FATIGUE CRAZE INITIATION IN POLYCARBONATE - STUDY BY TRANSMISSION ELECTRON-MICROSCOPY

Fatigue craze initiation in bulk, amorphous polycarbonate (PC) is inve stigated by means of transmission electron microscopy. The results agr ee very well with small angle X-ray scattering measurements of the sam e set of samples, and confirm that void generation is the main charact eristic of the initiation process. The evolution of the initial void-l ike structures or 'protocrazes' with dimensions of approximately 50 nm into crazes with dimensions of several micrometres is presented in co nsiderable detail. It is found that some similarities exist between cr azes induced by cyclic fatigue at room temperature and crazes produced in monotonic loading at temperatures close to the glass transition. T he similarties suggest that disentanglement of polymer chains plays an important role in the fatigue craze initiation process in bulk, amorp hous PC near room temperature.