Dynamic fracture of glass and single-crystalline silicon

The dynamic brittle fracture of amorphous soda-lime glass and single-crysta lline silicon was studied in a comparative experimental investigation. A po tential drop technique was used to accurately determine the crack velocity. A terminal crack velocity ve of about 50 % of the Rayleigh wave velocity v (R) was determined for glass. The terminal crack velocity in single-crystal line silicon is significantly higher, reaching about 0.85 v(R) = 3800 m/s. Inspection of the fracture surface revealed significant differences between the amorphous and the single-crystalline materials. A continuous increase in the size of the characteristic features is typical for the transition fr om mirror to mist and hackle regions of the fracture surface in glass. In c ontrast, the onset of a rough, hackle-like region is clearly discontinuous in silicon single crystals. Mirror-like flat and hackle regions may coexist at the same location on the fracture surface.