A hyper-viscoelastic constitutive model for polyurea

This letter presents a new constitutive model for polyurea by superposing the hyperelastic and viscoelastic behaviors of polyurea. The Ogden model is used for the hyperelastic part and its parameters are determined from curve fitting of quasi-static test data. A nonlinear viscoelastic model is employed for describing the viscoelastic behavior and its relaxation time is obtained based on the test data of shear relaxation modulus. A special form of Zapas kernel for the damping function is found to be very effective to capture the viscoelastic behavior of polyurea subjected to wide ranges of strain rate. Both the versatility and accuracy of the model are examined via virtual testing.