Development of back-face coatings for the characterization of non-reflective and opaque materials by laser shocks

Abstract

The present study intends to make possible the dynamic characterization of a non-reflective and opaque material using a laser shock test which must lead to the establishment of an equation of state and a constitutive law. The instrumentation used is a back-face velocity measurement by a green laser interferometry (VISAR). In this study, a metallic coating (aluminum) is added to the back-face of the non-reflective material to be characterized (here an elastomer). The influence of the back-face coating thickness on material characterization is studied experi­mentally and numerically. The experimental results indicate that, whatever the thickness of the metal coating, it is possible to determine the equation of state of the material using a simulation model. Limitations of the pro­ posed protocol are then finally discussed to get a constitutive law at loading up to 20 GPa. The role of a probable early damaging at the back-face of the sample and improvements proposals are given through numerical analysis of the shock tests.