The study of cavitation in HDPE using time resolved synchrotron X-ray scattering during tensile deformation

Real time synchrotron Small-Angle and wide-Angle X-ray Scattering was performed during the tensile deformation of a high-density polyethylene copolymer. The changes of the structure in the crystalline and in the amorphous domains were followed during the three characteristic stages of the load-displacement curves: The elastic stage and the plastic range composed of the stage of the lowering load in the force-displacement-curve (yielding) and the strain hardening. Competitive phenomena like crystallite fragmentation and cavitation were found to occur simultaneously in the phase of lowering the load but at different length scale. We prove that the void formation occurs mainly during yielding. During strain hardening there was no further increase of the void volume fraction, only changes in void size.