Numerical and experimental study on the curing process of NEPE solid rocket propellant considering multi-physical field effects

A multi-physical field numerical model considering the thermo-chemical and mechanical effects was used to simulate the curing process of a nitrate ester plasticized polyether (NEPE) solid propellant. The curing process of solid rocket propellants was detected through physical experiments such as differential scanning calorimetry (DSC) and heat transfer. The variation laws and distribution patterns of the temperature field and curing degree field during the propellant curing process were numerically and experimentally analyzed, and the residual and contact stresses caused by the effects of temperature, chemical reaction, and pressure were studied. The results showed that the internal temperature field of the NEPE propellant during the curing process was closely related to the curing time. At about 3 d of curing time, the propellant curing rate was the fastest, and the temperature reached a maximum value of 58 °C. During curing, the NEPE solid propellant produces an unevenly distributed temperature field and curing degree field distribution, which aggravates the residual stress. The molding pressure can reduce the residual stress; however, when the pressure exceeds approximately 3 MPa, it causes extrusion stress on the interface layer between propellant-to-case and propellant-to-core mold. Based on the numerical calculation results, an optimal pressure calculation formula for multiple parameters that can quickly estimate the optimal pressure is derived.