Anisotropic Reaction Properties for Different HMX/HTPB Composites: A Theoretical Study of Shock Decomposition

Plastic-bonded explosives (PBXs) consisting of explosive grains and a polymer binder are commonly synthesized to improve mechanical properties and reduce sensitivity, but their intrinsic chemical behaviors while subjected to stress are not sufficiently understood yet. Here, we construct three composites of beta-HMX bonded with the HTPB binder to investigate the reaction characteristics under shock loading using the quantum-based molecular dynamics method. Six typical interactions between HMX and HTPB molecules are detected when the system is subjected to pressure. Although the initial electron structure is modified by the impurity states from HTPB, the metallization process for HMX does not significantly change. The shock decompositions of HMX/HTPB along the (100) and (010) surface are initiated by molecular ring dissociation and hydrogen transfer. The initial oxidations of C and H within HTPB possess advantages. As for the (001) surface, the dissociation is started with alkyl dehydrogenation oxidation, and a stronger hydrogen transfer from HTPB to HMX is detected during the following process. Furthermore, considerable fragment aggregation is observed, which mainly derives from the formation of new C-C and C-N bonds under high pressure. The effect of cluster evolution on the progression of the following reaction is further studied by analyzing the bonded structure and displacement rate.

Automated summary

In this study, the reaction characteristics of plastic-bonded explosives (PBXs) under shock loading were investigated using quantum-based molecular dynamics method. The results show that there are different interactions between HMX and HTPB molecules, and shock decompositions of HMX/HTPB are initiated by molecular ring dissociation and hydrogen transfer. Considerable fragment aggregation is observed under high pressure.