Influence of Prestrain on the Mechanical Properties and Constitutive Model of Hydroxyl-Terminated Polybutadiene Films as Used for Coatings in Solid Rocket Motors

Abstract

Low-field 1H NMR tests and uniaxial tensile tests of hydroxyl-terminated polybutadiene (HTPB) films, subjected to a prestrain before the NMR and tensile tests related to the use of the HTPB as coatings for solid rocket motors, were carried out. The mechanisms of the variations of crosslinking density, tensile strength and maximum elongation of the HTPB films with prestrain were analyzed, and a Gaussian function model of the variation of the crosslinking density with prestrain was obtained. By introducing crosslinking density and prestrain as correction coefficients, two prestrain constitutive models of the stress-strain relationship of HTPB films related to the Mooney-Rivlin and Ogden hyperelastic constitutive models, respectively, were established and the parameters of the models were obtained based on nonlinear least squares fitting. The accuracy and effectiveness of the prestrain constitutive models were determined with that based on the Ogden model proven to be of important engineering value.