Dynamic and Static Compressibility of Porous Granular Hexanitrostilbene

Abstract

Hexanitrostilbene (HNS) is a binderless, granular explosive prepared over wide ranges of initial grain size and final bulk density. During shock initiation of HNS, ignition initially occurs at discrete hot spots formed during the dynamic compaction of the porous material. In order to develop a predictive understanding of the shock initiation mechanisms occurring in this explosive, it is necessary to formulate constitutive relations modeling the mechanical response of HNS materials under compressive loading. In an early study of HNS properties, Sheffield et al. [1] established shock Hugoniot properties and formulated an equation of state for bulk densities of 1.0 – 1.7 g/cc (crystal density is 1.74 g/cc). Subsequently, Hayes and Mitchell [2] and Hayes [3] developed a model for the shock compaction and chemical decomposition of HNS. In these studies, the non-reactive material response was treated as depending only on the initial bulk density (related to initial porosity) of the HNS sample. Our recent studies [4,5] have established that the shock sensitivity of HNS samples pressed to a common density depends critically on the initial grain size distribution of the material. In the present study, we have undertaken both experimental and analytical studies of the compressibility behavior of HNS under non-reactive conditions.