Effect of thermal treatment on the impact strength of polycarbonate

Thermal treatment of polymers has been found to have a pronounced effect on the residual stress state and the impact properties of these materials. Researchers have found that compressive residual stresses can be used to bring about a transition from a brittle to higher-energy absorbing impact failure in polycarbonate and have subsequently proposed that this transition is predominately a function of the local stress state at the notch tip. In this study the impact strength of polycarbonate has been measured as a combined function of the residual compressive stress in the material, the thickness of the material, the radius of the notch tip and the location of the notch relative to the residual stress field. The transition in the energy absorption capability of the material was found to be highly dependent on these local variables at the notch tip.