Dynamic Fracture Criteria for Polycarbonate and Polymide.
STANFORD RESEARCH INST MENLO PARK CALIF
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Disk-shaped specimens of polycarbonate, and polyimide were subjected to flat-plate impact in a light gas gun under well- controlled and well-monitored conditions. For polycarbonate the stress-volume loading and unloading paths were determined under both static and dynamic conditions. Quantitative fractographic analyses on the impacted polycarbonate specimens were carried out and the results were correlated with computed stress histories to obtain analytical relations and graphs enabling one to predict the extent of damage which will be produced in polycarbonate by an arbitrary dynamic load. A similar detailed analysis was not carried out for polyimide because this brittle material fractured in a much more catastrophic manner for a given stress duration a small stress increment covered the range from incipient shock damage to complete disintegration. However, static stress-volume loading and unloading curves, an approximate constitutive relation, and the shock damage threshold stress for stress durations of about a microsecond were obtained for polyimide. A detailed study of the fracture mechanism was made for both materials. Author, modified-PL