Determination of fracture parameters for propellant/liner interface affect zone through measuring J-integral

The debonding of propellant/liner interface is one of the primary failure modes that impact the structural integrity of solid rocket motors. In order to study the mechanical properties of propellant/liner interface, tensile tests on rectangular specimens with various prefabricated crack lengths were conducted at different temperatures and loading rates, as well as uniaxial tensile tests on the propellant. Utilizing the digital image correlation(DIC) method, the strain field including the whole rectangular specimen and the propellant part was analyzed, and the change law of the crack length of the rectangular specimen with time was extracted by programming batch processing at different temperatures. Meanwhile, the fracture toughness of the NEPE propellant/liner interface under different loading conditions was obtained using J-integral theory. The results show that the area near the propellant/liner interface forms an interface affect zone (IAZ), where cracks grow steadily in a continuous and smooth way without significant fluctuations. The effect of temperature and loading rate on J-integral is interactive. The lower the temperature, the greater the fracture toughness of the interface and the lower the crack propagation rate. Finally, based on the bi-linear cohesive model, the numerical simulation of the interface affect zone (IAZ) in the rectangular specimen is carried out, which shows that the J-integral can effectively represent the energy required for the interface affect zone failure. A method to determine the fracture parameters for the propellant/liner interface affect zone is proposed.