Digital image correlation method for measuring viscoelastic Poisson's ratio of propellant

Solid propellant belongs to typical viscoelastic material, whose Poisson's ratio is the function of time. However, the occupation standards regard the propellant Poisson's ratio as a constant with the contact measurement, which have a bad influence on the accuracy of structural integrity analysis for grain. In this study, a relaxation definition of the viscoelastic Poisson's ratio was derived. A high precision measuring method for propellant Poisson's ratio based on Digital Image Correlation (DIC) method was proposed. Using this method, a measuring system for propellant Poisson's ratio was developed, and the time-varying viscoelastic Poisson's ratio of a certain HTPB propellant was measured. Test results show that the strain measuring accuracy of the system attains 20 με, which can solve the problem of milli-measuring inaccuracy for solid propellant Poisson's ratio. The results show that the Poisson's ratio increases with the time increasing, which exhibits obviously viscoelastic property. The present method is available for the noncontact measurement of other viscoelastic materials.