Discovering Analogues for Solar System Ices: Physical and Numerical Modeling of Highly Porous Sintered Soda-Lime Glass Powder
Mentor:Jose Andrade, Associate Professor of Civil and Mechanical Engineering, California Institute of Technology
The 2013 Planetary Decadal Survey supports the exploration of small bodies as primary sources of information to understanding the evolution of the Solar System due to their volatile-rich compositions and low velocities permitting tractable exploration. Ice agglomerates, which are highly porous, constitute a significant fraction of these small bodies. We study these in a size continuum from grain-level to a larger metric scale to aid in the development of surface sampling methods and the documentation and preservation of samples. Ice is currently synthesized for these purposes, but because it requires dedicated facilities and very controlled conditions we are interested in developing low-cost simulants that are readily available and require no storage. Based on these criteria we examined the mechanical properties of sintered soda-lime glass powder, as ground-based observations show that planetary ice (existing around 100 K) exhibits brittle behavior which is characteristic of ceramics. Glass beads of 110-190 μm in diameter were sintered on two different heating schedules at atmospheric pressure, achieving near 44% porosity. Samples were loaded under uniaxial compression, and those sintered for a three-hour duration at 670°C exhibited a Young's modulus of 0.15-0.3 GPa, developed cracks and fractured into many smaller fragments, showing much similarity to the behavior observed for ice. Samples sintered for five hours were too strong and did not show this behavior. A discrete element method (DEM) model was developed to simulate uniaxial compression of the softer material and internal dynamic properties including strain energy and percentage of broken bonds were calculated. The results suggest that our material is a suitable, inexpensive simulant for ice. In future work, we will examine the material via scanning electron microscopy to determine its grain-level structure and behavior, allowing us to make a better assessment of its similarities to ice.