Shock Wave Compression of ‘Plexiglas’ in the 2.5 to 20 Kilobar Region

Abstract

PRECISE data concerning the Hugoniot equation of state for polymethyl methacrylate (‘Plexiglas’, ‘Lucite’ polymers, and ‘Perspex’) are lacking at pressures below 20 kbar. Accurate dynamic data in this pressure region are helpful when the polymer is used as an attenuator material for forming shocks in the lower pressure region, and in general are necessary to understand its rheological behaviour under the high strain-rate conditions of shock compression. Solid materials customarily exhibit shock instability at pressures somewhat larger than the yield stress in uniaxial strain. This instability gives rise to an ‘elastic precursor’ wave front preceding the main shock front¹. Such a structural wave might be expected in ‘Plexiglas’ since an indication of a yield zone was found in the vicinity of 2 kbar in measurements of the static linear compressibility by the method of Hughes and Maurette², and it is of interest to know if it does occur.