Abstract
In this research, an initial exploration of the viscous effects present in heterogeneous solid rocket propellant is conducted through experimental analysis. To achieve this, uniaxial tensile and relaxation experiments were conducted on the Joint Army-Navy-NASA-Air Force Propulsion Committee (JANNAF) standard[1], specimens using the Zwick Z050 universal testing machine. The work involved conducting destructive tensile tests at different strain rates and relaxation tests at different strain levels and temperatures, with three values being considered. The resulting data from the experiments are illustrated in appropriate diagrams, and depending on these data, the viscoelastic behavior of this material was confirmed. Additionally, mathematical modeling of this studied phenomenon using the generalized Maxwell model, identified on the basis of experimental data, is presented. The material parameters of the constitutive model are determined numerically using MATLAB software based on the Prony series procedure. The efficiency of the model and the identification approach are discussed. A high agreement between the calculation and the experimental results was found based on the Prony coefficients of relaxation modulus, with a maximum error of about 2.35%. Finally, numerical modeling of the relaxation tests was conducted to simulate the stress relaxation behavior of the AP-HTPB composite solid propellant using the ANSYS program. The Prony coefficients were added to the nonlinear viscoelastic components to define the material model in ANSYS, and the maximum difference between the numerical and experimental results is 3.98%.