Novel measurements of high-dynamic crystal strength by picosecond x-ray diffraction

The fracture strength of many brittle materials is known to increase with the cubed root of the strain rate. At ultrahigh strain rates, the strengths should approach the ideal fracture strength. We have made direct measurements of the dynamic tension in laser-shocked silicon wafers at strain rates in excess of 108 s−1 by the use of picosecond x-ray diffraction. The elastic strains observed (3.4%±0.2%) correspond to tensile stresses of the order of 70 kbar, and are comparable to the highest fracture strengths observed in static measurements.