Compositescomposite
Aramid Fibre Composite (AFRP)
The impact laminate. Kevlar in epoxy: less stiff than carbon, far tougher, and it absorbs energy instead of shattering — ballistic panels, helmet shells, pressure vessels.
Properties
- Family
- Composites
- Category
- composite
- Density
- 1.38 g/cm³ · 1380 kg/m³
Densityhow aramid fibre composite (afrp) compares
Laminate propertiesKevlar 49 in epoxy · 60% fibre by volume
- Fibre / matrix
- Kevlar 49 · Epoxy
- Fibre volume fraction
- 60%
- Tensile strength, along the fibres
- 1,280 MPa
- Tensile strength, across the fibres
- 30 MPa · 43× lower than along them
- Modulus, along the fibres
- 87 GPa · 5.5 GPa across
- Compressive strength, along the fibres
- 335 MPa · Poisson’s ratio 0.34
Values are for a unidirectional laminate of Kevlar 49 in epoxy at 60% fibre volume fraction, from fib Bulletin 40 (FRP reinforcement), unidirectional laminate values. Longitudinal means load along the fibres, transverse means load across them; change the fibre fraction or the layup and every figure here changes with it.
Applicationswhere aramid fibre composite (afrp) is normally specified
Ballistic panelsHelmet shellsPressure vesselsImpact bumpersCut-resistant panels
Working & joiningtrade experience, not measured values
- Machining
- Difficult to cut cleanly: the fibres fuzz rather than sever, and scissors or a dull blade will pull them. Waterjet or a sharp abrasive disc gives the only clean edge.
- Joining
- Bolted joints lose much of the laminate's strength because the fibres buckle in compression around the hole — and the material creeps under a sustained bearing load.
- Durability
- Tough under impact, and the reason it is used, but it takes up water and degrades in UV. It is also sensitive to strong acids and bases, which attack the fibre itself rather than the matrix.
As with the wood and metal pages, these lines are not measurements. The longitudinal figures above assume the load arrives along the fibres; a bolted joint is usually the place where it does not, which is why the joining note is the one to read first.
Practical notes
- Lightest of the three laminates here, and the least stiff
- Poor in compression — the fibres buckle, which is what limits structural use
- Absorbs water and degrades in UV unless the matrix protects it