Numerical study on tailoring the shock sensitivity of TATB-based explosives using sub-millimeter features

The objective of this numerical study is to demonstrate how the shock sensitivity of TATB-based explosives can be altered with the addition of sub-millimeter features. Such simulation-based studies are important because structure-property relationships are not well established for reacting energetic materials. For this study, we use LX-17 (92.5%wt TATB, 7.5%wt Kel-F 800) as the prototypical insensitive TATB-based explosive. Simulations are performed in the multi-physics hydrocode, ALE3D. The Lee-Tarver Ignition and Growth reactive flow model is used to simulate the shock initiation response of the explosives. Our metric for shock sensitivity in this study is run distance to detonation as a function of applied pressure. In the first part of our study, we examine changes to shock sensitivity of one dimensional TATB-HMX laminates where a thin HMX explosive layer has been inserted into the TATB explosive bulk. We investigate HMX layer thickness, HMX volume fraction, as well as uniform and non-uniform HMX layer spacing. Uniformly spaced TATB-HMX laminate calculations show increased shock sensitivity with higher HMX volume fraction. As HMX layer thickness decreases, the overall laminate shock initiation response becomes more TATB-like. Calculations demonstrate differences in shock sensitivity with the forward graded and reverse graded structures. In the second part of the study, we examine changes to shock sensitivity when tungsten chevron features are embedded in the TATB. The high shock impedance tungsten coupled to the unique chevron shape effectively amplifies the incoming shock in the TATB. High impedance tungsten is capable of amplifying the shock in TATB by nearly 2.5 times the input pressure without consideration of chevron shape. The addition of the chevron feature has a focusing effect that is directional in nature. This can accelerate the transition to detonation. Reactive calculations show the shock sensitivity increasing for all chevron geometries considered.