Long-Term and Short-Term Creep Characteristic Analysis for HTPB Propellant

A solid rocket motor is in storage for most of its life cycle, and propellant creep occurs subjected to gravity load. To analyse the creep characteristics of HTPB propellant during long-term storage, MSC Marc is used to calculate the maximum von Mises stress of the motor under horizontal and vertical storage conditions. Based on the numerical results, the short-term reciprocating creep test and long-term creep test are designed and carried out. The results illustrate that the process of propellant creep from deformation to final failure can be divided into four stages: instantaneous deformation stage, attenuation creep stage, steady-state creep stage and accelerated creep failure stage. When the creep stress level is less than 0.1 MPa, the creep characteristics tend to be stable. When the creep strain exceeds a certain critical value, the propellant will enter the steady-state creep stage. The damage caused by creep rises with the increase of creep time and stress. When the maximum creep strain is less than 10 %, the creep damage can be fully recovered. The splicing curve of short-term creep test data is in good agreement with that of long-term creep test data. A mechanical long-term creep test method is provided, and the parameters of the modified Burgers model are fitted. The text methods and conclusions can provide a reference for the evaluation of structural integrity and storage life of solid motor.