Mesoscale behavior of an aluminum-manganese dioxide-epoxy mixture under shock loading: from milli to nano-sized aluminum particles
Date of Award
Master of Science (MS)
Borg, John P.
Widera, G.E. Otto
The main focus of this thesis is to explore the dynamic shock compaction of multiple component mixtures, specifically Al-MnO2-Epoxy. This will be facilitated by initially simulating the bulk dynamic response in a mesoscale configuration and then comparing these results to experimental data. The mesoscale simulations were performed in the shock code CTH. The first section will discuss the matching of experimental data to computational results. With the goal of determining the bulk shock Hugoniot, a one-dimensional flyer plate configuration was created while using a grain-geometry imported from an scanning electron microscope (SEM) micrograph of the mixture. Both the aluminum and manganese dioxide were assigned a strain dependent material strength: Aluminum- Johnson Cook and MnO2- Johnson Ceramic II; this enabled the multiscale investigation down to the nanometer particle sizes as discussed in the second section.
The second section will discuss what effect changing the size of the aluminum particles and the alumina coating has on the formation of local hot spots. In addition the presence of voids and their effect on the hot spot formation was also investigated. A representative volume was created where aluminum particle diameters ranged from millimeter to nanometer; also, in the nano-sized setup, the alumina coating was varied from 0 to 3 nanometers. It was noticed that changing the aluminum grain size had a slight effect on the hotspot formation. Changing the alumina coating had an apparently random effect on the maximum temperature reached as no trend is clear. Also, it was found that inserting randomly placed voids into the epoxy binder created a large spike in initial temperature.