ForMatter/Materials/composite/Kevlar (Aramid Fiber, Para-Aramid)
mat_kevlar_aramid

Kevlar (Aramid Fiber, Para-Aramid)

synthetic high-performance fiber, para-aramid (poly-paraphenylene terephthalamide), woven cloth or laminate use · Kevlar (DuPont trade name), Twaron (Teijin trade name), para-aramid, aramid fiber, ballistic aramid

The yellow fiber of every bullet-resistant vest, every cut-resistant glove, every Kevlar-Carbon composite bicycle helmet, every aerospace cable, every reinforcement against explosion / impact. Kevlar (DuPont's trade name; Twaron is the Teijin equivalent) is a para-aramid synthetic fiber developed by Stephanie Kwolek at DuPont in 1965 — the polymer molecules are aromatic rings linked by amide bonds, packed and oriented along the fiber axis to give exceptional tensile strength (5x steel by weight) at a low fiber density. Used as woven cloth (the bullet-resistant vest format), as a unidirectional tape (composite reinforcement layup), as a cable strand, as a protective sheath. The yellow color is intrinsic to the polymer chemistry, not a dye. Vulnerable to UV (degrades 50 percent strength in 100+ hours of direct sun exposure) so almost always used either in a UV-protected configuration (woven into a vest under cover, embedded in resin matrix as composite). Buy as cloth from Composite Envisions / Fibre Glast for hobby use; from DuPont / Teijin directly for industrial-volume.

Synthetic organic fiber, structural unit poly-paraphenylene terephthalamide (PPTA, the para-aramid chemistry). Fiber density 1440 kg/m³ (lighter than carbon fiber, much lighter than steel). Tensile strength 2900-3600 MPa (single fiber). Tensile modulus 70-130 GPa depending on Kevlar grade (29 / 49 / 149). Elongation at break 2.4-4.4 percent. Specific tensile strength (strength per density) ~5x steel. Service temperature 250 °C continuous, decomposes around 500 °C without melting (aromatic backbone provides the high-temperature stability). UV degradation is the major service-life concern: 50 percent strength loss in 100-300 hours of direct UV exposure, requiring protective overlay (carbon-fiber face plies on Kevlar-cored composites; opaque cover on Kevlar-based vests). Bonds with epoxy and vinyl-ester resins for composite layup; bonds poorly with polyester (the polyester-Kevlar interface is the weak point in marine composites built from these materials). Cuts only with specialized aramid scissors or carbide-tipped shears (regular fabric scissors dull and tear; the aramid fiber has 'self-sharpening' resistance to cutting). Soft against the hand in cloth form; reads as a heavy yellow gauze.

mechanical

  • density_kg_m31440
  • tensile_strength_mpa_fiber3300
  • tensile_modulus_gpa110
  • elongation_at_break_percent3.5
  • service_temperature_c250
source: DuPont Kevlar 29 / 49 / 149 datasheets; Teijin Twaron technical literature; ASTM D885 textile fiber test methods

Sustainability

  • embodied carbon kg co2e per kg11.0
  • sourceEditorial estimate from ICE / Granta CES EduPack class data for aramid fibers, cradle-to-gate. PPTA polymerization and dry-jet wet-spun fiber formation are energy-intensive.
  • recyclabilitylow — aramid fibers are difficult to recycle; ballistic vest end-of-life often goes to industrial-felt recycling or landfill
  • biodegradableFalse
  • certificationsNIJ Standard 0101.06 (US ballistic protection levels for body armor), ASTM D885 (textile fiber test), REACH compliant
  • localityglobal production by DuPont (US — Kevlar), Teijin (Netherlands/Japan — Twaron), Hyosung (Korea — Alkex); designer-quantity cloth via Composite Envisions, Fibre Glast
visual
the canonical bright yellow (or yellow-green for some grades); woven cloth reads as a tight smooth weave, distinctly thicker than equivalent fiberglass cloth; composite layup with Kevlar shows the characteristic yellow fiber pattern through clear epoxy
tactile
soft and surprisingly light in cloth form; cut edge of cured composite is glass-hard; the cloth has a slightly waxy feel from the fiber finish (sizing applied during manufacturing)
weight perception
light — reads as half the weight of equivalent fiberglass at the same volume
acoustic
muted in cloth form; cured composite has a moderate ring when struck

PBR starter values

finish · fibrous — open for table, JSON, host snippets, downloads

Principled BSDF defaults derived from the sphere fibrous finish. Reasonable seed for Blender, Substance, Keyshot, Rhino — tune per material. Or grab the whole library at once: ForMaterials library →

# finish:                   fibrous
albedo                      #d8c850
metallic                    0.00
roughness                   0.70
ior                         1.45
transmission                0.00
clearcoat                   0.00
sheen                       0.70
anisotropic                 0.50
copy as JSON
{
  "albedo": "#d8c850",
  "metallic": 0.0,
  "roughness": 0.7,
  "ior": 1.45,
  "transmission": 0.0,
  "clearcoat": 0.0,
  "sheen": 0.7,
  "anisotropic": 0.5
}
Blender 4.x Python
# Blender 4.x — Principled BSDF
# Kevlar (Aramid Fiber, Para-Aramid) · finish: fibrous
import bpy
mat = bpy.data.materials.new(name="mat_kevlar_aramid")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value         = (0.6867, 0.5776, 0.0802, 1.0)
bsdf.inputs["Metallic"].default_value           = 0.000
bsdf.inputs["Roughness"].default_value          = 0.700
bsdf.inputs["IOR"].default_value                = 1.450
bsdf.inputs["Transmission Weight"].default_value = 0.000
bsdf.inputs["Coat Weight"].default_value        = 0.000
bsdf.inputs["Sheen Weight"].default_value       = 0.700
bsdf.inputs["Anisotropic"].default_value        = 0.500
KeyShot Python (lux)
# KeyShot 11+ — lux Python API, Generic material
# Kevlar (Aramid Fiber, Para-Aramid) · finish: fibrous
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_kevlar_aramid", materialType="Generic")
mat.setProperty("diffuse",      (216, 200, 80))   # 8-bit sRGB
mat.setProperty("metallic",     0.000)
mat.setProperty("roughness",    0.700)
mat.setProperty("indexOfRefraction", 1.450)
mat.setProperty("transparency", 0.000)
mat.setProperty("coatingWeight", 0.000)
Substance pbrMetalRough
{
  "_format": "Substance Designer / Painter \u2014 pbrMetalRough constants",
  "_about": "Kevlar (Aramid Fiber, Para-Aramid) \u00b7 finish: fibrous",
  "baseColor": {
    "r": 0.6867,
    "g": 0.5776,
    "b": 0.0802
  },
  "metallic": 0.0,
  "roughness": 0.7,
  "ior": 1.45,
  "opacity": 1.0,
  "anisotropyLevel": 0.5,
  "_notes": "Channels listed are the standard Substance pbrMetalRough output. Drop into a Uniform Color node per channel, or as the constant input on a layered stack."
}
glTF 2.0 Metallic-Roughness
{
  "asset": {
    "version": "2.0",
    "generator": "ForMatter"
  },
  "materials": [
    {
      "name": "mat_kevlar_aramid",
      "pbrMetallicRoughness": {
        "baseColorFactor": [
          0.6867,
          0.5776,
          0.0802,
          1.0
        ],
        "metallicFactor": 0.0,
        "roughnessFactor": 0.7
      },
      "extensions": {
        "KHR_materials_ior": {
          "ior": 1.45
        },
        "KHR_materials_sheen": {
          "sheenColorFactor": [
            1.0,
            1.0,
            1.0
          ],
          "sheenRoughnessFactor": 0.7
        }
      }
    }
  ]
}
USD Preview Surface
# USD Preview Surface — UsdShade.MaterialLook prim attributes
# Kevlar (Aramid Fiber, Para-Aramid) · finish: fibrous
def Material "mat_kevlar_aramid" {
    token outputs:surface.connect = </mat_kevlar_aramid/PreviewSurface.outputs:surface>

    def Shader "PreviewSurface" {
        uniform token info:id = "UsdPreviewSurface"
        color3f inputs:diffuseColor = (0.6867, 0.5776, 0.0802)
        float   inputs:metallic     = 0.000
        float   inputs:roughness    = 0.700
        float   inputs:ior          = 1.450
        float   inputs:opacity      = 1.000
        float   inputs:clearcoat    = 0.000
        token   outputs:surface
    }
}
↓ download glTF material

Second life

repairabilitymoderate — kevlar fabric accepts patch-and-overlay repair with epoxy.
recyclabilityvery low — aramid fibers are very hard to recycle.
disposal pathgeneral waste.
typical longevity15 years (typical)
failure modes
  • UV degradation (the canonical kevlar failure — yellows and loses strength in sun)
  • moisture-absorption weakness
  • creep under sustained load

DuPont Kevlar technical literature.