Specific surface: a missing parameter in high-explosive modeling

摘要

To accurately describe the constitutive response of high explosives such as PBX 9501, we need to consider the heterogeneous explosive as a composite rather than a homogeneous solid. Because of the extremely complex nature of the structural distribution of the contituents, the phase-volume fractions alone are insufficient to characterize such a complicated microstructure. What other parameter (or parameters) do we need to consider. How do we incorporate the parameter (or parameters) into a theoretical framework for developing a constitutive theory for high explosives. In this report we identify the so-called specific surface (i.e., the interfacial area-per-unit-volume of a multi-phase heterogeneous solid) as an additional parameter used in modeling the constitutive behavior of high explosives. Both the phase-volume fractions and the specific surface are needed to characterize the microstructure of the material. This report (1) provides a detailed argument that supports this conclusion, (2) presents a method (based on optical micrographs) for estimating the specific surface of PBX 9501, and (3) discusses the charcateristics of theoretical frameworks designed to construct constitutive models of high explosives.