Kevlar K29
Grade
also AFRP
K29 = kevlar 29 reinforcement
Pick for armour, ballistic panels and ropes where energy absorption matters more than stiffness.
Values for the K29 condition
Other Kevlar grades and fills
Kevlar is listed in 7 conditions; see the grade overview at Kevlar.
Compare all 7 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
aramid/phenolic honeycomb & interior laminate | Aircraft interiors, ducting and Nomex-type honeycomb faces where FAR 25.853 fire/smoke/toxicity and V-0 rating dominate over strength. | — | 450 | 1.5 | 88 Shore D |
aramid/PA or PP organosheet | Stampable, weldable and re-formable aramid composite for high-rate parts and impact liners; lower stiffness and creep resistance than epoxy. | — | 450 | 2.5 | 78 Shore D |
epoxy laminate | Carbon supplies compressive strength and stiffness while aramid supplies damage tolerance — the usual fix for AFRP's weak compression. | — | 800 | 1.3 | 88 Shore D |
K29This page Kevlar 29 reinforcement | Pick for armour, ballistic panels and ropes where energy absorption matters more than stiffness. | — | 1,150 | 3.4 | 85 Shore D |
aramid/VE laminate | Marine and corrosion service: cheaper wet-layup/infusion than epoxy, better hydrolysis resistance than polyester, slightly weaker bond to aramid. | — | 1,150 | 1.7 | 85 Shore D |
Kevlar 149 reinforcement | Use where maximum specific stiffness and lowest moisture pickup are required (antennas, precision structures); most expensive and least tough. | — | 1,250 | 1.3 | 88 Shore D |
Epoxy MatrixDefault Kevlar 49 / epoxy laminate (UD, Vf ≈ 60 %) | Default structural aramid composite: best stiffness/strength and adhesion, for aerospace panels, filament-wound vessels and marine hulls up to ~120 °C. | — | 1,350 | 1.8 | — |
What is Kevlar K29?
Kevlar K29 is Kevlar in the K29 grade — pick for armour, ballistic panels and ropes where energy absorption matters more than stiffness. Kevlar K29 has a tensile strength of 1,150 MPa (167 ksi), stronger than 73% of composite grades. Elongation at break is 3.4% and the elastic modulus is 50 GPa (7.25 Msi). Kevlar K29 has a density of 1.36 g/cm³ (0.0491 lb/in³), lighter than 70% of composite grades. Its glass-transition temperature is 135°C (275 °F). Epoxy Matrix is the default condition FabDigit quotes; K29 is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 45 MPa·√m (41 ksi·√in), better than 100% of composite grades
- Ductile — tolerates forming and impact — 3.4%, better than 78% of composite grades
Limitations
- Degrades in UV without stabilisers — 25/100, worse than 86% of composite grades
- Difficult to machine — 18/100, worse than 80% of composite grades
- Limited service temperature — 120°C (248 °F), worse than 78% of composite grades
Kevlar K29 properties
Typical room-temperature values for Kevlar K29; 14 are specific to this condition. Other listed values are Kevlar reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
Kevlar K29 has a density of 1.36 g/cm³ (0.0491 lb/in³), lighter than 70% of composite grades. Its glass-transition temperature is 135°C (275 °F).
Mechanical12
Kevlar K29 has a tensile strength of 1,150 MPa (167 ksi), stronger than 73% of composite grades. Elongation at break is 3.4% and the elastic modulus is 50 GPa (7.25 Msi).
Thermal9
Kevlar K29 is rated for continuous service to 120°C (248 °F). It conducts heat at 0.45 W/m·K (0.26 BTU/hr·ft·°F), better than 56% of composite grades. Thermal expansion is -2 µm/m·K (-1.11 µin/in·°F).
Electrical5
Kevlar K29 is an electrical insulator with a dielectric strength of 18 kV/mm (457.2 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 54% of composite grades. UV resistance is poor.
Sustainability3
Producing a kilogram of Kevlar K29 takes about 250 MJ of energy and emits 14 kg of CO₂ — more than 54% of composite grades. Typical recycled content is 0%.
Manufacturability2
Kevlar K29's machinability is poor (18/100, worse than 80% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Kevlar K29
Is Kevlar easy to machine?
Fibers do not cut cleanly — use sharp carbide/PCD shear-angle or serrated 'Kevlar' router bits, back-up plates, or waterjet/laser trimming to avoid fuzzing and delamination.
Can Kevlar be welded?
Thermoset epoxy laminates cannot be welded; join by secondary bonding with film/paste adhesive or bolted joints with bushed holes (thermoplastic-matrix variants can be resistance or ultrasonic welded).
Can Kevlar be formed, bent or molded?
Processed as prepreg autoclave/oven cure (120–180 °C), resin infusion/RTM, wet layup or filament winding; aramid fabric drapes well but must be dried before cure to avoid moisture-induced porosity.
What surface finishes work on Kevlar?
Cut edges must be sealed with resin or edge tape; paint or gel-coat with UV-blocking pigment is essentially mandatory for outdoor service, and surfacing film gives a smooth paintable skin.
Kevlar 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 |
|---|---|---|
| para-aramid fiber (PPTA, poly-p-phenylenfiber volume fraction ≈ 55–62 % for prepreg laminates | 50 – 65 | 60 |
| sizing / finishfiber surface treatment for adhesion | 0.1 – 1 | 0.5 |
| epoxy resin (DGEBA / amine or dicyandiammatrix; substituted by vinyl ester, phenolic or thermoplastic in other variants | ≥ 35 (balance) | — |
Kevlar K29 — frequently asked
What is Kevlar K29 used for?
Kevlar K29 is typically used for body armor, ballistic panels, aerospace interior and secondary structure panels, filament-wound pressure vessel overwraps, boat hulls and impact skins and sports equipment shells. In short: aramid impact laminate.
What is the tensile strength of Kevlar K29?
Kevlar K29 has a typical tensile strength of 1,150 MPa (167 ksi) — stronger than 73% of composite grades. Strength varies by condition: see the 7 listed tempers.
Is Kevlar K29 easy to machine?
Not especially — machinability is rated poor (18/100, worse than 80% of composite grades). Fibers do not cut cleanly — use sharp carbide/PCD shear-angle or serrated 'Kevlar' router bits, back-up plates, or waterjet/laser trimming to avoid fuzzing and delamination.
Can Kevlar K29 be welded?
Thermoset epoxy laminates cannot be welded; join by secondary bonding with film/paste adhesive or bolted joints with bushed holes (thermoplastic-matrix variants can be resistance or ultrasonic welded).
What surface finishes work on Kevlar K29?
Cut edges must be sealed with resin or edge tape; paint or gel-coat with UV-blocking pigment is essentially mandatory for outdoor service, and surfacing film gives a smooth paintable skin.
Can Kevlar K29 be formed, bent or molded?
Processed as prepreg autoclave/oven cure (120–180 °C), resin infusion/RTM, wet layup or filament winding; aramid fabric drapes well but must be dried before cure to avoid moisture-induced porosity.
What is the maximum service temperature of Kevlar K29?
Kevlar K29 is rated for continuous use to about 120°C (248 °F), and briefly to 200°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in Kevlar K29?
Yes — Kevlar K29 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- Kevlar Aramid Fiber Technical Guide — DuPont (2017)
- ASM Handbook Vol. 21 — Composites — ASM International (2001)
- CMH-17 (MIL-HDBK-17) Composite Materials Handbook, Vol. 3 Polymer Matrix Composites — SAE International / CMH-17 (2012)
- Aramid fabric prepreg datasheets — Hexcel / Toray Advanced Composites (2022)
- CES EduPack material data — aramid fiber reinforced epoxy — Granta/Ansys (2021)
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.