Using Neutron Diffraction to Investigate Texture Evolution During Consolidation of Deuterated Triaminotrinitrobenzene (d-TATB) Explosive Powder

Abstract

Triaminotrinitrobenzene (TATB) is a highly anisotropic molecular crystal used in several plastic-bonded explosive (PBX) formulations. A complete understanding of the orientation distribution of TATB particles throughout a PBX charge is required to understand spatially variable, anisotropic macroscale properties of the charge. Although texture of these materials can be measured after they have been subjected to mechanical or thermal loads, measuring texture evolution in situ is important in order to identify mechanisms of crystal deformation and reorientation used to better inform thermomechanical models. Neutron diffraction measurements were used to estimate crystallographic reorientation while deuterated TATB (d-TATB) powder was consolidated into a cylindrical pellet via a uniaxial die-pressing operation at room temperature. Both the final texture of the pressed pellet and the in situ evolution of texture during pressing were measured, showing that the d-TATB grains reorient such that (001) poles become preferentially aligned with the pressing direction. A compaction model is used to predict the evolution of texture in the pellet during the pressing process, finding that the original model overpredicted the texture strength compared to these measurements. The theory was extended to account for initial particle shape and pore space, bringing the results into good agreement with the data.

Microcomputed X-Ray Tomographic Imaging and Image Processing for Microstructural Characterization of Explosives

“…The dark regions here are likely agglomerates of TATB crystals, indicating that there are multiple length scales of interest when characterizing the PBX 9502 microstructure; that is, the individual crystal scale and the crystal agglomerate/molding prill scale. This finding also reinforces some recent modeling approaches in the literature that account for multiple length scales to match experimental data [ 42 , 43 ].…”

Coefficient of Thermal Expansion during Ratchet Growth of TATB Compactions

“…The crystal structure of TATB is graphitic, like a stacked deck of cards, which endows TATB-based compactions (with or without binder) with unusual properties such as thermal and mechanical anisotropy and irreversible volume expansion or ratchet growth [2][3][4][5][6]. The anisotropy is caused by preferential alignment of the TATB crystals during the compaction process [7] and the significant underlying thermal expansion and mechanical anisotropy of those crystals [8,9]. Irreversible volume expansion occurs upon thermal cycling and has also been observed to be anisotropic.…”

Irreversible Deformation Mechanisms for 1,3,5-Triamino-2,4,6-Trinitrobenzene Single Crystal through Molecular Dynamics Simulations

“…It crystallizes in a triclinic cell of space group P1 1,2 and exhibits very anisotropic thermo-mechanical and chemical behavior 3,4 due to the arrangement in layers of the two C 6 H 6 N 6 O 6 molecules (see Figure 1). Such anisotropic properties are also the consequences of the directional interactions within the molecular crystal, which give to the strength a high sensitivity toward the direction of loading (up to a factor 20 for shear), as indicated by computations of the second order stiffness tensor C. [5][6][7] Experiments have pointed out that TATB grown single crystals are noticeably defective, [8][9][10][11][12] with the presence of porosities, twinned structures, etc. Until recently TATB single crystals of size compatible with standardized mechanical experiments (e.g.…”