Mesoscopic damage evolution and rate-dependent porosity prediction model of a composite propellant by in situ X-ray tomography

Nitrate ester plasticized polyether (NEPE) composite propellant is widely used in solid rocket motors, serving as the power source of the launch vehicles. The propellant is always subjected to complex mechanical loads during the service, which could induce mesoscopic damage represented by cracks and pores, then eventually reduces carrying capacity of the composite. To illustrate the internal damage evolution mechanisms of NEPE propellant under uniaxial tension, this study developed an in situ X-ray tomography to extract the changing of mesosturctures at different strain rates, then reconstruction of components and pores was conducted to track the damage morphologies’ evolution. As the interfacial debonding preferred to initiate at the large particles, the debonded interfaces would grow into pores with extension of strain, then formed different damage morphologies depending on mesostructures. In addition, the porosity evolution was analyzed at different strain rates, which presented distinct rate-dependent characteristics. By introducing critical debonding stress criteria with a pore evolution model, a rate-dependent porosity prediction model was proposed, and this model provided an excellent agreement with experiment results, which is valuable to damage assessment and integrity analysis of the composite propellant.