EXPERIMENTAL METHODS FOR OBTAINING FRACTURE DATA FROM SMALL SPECIMENS

This paper first examines the problems of using impact methods to achi eve fast fracture of polymers. On-specimen gauges are employed to obta in the distribution of transient and other stresses in different parts of the specimen. A new method is then introduced that avoids transien t forces and achieves crack velocities in small specimens of tough pol ymers of over 300 m s(-1). It provides for the measurement of load to just sustain a running crack and for determining the limiting crack ve locity. An important point about the new method is that the material c an be allowed to stress relax to various degrees before launching a cr ack to simulate these different working conditions.