Schematic stress-strain curves for the three primary shock-hardening behaviors.
Temperature-pressure phase diagram for PTFE and crystalline structure of PTFE in phase II. Soft recovery experiments from three velocities are shown together with the approximate shock-induced heating based on Grüneisen EOS and thermodynamics relationship following Meyers.53
Crystalline structure of PTFE in phases II and III. Values for phase II from Holt and Farmer54 and for phase III from Eby et al. 50
Historic (a) high- and (b) low-pressure Hugoniot data for PTFE.
Schematic of the momentum trapped assembly.
Preshock momentum trapped assembly and postshock soft-recovered sample at .
The (a) shock impedance and (b) pressure of PTFE, PC, and PMMA at low particle velocities assuming a linear relationship. Assuming a constant amplitude pressure wave in three polymers, the relevant and associated shock impedance values for the three loading conditions are shown.
Material motion plots for a recovery shot at at impact and after .
A plot of pressure in the recovery fixture at 2 and after impact at .
Pressure vs time for four points spaced from the center of the specimen.
Crystallinity in virgin and shock prestrained PTFE 7C as determined by density and DSC. Material was taken from near the impact face and away from the core of the recovered samples.
(a) Stress-strain response of virgin and shocked PTFE 7C for multiple pressures and (b) mechanical response of PTFE 7C accounting for the effective strain calculated as based on peak shock pressure.
Compressive strain hardening as a function of strain rate at . Error bars fall within data points.
Path dependence of PTFE stress-strain response.
Stress-strain response of PTFE 7C accounting for the effective viscoelastic shock path strain based on peak shock pressure and viscoelastic unload.
Tapping mode AFM maps showing the crystalline domain structure of virgin and shocked PTFE 7C as a function of pressure.
Mass fraction crystallinity values for PTFE 7C by standard methods.1
Hugoniot values used in the CTH calculations.
Flow stress and Poisson data used in the CTH modeling.
Mechanical properties of PTFE 7C in compression as a function of shock pressure .
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