Stress-Strain Relationships in Yarns Subjected to Rapid Impact Loading: Part X: Stress-Strain Curves Obtained by Impacts with Rifle Bullets

Abstract

When a yarn is struck transversely, a V-shaped wave of transverse motion is caused to spread outwards at a velocity Ū depending upon the impact velocity V. In this research data on Ū vs V for impact velocities between 10 m/sec and 700 m/sec are analyzed to determine stress-strain behavior in high-tenacity nylon and polyester yarns. The data are obtained by shooting rifle bullets at a yarn and recording the resulting configurations by microflash photography. A strain-rate-independent theory for transverse impact behavior is used to calculate stress-strain data. It was found that the time required to break a yarn depended upon the impact velocity. Nylon yarns broke 10 μsec after impact at 650 m/sec with a calculated breaking strain of 10.0% and tenacity of 77 g/tex. At 495 m/sec velocity the yarn broke within 100 μsec at 7.4% strain and 52 g/tex tenacity. The corresponding values in polyester yarn were, for a 10-μsec break, 620 m/sec, 10.5%, and 67 g/tex; for a 100-μsec break, 420 m/sec, 6.5%, and 40 g/tex.