M55J UD-EP
Matrix
UD-EP = 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.
Values for the UD-EP condition
Other M55J grades and fills
M55J is listed in 4 conditions; see the grade overview at M55J.
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-EPThis page 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 | — |
What is M55J UD-EP?
M55J UD-EP is M55J in the UD-EP condition — standard aerospace UD prepreg lay-up — pick for maximum axial stiffness in booms, struts and optical benches up to ~150 °C. M55J UD-EP has a tensile strength of 2,000 MPa (290 ksi), stronger than 77% of composite grades. Elongation at break is 0.65% and the elastic modulus is 320 GPa (46.4 Msi). M55J UD-EP has a density of 1.66 g/cm³ (0.06 lb/in³), lighter than 52% of composite grades. TOW-6K is the default condition FabDigit quotes; UD-EP is available on request or by drawing note.
Advantages
- Stiff — 320 GPa (46.4 Msi), better than 93% of composite grades
- Conducts heat well — 75 W/m·K (43.3 BTU/hr·ft·°F), better than 87% of composite grades
- Low moisture uptake — 0.1%, better than 85% of composite grades
Limitations
- High embodied carbon — 50 kg CO₂/kg, worse than 93% of composite grades
- Limited ductility — 0.65%, worse than 87% of composite grades
M55J UD-EP properties
Typical room-temperature values for M55J UD-EP; 18 are specific to this condition. Other listed values are M55J reference data and may not represent this condition. Bars are the position among composite grades.
Physical2
M55J UD-EP has a density of 1.66 g/cm³ (0.06 lb/in³), lighter than 52% of composite grades.
Mechanical4
M55J UD-EP has a tensile strength of 2,000 MPa (290 ksi), stronger than 77% of composite grades. Elongation at break is 0.65% and the elastic modulus is 320 GPa (46.4 Msi).
Thermal6
M55J UD-EP is rated for continuous service to 150°C (302 °F). It conducts heat at 75 W/m·K (43.3 BTU/hr·ft·°F), better than 87% of composite grades. Thermal expansion is -0.9 µm/m·K (-0.5 µin/in·°F).
Electrical2
M55J UD-EP has an electrical resistivity of 8×10⁻⁶ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 77% of composite grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of M55J UD-EP 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 UD-EP's machinability is poor (25/100, worse than 65% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M55J UD-EP
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.
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.
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) | — |
M55J UD-EP — frequently asked
What is M55J UD-EP used for?
M55J UD-EP 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 UD-EP?
M55J UD-EP has a typical tensile strength of 2,000 MPa (290 ksi) — stronger than 77% of composite grades. Strength varies by condition: see the 4 listed tempers.
Is M55J UD-EP easy to machine?
Not especially — machinability is rated poor (25/100, worse than 65% 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 UD-EP 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 UD-EP?
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 UD-EP 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 UD-EP?
M55J UD-EP is rated for continuous use to about 150°C (302 °F), and briefly to 500°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.