Kevlar 149 UD-EP
Matrix
UD-EP = unidirectional Kevlar 149 / epoxy laminate
Pick when maximum specific tensile stiffness along one axis is required and compression loads are low.
Values for the UD-EP condition
Other Kevlar 149 grades and fills
Kevlar 149 is listed in 2 conditions; see the grade overview at Kevlar 149.
- FAB-EP
- UD-EP
Compare all 2 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Woven Kevlar 149 fabric / epoxy laminate | Pick for panels, radomes and impact-tolerant shells needing balanced biaxial stiffness and high damage tolerance. | — | 620 | 1.8 | — |
UD-EPThis page Unidirectional Kevlar 149 / epoxy laminate | Pick when maximum specific tensile stiffness along one axis is required and compression loads are low. | — | 1,750 | 1.6 | — |
What is Kevlar 149 UD-EP?
Kevlar 149 UD-EP is Kevlar 149 in the UD-EP condition — pick when maximum specific tensile stiffness along one axis is required and compression loads are low. Kevlar 149 UD-EP has a tensile strength of 1,750 MPa (254 ksi), stronger than 76% of composite grades. Elongation at break is 1.6% and the elastic modulus is 105 GPa (15.2 Msi). Kevlar 149 UD-EP has a density of 1.37 g/cm³ (0.0495 lb/in³), lighter than 67% of composite grades. Its glass-transition temperature is 360°C (680 °F).
Limitations
- Poor heat conductor — 0.05 W/m·K (0.0289 BTU/hr·ft·°F), worse than 87% of composite grades
- Degrades in UV without stabilisers — 25/100, worse than 86% of composite grades
- Limited service temperature — 120°C (248 °F), worse than 78% of composite grades
- Hard to polish — 25/100, worse than 76% of composite grades
Kevlar 149 UD-EP properties
Typical room-temperature values for Kevlar 149 UD-EP; 13 are specific to this condition. Other listed values are Kevlar 149 reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
Kevlar 149 UD-EP has a density of 1.37 g/cm³ (0.0495 lb/in³), lighter than 67% of composite grades. Its glass-transition temperature is 360°C (680 °F).
Mechanical6
Kevlar 149 UD-EP has a tensile strength of 1,750 MPa (254 ksi), stronger than 76% of composite grades. Elongation at break is 1.6% and the elastic modulus is 105 GPa (15.2 Msi).
Thermal8
Kevlar 149 UD-EP is rated for continuous service to 120°C (248 °F). It conducts heat at 0.05 W/m·K (0.0289 BTU/hr·ft·°F), worse than 87% of composite grades. Thermal expansion is -3 µm/m·K (-1.67 µin/in·°F).
Electrical4
Kevlar 149 UD-EP has an electrical resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (65/100), worse than 72% of composite grades. UV resistance is poor.
Sustainability4
Producing a kilogram of Kevlar 149 UD-EP takes about 285 MJ of energy and emits 16 kg of CO₂ — more than 65% of composite grades. Typical recycled content is 0%.
Manufacturability2
Kevlar 149 UD-EP's machinability is poor (22/100, worse than 73% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Kevlar 149 UD-EP
Is Kevlar 149 easy to machine?
Cut with hot knife, ultrasonic blade or shear-type scissors; drill laminates with special aramid (C-point/brad) drills and backing plate to avoid fuzz and delamination.
Can Kevlar 149 be welded?
Not weldable — join by adhesive bonding, mechanical fasteners with bushings, or co-cured composite splices.
Can Kevlar 149 be formed, bent or molded?
Processed as prepreg autoclave lay-up, RTM/VARTM or filament winding; the fiber is difficult to wet out and cannot be hot-formed, so drape and tack are controlled by the matrix.
What surface finishes work on Kevlar 149?
Seal cut edges with resin or edge tape to stop wicking and fuzzing; paint or gelcoat with UV-blocking pigment since bare aramid yellows and loses strength in sunlight.
Kevlar 149 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 |
|---|---|---|
| finish / sizingSurface finish level depends on yarn type (standard, epoxy-compatible, rubber-compatible) | 0.1 – 1 | 0.5 |
| poly(p-phenylene terephthalamide) (PPTA)Condensation polymer of p-phenylenediamine and terephthaloyl chloride; Kevlar 149 has the highest crystallinity/orientation of the series | balance | — |
Kevlar 149 UD-EP — frequently asked
What is Kevlar 149 UD-EP used for?
Kevlar 149 UD-EP is typically used for high-stiffness aerospace parts, pressure vessels and specialty ropes. In short: stiffest para-aramid grade; lowest aramid moisture pickup; hard to wet out.
What is the tensile strength of Kevlar 149 UD-EP?
Kevlar 149 UD-EP has a typical tensile strength of 1,750 MPa (254 ksi) — stronger than 76% of composite grades. Strength varies by condition: see the 2 listed tempers.
Is Kevlar 149 UD-EP easy to machine?
Not especially — machinability is rated poor (22/100, worse than 73% of composite grades). Cut with hot knife, ultrasonic blade or shear-type scissors; drill laminates with special aramid (C-point/brad) drills and backing plate to avoid fuzz and delamination.
Can Kevlar 149 UD-EP be welded?
Not weldable — join by adhesive bonding, mechanical fasteners with bushings, or co-cured composite splices.
What surface finishes work on Kevlar 149 UD-EP?
Seal cut edges with resin or edge tape to stop wicking and fuzzing; paint or gelcoat with UV-blocking pigment since bare aramid yellows and loses strength in sunlight.
Can Kevlar 149 UD-EP be formed, bent or molded?
Processed as prepreg autoclave lay-up, RTM/VARTM or filament winding; the fiber is difficult to wet out and cannot be hot-formed, so drape and tack are controlled by the matrix.
What is the maximum service temperature of Kevlar 149 UD-EP?
Kevlar 149 UD-EP is rated for continuous use to about 120°C (248 °F), and briefly to 300°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Kevlar Technical Guide (aramid fiber properties, K29/K49/K149) — DuPont (2017)
- ASM Handbook Vol. 21: Composites — ASM International (2001)
- ASTM D7269 — Tensile Testing of Aramid Yarns — ASTM International (2020)
- MatWeb / CES EduPack aramid fiber and aramid-epoxy laminate records — MatWeb LLC / Granta (2023)
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.