REAL-TIME SMALL-ANGLE X-RAY SCATTERING STUDIES OF FATIGUE IN POLYSTYRENE.

Synchrotron radiation has been used to examine the effect of mechanical fatigue on craze structures in polystyrene. At the maximum of the load cycle the SAXS pattern shows a well-defined streak normal to the craze films. During unloading the streak decreases in intensity and spreads into a diffuse fan. On reloading the streak reappears. The short-term changes in the pattern are caused by the fibril deformation and bending on unloading. Long-term changes, particularly changes in the fully loaded pattern over many cycles, can be related to changes in fibril structure and fibril failure.