Thermo-damage-viscoelastic constitutive model of HTPB composite propellant

The main goal of this work is to establish a thermo-damage-viscoelastic model for Hydroxyl-Terminated Polybutadiene (HTPB) composite propellant based on the thermodynamic theory and elastic–viscoelastic correspondence principles. The model will also consider the influence of temperatures. The parameter α which represent the damage evolution rate and the material constants a, b are defined as exponential functions of temperature T, i.e. α(T), a(T) and b(T). Relaxation tests and uniaxial constant rate tensile tests are used to acquire the model parameters, and C(S) curves of different rates under the same temperature states are considered to be overlapped in this paper, while noncoincidence under the different temperature states. Then, uniaxial constant rate tensile tests and multi-step tensile-relaxation tests are used to verify the accuracy of the model. The results show that, the model is highly accurate in describing the mechanical property of HTPB under various loading conditions, but some drawback in describing the relaxation property inside of the HTPB’s nonlinear viscoelastic segments.