Mechanical and thermophysical properties of energetic crystals: evaluation methods and recent achievements

The mechanical properties of energetic crystals (ECs) are relevant to the safety and performance of ammunitions and propellants. Several experimental and theoretical investigations have been conducted on different ECs to study their mechanical properties and effects on sensitivity and stability. Using evaluation methods such as nanoindentation, Raman spectroscopy, and molecular dynamic simulations, a significant amount of helpful information on this topic has emerged, some of which are summarized herein. The overall safety and performance of energetic materials depend on the properties of the energetic crystalline ingredients. Properties such as the thermostability and sensitivity of such crystals have been greatly improved using methods such as cocrystallization, recrystallization, coating, and intercalation. The overall strength and, thus, the safety of formulations largely depend on the quality and mechanical strength of included ECs. Therefore, it is essential to investigate the mechanical strengths of the modified ECs. This review also summarizes various theoretical and experimental methods to study the mechanical properties of pure ECs. As a proposal, additional research on the mechanical strength of modified hybrid ECs with improved energy density and sensitivity is necessary to ascribe the inherent mechanisms

The effect of Al/oxidizers interfacial structure on the mechanical properties of composite propellants

In this paper, the mechanical properties of a typical four-component composite solid propellants with various designed Al/oxidizer interfaces have been studied. The Al/oxidizer interfacial control is mainly realized by using the core-shell composites AP@Al and Al@RDX with different particle sizes, where Al powder was coated with a thin layer of polydopamine (PDA) as the binding sites, so that the oxidizers could crystalize on it during a rapid spray granulation process. The stress-strain curves of the above propellants at different temperatures and different tensile rates have been obtained. The dependence of the loss factor on temperature was studied by using a dynamic thermomechanical analysis (DMA). It has been shown that the fracture elongation of the interfacial modified propellants can reach 51.81% at room temperature, which is 127.3% higher than that of the blank formulation under the same formulation. Moreover, the temperature and strain rate sensitivity of interfacial controlled HTPB propellants is much less than that of traditional ones. The microstructure of these propellants at the crack sites was investigated by scanning electron microscopy (SEM) supported with micro-area in-situ tensile CT scanning technology, to clarify their damage and failure mechanisms