M55J
M55J is an ultra-high-modulus PAN-based carbon fiber rated at 540 GPa tensile modulus, 4020 MPa tensile strength and 1.91 g/cm3, available as 6K tow and as unidirectional, quasi-isotropic and fabric prepreg in epoxy or cyanate-ester matrices.
Reference datasheet — M55J 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-6K condition
M55J grades and fills
M55J is supplied in 4 conditions, soft to hard. TOW-6K is the default FabDigit quotes; the values on this page are for it.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Quasi-isotropic epoxy laminate [0/±45/90]s, Vf ≈ 58 % | Use for panels, mirror backplanes and bolted joints needing near-zero in-plane CTE and balanced bi-axial stiffness. | 620 | 0.55 | ||
UD cyanate-ester prepreg laminate, Vf ≈ 60 % | Choose for spacecraft optics and antennas where low moisture-induced dimensional change, low outgassing and >180 °C service are required. | 1,850 | 0.6 | ||
UD epoxy prepreg laminate, Vf ≈ 60 % | Standard aerospace UD prepreg lay-up — pick for maximum axial stiffness in booms, struts and optical benches up to ~150 °C. | 2,000 | 0.65 | ||
TOW-6KDefault M55J-6000 | Bare 6K tow as supplied on spools — use for prepregging, filament winding and weaving; properties are fiber-axis values. | 4,020 | 0.8 |
Supply forms, finishes and certifications
Ways M55J is supplied — form, process route, surface or paperwork — without a datasheet of their own. A reinforced fill changes stiffness and elongation; the branded products above carry the filled values.
| Option | What it is | Type |
|---|---|---|
FABRIC | Woven fabric / plain-weave laminate from M55J tow | Reinforcement |
What is M55J?
M55J is an ultra-high-modulus PAN-based carbon fiber rated at 540 GPa tensile modulus, 4020 MPa tensile strength and 1.91 g/cm3, available as 6K tow and as unidirectional, quasi-isotropic and fabric prepreg in epoxy or cyanate-ester matrices. It is specified for dimensionally stable space optics and booms, where 155 W/m·K axial thermal conductivity and near-zero-CTE layups limit thermal distortion; laminates serve to about 400 °C depending on resin. Strain to failure is only 0.8 %, so the fiber is brittle, costly and low-volume. M40J gives more strength margin, M60J more stiffness. M55J has a density of 1.91 g/cm³ (0.069 lb/in³), heavier than 72% of composite grades. M55J has a tensile strength of 4,020 MPa (583 ksi), stronger than 90% of composite grades. Elongation at break is 0.8% and the elastic modulus is 540 GPa (78.3 Msi).
What is M55J used for?
- space telescope structures
- satellite booms
- precision instrument frames
Advantages
- Stiff — 540 GPa (78.3 Msi), better than 98% of composite grades
- Good corrosion resistance — 92/100, better than 94% of composite grades
- Conducts heat well — 155 W/m·K (89.6 BTU/hr·ft·°F), better than 92% of composite grades
- Low moisture uptake — 0.1%, better than 85% of composite grades
- High service temperature — 400°C (752 °F), better than 78% of composite grades
Limitations
- High embodied carbon — 50 kg CO₂/kg, worse than 93% of composite grades
- Limited ductility — 0.8%, worse than 82% of composite grades
- Difficult to machine — 18/100, worse than 80% of composite grades
M55J properties
Typical room-temperature values for M55J-TOW-6K; bars are the position among composite grades.
Physical2
M55J has a density of 1.91 g/cm³ (0.069 lb/in³), heavier than 72% of composite grades.
Mechanical4
M55J has a tensile strength of 4,020 MPa (583 ksi), stronger than 90% of composite grades. Elongation at break is 0.8% and the elastic modulus is 540 GPa (78.3 Msi).
Thermal6
M55J is rated for continuous service to 400°C (752 °F). It conducts heat at 155 W/m·K (89.6 BTU/hr·ft·°F), better than 92% of composite grades. Thermal expansion is -1.1 µm/m·K (-0.611 µin/in·°F).
Electrical2
M55J has an electrical resistivity of 8×10⁻⁶ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 94% of composite grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of M55J takes about 750 MJ of energy and emits 50 kg of CO₂ — more than 93% of composite grades. Typical recycled content is 0%.
Manufacturability1
M55J's machinability is poor (18/100, worse than 80% 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. M55J is highlighted; hover a dot for its name, or open the interactive family chart.
Working with M55J
Is M55J easy to machine?
Cured laminates must be cut with diamond-coated or PCD tooling at high speed/low feed with vacuum dust extraction; UHM fibers splinter and delaminate easily, so back up exit faces and prefer abrasive waterjet for trimming.
Can M55J be welded?
Not weldable — joints are made by co-curing, secondary adhesive bonding (film epoxy) or bolted/bonded titanium fittings; avoid direct aluminium contact to prevent galvanic attack.
Can M55J be formed, bent or molded?
Prepreg is laid up by hand or AFP and autoclave cured (typ. 120–180 °C, 0.3–0.7 MPa); the fiber is brittle and low-elongation, so respect minimum bend radii and avoid sharp tow turns in winding or braiding.
M55J 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 from PAN precursor | ≤ 0.5 | 0.2 |
| sizing (epoxy-compatible, type 50B)surface size, burns off above ~400 °C | 0.4 – 1.2 | 0.7 |
| Na+K (alkali)trace impurities | ≤ 0.01 | |
| Cgraphitized PAN-based carbon | ≥ 99 (balance) |
What surface finishes work on M55J?
Post-cure dimensional stabilization plus moisture-desorption bake is standard for space optics; surfaces are sealed with a glass veil, primer or white thermal-control paint for UV and galvanic isolation.
How much does M55J cost?
M55J is a high-cost composite ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
M55J — frequently asked
What is M55J used for?
M55J is typically used for space telescope structures, satellite booms and precision instrument frames. In short: ultra-high-modulus space fiber; thermally conductive, dimensionally stable; low strain to failure.
What is the tensile strength of M55J?
M55J has a typical tensile strength of 4,020 MPa (583 ksi) — stronger than 90% of composite grades. Strength varies by condition: see the 4 listed tempers.
Is M55J easy to machine?
Not especially — machinability is rated poor (18/100, worse than 80% of composite grades). Cured laminates must be cut with diamond-coated or PCD tooling at high speed/low feed with vacuum dust extraction; UHM fibers splinter and delaminate easily, so back up exit faces and prefer abrasive waterjet for trimming.
Can M55J be welded?
Not weldable — joints are made by co-curing, secondary adhesive bonding (film epoxy) or bolted/bonded titanium fittings; avoid direct aluminium contact to prevent galvanic attack.
What surface finishes work on M55J?
Post-cure dimensional stabilization plus moisture-desorption bake is standard for space optics; surfaces are sealed with a glass veil, primer or white thermal-control paint for UV and galvanic isolation.
Can M55J be formed, bent or molded?
Prepreg is laid up by hand or AFP and autoclave cured (typ. 120–180 °C, 0.3–0.7 MPa); the fiber is brittle and low-elongation, so respect minimum bend radii and avoid sharp tow turns in winding or braiding.
What is the maximum service temperature of M55J?
M55J is rated for continuous use to about 400°C (752 °F), and briefly to 500°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does M55J cost?
M55J is a high-cost composite ($$$$), 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
- Torayca M55J Technical Data Sheet — Toray Composite Materials (2023)
- ASM Handbook Vol. 21 — Composites — ASM International (2001)
- MIL-HDBK-17 / CMH-17 Polymer Matrix Composites (typical UHM CFRP lamina values) — CMH-17 (2012)
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.