When a filamentous material is subjected to impact either transversely or longitudinally in tension, a strain wave is produced which propagates along the filament away from the point of impact. For small strain waves, the behavior of the material can be characterized by stress-strain and specific breaking energy data obtained with a transverse impact tester and a rotating disk longitudinal impact tester operating at impact speeds up to 70 m per sec. For large strains the material may be characterized by stress-strain and critical breaking velocity data obtained from photographs of configurations and strain distributions of filaments struck by rifle bullets.

Impact behavior in textile yarns is illustrated with stress-strain data obtained at strain rates up to 5000 per cent per sec. The critical velocity at which a filament breaks immediately upon transverse or longitudinal impact is discussed theoretically and tested for nylon yarn by transverse impact experiments with rifle bullets. At impact velocities near 600 m per sec the breaking tenacity and breaking elongation for this yarn are much less than the values obtained at conventional strain rates, and there is a marked dependence of breaking time upon the impact velocity. The critical velocity concept is also tested by longitudinal impact tests on copper wire and paper.