Dynamic shearing resistance of a polymer-bonded energetic simulant: Composite of sucrose and hydroxyl-terminated polybutadiene (HTPB)

Abstract

The mechanical behavior of polymer-bonded explosives (PBXs) and polymer-bonded simulants has been widely studied under normal impact. However, their shearing response under large pressures and shear strain-rates has not been explored, to the best of our knowledge. Such measurements are crucial in informing constitutive models that aim to predict hot-spot formation and ignition behavior of PBXs subject to multi-axial loading. Pressure-shear plate impact experiments have been conducted on a composite of hydroxyl-terminated polybutadiene (HTPB) binder and sucrose (an energetic simulant) under normal stresses of 3-10 GPa nominally and shear strain-rates of the order of 105 s-1. The shear strength of the composite shows a dramatic drop after reaching a critical shear strain. Such a drop could be due to fracture or localization in either of the two phases, further compounded by other mechanisms such as friction between the resulting interfaces or collapse of voids. It is also observed that the shear strength of the composite is highly pressure-sensitive, increasing from 176 to 453 MPa as the normal stress increases nominally from 3 to 9.5 GPa. Comparison of the shearing behavior of the composite with that of a granular aggregate of sucrose grains at low normal stresses (∼3 GPa) indicates that the binder plays the role of a lubricant between the sucrose grains at those normal stresses. However, at normal stresses of ∼9-10 GPa, the shear strength of HTPB becomes similar to sucrose, and beyond these normal stresses, a transition in the failure mode and its location is expected.