Damage softening constitutive model of HTPB propellant for biaxial loading

Abstract

In order to establish the damage constitutive model of composite solid propellant, it is assumed that the micro element strength in HTPB propellants follows Weibull distribution. Using the twin-shear unified strength theory, a damage distribution variable is established, and a constitutive model characterizing the damage deformation process of HTPB propellants is established. Based on the biaxial loading experimental data of HTPB propellant at room temperature (298.15 K) and three loading rates (0.40 s−1, 4.00 s−1, and 14.29 s−1), the model parameters were fitted, and the relationship between the parameters in the damage constitutive model and strain rate was given. The model was validated using experimental results at room temperature (298.15 K) and three other loading rates (1.00 s−1, 2.00 s −1, and 8.00 s−1). The results show that the damage constitutive model can well describe the stress strain relationship of HTPB propellant under biaxial loading, although the model prediction effect of the nonlinear transition region of the stress strain curves is poor. Finally, it is concluded that the constitutive model established in this paper reflects the softening characteristics of HTPB propellants and the phenomenon that the strength of HTPB propellants is affected by the stress state. The damage constitutive model can provide a reference for the damage analysis of composite solid propellants under complex loading conditions.