Crack Propagation in Polystyrene under Fixed Elongation.
Interim technical rept.,
CASE WESTERN RESERVE UNIV CLEVELAND OH DEPT OF MACROMOLECULAR SCIENCE
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Microscopic obsevations of precracked polystyrene samples under fixed elongation conditions reveal that crack propagates discontinuously under diminishing stress to a stable configuration. A zone of intensive crazes in the vicinity of the crack tip evolves currently with crack growth. Fracture occurs as the translation and expansion of the crazed zone ahead of the crack. The phenomenon has been successfully explained using a crack layer model. Contrary to conventional fracture mechanics ideas, crack propagation is found to be controlled by the differnce between the energy dissipated in damage crazing growth and the relevant energy release rate. Conditions of stability have been determined in terms of the relationship between these energies.