Effect of matrix material properties on the mechanical behavior of HTPB composite propellant

The matrix material of hydroxylterminated polybutadiene (HTPB) composite propellant was manufactured according to the requirement of production process. To obtain the matrix material with different relaxation characteristics, the relaxation tests of material specimens were conducted under different temperatures (-50, -35, -20, 0, 20,35℃), and the test results were fitted by Prony series. The experimental results provided necessary parameters for the followup simulation calculation. Then the mesoscale model of the composite propellant was generated by combining molecular dynamics method with cohesive element. To verify the applicability of the random packing numerical model, the relaxation tests of HTPB propellant were conducted under room temperature. The simulation results agreed well with the real relaxation tests and the error between the two curves was less than 20%. This shows that the developed mesoscale numerical model is capable of reflecting the mechanical behavior of HTPB propellant. Finally, the numerical simulation of HTPB propellant with different random spatial distributions and matrix material properties was conducted on the Abaqus program. The results show that the random distribution of particles does not affect the macroscopic mechanical properties of HTPB propellant. However, the matrix properties have a significant impact on macroscopic mechanical behavior of HTPB propellant, and the relationship between macroscopic mechanical parameters (initial modules, elongation and strength) and the environment temperatures of binder follows the rule of exponential equation.