Anticrack-type fracture in brittle foam under compressive stress

Fracture events initiating and propagating under negative mode I stress intensity factor, K-I, have been observed in laboratory experiments on cellular foam glass. The material at the crack tip collapses almost instantly in the event of fracture, leaving behind an accumulation of debris packing denser than the intact material. The fracture behavior comes close to that of anticracks, but essential differences remain. The fracture energy under negative K-I was evaluated to be nearly 10-fold that under positive K-I.