A three-dimensional viscoelastic constitutive model of solid propellant considering viscoelastic Poisson's ratio and its implementation

A three-dimensional viscoelastic constitutive model of solid propellant grains incorporating with viscoelastic Poisson's ratio is proposed. To apply the new constitutive equations in the commercial finite element software MSC. Marc, a fully explicit numerical algorithm is developed. Two examples are presented to illustrate the viscoelastic behavior of solid propellant grains under thermal cycling and ignition pressurization loading, respectively. The finite element analysis results show that the Von Mises strain response is safer and more conservative for propellant with viscoelastic Poisson's ratio, while the Von Mises stress response is more dangerous than those for propellant with elastic Poisson's ratio. In analyzing ignition pressurization, the Von Mises strain and Von Mises stress along the interface of solid rocket motor have a similar distribution law, regardless of viscoelastic and elastic Poisson's ratios. Thus viscoelastic Poisson's ratio of solid propellant should be taken into account for better understanding the viscoelastic behavior of solid propellant grains.