Experimental methods for obtaining fracture data from small specimens

This paper first examines the problems of using impact methods to achieve fast fracture of polymers. On-specimen gauges are employed to obtain the distribution of transient and other stresses in different parts of the specimen. A new method is then introduced that avoids transient forces and achieves crack velocities in small specimens of tough polymers of over 300 m s-l. It provides for the measurement of load to just sustain a running crack and for determining the limiting crack velocity. An important point about the new method is that the material can be allowed to stress relax to various degrees before launching a m c k to simulate these different working conditions.