Measurement of Energy Release Rate of Multiply Branching Crack by Caustic Method

Abstract

Caustic method is applied to measure energy release rate of multiple branching cracks in PMMA plate specimens. A crack arises at the center of upper boundary of the specimen and propagates at a speed more than 700 m/s. The number of cracks increases with repeating crack bifurcation, and about ten cracks propagate simultaneously. The total energy release rate increases with the extension of the cracks and becomes about 6 kJ/m2 around the center of specimen.