A CROSSBOW SYSTEM FOR HIGH-STRAIN-RATE MECHANICAL TESTING

This paper describes a technique developed to measure the uniaxial com pressive stress-strain properties of polymers at strain rates appropri ate to ballistic and impact events over time scales of tens of microse conds using a crossbow as the projectile launch system. The instrument constructed represents a novel development of existing equipment type s. The system is used for compression testing giving stress-strain mea surements at strain rates of up to 10(4) s(-1) and over a temperature range of 20-200 degrees C. Stress is calculated directly from a measur ed force obtained from a calibrated pressure bar. Strain is calculated from the sample displacement measured directly from the intensity red uction of a laser-photodiode unit. The crossbow system provides a rela tively inexpensive, reliable and compact alternative to a standard Hop kinson bar.