Relationships Between Mechanical Behavior and Craze Morphology in Thin Films of Polystyrene.
CASE WESTERN RESERVE UNIV CLEVELAND OHIO DEPT OF MACROMOLECULAR SCIENCE
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A new technique has been developed to study the relationship between mechanical properties and craze microstructure in thin films 1-10 micrometers of polystyrene. These thicknesses allowed us to strain the films in a conventional testing machine and subsequently examine them in the deformed state in an electron microscope. Strain rate was systematically varied and its effect was investigated on both quenched and annealed samples correlations were found between craze morphology and ductility. A new craze parameter fundamental to our theoretical interpretation has been defined as the width of a strip of material which is involved in the development of a craze. 0From this value, the average strain and the average volume fraction of fibrils within a craze can be calculated. In order to obtain a mechanistic model which is consistent with observed data, a changing relative local strain rate during craze formation had to be assumed. Author