The paper describes a study of the behaviour of fibres and woven fabrics when impacted at velocities in
the range up to - l000m 1. The projectiles, typically steel balls of 2 or 5mm diameter, were accelerated
by a double diaphragm gas gun which allowed velocities to be controlled within a few metres per second.
The impact events were viewed using high-speed photography. Photography at microsecond framing
intervals was made using an image converter camera (the Hadland Imacon). This camera was triggered
when the projectile interrupted a laser beam positioned just in front of the specimen. In experiments with
single fibres, it was possible to measure the transverse wave speeds. Experiments were made with a
number of fibre materials covering a wide range of moduli and strength properties. A number of
experiments were also made with woven fabrics of different densities and laminates. The velocity range
covered included non-penetrating and penetrating events. The fibre materials which had the best ballistic
performance were those which combined a high dynamic modulus with the ability to reach large strains
before failure. The high modulus is important since it affects both the strength and the stress wave
velocities. If a material has high wave velocities it can spread the load onto other fibres and layers more
quickly which is beneficial.