Spallation strength of single crystal and polycrystalline copper

The spallation strength of single crystal copper foils 100 micrometers thic k of the < 110 > and < 100 > orientations and of polycrystalline copper foi ls has been determined. Laser driving was used to launch miniature plates. Also, the spallation strength of polycrystalline copper was measured using conventional gas gun techniques and plates for comparison. Experimental mea surements include VISAR records of the free surface particle velocity and m icrographs of recovered flyers. A ID hydrocode was used to simulate the VIS AR records to determine the dynamic pressure history of the spallation proc ess. Judging by the calculated pressures, it was found that the < 110 > foi ls were somewhat stronger than the < 100 > foils, which were about twice as strong as the polycrystalline foils. These were, in turn, substantially st ronger than the larger sample plates (1.5 mm thick) of the gas gun. In the polycrystalline foils, small voids are found in recovered samples impacted at flyer plate velocities almost producing spallation in the gas gun, indic ating that this sparse damage in the foils is able to grow substantially mo re in the much larger gas gun plates and under much slower gas gun loading.