A technique for rapid two-stage dynamic tensile loading of polymers

A method for rapid two-stage dynamic-dynamic tensile loading of polymers, b ased on a tensile Hopkinson bar apparatus, is established. In this techniqu e, the initial incident wave and its reflection are used to load a specimen in quick succession. Consequently, the specimen is stressed, momentarily u nloaded, then reloaded until fracture. By adopting appropriate assumptions, a procedure to obtain the associated stress-strain curves for such double- stage loading is formulated. These assumptions are examined experimentally and analytically to substantiate their validity. To verify the proposed app roach, a relatively rate-insensitive material, LEXAN 141 polycarbonate, was subjected to two-stage dynamic tension. The stress-strain curves obtained via the procedure established were compared with results from static loadin g. Favorable correlation between the two indicates that the proposed techni que can be applied to the study of load history effects on the dynamic beha vior of polymeric materials.