Damage Tolerant Microstructures for Shock Environments

While dynamic failure, due to shock loading, has been studied for many years, our current ability to predict and simulate evolving damage during dynamic loading remains limited. One reason for this is due to the lack of understanding for the linkages between process-induced as well as evolved microstructure and damage. To this end, the role of microstructure on the early stages of dynamic damage has been studied in high purity Ta and Cu. This work, which utilizes plate-impact experiments to interrogate these effects, has recently been extended to a subset to Cu-alloys (Cu-Pb, Cu-Nb, and Cu-Ag). These multi-length scale studies, have identified a number of linkages between damage nucleation and growth and microstructural features such as: grain boundary types, grain boundary orientation with respect to loading direction, grain orientation, and bi-metal interfaces. A combination of modeling and simulation techniques along with experimental observation has been utilized to examine the mechanisms for the ductile damage processes such as nucleation, growth and coalescence. This work has identified differing features of importance for damage nucleation in high purity and alloyed materials, lending insight into features of concern for mitigating shock induced damage in more complicated alloy systems.