Characterizing the dynamic strength of a polymer epoxy using the Richtmyer-Meshkov Instability*

Solid materials can exhibit fluid mechanical instabilities, such as the Richtmyer-Meshkov instability (RMI), when subjected to shock compression loading. Dynamic strength acts as a dissipating force to arrest RMI growth, similar to viscosity in fluids. In this study, we use RMI to characterize the dynamic strength and equation of state of the epoxy created by curing Epon 828 resin with diethanolamine (DEA). At the Dynamic Compression Sector of the Advanced Photon Source, plate impact experiments were performed to drive a steady shock compression wave through a sinusoidally corrugated copper-Epon 828/DEA interface, generating RMI at stresses ranging 4-12 GPa and strain rates near 10⁶ /s.  X-ray phase contrast imaging recorded shock propagation and interface evolution. Analysis of these images calibrated the equation of state of Epon 828/DEA and, in conjunction with numerical modeling, its dynamic strength. The equation of state was validated against plate impact experiments. The dynamic strength was compared to prior data for Epon-based epoxies at lower strain rates and found to exhibit significant strain rate and pressure-hardening effects. These findings suggest that Epon 828/DEA exhibits dynamic strengths comparable to high strength metals at these dynamic conditions.