Dynamic fragmentation of cellular, ice-templated alumina scaffolds

The article of record as published may be located at http://dx.doi.org/10.1063/1.4939702Yi Ming Tan, Octavio Cervantes, SeanWoo Nam, John D. Molitoris, and Joseph P. Hooper, "Dynamic fragmentation of cellular, ice-templated alumina scaffolds". Journal of Applied Physics, Volume 119, Issue 2(Received 9 November 2015; accepted 28 December 2015; published online 8 January 2016)We examine the dynamic failure of ice-templated freeze-cast alumina scaffolds that are being considered as biomimetic hierarchical structures. Three porosities of alumina freeze-cast structures were fabricated, and a systematic variation in microstructural properties such as lamellar width and thickness was observed with changing porosity. Dynamic impact tests were performed in a light-gas gun to examine the failure properties of these materials under high strain-rate loading. Nearly complete delamination was observed following impact, along with characteristic cracking across the lamellar width. Average fragment size decreases with increasing porosity, and a theoretical model was developed to explain this behavior based on microstructural changes. Using an energy balance between kinetic, strain, and surface energies within a single lamella, we are able to accurately predict the characteristic fragment size using only standard material properties of bulk alumina.Defense Threat Reduction Agency under the supervision of Bill Wilson. Freeze casting work at LLNL was performed through the AMEA collaboration fostered by the LLNL National Security Office. All LLNL work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52- 07NA27344. Lawrence Livermore National Security, LLC