial parts such as fuselage panels and skins; 950 MPa and 67 GPa are engineering estimates that include open-hole design margin. | 950 | 1.4 | ||
Woven fabric (5HS) epoxy laminate | Choose the 5-harness satin woven epoxy laminate for draping over curvature and better impact-damage tolerance, giving up in-plane performance to 950 MPa and 72 GPa versus unidirectional. | 950 | 1.3 | ||
Unidirectional PEEK (thermoplastic) laminate | Use the thermoplastic PEEK laminate when high toughness, unlimited prepreg shelf life and weldable or re-formable structure are required; 240 °C service and 2900 MPa at 0°. | 2,900 | |||
Filament-wound epoxy | Choose the filament-wound epoxy form for high-pressure vessels and solid rocket motor cases qualified by NOL ring or burst testing; 3000 MPa at 0°, but service limited to 90 °C. | 3,000 | 1.7 | ||
Unidirectional bismaleimide (BMI) laminate | Select the bismaleimide matrix for 180–230 °C continuous service such as engine nacelles and supersonic skins; Tg 295 °C, with 0° strength slightly lower at 3100 MPa. | 3,100 | 1.7 | ||
Unidirectional epoxy laminate, 60% Vf | Use these 0° values from the 177 °C-cured toughened epoxy prepreg for primary load paths: 3300 MPa and 185 GPa along the fiber, with service capped near 120 °C despite a Tg of 200 °C. | 3,300 | 1.7 | ||
Unsized tow | Choose the unsized tow when a custom sizing is applied or the fiber goes into metal-, ceramic-matrix or high-temperature thermoplastic systems; 5850 MPa and 450 °C, but no epoxy compatibility. | 5,850 | 1.9 | ||
TOW-12K-GDefault 12K tow, epoxy-compatible sizing | Pick the sized continuous dry 12K tow as the standard supply form for prepreg production, filament winding and braiding; 5930 MPa and 304 GPa are axial fiber values, not laminate allowables. | 5,930 | 2 |
What is IM8?
IM8 is a Hexcel high-strength intermediate-modulus PAN carbon fiber at 5930 MPa tensile strength, 304 GPa tensile modulus, 1.95 % elongation and 1.79 g/cm3, giving both higher strength and higher stiffness than IM7. It is supplied as sized and unsized 12K tow and as unidirectional, fabric and quasi-isotropic epoxy, BMI and PEEK prepregs, plus wet-wound forms, with laminates usable to about 400 °C in the highest-temperature matrices. Qualification base, availability and cost are less favourable than IM7, which remains the standard fallback for production airframe work. IM8 has a density of 1.79 g/cm³ (0.0647 lb/in³), heavier than 56% of composite grades. IM8 has a tensile strength of 5,930 MPa (860 ksi), stronger than 99% of composite grades. Elongation at break is 2% and the elastic modulus is 304 GPa (44.1 Msi).
What is IM8 used for?
- aerospace primary structures
- pressure vessels
- high-end sporting goods
Advantages
- Low moisture uptake — 0.05%, better than 94% of composite grades
- Stiff — 304 GPa (44.1 Msi), better than 91% of composite grades
- High service temperature — 400°C (752 °F), better than 78% of composite grades
Limitations
- High embodied carbon — 30 kg CO₂/kg, worse than 80% of composite grades
- Difficult to machine — 20/100, worse than 77% of composite grades
IM8 properties
Typical room-temperature values for IM8-TOW-12K-G; bars are the position among composite grades.
Physical2
IM8 has a density of 1.79 g/cm³ (0.0647 lb/in³), heavier than 56% of composite grades.
Mechanical5
IM8 has a tensile strength of 5,930 MPa (860 ksi), stronger than 99% of composite grades. Elongation at break is 2% and the elastic modulus is 304 GPa (44.1 Msi).
Thermal6
IM8 is rated for continuous service to 400°C (752 °F). It conducts heat at 5.4 W/m·K (3.12 BTU/hr·ft·°F), better than 66% of composite grades. Thermal expansion is -0.55 µm/m·K (-0.306 µin/in·°F).
Electrical1
IM8 has an electrical resistivity of 1.55×10⁻⁵ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 65% of composite grades. UV resistance is good.
Sustainability4
Producing a kilogram of IM8 takes about 480 MJ of energy and emits 30 kg of CO₂ — more than 81% of composite grades. Typical recycled content is 0%.
Manufacturability1
IM8's machinability is poor (20/100, worse than 77% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the composite family
Yield strength against density for every composite grade FabDigit runs. IM8 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with IM8
Is IM8 easy to machine?
Machine dry with diamond-coated or PCD tooling, or use abrasive waterjet; run high speed and low feed to limit delamination and fraying. The dust is conductive and hazardous, so enclosed extraction is required.
Can IM8 be welded?
The fiber itself is not weldable; PEEK/PEKK-matrix laminates can be ultrasonically, resistance- or induction-welded, while epoxy and BMI parts are adhesively bonded or mechanically fastened.
Can IM8 be formed, bent or molded?
Main route is hand or automated fiber placement of prepreg with autoclave cure at 177 °C; dry fiber can be processed by RTM, VARTM or wet filament winding. The high fiber modulus restricts minimum bend radius.
IM8 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Nresidual nitrogen | 3 – 5 | 4 |
| Osurface oxygen from electrochemical oxidation | 0.2 – 1 | 0.5 |
| sizing (epoxy-compatible)G-type sizing content | 0.6 – 1.3 | 1 |
| Na+Kalkali metal impurities | ≤ 0.01 | |
| Cgraphitized PAN-based carbon | ≥ 94 (balance) |
What surface finishes work on IM8?
Laminates take primer plus polyurethane topcoat, with copper mesh where lightning-strike protection is required. Use fiberglass plies or sealant at aluminium and steel joints to block galvanic corrosion.
How much does IM8 cost?
IM8 is a high-cost composite ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
IM8 — frequently asked
What is IM8 used for?
IM8 is typically used for aerospace primary structures, pressure vessels and high-end sporting goods. In short: higher strength than IM7; stiffer intermediate-modulus fiber; limited qualification base.
What is the tensile strength of IM8?
IM8 has a typical tensile strength of 5,930 MPa (860 ksi) — stronger than 99% of composite grades. Strength varies by condition: see the 8 listed tempers.
Is IM8 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 77% of composite grades). Machine dry with diamond-coated or PCD tooling, or use abrasive waterjet; run high speed and low feed to limit delamination and fraying. The dust is conductive and hazardous, so enclosed extraction is required.
Can IM8 be welded?
The fiber itself is not weldable; PEEK/PEKK-matrix laminates can be ultrasonically, resistance- or induction-welded, while epoxy and BMI parts are adhesively bonded or mechanically fastened.
What surface finishes work on IM8?
Laminates take primer plus polyurethane topcoat, with copper mesh where lightning-strike protection is required. Use fiberglass plies or sealant at aluminium and steel joints to block galvanic corrosion.
Can IM8 be formed, bent or molded?
Main route is hand or automated fiber placement of prepreg with autoclave cure at 177 °C; dry fiber can be processed by RTM, VARTM or wet filament winding. The high fiber modulus restricts minimum bend radius.
What is the maximum service temperature of IM8?
IM8 is rated for continuous use to about 400°C (752 °F), and briefly to 600°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does IM8 cost?
IM8 is a high-cost composite ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- HexTow IM8 Carbon Fiber Product Data Sheet — Hexcel Corporation (2020)
- HexPly 8552 Epoxy Matrix Product Data Sheet — Hexcel Corporation (2020)
- ASM Handbook Vol. 21 — Composites — ASM International (2001)
- CMH-17 Composite Materials Handbook, Vol. 2 & 3 — SAE International / CMH-17 (2012)
- ASTM D4018 — Tensile Properties of Continuous Filament Carbon and Graphite Fiber Tows — ASTM (2017)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.