Shock Response of Sodalime Glass at Extraordinary Pressures and Strain Rates
Abstract
There is a significant interest in understanding the behavior of soda-lime glass (SLG) under extreme conditions of strain rate, temperature, and pressure (>20 GPa) as it undergoes a phase transformation with up to 40% or more volume change. During this process, several high density polymorphs, including the ultra-hard Stishovite phase which has a density of 4.313 g/cc, are formed. A significant amount of energy is consumed during this process. Since such extreme conditions are generated during impact of hypervelocity projectiles, there is a significant interest in the armor design community to incorporate soda-lime glass in advanced armor concepts for protection against shapedcharges that send explosively formed projectiles with speeds up to 10,000 m/s.The aim of this proposal is to explore the shock compression response of SLG in the ultrahigh pressure (> 40 GPa) and strain rate (> 108s1) regime, and to develop a new experimental setup to measure the local temperature rise in the shocked SLG samples. The high pressure shock data will be obtained in two ways.In the first effort, the shock pressure will enhanced by reducing the cross-sectional geometry of the samples. Specifically, SLG micropillars of varying diameters (100 2000 nm) and aspect ratios will be fabricated using lithography and each pillar impacted individually by aligning its axis with the center of micro flyer plate. Because of the relatively high inertia of the flyer platecompared to each micropillar, local stresses approaching 60 GPa at strain rates > 109s1 can be attained even with UCLAs current setup that can generate a maximum nominal shock pressure of 21GPa.In the second effort, the top hat beam element that converts the laser pulse with the Gaussian energy distribution into one with a flat energy profile will be redesigned and updated to attain flyer velocities nearing 4 km/s. Based on Professor Asimovs data that was recently shared with the ONR PIs, shock pressures around 55 GPa can be generated in flat SLG samples, withouteven considering the pillar effect. If this is successful, impacting a single pillar at this velocity will result in hitherto unreported pressure levels.Besides obtaining the EOS data, the deformed samples will be examined for stishovite formation using the HRTEM/SEM/FFT techniques as in our previous effort. It is noteworthy that in both of the above efforts, SLG samples will be subjected to strain rates of 108s1 and higher. By comparing the EOS data from this study with those from other investigations, the effect of ultrahighstrain rate on SLG deformation will be determined.Finally, in addition to examining the effects of high pressure and ultrahigh strain rate, the effect of temperature in the formation of high density polymorphs will be studied by measuring the local temperature rise in shocked samples by using the Time-domain Thermo Reflectance (TDTR) method. In this method, an Al film with a known dependence of its reflectance on temperature is deposited on the surface of the sample. The change in the reflectance suffered by the Al film due toshock-induced transient temperature rise is recorded by bouncing off a train of pulses from a highspeed femtosecond laser. The measured reflectance data is converted into the temperature using the known (calibrated) dependence of reflectance on temperature for the Al film. There is very limited experimental data available on shock-induced temperature rise in SLG.The basic science mechanisms resulting from this study should ultimately lead to the development of glass polycrystals and glass-based composites for integration into advance armors.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 31, 2020
- Source ID
- N000142012783
Entities
People
- Vijay Gupta
Organizations
- Office of Naval Research
- United States Navy
- University of California, Los Angeles