REGULAR PATTERNS ON FRACTURE SURFACES OF POLYMER GELS

The morphology on fracture surfaces of polymer gels has been studied. Two kinds of macroscopic morphology were found depending on the crack growth rate. One is similar to the well-known river pattern and is obs erved at large crack growth rates and the other looks like fish scales and is observed at small crack growth rates. The change of the patter n indicates the existence of a dynamic transition. The introduction of water into the cracks in the gels increased the characteristic dimens ion of the regular patterns.