Experimental determination of dynamic crack initiation and propagation fracture toughness in thin aluminum sheets

An experimental investigation was undertaken to characterize the dynamic fracture characteristics of 2024-T3 aluminum thin sheets ranging in thickness from 1.63-2.54 mm. Specifically, the critical dynamic stress intensity factor K-c(d) was determined over a wide range of loading rates (expressed as the time rate of change of the stress intensity factor (K)over dot(I)(d)) using both a servo-hydraulic loading frame and a split Hopkinson bar in tension. In addition, the dynamic crack propagation toughness, K-D, was measured as a function of crack tip speed using high sensitivity strain gages. A dramatic increase in both K-c(d) and K-D was observed with increasing loading rate and crack tip speed, respectively. These relations were found to be independent of specimen thickness over the range of 1.5 to 2.5 mm.