Experimental determination of the coefficients of thermal expansion of various high explosives

Detonation performance modeling of high explosives at elevated initial temperatures requires knowledge of the change in charge size with increasing temperature. In this study, we examine the thermally induced change in the radial and axial dimensions of isostatically-pressed cylindrical pellets of various explosives, including PBX 9502, Composition B, cyclotol and octol, during a single heating event.

In the case of PBX 9502, previous measurements of the coefficient of thermal expansion (CTE) have shown large variations across different studies, as well as anisotropic growth in directions parallel and perpendicular to the pressing direction [Skidmore et al., The Elusive Coefficients of Thermal Expansion in PBX 9502, LA-14003, 2003]. For our study, two virgin lots [BAE20F755-002 and HOL88H891–008] and one recycled lot [HOL88B891–007] are examined. We did not observe anisotropic growth for any of the virgin or recycled pellets between 20 °C and 75 °C, with comparable thermal expansion rates observed in both radial and axial directions. Our new growth rates for PBX 9502 are analyzed and compared with prior measurements. We show that the length scaling ratio versus temperature is slightly lower than that obtained by Skidmore et al. [2003]. The thermal expansion behaviors of Composition B, cyclotol and octol pellets also do not show anisotropic behavior for a single heating event.