Study on the interfacial interaction between ammonium perchlorate and hydroxyl-terminated polybutadiene in solid propellants by molecular dynamics simulation

Abstract

The interfacial interaction between the main oxidant filler ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene (HTPB) matrix in AP/HTPB propellants were studied via an all-atom molecular dynamics simulation. The results of the simulation showed the effects of the microscopic cross-linked structure of the matrix, stretching rate during uniaxial stretching, and contact area between the filler and matrix on the mechanical properties, such as the stress and strain of the composite solid propellant. Among the aforementioned factors, the stretching rate considerably affects the mechanical properties of the solid propellant, and the maximum stress of the solid propellant proportionally increases with the stretching rate. When defects were introduced on the surface of the AP filler, the contact area between the filler and matrix affected the strain type of the matrix molecules. Owing to the interaction between the molecules and atoms, the strain behaviour of the matrix molecule changed with the change in its microscopic cross-linked structure during uniaxial stretching. Molecular dynamics simulations were used to explore the characteristics at the AP–HTPB interface in AP/HTPB propellants. The aforementioned simulation results further revealed the interfacial interaction mechanism of the AP–HTPB matrix and provided a theoretical basis for the design of high-performance propellants.

Review on the Dewetting of the Particle‐Matrix Interface in Composite Solid Propellants

“…It was found that the interface strength increased with the increase of strain rate. This is consistent with the change trend of the macro mechanical properties of the propellant [129]. Segurado and Llorca, Shoukry et al.…”

Reaction Network of Ammonium Perchlorate (AP) Decomposition: The Missing Piece from Atomic Simulations

“…They observed significant changes in the atomic density distributions of the AP crystal and near surfaces compared to the corresponding distributions in the bulk phase. Dong et al 24 studied the interfacial interactions of the AP− HTPB matrix in composite solid propellants. The effects of the microstructure of the matrix molecule, the stretching rate, and the interfacial contact area on the mechanical properties of the AP−HTPB matrix interface were provided.…”

Molecular-Level Insights into the Improvement Mechanism of the Bonding Agent MAPO on the Mechanical Properties of the AP/HTPB-TDI Cross-Linked System

“…In this study, the COMPASS II force field is used in all MD simulations, which has been widely verified and can provide accurate predictions for the fundamental properties of the systems and materials in this paper, such as conformation, density, vibration, cohesive energy, and thermodynamic characteristics. − In MD simulation, AP is treated as a rigid body due to its relatively low vibration, and the integration time step is set to 0.5 fs unless otherwise mentioned. For different models, MD simulations of 0.5–1 ns are conducted, and the thermodynamic data and snapshots of configurations are captured every 1 ps for analysis.…”

“…The (011) crystal plane is cleaved with a thickness around 18.33 Å larger than the cutoff radius of nonbonding interactions and repeated into 6 × 6 in u and v directions corresponding to 55.3 Å × 56.7 Å to establish the AP surface. 28 The selection of crystal planes and related data is supplied in the SI. Periodic boundary conditions are applied, and an 80 Å vacuum layer is added above the threelayer model hidden in Figure 2.…”

“…The orthorhombic AP crystal unit with the Pnma space group is adopted, and the corresponding lattice parameters are a = 9.20 Å, b = 5.82 Å, and c = 7.45 Å and α = β = γ = 90°. The (011) crystal plane is cleaved with a thickness around 18.33 Å larger than the cutoff radius of nonbonding interactions and repeated into 6 × 6 in u and v directions corresponding to 55.3 Å × 56.7 Å to establish the AP surface . The selection of crystal planes and related data is supplied in the SI.…”