Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session F05: Shock and Impact of Soft matterFocus Recordings Available
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Chair: David Williamson, University of Cambridge Room: Anaheim Marriott Platinum 3 |
Monday, July 11, 2022 3:30PM - 4:00PM |
F05.00001: Deformation mechanisms and shock propagation in polymer particulate composites: Experimental study based on high speed visual and infrared imaging Invited Speaker: Addis Kidane Polymer bonded explosives are a class of polymer particulate composites with 80-95 % crystal and 5-20 % polymer binder by weight. The experimental study to understand the failure mechanism of such materials has been challenging due to the material's multiscale and heterogeneous deformation nature. Recently, using high-speed imaging, the shock propagation and deformation mechanisms at different loading conditions have been investigated. In this work, polymer-bonded sugar, a known mock material for polymer-bonded explosive, is subjected to impact loading, and its deformation mechanism and shock propagation characteristics are investigated. Different particle sizes and mass fractions are considered, and their effect on the deformation mechanism is investigated. It was shown that the crystal size affects the mechanical response in PBS; when the crystal size increases from 150 μm to above 650 μm, the ultimate compressive stress of the PBS decreases by 17 %. We also found that force chains are responsible for localized stress concentration in the material under impact loading, demonstrated by fracture of the crystals along the chain line. The nature of shock propagation in PBS was observed to be dissipative and can be associated with frictional heat dissipation caused by the fracture surface and crystals and the viscoelastic deformation of the polymer binder. The model composite's local temperature and deformation evolution reveal that the high relative movement between the crystal and the binder causes the highest local temperature rise. The temperature rise due to the relative movement of crystals and binder could be as high as four times higher than the temperature associated with other mechanisms such as the deformation of the binder, crystal fracture, and relative sliding of the fractured crystals. |
Monday, July 11, 2022 4:00PM - 4:15PM |
F05.00002: Shock induced energy transfer into a solid structure Kibaek Lee, Donald S Stewart, Alberto M Hernández, Brayden R Roque, Ryan Houim We present an analysis of energy deposition into a hyperelastic solid induced by shock impact generated by an explosive blast. Ecoflex 00-30 is used for the solid object and the shock is generated by a finite sized charge of HMX explosive that generates a shock in air. The solid sphere shaped rubber-like material is modeled by the Neo-Hookean equation of state (EOS) while for HMX we use the Wide-Ranging EOS.The diameters of the explosive charge and the solid object are 1 and 3 inches respectably, and the distance between their centers is 16 inches. Gauges where placed on the surface and inside the sphere to measure pressure and compare numerical results to from our novel multi-material simulation code to experimental data generated by Prof. Glumac's group at University of Illinois. Both experiments and numerical simulations observed high oscillations in the sphere. |
Monday, July 11, 2022 4:15PM - 4:30PM |
F05.00003: Shock Induced Virtual Glass Transition to Rapidly Reduce Deviatoric Stress in Polystyrene Alejandro H Strachan, Jalen Macatangay, Brenden W Hamilton Shock compression introduces a near-instantaneous increase in temperature and deviatoric stress as the shockwave propagates within a condensed matter system. When polymers are subjected to strong shocks, relaxation mechanisms, such as cooperative intramolecular motion and chain rearrangements, operate to reduce deviatoric stress towards a hydrostatic equilibrium state. However, these mechanisms and their associated rates are poorly understood, especially challenging are the initial response following shock loading. Therefore, we simulate shock loading on glassy polystyrene using molecular dynamic simulations with the multiscale shock technique (MSST) and characterize the stress relaxation processes. For strong shocks, the relaxation of deviatoric (Von Mises) stress exhibits two regimes: i) an initial fast relaxation lasting 2-5 ps, ii) followed by a more gradual process. Analysis of the torsional transition events in the polymer backbone bonds (dihedral angles switching between low-energy states) indicate that the fast relaxation is associated with shock-induced virtual melting. The second regime corresponds to glassy dynamics. |
Monday, July 11, 2022 4:30PM - 4:45PM |
F05.00004: Shockwave properties of SWIFT Silicone Foams Dana M Dattelbaum, Matthew N Lee, Rachel Huber, Joshua D Coe, Lloyd L Gibson Polymer foams are used extensively as structural supports and shock mitigating materials. Under shock wave compression, large compressions result in high temperatures, leading to chemical decomposition at low shock pressures. The high temperature rise is also known to give rise to anomalous compression even at relatively low initial porosities. Furthermore, stochastic porous structures can result in shock wavefront heterogeneities at the microscale. These features make shockwave measurements of highly porous foams plagued with difficulties in diagnostic data return and large experimental errors. Here, we report the results of a series of plate impact experiments on SWIFT silicone-based polymer foams using a shockwave transmission configuration, diagnosed with x-ray phase contrast imaging and photonic Doppler velocimetry. SWIFT foams are produced by a patent-pending Silicon/Water in Familiar Template method, which produces foams by a robust and flexible process, in which variables such as molecular weight, crosslink density, filler, and pore scale can be tightly controlled. We compare the shock properties of SWIFT foams to other polydimethylsiloxane foams, and will comment on the influence of microstructure on reducing error in measurements of the principal Hugoniot over a range of initial densities. |
Monday, July 11, 2022 4:45PM - 5:00PM |
F05.00005: Dynamic Compression of Stoichastic Foams with Velocimetry and Imaging Diagnostics Rachel Huber, Joshua D Coe, Dana M Dattelbaum, John M Lang, Lloyd L Gibson, Brian Bartram Foams and polymers undergo densification when dynamically compressed, transitioning the materials from reactants to products. During gas gun driven planar impact, we can observe shock driven compression and/or decomposition with velocimetry probes that capture the particle velocity traces. Due to the stochastic nature of these foam materials, they not only act to slow the shockwave but alter the arrival times and quality of the traces at the individual velocimetry probes introducing additional uncertainties into these measurements. Accounting for these uncertainties is difficult when using only velocimetry probes; however, imaging, such as phase contrast imaging (PCI) or radiography, provides the ability to capture both shock and particle velocity in situ. We have studied both SX358 and APO-BMI with PCI, radiography and velocimetry to, in theory, understand how each diagnostic affects uncertainties measured during dynamic compression of stochastic foam materials. |
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