Fracture analysis of superconducting composites with a sandwich structure based on electromagnetic-thermal coupled model

This paper analyzes a multilayer structure with a superconducting layer in the center and strengthening layers in the outer part. This represents a generalized structural form of multilayered high-temperature superconducting cable structures for space solar power station application. An analytical model for considering the influences of thermal-mechanical-electrical-magnetic coupling and the temperature on the stress distribution will be developed. The superposition method is used to solve the temperature distribution problem. After the temperature field is calculated, the magnetic field using a critical state model that considers the temperature effect will be developed. Finally, we analyzed the influence of material properties on the thermal and magnetically induced stress intensity factors in trapped field, zero field cooling and field cooling. Results show that the stress intensity factors induced either by thermal stress or by the Lorentz force must not be neglected. If the elastic module or the thickness of substrate layer increases, the stress intensity factor induced by thermal stress increases, while the one induced by the Lorentz force declines. Importantly, when reducing the thickness of the substrate layer, the total stress intensity factor will decrease at the early stage of heat conduction but increase at the late stage of heat conduction. This fact indicates that that thicker substrate layer is not always good from the reliability point of view.