STUDY OF DYNAMIC BIREFRINGENCE AND STRAIN PRODUCED IN TRANSPARENT POLYMERS BY MECHANICAL IMPACT
Technical progress rept. Jan 1964-Jun 1965
ARMY NATICK LABS MA CLOTHING AND ORGANIC MATERIALS LAB
Pagination or Media Count:
To obtain basic information about the mechanical and optical response of polymers, the stress-wave propagation in transparent plastics is being studied by observation of the dynamic strain and birefringence produced by mechanical impact. In this initial study, the dynamic strain-fringe constant of CR-39 plastic was studied over a range of apparent strain rates between 2,300 and 30,600 percent strain per second by the simultaneous measurement of the strain and birefringence occurring during the nearly linear leading edge of the strain pulse. Over this dynamic range no distinct dependence on the strain rate could be discerned. However, comparison of the average dynamic strain-fringe constant with the corresponding static value indicated a slight rate dependence over this larger total range of apparent strain rates.