Kevlar 29
Kevlar 29 is a low-modulus, high-tenacity para-aramid fiber (density 1.44 g/cm³, tensile strength 2920 MPa, elastic modulus 70.5 GPa, elongation 3.6 %) that serves as the baseline industrial aramid grade.
Reference datasheet — Kevlar 29 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.
Kevlar 29 grades and fills
Kevlar 29 is supplied in 5 conditions, soft to hard.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Woven Kevlar 29 fabric / epoxy laminate, Vf ≈ 50 % | Balanced quasi-isotropic panels — canoe hulls, protective shells, drone and motorsport bodywork with damage tolerance. | 500 | 2.2 | ||
Unidirectional Kevlar 29 / epoxy laminate, Vf ≈ 60 % | Use where axial tensile stiffness and impact/energy absorption matter and compressive load is low (pressure-vessel overwrap, panels, radomes). | 1,350 | 2 | ||
Braided/twisted K29 rope and sling cordage | Pick for low-stretch, non-conductive lifting slings, mooring and tow lines where creep and UV exposure are controlled. | 1,800 | 3 | ||
Highly fibrillated aramid pulp | Asbestos-replacement thickener/reinforcement for brake pads, clutch facings, gaskets, sealants and drilling fluids. | 2,900 | 3.6 | ||
Kevlar 29 AP | Pick when ~15 % more break strength per denier is needed in the same K29 modulus class (ropes, slings, thinner ballistic packs). | 3,400 | 3.6 |
Supply forms, finishes and certifications
Ways Kevlar 29 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 |
|---|---|---|
STAPLE | Cut/staple fibre and floc | Supply form |
YARNDefault | Continuous filament yarn | Supply form |
FABRIC | Woven ballistic fabric | Reinforcement |
What is Kevlar 29?
Kevlar 29 is a low-modulus, high-tenacity para-aramid fiber (density 1.44 g/cm³, tensile strength 2920 MPa, elastic modulus 70.5 GPa, elongation 3.6 %) that serves as the baseline industrial aramid grade. Engineers specify it where energy absorption, cut resistance and strength-to-weight matter more than laminate stiffness; it is supplied as continuous yarn, staple, pulp, woven fabric, rope and unidirectional or fabric epoxy prepreg. Service is limited to about 180 °C, the fiber is hygroscopic (moisture regain ~4–7 %) and loses strength rapidly under sunlight, so exposed parts need a UV-blocking cover. Move to Kevlar 49 when composite stiffness governs. Kevlar 29 has a density of 1.44 g/cm³ (0.052 lb/in³), lighter than 61% of composite grades. Its glass-transition temperature is 360°C (680 °F). Kevlar 29 has a tensile strength of 2,920 MPa (424 ksi), stronger than 80% of composite grades. Elongation at break is 3.6% and the elastic modulus is 70.5 GPa (10.2 Msi).
What is Kevlar 29 used for?
- ballistic vests
- ropes and cables
- protective fabrics
- tire reinforcement
- friction materials
Advantages
- Ductile — tolerates forming and impact — 3.6%, better than 81% of composite grades
Limitations
- Degrades in UV without stabilisers — 20/100, worse than 94% of composite grades
- Absorbs moisture — dry before molding — 4%, worse than 93% of composite grades
- Poor heat conductor — 0.04 W/m·K (0.0231 BTU/hr·ft·°F), worse than 91% of composite grades
- Hard to polish — 20/100, worse than 90% of composite grades
Kevlar 29 properties
Typical room-temperature values; bars are the position among composite grades.
Physical4
Kevlar 29 has a density of 1.44 g/cm³ (0.052 lb/in³), lighter than 61% of composite grades. Its glass-transition temperature is 360°C (680 °F).
Mechanical6
Kevlar 29 has a tensile strength of 2,920 MPa (424 ksi), stronger than 80% of composite grades. Elongation at break is 3.6% and the elastic modulus is 70.5 GPa (10.2 Msi).
Thermal8
Kevlar 29 is rated for continuous service to 180°C (356 °F). It conducts heat at 0.04 W/m·K (0.0231 BTU/hr·ft·°F), worse than 91% of composite grades. Thermal expansion is -2 µm/m·K (-1.11 µin/in·°F).
Electrical4
Kevlar 29 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 29 takes about 270 MJ of energy and emits 13 kg of CO₂ — more than 60% of composite grades. Typical recycled content is 0%.
Manufacturability2
Kevlar 29's machinability is poor (25/100, worse than 65% 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. Kevlar 29 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Kevlar 29
Is Kevlar 29 easy to machine?
Cut with sharp serrated/shear scissors, hot knife or waterjet; drilling and routing of laminates need special aramid (C-type/brad-point) tooling, backing plates and high rake angles to avoid fuzzing and delamination.
Can Kevlar 29 be welded?
Not weldable or fusible — the fibre decomposes near 500 °C without melting; joints are made by stitching, braiding, splicing or adhesive/resin bonding.
Can Kevlar 29 be formed, bent or molded?
Processed as textile (weaving, braiding, filament winding) or as prepreg/RTM laminate; dry the fibre before impregnation (moisture regain ~4–7 %) and keep cure below ~180 °C for standard epoxies.
Kevlar 29 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 |
|---|---|---|
| p-phenylenediamine (PPD) unitmonomer share of the repeat unit (mol basis) | ≈ 45 | 45 |
| terephthaloyl chloride (TCl) unitmonomer share of the repeat unit (mol basis) | ≈ 55 | 55 |
| spin finish / sizingtextile or RFL-compatible finish depending on end use | 0.1 – 0.8 | 0.4 |
| poly(p-phenylene terephthalamide) (PPTA)condensation polymer of p-phenylenediamine + terephthaloyl chloride, liquid-crystal spun from sulfuric acid | balance |
What surface finishes work on Kevlar 29?
Edges should be resin-sealed or bound to stop fraying; laminates must be painted, gel-coated or fabric-covered because unprotected aramid loses strength rapidly in sunlight.
How much does Kevlar 29 cost?
Kevlar 29 is a high-cost composite ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Kevlar 29 — frequently asked
What is Kevlar 29 used for?
Kevlar 29 is typically used for ballistic vests, ropes and cables, protective fabrics, tire reinforcement and friction materials. In short: baseline industrial para-aramid; highest-toughness aramid grade; rope and ballistic workhorse.
What is the tensile strength of Kevlar 29?
Kevlar 29 has a typical tensile strength of 2,920 MPa (424 ksi) — stronger than 80% of composite grades. Strength varies by condition: see the 5 listed tempers.
Is Kevlar 29 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 65% of composite grades). Cut with sharp serrated/shear scissors, hot knife or waterjet; drilling and routing of laminates need special aramid (C-type/brad-point) tooling, backing plates and high rake angles to avoid fuzzing and delamination.
Can Kevlar 29 be welded?
Not weldable or fusible — the fibre decomposes near 500 °C without melting; joints are made by stitching, braiding, splicing or adhesive/resin bonding.
What surface finishes work on Kevlar 29?
Edges should be resin-sealed or bound to stop fraying; laminates must be painted, gel-coated or fabric-covered because unprotected aramid loses strength rapidly in sunlight.
Can Kevlar 29 be formed, bent or molded?
Processed as textile (weaving, braiding, filament winding) or as prepreg/RTM laminate; dry the fibre before impregnation (moisture regain ~4–7 %) and keep cure below ~180 °C for standard epoxies.
What is the maximum service temperature of Kevlar 29?
Kevlar 29 is rated for continuous use to about 180°C (356 °F), and briefly to 250°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Kevlar 29 cost?
Kevlar 29 is a high-cost composite ($$$$), 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
- Kevlar Aramid Fiber Technical Guide (H-77848) — DuPont (2017)
- ASM Handbook Vol. 21 — Composites — ASM International (2001)
- ASTM D7269 — Tensile Testing of Aramid Yarns — ASTM International (2020)
- Granta/CES EduPack — Aramid fibre and aramid/epoxy composite records — Ansys Granta (2023)
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.