The unloading and reloading behavior of shock-compressed polymethyl methacrylate

Abstract

Samples of polymethyl methacrylate (PMMA) have been shock compressed to ?0.82 GPa and then further compressed by a reloading wave which approximately doubled the initial compressive stress. The reloading waves were observed to be acceleration waves rather than shocks. Assuming the material is Maxwellian, these waves have been analyzed to determine certain material properties characterizing the stress‐strain response of the material. These properties were found to be different than those obtained from previously reported unloading waves also propagating in shock‐compressed PMMA at ?0.82 GPa. This difference in stress‐strain response supports the existence of a yield‐type phenomenon previously suggested in PMMA at ?0.75 GPa.