Dynamic Brittle Fragmentation: Probing the Byproducts of Hypervelocity Impact in Space Open Access
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Improvements in computational and analytical modelling of large-scale impact and catastrophic disruption events will come from a better understanding of the failure processes that are active during high strain-rate events. In this study we investigate the dynamic compressive failure and fragmentation of basalt, paying particular attention to the role each constituent mineral phase has in these processes. Our results indicate the existence of two fragmentation mechanisms: I. a mechanism that creates small fragments that is associated with the spacing of critically activated defects. These fragments are primarily comprised of pyroxene (which has the lowest fracture toughness in this material). II. a mechanism related to larger fragments that is associated with the structural failure of the sample. These fragments are primarily polyphase and polygrain in composition. In the second part of the paper, we investigate the strength of fragmented basalt material for different initial fragment size distributions: 1. between 10 and 100 microns, 2. between 200 and 800 microns, and 3. between 300 and 1,800 microns. The porosity of each of the three samples was maintained between 30 and 35%. Understanding the composition of the fragments beforehand allows us to better interpret our experimental results, which indicate that the strengths of the fragmented material increased with decreasing fragment sizes, from 4 to 25 MPa, and then to 175 MPa. An increase in strength with smaller fragment sizes is expected because of the associated increase in frictional dissipation, and decrease in the relative contribution of compaction and fracturing mechanisms. However, we do note that fragments less than 100 microns fail as a result of the activation of a different critical defect type than in the bulk material and for fragments larger than 100 microns, where olivine grains are the key contributors to fracture. Altogether, these results highlight the influence of the composition and defect population of planetary materials on the associated length scales that arise from dynamic failure and fragmentation.
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Hogan, J., Mir, C., Plescia, J., and Ramesh, K. (2015). Dynamic Brittle Fragmentation: Probing the Byproducts of Hypervelocity Impact in Space. Procedia Engineering, 103(#N/A), 205-212.
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