Strain-rate correlation of biaxial tension and compression mechanical properties of HTPB and NEPE propellants

An effective biaxial tension and compression test method is proposed based on the shortcomings of current research for the mechanical properties of solid propellants under complex stress states. The equal proportion biaxial tension and compression test of HTPB (Hydroxyl-terminated polybutadiene) and NEPE (NitrateEster Plasticized Polyether) solid propellants is performed at different rates while at room temperature, and the damage morphology of the tension–compression zone is analyzed using micro-CT. The results show that the failure mode of the solid propellant under biaxial tension and compression loading is similar to that under uniaxial tension. Meanwhile, the compressive strength is much greater than the tensile strength, which will eventually cause tensile failure. With an increased loading rate, the growth trend of the initial modulus, ultimate strength, and maximum elongation of the propellant is gradually flattened, and the damage degree is gradually reduced. Additionally, damage that forms in the HTPB propellant is from dewetting and particle fracture while that for the NEPE propellant is from matrix tearing. The porosity can be used as the meso-damage parameter of the propellant.