Shock propagation and spall characterization of poly-methyl methacrylate (PMMA) using in-situ time-gated Raman Spectroscopy

In this study, shock deformation and spall behavior of poly-methyl methacrylate (PMMA) were investigated using multi-point time gated Raman spectroscopy and Photon Doppler Velocimetry (PDV). Laser driven flyers with a velocity of 1.2 km/s were used to generate shock waves for spallation in the sample. Raman spectra with 10 ns time-gated window was used to capture shock propagation at the sample for the characterization of the shock front. Peak shifts of C-H stretching mode at 2,957 cm^-1 were correlated to shock compression pressure up to 3 GPa. The spall strength and the corresponding strain rate of the sample was measured using PDV. Metastable phases were observed, providing information on shock-induced phase changes and chemical decomposition. This study highlights the capabilities of time-resolved Raman spectroscopy in capturing shock wave propagation in soft materials and characterizing the metastable phase changes. The combination of PDV and high-speed imaging provides an in-depth characterization of spall properties in polymeric materials.