Effect of Curing Pressure on the Microstructure and Mechanical Properties of NEPE Propellant

To elucidate the influence mechanism of curing pressure on the microstructure and mechanical properties of NEPE solid propellants, the curing experiments are conducted on the propellant billets under normal pressure and pressurized conditions. The effect of curing pressure on physicochemical properties, pore structure and interfacial morphology are systematically investigated through the thermophysical property test, the mechanical performance characterization, and the micro-CT and SEM analyses. The results show that the thermal conductivity of the propellant improves with the increase in curing pressure, and the reductions in the thermal expansion coefficient and the specific heat capacity show a downward trend. Meanwhile, the mechanical strength and stiffness of the propellant increase markedly; under a curing pressure of 5.0MPa, the ultimate tensile strength and elastic modulus are increased by 11.7 and approximately 60, respectively, while the ductility remains essentially unchanged. Microstructural analyses indicate that the pressurized curing suppresses the formation of residual bubbles and micropores during curing, thereby resulting in reduced pore size, more uniform pore distribution, and strengthened particle-binder interfacial bonding, which facilitates more uniform transfer of load within the propellant. In particular, the porosity decreases by 23.1 under 5.0MPa curing condition. Dynamic compression tests further demonstrate that the pressurized curing can simultaneously improves the load-bearing capacity and energy-absorption capability of the propellant and delays the occurrence of instability and failure. These results provide experimental evidence and mechanistic insight for the optimization of pressurized curing processes and engineering applications of NEPE solid propellants.